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Wang, Xin Jun. "Failure criterion for masonry arch bridges." Thesis, University of Dundee, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318150.
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McKernan, Scott John. "Anisotropic tensile probabilistic failure criterion for composites." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237601.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Wu, Edward M. "June 1990." Description based on title screen as viewed on October 16, 2009. Author(s) subject terms: Composite materials, probabilistic failure criterion, combined stress. Includes bibliographical references (p. 151). Also available in print.
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Lim, Jong Chun. "Composite failure criterion - probabilistic formulation and geometric interpretation." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22961.
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Zhang, Xuesong, and n/a. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion." Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051104.153239.
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Failure criteria play a vital role in the numerical analysis of reinforced concrete structures. The current failure criteria can be classified into two types, namely the empirical and theoretical failure criteria. Empirical failure criteria normally lack reasonable theoretical backgrounds, while theoretical ones either involve too many parameters or ignore the effects of intermediate principal stress on the concrete strength. Based on the octahedral shear stress model and the concrete tensile strength under the state of triaxial and uniaxial stress, a new failure criterion, that is, the simplified unified strength theory (UST), is developed by simplifiing the five-parameter UST for the analysis of reinforced concrete structures. According to the simplified UST failure criterion, the concrete strength is influenced by the maximum and intermediate principal shear stresses together with the corresponding normal stresses. Moreover, the effect of hydrostatic pressure on the concrete strength is also taken into account. The failure criterion involves three concrete strengths, namely the uniaxial tensile and compressive strengths and the equal biaxial compressive strength. In the numerical analysis, a degenerated shell element with the layered approach is adopted for the simulation of concrete structures. In the layered approach, concrete is divided into several layers over the thickness of the elements and reinforcing steel is smeared into the corresponding number of layers of equivalent thickness. In each concrete layer, three-dimensional stresses are calculated at the integration points. For the material modelling, concrete is treated as isotropic material until cracking occurs. Cracked concrete is treated as an orthotropic material incorporating tension stiffening and the reduction of cracked shear stiffness. Meanwhile, the smeared craclc model is employed. The bending reinforcements and the stirrups are simulated using a trilinear material model. To verify the correctness of the simplified UST failure criterion, comparisons are made with concrete triaxial empirical results as well as with the Kupfer and the Ottosen failure criteria. Finally, the proposed failure criterion is used for the flexural analysis of simply supported reinforced concrete beams. Also conducted are the punching shear analyses of single- and multi-column-slab connections and of half-scale flat plate models. In view of its accuracy and capabilities, the simplified UST failure criterion may be used to analyse beam- and slab-type reinforced concrete structures.
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Zhang, Xuesong. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365777.
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Failure criteria play a vital role in the numerical analysis of reinforced concrete structures. The current failure criteria can be classified into two types, namely the empirical and theoretical failure criteria. Empirical failure criteria normally lack reasonable theoretical backgrounds, while theoretical ones either involve too many parameters or ignore the effects of intermediate principal stress on the concrete strength. Based on the octahedral shear stress model and the concrete tensile strength under the state of triaxial and uniaxial stress, a new failure criterion, that is, the simplified unified strength theory (UST), is developed by simplifiing the five-parameter UST for the analysis of reinforced concrete structures. According to the simplified UST failure criterion, the concrete strength is influenced by the maximum and intermediate principal shear stresses together with the corresponding normal stresses. Moreover, the effect of hydrostatic pressure on the concrete strength is also taken into account. The failure criterion involves three concrete strengths, namely the uniaxial tensile and compressive strengths and the equal biaxial compressive strength. In the numerical analysis, a degenerated shell element with the layered approach is adopted for the simulation of concrete structures. In the layered approach, concrete is divided into several layers over the thickness of the elements and reinforcing steel is smeared into the corresponding number of layers of equivalent thickness. In each concrete layer, three-dimensional stresses are calculated at the integration points. For the material modelling, concrete is treated as isotropic material until cracking occurs. Cracked concrete is treated as an orthotropic material incorporating tension stiffening and the reduction of cracked shear stiffness. Meanwhile, the smeared craclc model is employed. The bending reinforcements and the stirrups are simulated using a trilinear material model. To verify the correctness of the simplified UST failure criterion, comparisons are made with concrete triaxial empirical results as well as with the Kupfer and the Ottosen failure criteria. Finally, the proposed failure criterion is used for the flexural analysis of simply supported reinforced concrete beams. Also conducted are the punching shear analyses of single- and multi-column-slab connections and of half-scale flat plate models. In view of its accuracy and capabilities, the simplified UST failure criterion may be used to analyse beam- and slab-type reinforced concrete structures.Thesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
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Chiu, Chi-kan, and 趙志勤. "Index properties and a three dimensional failure criterion of rocks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31222390.
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Al-Ajmi, Adel. "Wellbore stability analysis based on a new true-triaxial failure criterion." Doctoral thesis, Stockholm : Department of Land and Water Resources Engineering, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4037.
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Seidlitz, Holger, Lars Ulke-Winter, Colin Gerstenberger, and Lothar Kroll. "Dimensioning of Punctiform Metal-Composite Joints: A Section-Force Related Failure Criterion." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152889.
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Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material- adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and faulttolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.
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Vadlamani, Deepika. "Strain energy density based failure criterion for GFRP coupons under tension and bending." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5221.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains xxii, 209 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 207-209).
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Mehrapour, Mohammad Hadi, and Mohammad Hadi Mehrapour. "Development of a Failure Criterion for Rock Masses Having Non-Orthogonal Fracture Systems." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625679.
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Two new three-dimensional rock mass strength criteria are developed in this dissertation by extending an existing rock mass strength criterion. These criteria incorporate the effects of the intermediate principal stress, minimum principal stress and the anisotropy resulting from these stresses acting on the fracture system. In addition, these criteria have the capability of capturing the anisotropic and scale dependent behavior of the jointed rock mass strength by incorporating the effect of fracture geometry through the fracture tensor components. Another significant feature of the new rock mass strength criterion which has the exponential functions (equation 6.7) is having only four empirical coefficients compared to the existing strength criterion which has five empirical coefficients; if the joint sets have the same isotropic mechanical behavior, the number of the empirical coefficients reduces to two in this new strength criterion (equation 6.10).
The new criteria were proposed after analyzing 452 numerical modeling results of the triaxial, polyaxial and biaxial compression tests conducted on the jointed rock blocks having one or two joint sets by the PFC3D software version 5. In this research to have several samples with the same properties a synthetic rock material that is made out of a mixture of gypsum, sand and water was used. In total, 20 joint systems were chosen and joint sets have different dip angles varying from 15 to 60 at an interval of 15 with dip directions of 30 and 75 for the two joint sets. Each joint set also has 3 persistent joints with the joint spacing of 42 mm in a cubic sample of size 160 mm and the joints have the same isotropic mechanical behavior. The confining stress combination values were chosen based on the uniaxial compressive strength (UCS) value of the modeled intact synthetic rock. The minimum principal stress values were chosen as 0, 20, 40 and 60 percent of the UCS. For each minimum principal stress value, the intermediate principal stress value varies starting at the minimum principal stress value and increasing at an interval of 20 percent of the UCS until it is lower than the strength of the sample under the biaxial loading condition with the same minimum principal stress value.
The new rock mass failure criteria were developed from the PFC3D modeling data. However, since the joint sets having the dip angle of 60 intersect the top and bottom boundaries of the sample simultaneously, the joint systems with at least one of the joint sets having the dip angle of 60 were removed from the database. Thus, 284 data points from 12 joint systems were used to find the best values of the empirical coefficients for the new rock mass strength criteria. λ, p and q were found to be 0.675, 3.16 and 0.6, respectively, through a conducted grid analysis with a high R2 (coefficient of determination) value of 0.94 for the new criterion given by equation 6.9 and a and b were found to be 0.404 and 0.972, respectively, through a conducted grid analysis with a high R2 value of 0.92 for the new criterion given by equation 6.10.
The research results clearly illustrate how increase of the minimum and intermediate principal stresses and decrease of the joint dip angle, increase the jointed rock block strength. This dissertation also illustrates how different confining stress combinations and joint set dip angles result in different jointed rock mass failure modes such as sliding on the joints, failure through the intact rock and a combination of the intact rock and joint failures.
To express the new rock mass strength failure criteria, it was necessary to determine the intact rock strengths under the same confining stress combinations mentioned earlier. Therefore, the intact rock was also modeled for all three compression tests and the intact rock strengths were found for 33 different confining stress combinations. Suitability of six major intact rock failure criteria: Mohr-Coulomb, Hoek-Brown, Modified Lade, Modified Wiebols and Cook, Mogi and Drucker-Prager in representing the intact rock strength was examined through fitting them using the aforementioned 33 PFC3D data points. Among these criteria, Modified Lade, Modified Mogi with power function and Modified Wiebols and Cook were found to be the best failure criteria producing lower Root Mean Square Error (RMSE) values of 0.272, 0.301 and 0.307, respectively. Thus, these three failure criteria are recommended for the prediction of the intact rock strength under the polyaxial stress condition.
In PFC unlike the other methods, macro mechanical parameters are not directly used in the model and micro mechanical parameter values applicable between the particles should be calibrated using the macro mechanical properties. Accurate calibration is a difficult or challenging task. This dissertation emphasized the importance of studying the effects of all micro parameter values on the macro mechanical properties before one goes through calibration of the micro parameters in PFC modeling. Important effects of two micro parameters, which have received very little attention, the particle size distribution and the cov of the normal and shear strengths, on the macro properties are clearly illustrated before conducting the said calibration. The intact rock macro mechanical parameter values for the Young’s modulus, uniaxial compression strength (UCS), internal friction angle, cohesion and Poisson's ratio were found by performing 3 uniaxial tests, 3 triaxial tests and 5 Brazilian tests on a synthetic material made out of a mixture of gypsum, sand and water and the joint macro mechanical parameter values were found by conducting 4 uniaxial compression tests and 4 direct shear tests on jointed synthetic rocks with a horizontal joint. Then the micro mechanical properties of the Linear Parallel Bond Model (LPMB) and Modified Smooth Joint Contact Model (MSJCM) were calibrated to represent the intact rock and joints respectively, through the specific procedures explained in this research. The similar results obtained between the 2 polyaxial experiments tests of the intact rock and 11 polyaxial experimental tests of the jointed rock blocks having one joint set and the numerical modeling verified the calibrated micro mechanical properties and further modification of these properties was not necessary.
This dissertation also proposes a modification to the Smooth Joint Contact Model (SJCM) to overcome the shortcoming of the SJCM to capture the non-linear behavior of the joint closure varying with the joint normal stress. Modified Smooth Joint Contact Model (MSJCM) uses a linear relation between the joint normal stiffness and the normal contact stress to model the non-linear relation between the joint normal deformation and the joint normal stress observed in the compression joint normal stiffness test. A good agreement obtained between the results from the experimental tests and the numerical modeling of the compression joint normal test shows the accuracy of this new model. Moreover, another shortcoming associated with the SJCM application known as the interlocking problem was solved through this research by proposing a new joint contact implementation algorithm called joint sides checking (JSC) approach. The interlocking problem occurs due to a shortcoming of the updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem increases the joint strength and dilation angle and creates unwanted fractures around the intended joint plane.
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Mbavhalelo, M., and G. Oliver. "The development and implementation of finite element analysis techniques in the design of press tooling." Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/541.
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Published ArticleRapid and reliable methods for component development and economic manufacturing layout are today crucial factors for the application of press tooling techniques in mass production of automotive industry components. The use of Finite Element Analysis (FEA) based forming simulation can provide a more detailed insight into the real behaviour of a structure. An LS-DYNA finite element model was developed to analyse the material behaviour during the piercing process of a drainage hole for a shock absorber seat. The simulation is intended to simulate tearing that occurs during the manufacturing stage. Once the current punch produces the observed tearing we can modify the punch to eliminate the problem.
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Gerguri, Shpend. "Brittle fracture criterion for failure prediction of notches and brazed metal-to-ceramic joints." Thesis, Oxford Brookes University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532050.
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Aly, Ibrahim M. Mohamed. "Prediction of Business Failure as a Criterion for Evaluating the Usefulness of Alternative Accounting Measures." Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc332393/.
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This study examines the usefulness of general price level information (GPL) and current cost information (CC) originally provided by SFAS No. 33 as compared to historical cost information (HC) in predicting bankruptcy. The study also examines the usefulness of GPL data versus CC data when each supplements HC data. In addition, this study tests the usefulness of the three types of information systems combined in one model (HC, GPL, and CC) versus HC data in predicting bankruptcy. The study focuses on the predictability of business failure using financial ratios as predictors. A comparison of these predictors is made in order to identify the accounting system that yields a better prediction of bankruptcy. Two multivariate statistical techniques, multiple discriminant analysis (MDA) and logistic regression analysis (LRA), are used to derive the ex—post classification and the ex-ante prediction results. Six functions are developed, based on ratios computed with HC, CC, GPL, the combined HC and GPL, the combined HC and CC, and the combined HC, GPL, and CC. The resulting functions are used to classify 40 firms as failed or nonfailed. The analysis is repeated for three time bases—one, two, and three years before bankruptcy. The main results of the various analyses indicate that the combined HC and CC model has more discriminant power than does the HC, the GPL, or the combined HC and GPL models in each of the three years before bankruptcy. The results also show that there are significant differences in the overall classification rate derived from the combined HC, GPL, and CC model and the HC model, the GPL model, or the combined HC and GPL model . The differences between the combined HC and CC and the combined HC, GPL, and CC models are not significant in each of the three years before bankruptcy. The results also indicate that the differences in the the performance of MDA and LRA are not significant except in the second year before bankruptcy when the combined HC and GPL model is used.
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Osypenko, Volodymyr, and Gregory Ivachnenko. "Algorithm for intelligent prediction of failure moments in computer systems." Thesis, Київський національний університет технологій та дизайну, 2021. https://er.knutd.edu.ua/handle/123456789/19177.
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Thalur, Jagadesh Rao. "Progressive failure analysis of [0/+/-60] laminates under bi-axial stress by generalized Yeh-Stratton criterion." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10116146.
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The light weight of composite materials has attracted interests to improve fuel economy of aircrafts and to extend flight range. The usage of composite materials is increasing in airframes and other parts of aerospace industry. Although most tests on composites are conducted uniaxially, they are subjected to multi-axial loads in real life applications. Hence, there is a need to better understand the complex failure mechanisms in composite structures. More reliable failure theories and damage progression models should be devised. Also, reliable criteria for predicting failure of fiber composite laminates are necessary for rational analysis and design. In this thesis, the behavior of a symmetric composite material under bi-axial loading is studied and the failure of the composite material is predicted by Yeh-Stratton criterion. A MATLAB program is prepared for the study of failure in tubular specimens composed of AS4/3501-6 carbon/epoxy laminates, which were subjected to internal pressure and axial force simultaneously to vary the states of stress. It is shown that the Yeh-Stratton criterion is in a good agreement with the experimental results. Future work may include collection of more accurate and different kind of experimental data on composite materials and modification of the interaction factor B12 value to evaluate its effect on the theoretical prediction by the Yeh-Stratton criterion.
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Bardelcik, Alexander. "Effect of Pre-Bending and Hydroforming Parameters on the Formability of Advanced High Strength Steel Tube." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2829.
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With increasing fuel costs and the current drive to reduce greenhouse gas emissions and fuel consumption, a need to reduce vehicle weight is apparent. Weight reduction can be achieved by replacing conventionally stamped structural members with hydroformed parts. The weight reduction can be further enhanced by reducing the thickness of the hydroformed members through the use of advanced high strength steel (AHSS). A primary limitation in hydroforming AHSS, is the limited ductility or formability of these materials. This limitation becomes acute in multi-stage forming operations in which strain path changes become large making it difficult to predict formability. Thus, the focus of the current work is to study the effects of pre-bending on the subsequent hydroformability of Dual-Phase DP600 steel tubes. As part of this effort, the effect of key bending and hydroforming process parameters, bending boost and hydroforming end-feed, have been studied in a parametric fashion. Multi-step pre-bending and hydroforming experiments were performed on 76. 2 mm (3. 0") OD tubes with a wall-thickness of 1. 85mm (DP600). Experiments were also performed on 1. 74mm Interstitial Free (IF) steel tube, which provided a low strength, high formability baseline material for comparison purposes. A fully instrumented servo-hydraulic mandrel-rotary draw tube bender was used in the pre-bending experiments in which various levels of boost were applied. The results showed that increased boost reduced the major (tensile) strain and thinning at the outside of the bend. At the inside of the bend, the compressive minor strain became larger and thickening increased.
Hydroforming of the straight and pre-bent tubes was conducted using various levels of load-control end-feed (EF). For both straight and pre-bend tube hydroforming, an increase in hydroforming EF resulted in increased burst pressure and corner-fill expansion (CFE). The effect of bending boost on CFE was also measured. For a given hydroforming EF case, a tube bent with greater boost achieved a higher burst pressure and consequently a greater CFE which increased the hydroformability of the material. Pre-bending was shown to consume a considerable amount of the formability of the tube in the hydroforming experiments. For the same EF case, the pre-bent tubes could only achieve a fraction of the straight tube CFE at burst.
The pre-bending and hydroforming experiments were complimented by finite element simulation in the hope of providing additional insight into these processes. The finite element (FE) models were able to accurately predict the strain and thickness changes imposed during pre-bending. The models were able to accurately predict the CFE, EF displacement, and strain and thickness distributions after hydroforming.
The extended stress-based forming limit curve (XSFLC) failure criterion was applied to predict failure (onset of necking) during hydroforming, which was measured as the burst pressure in the experiments. For straight tube hydroforming, the XSFLC predicted the correct failure pressure versus hydroforming EF load trend, but over predicted the failure pressures. In pre-bend hydroforming, the models were able to capture the effect of bending boost and hydroforming EF on the hydroformability of the tubes. The XSFLC was able to capture the drop in formability for bending versus straight tube hydroforming, but was unable to capture the failure pressure versus hydroforming EF load trend or magnitude. Further work is required to make the XSFLC applicable to straight and pre-bend hydroforming.
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Staudt, Yves [Verfasser], Chrsitoph [Akademischer Betreuer] Odenbreit, and Jens [Akademischer Betreuer] Schneider. "Proposal of a Failure Criterion of Adhesively Bonded Connections with Silicone / Yves Staudt ; Chrsitoph Odenbreit, Jens Schneider." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/1158896956/34.
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Thuramalla, Naveen. "MULTISCALE MODELING AND ANALYSIS OF FAILURE AND STABILITY DURING SUPERPLASTIC DEFORMATION -- UNDER DIFFERENT LOADING CONDITIONS." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/323.
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Superplastic forming (SPF) is a valuable near net shape fabrication method, used to produce very complex, contoured and monolithic structures that are often lighter, stronger and safer than the assemblies they replace. However, the widespread industrial use of Superplastic (SP) alloys is hindered by a number of issues including low production rate and limited predictive capabilities of stability during deformation and failure. Failure during SPD may result from geometrical macroscopic instabilities and/or microstructural aspects. However, the available failure criteria are either based on geometrical instabilities or microstructural features and do not account for both failure modes. The present study presents a generalized multi-scale stability criterion for SP materials, accounting for both aspects of failure under various loading conditions. A combined model accounting for cavity nucleation and plasticity controlled cavity growth along with a grain growth model and a modified microstructure based constitutive equation for SP materials is incorporated into Harts stability analysis to develop the proposed stability criterion for different loading conditions. Effects of initial grain size, initial levels of cavitation, nucleation strain, strain-rate sensitivity, and grain-growth exponent on the optimum forming curves of different SP alloys are investigated, for different loading conditions.
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Nicolas, Elias Antonio. "Estudo de criterios de resistencia de materiais anisotropicos aplicados a madeira." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257999.
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Orientador: Nilson Tadeu MasciaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-07T08:37:01Z (GMT). No. of bitstreams: 1 Nicolas_EliasAntonio_D.pdf: 5212612 bytes, checksum: 6374b5ff3649878b30250be16c1a8e76 (MD5) Previous issue date: 2006
Resumo: Esta pesquisa refere-se ao estudo de critérios de resistência de materiais anisotrópicos, especialmente o critério tensorial de resistência de TSAI- WU, com aplicações teóricas e experimentais para a madeira. Neste sentido foi realizada uma revisão teórica dos principais temas relacionados à presente pesquisa, como: critérios gerais de resistência, fórmula de hankinson, critério de TSAIWU, modos de ruptura da madeira, fatores que influenciam na resistência da madeira,equipamentos e corpos-de-prova para realização de ensaios uniaxiais e biaxiais, prescrições de cálculo das normas de estruturas de madeira. O objetivo principal deste trabalho foi determinar os parâmetros de resistência do critério tensorial de TSAI-WU, com a finalidade de definir uma superfície de ruptura, para a espécie de madeira estudada, cupiúba (Goupia glabra), e comparar os dados dos ensaios com as estimativas do critério. No estudo experimental foram realizados os seguintes ensaios: tração e compressão, uniaxiais, com ângulos das fibras inclinados em relação ao carregamento (0°, 15°, 30°, 45°, 60°, 75° e 90°); ensaios de cisalhamento paralelo às fibras e ensaios de compressão biaxial. As estimativas do critério de TSAI- WU ficaram próximas das estimativas da fórmula de Hankinson e também dos dados dos ensaios uniaxiais de tração e compressão. Por outro lado, para ensaios biaxiais, o critério de TSAI-WU sofre grande influência do coeficiente de interação.De um modo geral, o critério de TSAI-WU apresenta bons resultados, facilidade de utilização se comparado a outros critérios, devido especialmente a seu caráter tensorial, podendo ser aplicado na avaliação de resistência da madeira e de outros materiais anisotrópicos
Abstract: This research deals with the study of anisotropic material failure criteria, specifically TSAI- WU tensor failure criteria, and theoretical and experimental applications for wood. Thus it was carried out a theoretical revision of the principal themes related to this research: general failure criteria, Hankinson's formula, TSAI-WU tensor criterion, failure modes of wood, factors that affect wood strength, equipaments and specimens for development of uniaxial and biaxial tests and rules of design codes of wood structures. The main objective of this work was to determine the TSAI-WU tensor failure criterion parameters, with the purpose of defining the failure surface, for the wood specie Cupiúba (Goupia Glabra) and of comparing the test results and criterion estimates as well. In the experimental development it was performed the following axial tests: tension and compression, with inclined grain angles in related to the load (0°, 15°, 30°, 45°, 60°, 75° and 90°); shear tests and biaxial compression. The estimates of TSAI-WU criterion were close of Hankinson's formula and the tension and compression tests results too. On the other hand, for biaxial compressive test, TSAI- WU criterion influence ofthe interaction coefficient (F12). In general, TSAI- WU criterion can be applied to evaluate wood strength and other anisotropic materials too, by presenting good results and facility in utilizing especially when comparing to other criteria due to its tensor form
Doutorado
Estruturas
Doutor em Engenharia Civil
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山崎, 真理子, Mariko YAMASAKI, 康寿 佐々木, and Yasutoshi SASAKI. "複合応力下における木材 (ヒノキ) の破壊挙動 (載荷方式および載荷経路の影響)." 日本機械学会, 2000. http://hdl.handle.net/2237/8983.
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Shipsha, Andrey. "Failure of Sandwich Structures with Sub-Interface Damage." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3184.
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Xu, Rongxin. "Optimal design of a composite wing structure for a flying-wing aircraft subject to multi-constraint." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7290.
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This thesis presents a research project and results of design and optimization of a composite wing structure for a large aircraft in flying wing configuration. The design process started from conceptual design and preliminary design, which includes initial sizing and stressing followed by numerical modelling and analysis of the wing structure. The research was then focused on the minimum weight optimization of the /composite wing structure /subject to multiple design /constraints. The modelling, analysis and optimization process has been performed by using the NASTRAN code. The methodology and technique not only make the modelling in high accuracy, but also keep the whole process within one commercial package for practical application.
The example aircraft, called FW-11, is a 250-seat commercial airliner of flying wing configuration designed through our MSc students Group Design Project (GDP) in Cranfield University. Started from conceptual design in the GDP, a high-aspect-ratio and large sweepback angle flying wing configuration has been adopted. During the GDP, the author was responsible for the structural layout design and material selection. Composite material has been chosen as the preferable material for both the inner and outer wing components. Based on the derivation of structural design data in the conceptual phase, the author continued with the preliminary design of the outer wing airframe and then focused on the optimization of the composite wing structure. Cont/d.
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Yi, Xianjie. "Numerical and analytical modeling of sanding onset prediction." Texas A&M University, 2003. http://hdl.handle.net/1969/369.
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Kakogiannou, Evanthia. "Rainfall-induced landslides: simulation and validation through case studies with a multiphase porous media model in conjunction with the second order work criterion." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3421801.
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Rainfall is one of the most common triggering factors of landslides. Due to the usual large extension of rainfall events, hydrologically-driven instability can be triggered over large areas and frequently results in a diffuse, flow type of failure which occurs abruptly, involving a shallow soil deposit of different grading and origin. Considering the destructiveness of this type of landslides, the forecast of this risk consists a fundamental issue.
This PhD thesis is primarily motivated by the need for a better understanding of the slope's mechanical response to rainfall infiltration and for a more accurate and realistic prediction of the location and time of the slope failure occurrence with regards to physical, mathematical and numerical modelling. To this end, the modelling of rainfall induced landslides is considered as a coupled variably saturated hydro-mechanical problem. For the numerical simulations the geometrically linear finite element code Comes-Geo is used, in which soils are considered as non-isothermal elasto-plastic multiphase solid porous materials.
Furthermore, this PhD manuscript is dedicated to the concept of material instability in multiphase geomaterials, with particular reference to rainfall-induced landslides. A recently proposed criterion, the second order work criterion, based on Hill's sufficient condition of stability (Hill, 1958) has been implemented on the abovementioned code. It consists in studying the sign of the second order work at the material point level and it is used for the detection of the onset of the local failure. The definition of the second order work criterion is reviewed and three different expressions are presented additionally, which could be used in the case of variably saturated porous materials; the second order work is expressed in terms of effective stress, of total stress and thirdly by taking into account the hydraulic energy contribution for the case of partially saturated soils.
The abovementioned modelling framework in conjunction with Hill's criterion is applied for the finite element analysis of three initial boundary value problems: a plane strain compression test on dense sand and isochoric granular material where strain localisation is observed; the failure initiation of a well-documented flowslide (Sarno-Quidinci event, southern Italy 1998); a large scale slope stability experimental test subjected to rainfall infiltration (University of Padua, 2014).La pioggia è una delle maggiori cause delle frane. A causa della grande estensione dei fenomeni piovosi, l'instabilità idro-geologica può verificarsi su aree estese, e spesso si trasforma in una rottura di tipo diffusa causando colate che avvengono improvvisamente, coinvolgendo strati superficiali di suolo di diversa origine e classificazione. Considerando la capacità distruttiva di questo tipo di eventi, la valutazione del rischio corrispondente è di fondamentale importanza. Questa tesi è motivata principalmente dalla necessità di una migliore conoscenza della risposta di un pendio all'infiltrazione della pioggia e da una predizione più precisa e realistica dell'istante e del luogo del distacco di frane mediante opportuna modellazione fisico-matematica e numerica. A questo scopo, la modellazione delle frane causate dalla pioggia avviene considerando questi eventi come un problema idro-meccanico accoppiato in condizioni di saturazione variabile. Per le simulazioni numeriche è stato utilizzato il codice agli elementi finiti 'Comes-Geo', in cui il materiale costituente i pendii è analizzato come un solido poroso multifase elasto-plastico in condizioni non-isoterme. In questa tesi inoltre è discusso il problema dell'instabilità dei geomateriali multifase, con particolare applicazione alle frane indotte dalla pioggia. A tal fine, il criterio del lavoro del secondo ordine, basato sulla condizione sufficiente di stabilità di Hill (1958), è stato implementato nel codice di calcolo agli elementi finiti sopra menzionato. Esso consiste nello studio del segno del lavoro del secondo ordine a livello di punto materiale ed è utilizzato nella tesi per rilevare la rottura locale. La formulazione analitica di questo criterio è stata modificata per i solidi porosi proponendo tre diverse espressioni che possono essere utilizzate per i materiali porosi multifase in condizione di saturazione variabile; il lavoro del secondo ordine è stato espresso in funzione della tensione efficace (i), della tensione totale (ii) e considerando il contributo dell'energia idraulica nel caso di terreni parzialmente saturi (iii). L'approccio modellistico sopra menzionato e il criterio di Hill sono stati applicati all'analisi agli elementi finiti di tre problemi di collasso di suoli: un test di compressione biassiale (in stato piano di deformazioni) di una sabbia densa e un materiale granulare isocorico, in cui è stata osservata sperimentalmente la localizzazione di deformazioni, il distacco di una frana ben documentata della zona di Sarno-Quindici (Italia meridionale, 1998), un test di stabilità di un pendio sperimentale di grande scala soggetto a pioggia (Università degli Studi di Padova, 2014).
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Gagliardo, Debora Pierini. "Analise de estruturas sanduiche : parametros de projeto." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/325624.
Full textAbstract:
Orientador: Nilson Tadeu MasciaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-11T20:02:44Z (GMT). No. of bitstreams: 1 Gagliardo_DeboraPierini_M.pdf: 2748592 bytes, checksum: 3f4f2274fa55f9b27f8663ca912c32fc (MD5) Previous issue date: 2008
Resumo: As estruturas sanduíche têm despertado grande interesse e já estão bastante difundidas em diversos segmentos industriais, sendo suas principais utilizações nas indústrias aeroespacial, militar, naval e civil. Este fato se deve à sua propriedade de combinar alta rigidez à flexão e baixo peso, resultando em uma estrutura muito eficiente. Neste sentido, a análise e cálculo das estruturas sanduíche são de extrema importância no desenvolvimento de projetos de aplicação do mesmo. Neste trabalho, foram analisados os critérios de falha dos painéis, bem como os materiais e suas propriedades mecânicas, considerando as alterações e considerações que devem ser feitas nos projetos de acordo com as características do material. Na parte final dessa pesquisa, são apresentadas a teoria de cálculo e a rotina para elaboração de projetos relacionados com a construção civil utilizando as estruturas sanduíche, com ênfase em estruturas planas, tais como vigas e placas. Por fim emprega-se uma ferramenta, planilha eletrônica, para analisar e avaliar a aplicação de diversos materiais de construção em estruturas sanduíche.
Abstract: The sandwich structures have aroused great interest and have already been very widespread in several branches in industries, such as in the aerospace, military, naval and civil construction industries. This is due to their property to combine both high bending rigidity and the low weight, resulting in a very efficient structure. Thus, the analysis and also the calculation of sandwich structures are very important in developing the application projects. In this work, it was reviewed the failure criteria of the panels, as well as the materials and their mechanical properties, considering the changes and considerations that have to be performed in the project in accordance with the characteristics of the material. At the final part of this research, the theory of calculation and also the routine for development projects related with the civil construction using the sandwich structures are presented, with emphasis on flat structures, such as beams and plates. Finally employs is a tool, spreadsheet, to analyse and evaluate the implementation of various building materials in sandwich structures.
Mestrado
Estruturas
Mestre em Engenharia Civil
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Rameau, Jean-Michel. "Multi-axial damage and failure models for thick composite lugs under static and cyclic loading." Thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185174.
Full textAbstract:
The thesis deals with quasi-static and fatigue simulations of thick composite lugs subjected to three-dimensional stress states. This includes damage prediction of hybrid laminates made of GRFP and CRFP containing unidirectional and woven fabric plies.Focus lies on the development of a progressive damage model in fatigue which accounts for sti˙ness and strength degra-dations. Two methods based on Puck’s failure criterion are proposed to predict failure of unidirectional plies: one for plane stress analysis and and the other which takes out-of-plane damage into account.Virtual testing in FEM is conducted in quasi-static and fatigue analysis on thick composite lugs subjected to uni-axial loading. Damage, strength and life predictions are then compared with experimental results to validate the numerical models under investigations.In der vorliegenden Arbeit wird die Berechnung der Festig-keit von dickwandigen Lochleibungslaminaten im Faserver-bundwerksto˙en unter dreidimensionalen Spannungszustän-den untersucht. Nichtlineare Materialverhalten von Hybrid-laminaten in CFK und GFK werden für Unidirektionalfa-serlagen und Gewebelagen berücksichtigt.Der Schwerpunkt liegt auf der Entwicklung von progressi-ven Versagensmodellen unter der Berüsichtigung von Rest-festigkeit und Reststeifigkeit des Materials. Zwei Modelli-erungsmethoden nach Puck-Kriterium zur Vorhersage des Versagens in UD-Lagen werden vorgeschlagen: eine Degra-dierungstechnik für ebene Spannungszustände und ein me-hrachsiges Modell.Numerische Simulationen mit der Finite-Elemente-Methode werden in Statik- und Ermüdungsanalyse an dickwandigen Lochleibungslaminaten unter einachsiger Belastung durch-geführt. Beschädigungen, Festigkeiten und Ermüdungsle-bensdauer werden dann mit experimentiellen Daten ver-glichen, um die numerischen Methoden zu validieren.
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Hanák, Jiří. "Numerická simulace porušování keramických pěn při mechanickém zatížení." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401524.
Full textAbstract:
The master’s thesis deals with a numerical simulation of failure of ceramic foams with open-cell structure and with understanding of conditions required for the failure of the structure under various mechanical loading conditions. To this purpose, the so-called stress-energy coupled criterion was utilized. The motivation for this thesis was to create a model able of the most accurate prediction of the ceramic foam strength in comparison with experimental observations. First part of the thesis is focused on the theoretical background required for solving the problem. More specifically there are mentioned methods of the foam material modelling, Linear Elastic Fracture Mechanic (LEFM) and coupled stress-energy criterion used for definition of the crack initiation. In the second part of the thesis, numerical Finite Element Analyses (FEA) whose main purpose was to determine critical conditions necessary for the initiation of strut failure within the foam structure, were performed. These pieces of knowledge were then used for creation of the numerical simulation algorithm of the mechanical test of foam material with regular cell pattern. Outputs of numerical simulations were at the end of this work compared with experimental results (of the compression test) made on the real Al_2 O_3 foams prepared by 3D printing technology and provided by the Institute of Physics of Materials Czech Academy of Science. It can be concluded that a good agreement between results of both approaches was reached and the prediction of the ceramic foam mechanical strength using the developed model is in the meanwhile the most accurate estimation from recently published approaches.
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Bonetti, Rodolfo Arturo. "Ultimate Strength of the Local Zone in Load Transfer Tests." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31392.
Full textAbstract:
An improved equation is presented for the prediction of the ultimate strength of the local zone in Load Transfer Tests. The derivation of this new formulation is the result of the investigation of the ultimate bearing strength of plain and reinforced concrete blocks, concentrically loaded. A total of 199 bearing tests were performed on plain and reinforced concrete prisms to evaluate the variables involved in the bearing problem. A finite element analysis of a typical square block loaded with different bearing areas was performed. Two equations, one for plain concrete and the other for reinforced concrete were derived using the Mohr failure criterion.
The performance of the derived equations was evaluated against actual test data. The results of this evaluation showed very good agreement between the predicted ultimate strength and the actual test strength for both plain and reinforced concrete. For plain concrete specimens the ratio Ptest/Ppred was 1.05 with a coefficient of variation of 9 percent. In the case of reinforced concrete blocks the ratio Ptest/Ppred was 1.00 with a coefficient of variation of 14 percent.Master of Science
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D'Alessandro, Kacie Caple. "Biaxial Behavior of Ultra-High Performance Concrete and Untreated UHPC Waffle Slab Bridge Deck Design and Testing." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23731.
Full textAbstract:
Ultra-high performance concrete (UHPC) was evaluated as a potential material for future bridge deck designs. Material characterization tests took place to identify potential challenges in mixing, placing, and curing UHPC. Biaxial testing was performed to evaluate behavior of UHPC in combined tension and compression stress states. A UHPC bridge deck was designed to perform similarly to a conventional concrete bridge deck, and a single unit bridge deck section was tested to evaluate the design methods used for untreated UHPC.
Material tests identified challenges with placing UHPC. A specified compressive strength was determined for structural design using untreated UHPC, which was identified as a cost-effective alternative to steam treated UHPC.
UHPC was tested in biaxial tension-compression stress states. A biaxial test method was developed for UHPC to directly apply tension and compression. The influence of both curing method and fiber orientation were evaluated. The failure envelope developed for untreated UHPC with random fiber orientation was suggested as a conservative estimate for future analysis of UHPC. Digital image correlation was also evaluated as a means to estimate surface strains of UHPC, and recommendations are provided to improve consistency in future tests using DIC methods.
A preliminary bridge deck design was completed for untreated UHPC and using established material models. Prestressing steel was used as primary reinforcement in the transverse direction. Preliminary testing was used to evaluate three different placement scenarios, and results showed that fiber settling was a potential placement problem resulting in reduced tensile strength. The UHPC bridge deck was redesigned to incorporate preliminary test results, and two single unit bridge deck sections were tested to evaluate the incorporated design methods for both upside down and right-side up placement techniques. Test results showed that the applied design methods would be conservative for either placement method.Ph. D.
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Ríos, Bayona Francisco. "Analytical and numerical approaches to estimate peak shear strength of rock joints." Licentiate thesis, KTH, Jord- och bergmekanik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-248019.
Full textAbstract:
In Sweden, there exists a large number of dams. Many of them are founded on rock masses normally affected by the presence of sub-horizontal rock fractures, which makes sliding along rock joints under the dam foundation one of the most critical failure mechanism. Various attempts have been made to relate the peak shear strength of rock joints to measurable parameters. However, the uncertainty in the determination of the shear strength of rock joints is nonetheless still significant.The main aim of this thesis is to investigate, develop and apply analytical and numerical techniques for estimation of peak shear strength of natural and unfilled rock joints. In a first step, the peak shear strength of several natural and unfilled rock joint was calculated by using surface aperture measurements from high-resolution optical scanning and a modified version of the analytical criterion previously developed by Johansson and Stille in 2014. In a second step, PFC2D was utilised to perform numerical shear tests on two-dimensional profiles selected from high-resolution optical scanning on unweathered and perfectly mated tensile induced rock joints.The results from the analytical approach show that the calculated peak shear strengths of the analysed samples are in good agreement compared with the laboratory investigations. Conversely, the obtained results from the numerical approach show lower peak shear strengths in the analysed two-dimensional profiles compared with the conducted laboratory shear tests.The analytical approach together with the advanced techniques to measure surface roughness available today, may be a possible way forward towards a methodology to determine peak shear strength of large-scale natural rock joints in-situ.Bergsprickors skjuvhållfasthet är en avgörande faktor för att kunna bestämma säkerheten mot gliding för dammar där sub-horisontella utbredda bergsprickor existerar. Samtidigt är parametern svår att bestämma då den påverkas av flera faktorer som sprickytans råhet, vittringsgrad, normalspänning, skala samt passning. Skjuvhållfasthet av bergsprickor kan bestämmas genom att använda empiriska och analytiska brottkriterier samt numeriska metoder. Problemet med de befintliga metodikerna är att de inte beaktar inverkan från sprickans passning. Detta innebär att hållfastheten riskerar att överskattas.Det övergripande syftet med denna licentiatuppsats är att studera, utveckla och tillämpa analytiska och numeriska metoder för uppskattning av skjuvhållfasthet för naturliga och ofyllda bergsprickor. I ett första steg beräknades skjuvhållfastheten för ett antal naturliga och ofyllda bergsprickor. Detta gjordes genom att mäta aperturen baserat på högupplöst skanning och en vidareutvecklad version av det analytiska kriteriet som föreslogs av Johansson och Stille 2014. I ett andra steg användes PFC2D för att genomföra numeriska skjuvtester på två-dimensionella sprickprofiler baserat på högupplöst skanning av perfekt passade och draginducerade bergsprickor.Resultaten från uppskattad skjuvhållfasthet med den analytiska metodiken visar på en bra överensstämmelse i jämförelse med de utförda skjuvförsöken. Resultaten från de utförda analyserna med PFC2D visar på en något lägre skjuvhållfasthet än vad som observeras i verkligheten.Den utvecklade analytiska metodiken, tillsammans med de avancerade tekniker som idag finns för att mäta sprickytornas råhet, bedöms kunna utgöra ett första steg mot att bättre kunna bestämma den storskaliga skjuvhållfastheten för bergsprickor i fält.
QC 20190402
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Petras, Achilles. "Design of sandwich structures." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/236995.
Full textAbstract:
Failure modes for sandwich beams of GFRP laminate skins and Nomex honeycomb core are investigated. Theoretical models using honeycomb mechanics and classical beam theory are described. A failure mode map for loading under 3-point bending, is constructed, showing the dependence of failure mode and load on the ratio of skin thickness to span length and honeycomb relative density. Beam specimens are tested in 3-point bending. The effect of honeycomb direction is also examined. The experimental data agree satisfactorily with the theoretical predictions. The results reveal the important role of core shear in a sandwich beam's bending behaviour and the need for a better understanding of indentation failure mechanism. High order sandwich beam theory (HOSBT) is implemented to extract useful information about the way that sandwich beams respond to localised loads under 3-point bending. 'High-order' or localised effects relate to the non-linear patterns of the in-plane and vertical displacements fields of the core through its height resulting from the unequal deformations in the loaded and unloaded skins. The localised effects are examined experimentally by Surface Displacement Analysis of video images recorded during 3-point bending tests. A new parameter based on the intrinsic material and geometric properties of a sandwich beam is introduced to characterise its susceptibility to localised effects. Skin flexural rigidity is shown to play a key role in determining the way that the top skin allows the external load to pass over the core. Furthermore, the contact stress distribution in the interface between the central roller and the top skin, and its importance to an indentation stress analysis, are investigated. To better model the failure in the core under the vicinity of localised loads, an Arcan- type test rig is used to test honeycomb cores under simultaneous compression and shear loading. The experimental measurements show a linear relationship between the out-of-plane compression and shear in honeycomb cores. This is used to derive a failure criterion for applied shear and compression, which is combined with the high order sandwich beam theory to predict failure caused by localised loads in sandwich beams made of GFRP laminate skins and Nomex honeycomb under 3-point bending loading. Short beam tests with three different indenter's size are performed on appropriately prepared specimens. Experiments validate the theoretical approach and reveal the nature of pre- and post-failure behaviour of these sandwich beams. HOSBT is used as a compact computational tool to reconstruct failure mode maps for sandwich panels. Superposition of weight and stiffness contours on these failure maps provide carpet plots for design optimisation procedures.
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Stewart, Scott William. "Rock mass strength and deformability of unweathered closely jointed New Zealand greywacke." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1224.
Full textAbstract:
Closely jointed greywacke rock masses are widespread throughout both the North and South Islands of New Zealand and much of New Zealand's infrastructure is constructed upon greywacke rock masses. This thesis deals with determining the rock mass strength of unweathered closely jointed New Zealand greywacke rock masses. Currently, the estimation of rock mass strength and deformability is reasonably well predicted through the use of such empirical failure criteria as the Hoek-Brown failure criterion and empirical expressions to predict deformability. However, previous studies upon predicting the strength and deformability of unweathered closely jointed New Zealand greywacke rock masses has shown that existing empirical methods of determining strength and deformability are unsatisfactory. The problem with predicting rock mass strength and deformability moduli of New Zealand greywacke and the lack of adequate data to calibrate a failure criterion was the starting point for this work. The objective of this thesis was to increase the knowledge of intact and defect properties of closely jointed greywacke, develop reliable rock mass data with which to calibrate a failure criterion and improve the ability to estimate the rock mass strength of greywacke rock masses. A review of existing failure criteria for rock masses was conducted and of these criteria, the Hoek-Brown rock mass failure criteria was selected to calibrate to both the intact rock and rock mass failure data, because of its broad acceptance in the rock mechanics community. A database of greywacke properties was developed based on previous studies upon unweathered greywacke around New Zealand and is attached to the thesis as an Appendix. The database included descriptions of greywacke defect properties and mechanical properties of the intact rock and joints. From this database, inputs could be justified for numerical modelling and later analyses of failure criteria. Records from the construction archives of the Benmore and Aviemore hydroelectric power projects in the South Island of New Zealand were reviewed to obtain information and results from a series of shear tests carried out on unweathered closely jointed greywacke in the 1960s. Data on rock mass strength at failure and rock mass deformability were extracted from these records to assess the predictability of the failure criterion and deformability expressions. Problems experienced during the shear tests at the Aviemore dam site created doubt as to the actual rock mass strengths achieved at failure. The behaviour of these tests was studied using the finite difference code FLAC. The work was aimed at investigating the potential for transfer of shear force between the two concrete blocks sheared in each test and the impact shear force transfer had upon the likely normal stresses beneath each block at failure. The numerical modelling results indicated that a combination of preferential failure occurring in one direction, and doubt in the actual normal load applied to the concrete blocks during testing lead to premature failure in the blocks sheared upstream. The blocks sheared in the opposite direction failed at normal stresses that are reflective of the strength of an unweathered greywacke rock mass, but these results could be explained by failure occurring along defects therefore not satisfying the assumptions of homogeneity typically required of a rock mass failure criterion. The Hoek-Brown failure criterion for intact rock was investigated by fitting it to the largest intact greywacke datasets. For a full set of test data (i.e. including tensile data), the Mostyn & Douglas (2000) variant of the Hoek-Brown failure criterion gave the best fit for a full set of rock mass data. A multiple regression method was developed which improved the fitted curve to intact data in the tensile region and gave the best estimate of tensile strength if no existing lab results for tensile strength were available. These results suggest that the Hoek-Brown failure criterion is significantly limited in its applicability to intact NZ greywacke rock. Hoek-Brown input parameters different to those suggested by Hoek et al (2002) are recommended for using the Hoek-Brown failure criterion for intact NZ greywacke. For closely jointed NZ greywacke rock masses, the results from the shear tests at Aviemore and Benmore were separated into different GSI classes and Hoek-Brown envelopes fitted to the datasets by multiple regression. Revised expressions were proposed for each Hoek-Brown input parameter (mb, s, ab) as a function of the GSI. The resulting revised Hoek-Brown failure envelopes for NZ greywacke offer a significant improvement on the existing criterion used to predict the strength of NZ greywacke intact rock and rock masses. The differences in the behaviour of the reaction blocks that failed before the test blocks and the reduction in rock strength due to sliding along defects from that predicted could be reasoned from recorded observations and the behaviour of the concrete blocks during the shear tests. This study has clearly illustrated the need for continued research in this area. This includes (1) a means of assessing the role of defects upon the shear strength of closely jointed greywacke rock mass into a failure criterion, (2) further modelling of the in-situ shear tests by a discrete element procedure to expressly determine the role of the defect on failure, (3) more testing on rock masses to obtain more data to calibrate a rock mass failure criterion, and (4) more studies on predicting the strength of extremely disturbed rock masses.
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Perret, Adrien. "Étude du comportement en post-flambement d’un panneau de fuselage composite infusé avec structures intégrées." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0035/document.
Full textAbstract:
Ces travaux concernent l’étude numérique et expérimentale d’un panneau composite autoraidi fabriqué par le procédé d’infusion de résine (Liquid Resin Infusion LRI). Le procédé LRI permet d’intégrer des structures sur les peaux d’un panneau représentatif d’un fuselage composite. Dans l’étude numérique, des modèles éléments finis sont réalisés, pour étudier le comportement global du panneau en post-flambement. Cela permet de mettre au point un dispositif d’essai. L’approche expérimentale consiste en l’application de différentes méthodes pour contrôler la pièce et réaliser l’essai. Des essais de caractérisation sont aussi réalisés pour obtenir les propriétés mécaniques nécessaires à l’élaboration de modèles numériques locaux, permettant de décrire la décohésion des structures intégréesThese works are related to the numerical and experimental study of a composite stiffened panel, which is manufactured by a resin infusion process (Liquid Resin Infusion LRI). This manufacturing process allows structures to be integrated onto the skins of a panel being representative of a composite fuselage. Finite element models are built along with the numerical study, in order to deal with the post-buckling global behaviour of this panel. This leads to perfect a test set-up addressed during the experimental investigation. Several experimental methods are used to check the test panel and achieve the test. Material properties are also determined through material testing intended for the development of local numerical models, describing the integrated structures decohesion
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Uguen, Alexandre. "Influence de l'endommagement plan sur le comportement hors-plan des composites stratifiés et des assemblages collés." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0004/document.
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Les matériaux composites sont utilisés dans le domaine maritime depuis des dizaines d’années que ce soit par exemple pour les éoliennes offshore ou encore les navires militaires étant donné leurs propriétés intrinsèques avantageuses pour de telles applications (faible masse, faible signature magnétique ...). Jusqu’ici les composites employés sont surtout composés de fibres de verre et de matrice polyester. Cependant, les demandes croissantes de navires toujours plus légers et rapides conduisent peu à peu les industriels à se tourner vers les composites à haute performance composés de fibres de carbone et de matrice époxyde. L’utilisation de cette nouvelle génération de matériau nécessite de connaître l’influence de l’endommagement plan, qui peut être d’origine hydrique ou mécanique, sur leur tenue hors-plan. Cette étude a montré une diminution importante de l’enveloppe de rupture du matériau étudié lorsqu’il a séjourné en eau de mer jusqu’à saturation. La résistance en traction hors-plan du composite n’est quant à elle que très peu affectée par la présence de fissures transverses dans le matériau, quel que soit son état de vieillissement. Des travaux ont également été menés sur des assemblages composites collés et mis en avant à la fois la chute de la tenue de l’assemblage due à la présence d’eau de mer dans la matrice époxyde, mais également la nécessité de la prise en compte du couplage endommagement plan/endommagement hors-plan pour la prédiction de la tenue hors-plan de tels assemblages. Enfin, différentes méthodes de prédiction ont été utilisées pour valider les résultats expérimentaux confirmant ainsi l’importance de la prise en compte de l’endommagement plan sur la tenue hors-plan des composites et des assemblages composites collésComposite materials have been used in marine applications for decades for offshore windmills or even battleships because of its intrinsic properties which are assets for such applications (low weight, low magnetic signature...). Until now the composites used are almost made of glass fibers and polyester matrix. However the increasing demand for faster and lighter ships gradually leads manufacturers to turn to high performance composites made of carbon fibers and epoxy matrix. Using this new generation of material requires knowing the influence of the in-plane damage which can be due to water or mechanical damage on its out-of-plane strength. This study has shown a significant reduction of the out-of-plane failure envelope of the studied material after an extended stay in seawater until the saturation point.The out-of-plane tensile strength of the composite is very little affected by transverse cracking in the material whatever the aging state. Work has also been carried out on composite bonded assemblies and pointed out, on the one hand, the drop of the assembly strength because of the water aging and, on the other hand, the necessity to take into account the coupling between in-plane and out-of-plane damage for the prediction of the out-of-plane strength of such assemblies. Finally, different methods of prediction have been used to validate the experimental results confirming the importance to take into account the in-plane damage to predict the out-of-plane strength of composites and composite bonded assemblies
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Oliveira, Alex Duarte de. "Soil mechanical behavior artificially cemented: essays modeling and application." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15769.
Full textAbstract:
Considering the similarity between the mechanical behavior of artificially cemented soils and
rock masses, this study proposes a methodology to obtain the envelopes resistance of
artificially cemented soils, using the Hoek-Brown failure criterion. The proposed
methodology consists basically in performing two triaxial tests, with the soil non-cemented
and cemented with a high cement content, and estimate the strength envelopes for
intermediate cement contents, using the equations presented in this research. To develop the
methodology, initially, a number of unconfined compression tests and triaxial tests were
carried out in order to quantify the influence of the porosity/cement ratio (n/Civ) on the
strength parameters of the cement mixtures used. From the tests results and the Hoek-Brown
failure criterion, new equations were developed to calculate the envelope parameters (a, m, s),
as functions of porosity/cement ratio. The proposed method was applied to triaxial tests data
presented in four different studies and the results showed that the Hoek-Brown envelope is
suitable to represent the resistance of artificial cemented soils, being able to incorporate the
effects caused by the confining pressure and by the cement content. The envelopes estimated
and those obtained from the triaxial tests were very close, indicating that the proposed
methodology can be used with a reasonable degree of reliability. The results obtained with the
proposed methodology were used to simulate, by the Finite Element Method, the pressuresettlement
behavior and the variation of the safety factor of a shallow foundation bearing on a
double-layered system formed by an artificially cemented soil layer overlaying a soil stratum.
The simulations were performed using as variables the cement content of the enhanced layer
and the relationship between the thickness of the treated layer (H) and the diameter of the
foundation (D). The results show that the use of artificially cemented layers considerably
increases the vertical pressure required for an specific settlement and also the foundation
safety factor. Thus, the execution of shallow foundations, replacing deep foundations,
becomes feasibleConsiderando a semelhanÃa existente entre o comportamento mecÃnico dos solos artificialmente cimentados e dos maciÃos rochosos, o presente trabalho propÃe uma metodologia para a obtenÃÃo das envoltÃrias de resistÃncia dos solos artificialmente cimentados, utilizando o critÃrio de ruptura geral de Hoek-Brown. A metodologia proposta consiste, basicamente, em realizar dois ensaios triaxiais, um com o solo nÃo cimentado e outro com o solo cimentado com um teor de cimento elevado, e estimar as envoltÃrias de resistÃncia para os teores de cimento intermediÃrios, atravÃs das equaÃÃes desenvolvidas. Para o desenvolvimento da metodologia, inicialmente, foram realizados ensaios de compressÃo simples e triaxiais nÃo drenados, com o objetivo quantificar a influÃncia do fator vazio/cimento (n/Civ) sobre os parÃmetros de resistÃncia das misturas cimentadas utilizadas. A partir dos resultados dos ensaios de resistÃncia e da equaÃÃo geral do critÃrio de Hoek-Brown, foram desenvolvidas equaÃÃes para calcular os parÃmetros da envoltÃria (a, m, s), em funÃÃo do fator vazio/cimento. A metodologia proposta foi aplicada aos resultados dos ensaios triaxiais apresentados em outros quatro trabalhos e os resultados mostraram que a envoltÃria de Hoek-Brown à adequada para representar a resistÃncia dos solos artificialmente cimentados, sendo capaz de incorporar os efeitos causados pela tensÃo confinante e pelo nÃvel de cimentaÃÃo. As envoltÃrias estimadas e as obtidas com os ensaios triaxiais ficaram bem prÃximas, indicando que a metodologia proposta pode ser empregada com um razoÃvel grau de confiabilidade. Os resultados obtidos com a metodologia proposta foram utilizados para simular, atravÃs do MÃtodo dos Elementos Finitos, o comportamento carga-recalque e a variaÃÃo do fator de seguranÃa de uma fundaÃÃo superficial assente sobre um sistema de dupla camada, sendo a superior cimentada. As simulaÃÃes foram realizadas utilizando como variÃveis o teor de cimento da camada reforÃada e a relaÃÃo entre a altura da camada cimentada (H) e o diÃmetro da fundaÃÃo (D). Os resultados obtidos mostram que a utilizaÃÃo de camadas artificialmente cimentadas eleva consideravelmente as tensÃes verticais necessÃrias para um recalque relativo especÃfico e, tambÃm, o fator de seguranÃa da fundaÃÃo. Com isso, a execuÃÃo de fundaÃÃes superficiais, em substituiÃÃo a fundaÃÃes profundas, torna-se viÃvel.
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Mendes, Cláudia Luisa. "Análise em elementos finitos de projetos em fibra de carbono com valores de propriedades obtidas experimentalmente." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153019.
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A exigência dos requisitos de desempenho em estruturas aeroespaciais, navais e automobilísticas vem proporcionando o desenvolvimento de novos materiais, bem como de novas técnicas de fabricação. Normalmente, elevados valores de resistência e rigidez específicas aliados ao baixo peso específico são procurados em projetos estruturais, obtendo-se soluções por meio da utilização de materiais compósitos, particularmente polímeros termo fixos dotados de reforços fibrosos. O entendimento do que é um material composto é necessário, pois trata-se da combinação de no mínimo dois materiais com fase heterogênea, que separados possuem propriedades e características distintas e sua combinação é desejada para a confecção de um material único, com a conformidade das propriedades de ambos os materiais, tornando atrativa sua aplicação. Para otimizar a confecção do laminado em cada projeto, é imprescindível a utilização do modelo em elementos finitos para a obtenção da faixa de tensões, pelo método do critério de falha, sofrida pela amostra e assim obter-se a melhor propriedade mecânica para o seu uso. O presente trabalho tem por objetivo elaborar um estudo comparativo entre os resultados obtidos experimentalmente e os obtidos virtualmente, para validar o uso do software de elementos finitos na execução de um projeto utilizando como material principal o compósito estrutural de fibra de carbono com resina epóxi. Para isso, foram realizados ensaios para obter as propriedades mecânicas, e a melhor temperatura de cura da resina SQ 2004. Posteriormente foram feitos laminados de fibra de carbono com esta resina e extraído suas propriedades mecânicas. Por fim, utilizou-se as propriedades obtidas como entrada do software de elementos finitos e comparou-se o resultado através de três critérios de falha: Hill, Hoffman e Tsai-Wu. Como resultado, constata-se que o critério de falha de Tsai-Wu é o mais indicado para o cálculo da integridade estrutural de um componente de compósito que utiliza fibra de carbono.
The demand of requirements in performance of aerospace, naval and automotive structures has been providing the development of new materials as well as new manufacturing techniques. High values of specific strength and stiffness combined with low specific gravity are usually sought in blade designs for wind generators and other components of these systems, obtaining solutions using composite materials, particularly thermoset polymers endowed with fibrous reinforcements. The understanding of what is a composite material is necessary because it is a combination of at least two materials with heterogeneous phase, which have different properties and characteristics and their combination is desired for the manufacture of a single material with conformity of the properties of both materials, making its application attractive. To optimize the preparation of the laminate in each project, it is essential to use the finite element model to obtain the stress range, by the failure criterion method, and to obtain the best mechanical property for its use. The present work has the objective of elaborating a comparative study between the results obtained experimentally and those obtained virtually to validate the use of finite element software in the execution of a project using the structural material of carbon fiber with epoxy resin as its main material. For this, tests were carried out to obtain the mechanical properties and the best curing temperature of the SQ 2004 resin. Later, carbon fiber laminates were made with this resin and extracted its mechanical properties. Finally, the obtained properties were used as inputs to the finite element software and the result was compared through three failure criteria: Hill, Hoffman and Tsai-Wu. It is concluded that the Tsai-Wu failure criterion is the most suitable for calculating the structural integrity of a composite component using carbon fiber.
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Ковров, Олександр Станіславович, Александр Станиславович Ковров, and O. S. Kovrov. "Геомеханічне обґрунтування параметрів стійких укосів кар’єрів в складноструктурному масиві м’яких порід." Thesis, Видавництво НГУ, 2011. http://ir.nmu.org.ua/handle/123456789/152.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.15.09 – «Геотехнічна і гірнича механіка». – ДВНЗ «Національний гірничий університет», Дніпропетровськ, 2011.Диссертация на соискание ученой степени кандидата технических наук по специальности 05.15.09 – «Геотехническая и горная механика». – ГВУЗ «Национальный горный университет», Днепропетровск, 2011.
Thesis for obtaining scientific degree of Candidate of Technical Sciences in specialty 05.15.09 - Geotechnical and rock mechanics. – State Higher Educational Institution “National Mining University”, Dnipropetrovs’k, 2011.
Дисертація присвячена вирішенню актуальної науково-технічної задачі вдосконалення геомеханічної оцінки стійкості укосів уступів на кар’єрах, що складаються з м’яких розкривних порід, з урахуванням складної геологічної структури, гідрогеологічних характеристик родовища й навантажень від гірничо-транспортного устаткування. У роботі виконаний аналіз впливу фізико-географічних, природно-геологічних, гідрогеологічних, інженерно-геологічних і гірничо-технічних факторів на геомеханічну стійкість укосів і бортів кар’єрів. Результати моделювання на еквівалентних матеріалах та чисельного моделювання методом кінцевих елементів дозволило проаналізувати геомеханічні процеси у породних уступах і встановити закономірності порушення їх стійкості. Отримані експериментальним шляхом фізико-механічні характеристики розкривних порід (суглинки, глини) для гірничо-геологічних умов кар’єрів №7 "Північ" й №7 "Південь" Вільногірського ГМК використані для геомеханічної оцінки стійкості укосів уступів залежно від фізико-механічних характеристик, вологості порід і навантажень від гірничо-транспортного устаткування. Закономірності, отримані в результаті експериментальних досліджень зразків гірських порід і чисельного моделювання використані для розробки рекомендацій із забезпечення геомеханічної стійкості укосів розкривних уступів для гірничо-геологічних та гірничотехнічних умов Мотронівсько-Анновської ділянки Малишевського комплексного циркон-рутил-ільменітового родовища, що планується до введення в експлуатацію на ВГМК.
Диссертация посвящена усовершенствованию геомеханической оценки устойчивости откосов уступов на карьерах, сложенных мягкими вскрышными породами, с учетом сложной геологической структуры, гидрогеологических характеристик месторождения и нагрузок от горно-транспортного оборудования. В работе выполнен анализ влияния физико-географических, природно-геологических, гидрогеологических, инженерно-геологических и горно-технических факторов на геомеханическую устойчивость откосов и бортов карьеров; рассмотрены основные подходы к расчету потенциальных поверхностей скольжения в прибортовом массиве пород, а также аналитические и эмпирические критерии прочности, которые наиболее часто используются в практике геомеханических исследований. Для моделирования устойчивости откосов и бортов карьеров, сложенных мягкими вскрышными породами, принят критерий прочности Кулона-Мора. В качестве инструмента численного моделирования использована программа конечно-элементного анализа Phase2 компании Rocscience Inc. широко используемая в практике инженерного анализа как в Украине, так и за рубежом. Использование метода моделирования на эквивалентных материалах позволило проанализировать геомеханические процессы, происходящие при сдвижении массива пород, слагающих породный уступ, и установить закономерности нарушения его устойчивости. Выполнены серийные испытания образцов на одноплоскостном срезном приборе П10-С и определены физико-механические характеристики вскрышных пород (суглинки, глины) для горно-геологических условий карьеров №7 «Север» и №7 «Юг» Вольногорского ГМК. Полученные экспериментальным путем значения сцепления и угла внутреннего трения использованы для геомеханической оценки устойчивости откосов уступов действующих и проектируемых карьеров ВГМК. Разработана гидрогеомеханическая модель, описывающая распределение деформаций и напряжений в откосах уступов карьера с учетом физико-механических характеристик верхнего слоя вскрыши и влагонасыщения пород за счет инфильтрации атмосферных осадков. По результатам моделирования определены коэффициенты запаса устойчивости борта карьера в зависимости от физико-механических характеристик, влажности вмещающих пород и внешних нагрузок горно-транспортного оборудования. Закономерности, полученные в результате экспериментальных исследований образцов горных пород и численного моделирования использованы для разработки рекомендаций по обеспечению геомеханической устойчивости откосов вскрышных уступов для горно-геологических и горнотехнических условий Мотроновско-Анновского участка Малышевского комплексного циркон-рутил-ильменитового месторождения, которое планируется к введению в эксплуатацию на ВГМК. Разработан алгоритм оценки долговременной геомеханической устойчивости откосов и бортов карьеров, учитывающий геометрические параметры уступов, сложную геологическую структуру породного массива, гидрогеологические характеристики месторождения и нагрузки от горно-транспортного оборудования. Рассчитаны зависимости угла откоса уступа от влажности верхнего вскрышного горизонта суглинков. Установлено, что для существующих гидро-геологических условий с учетом физико-механических свойств пород рекомендуемые значения КЗУ=1,1…1,3 будут обеспечены при угле наклона откоса α=37…47°. В результате комплексной оценки геомеханической устойчивости откосов разработана номограмма для расчета КЗУ и рациональных геометрических параметров вскрышных уступов, сложенных суглинками. Установлено, что при средней высоте вскрышного уступа 20 м и изменении угла наклона откоса с проектных 37º до рекомендуемых 47º для условий Вольногорского горно-металлургического комбината сокращение объемов вскрышных работ на 1 км длины фронта работ составит ∆V=78,91тыс.м3. В результате корректировки угла наклона откоса и формировании более крутого геометрического профиля уступа, при его высоте Н=20 м, на 10° (α1-α2=47°-37°) рассчитан экономический эффект Сэ=0,72…0,90 млн. грн на 1 км длины фронта горных работ при средней себестоимости вскрыши Св=10,85…13,40 грн/м3.
The dissertation is devoted to solving an actual scientific and technical task of improving geomechanical evaluation of slope stability in open-pit benches composed of soft rocks with consideration of complex geological structure, deposit hydro-geological characteristics and loads of mining-transportation equipment. Analysis of influence of physiographic, geological, hydro-geological, geotechnical and mining-technical factors on geomechanical stability of slopes and pitedges is carried out. Results of simulation of equivalent materials and FEM numerical modeling allowed analyze geomechanical processes in rock benches and ascertain laws of their instability. Experimentally derived physical and mechanical characteristics of overburden rocks (loams, clays) for geological conditions of open-pits №7 "Sever" and №7 "Yug" of Vil’noghirs’k Mining and Metallurgical Plant (VGMK) are used for geomechanical evaluation of slope stability depending on physical and mechanical characteristics, rock moisture, and external loads from mining and transport equipment. Regularities obtained in experimental research of rock samples and numerical modeling are used to develop recommendations for ensuring geomechanical slope stability of overburden benches for geological and mining conditions of Motronivs’ko-Annovs’kyi section of Malyshevs’ke complex zircon-rutile-ilmenite placer deposit which is planned to put into exploitation on VGMK.
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Morley, Kevin P. "Criteria of failure for polymer blends." Thesis, Manchester Metropolitan University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303218.
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Triantafillou, Thanasis C. (Thanasis Christos). "Multiaxial failure criteria for celluar materials." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14315.
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Barbosa, Catarina de Lemos Grilo Ferreira. "Modelling metal punching using ductile failure criteria." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14422.
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Mestrado em Engenharia MecânicaDuring the process of mechanical conforming of metal sheet by punching process, several factors influence the accuracy and final geometry of the hole punched. The properties of material used and its behavior in the face of imposed deformations, as well as process parameters influence the final result. High Strength Low Alloy steels (HSLA) are particularly suitable for structural parts that do not require severe forming, such as industrial shelving systems or furniture. Knowledge of mechanical punching operation is of utmost importance to planners of product, process and tooling, so you can get quality products at an acceptable level of waste. The numerical simulation can contribute significantly to the prediction of behavior, still in the planning phase of the product. The goal of this paper is analyze the influence of gap between punch and die during punching. The metal plate material was used with a thickness of 8mm DIN EN 10268 H 360 LA with gaps between punch and die ranging from 2% to 10%. For this we developed a 2D axisymmetric model in ABAQUS/Explicit software, Version 6.7 and the result were compared with literature data and practical experiment. Test showed that the gap of 2% showed the best result..
Durante o processo de conformação metálica por embutidura vários fatores influenciam na geometria final do puncionado. As propriedades do material usado e o seu comportamento perante conformações impostas, assim como característica do processo comprometem o resultado final. Aços HSLA são particularmente apropriado para componentes estruturais que não requerem conformação profunda, tal como os usados na industria de mobiliário metálico. Conhecimento em operações de embutidura mecânica é de maior importância para gestores de produto, processo e ferramentas, para obtenção de produtos de elevada qualidade e desperdício mínimo. A simulação numérica contribui significativamente para a previsão do comportamento ainda na fase de planeamento. O objetivo deste trabalho é analisar a influência da distância entre o punção e a matriz. Considerou-se uma variação entre 2 a 10% nesta análise. Para cumprir estes objetivos criou-se um modelo axissimetrico 2D no ABAQUS/Explicit Software versão 6.7 e o resultado foi comparado com dados bibliográficos e ensaios laboratoriais. Testes demonstraram que a distância entre o punção e a matriz de 2% proporciona o melhor resultado.
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Ritter, Laura. "Der Einfluss von Querzug auf den Verbund zwischen Beton und Betonstahl." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-132733.
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Der Verbundwerkstoff Stahlbeton zeichnet sich durch das effektive Zusammenwirken seiner beiden Einzelkomponenten Stahl und Beton aus. Dieses wiederum kann nur durch ausreichend gute Verbundbedingungen zwischen beiden Baustoffen gewährleistet werden. Die Verbundeigenschaften werden von zahlreichen Faktoren beeinflusst, zu denen u.a. die Oberflächenprofilierung des Stahls, die Betonfestigkeit und die Umschnürungswirkung durch den umgebenden Beton oder eine Querbewehrung zählen. Auch eine quer zum Stab angreifende Belastung kann einen erheblichen Einfluss auf den Verbundmechanismus und die Verbundversagensart haben. Bei Stahlbetonbauteilen unter einer zweiaxialen Zugbelastung, wie sie z.B. in Behälterwänden oder zweiachsig gespannten Platten auftritt, unterliegt die Bewehrung sowohl einer Längszug- als auch einer Querzugbeanspruchung. Im Rahmen der vorliegenden Arbeit wurde der Einfluss einer Querzugbelastung auf das Verbundverhalten zwischen Rippenstählen und Normalbeton mit Hilfe von würfelförmigen Ausziehkörpern mit einer kurzen Verbundlänge untersucht. Dabei lag das Querzugniveau stets unterhalb der Risslast des Betons, so dass keine Risse entlang des einbetonierten Stabes auftraten. Neben der Höhe der Querzugbelastung wurden im Versuchsprogramm die Betonfestigkeit, der Stabdurchmesser und die Betondeckung variiert. Anhand der Versuchsergebnisse konnte gezeigt werden, dass sich auch unter einer Querzugbelastung der Verlauf der Verbundspannungs-Schlupf-Beziehung nicht ändert. Die Art des Verbundversagens wird jedoch maßgeblich durch den Querzug beeinflusst, welcher ein Spaltbruchversagen in jedem Fall begünstigt. Mit steigendem Querzug tritt auch bei großen Betondeckungen statt eines Ausziehversagens ein Spaltbruchversagen ein. Mittels des vorgeschlagenen Berechnungsmodells können in Abhängigkeit des Querzugniveaus und der Größe der Betondeckung Grenzlinien für den Wechsel im Verbundversagensmodus bestimmt werden. Hierbei wurde ebenfalls der Einfluss der Probekörpergeometrie auf die Versuchsergebnisse in die Berechnung einbezogen, so dass die angegebenen Grenzlinien auch für reale Einbettungslängen der Bewehrung gelten. Weiterhin wurde anhand der Versuchsdaten sowie eines Datensatzes aus der Literatur ein Verbundmodell für kurze Verbundlängen entwickelt, das den Einfluss der bezogenen Rippenfläche der Bewehrung und der Betonfestigkeit sowohl auf die Verbundspannungen als auch auf die zugehörigen Schlupfwerte berücksichtigt. Über einen zusätzlichen Datensatz zum Einfluss der Verbundlänge im Ausziehversuch konnte ebenfalls die Abhängigkeit zwischen den mittleren Verbundspannungen, den zugehörigen Schlupfwerten und der Verbundlänge spezifiziert werden. Somit ist eine Übertragbarkeit der Ergebnisse von Ausziehversuchen mit kurzen Verbundlängen auf eine reale Einbettungslänge im Bauteil möglich. Für die Bemessung von Stahlbetonkonstruktionen in den Grenzzuständen der Tragfähigkeit und der Gebrauchstauglichkeit erfolgt die Ableitung geeigneter Verformungskriterien für die Relativverschiebung zwischen Betonstahl und Beton und deren Verifizierung an Versuchsdaten aus der Literatur. Die aufgestellten Verformungskriterien in Abhängigkeit der Stahlspannung erlauben eine direkte Ermittlung bemessungsrelevanter Verbundspannungen anhand experimenteller Ausziehversuche. Die Berücksichtigung einer Querzugbelastung ist dabei in allen vorgestellten Berechnungsansätzen ebenfalls möglichReinforced concrete as composite material is characterised by an effective interaction of its individual components reinforcing steel and concrete. This only can be assured by adequate bond conditions between these two materials. The bond quality is influenced by a wide range of parameters, amongst others including the rib geometry of the bar, the concrete strength and the confining action by the surrounding concrete or transverse reinforcement. Moreover loads, which act transverse to the reinforcing bar, can influence the bond mechanism and the bond failure mode significantly. Reinforced concrete structures, such as containment walls or two-way slabs, are often exposed to multiaxial loading conditions. In case of biaxial tensile stresses, reinforcement and surrounding concrete are loaded in tension in longitudinal as well as in transverse direction. An extensive experimental program was carried out in order to investigate the bond behaviour between reinforcing steel and normal strength concrete due to transverse tension. Cubic-shaped pullout specimens with a short bond length were used. The transverse tension level remained always below the cracking stress of concrete, meaning that no crack occurred along the pullout bar. The test program contained the variation of the transverse tension level, the concrete strength, the bar diameter and the concrete cover. From the test results no systematic influence of the transverse tension level on the shape of the bond stress-slip-relationship can be detected. The bond failure mode is significantly influenced by transverse tension, which promotes splitting failure. The higher the transverse tension level, even for high concrete covers, splitting failure occurs instead of pulling out the bar. From the test results, a failure criterion depending on the concrete cover and the transverse tension level could be determined, which indicates the failure mode and corresponding bond stress. For this purpose, the influence of the specimen geometry on the test results was considered, which results in a failure criterion that is also valid for real embedment lengths of the reinforcement. Furthermore, a bond model for short bond lengths has been developed, based on the test results and a dataset from literature. The model considers the influence of the related rib area of the reinforcing bar and the concrete strength on the bond stresses as well as on the corresponding slip values. By an additional dataset concerning the influence of bond length in pullout tests, the bond stresses and corresponding slip values could be specified as a function of the bond length. Therefore, the test results of pullout test with short bond lengths are transferable to real embedment lengths in structural elements. For the structural design of reinforced concrete elements in the ultimate and serviceability limit states, appli\\-cable deformation criterions concerning the relative displacement between reinforcing steel and concrete has been derived and verified by test data from literature. By means of the developed deformations criterions dependent on the steel stress, design bond stresses can be determined directly from experimental pullout tests. The consideration of transverse tensile loads is also possible for all presented design formulas
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Peters, Timothy M. "Ultimate failure criteria for prestressed concrete T-beams." Thesis, Queensland University of Technology, 1989. https://eprints.qut.edu.au/36455/1/36455_Peters_1989.pdf.
Full textAbstract:
The adoption of a limit states design approach for concrete
design requires a realistic assessment of the flexural
capacity of reinforced, prestressed, and partially
prestressed concrete structures at their ultimate limit
state.
The author has investigated experimentally the post-elastic
behaviour of a series of continuous partially prestressed
concrete T-beams and draws comparison to tests on similar
beams of rectangular section.
Use of photogrammetric measuring techniques to produce
moment curvature relationships was made during the testing
process.
Results have shown that partially prestressed concrete
beams of Tee section can possess sufficient rotation
capacity to allow full redistribution of bending moments.
The rotation capacity was shown to increase as the
reinforcing index of a section decreased. A similar
relationship was found with the prestress ratio.
Softening of the section prior to failure was also observed
at the initial plastic hinge. It was also found that
torsional moments can have a significant effect on the in
plane moment-curvature relationship of a section.
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Sivapathasundaram, Mayooran. "Localised pull-through failures of thin steel roof battens subject to wind uplift loads." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/204638/1/Mayooran_Sivapathasundaram_Thesis.pdf.
Full textAbstract:
High wind events such as tropical cyclones, severe storms and tornadoes are more likely to impact the Australian coastal regions due to possible climate changes. Such events can be extremely destructive to building structures, in particular, low-rise buildings with lightweight roofing systems that are commonly made of thin steel roof sheeting and battens. Large wind suction loads that act on the roofs during high wind events cause premature failures of roof connections (fixings), leading to complete roof failures.
Past wind damage investigations showed that the roof sheeting to batten connection failed frequently during high wind events. These local connection failures have been extensively investigated by many researchers and suitable recommendations to eliminate such failures have been proposed. However, this meant the weakest point has now shifted to the batten to truss/rafter connection. These connections are predominantly subjected to localised pull-through failures in which the screw fastener head pulls through the bottom flanges of thin steel roof battens. However, these failures have not been investigated adequately despite the many roof batten pull-through failures and eventual losses of both roof sheeting and battens observed after recent high wind events. Currently available design rules for the pull-through capacity of cold-formed steel screw fastener connections do not address the specific pull-through failures in thin steel roof battens under wind uplift loading. Current design practice of roof battens is based on using the design wind uplift capacity tables published by their manufacturers. However, it is unclear whether these design capacity tables developed for specific roof battens adequately included the effects of pull-through failures.
As for the roof sheeting to batten connections, batten to rafter/truss connections are also subjected to both static and fatigue failures due to static and cyclic wind uplift loads, respectively. Although some experimental studies were conducted in the past using simulated static and cyclic wind loading, they were incomplete and no design rules were developed. Since the climate predictions indicate the likelihood of severe storm events with increased intensity in the future, they are more likely to cause static pull-through failures of roof battens. In addition, a thorough understanding of the static behaviour is first needed to evaluate the fatigue behaviour in depth. Hence this research was aimed at investigating the localised pull-through failures of thin steel roof battens under simulated static wind uplift loads, using laboratory experiments and finite element modelling.
A preliminary and detailed experimental study was first conducted using industrial roof battens and full scale air-box tests and three small scale tests such as two-span batten tests, cantilever batten tests and short batten tests. Suitable small scale test methods were identified to accurately simulate the localised pull-through failures of roof battens. The applicability of the proposed small scale test methods for other roof battens was verified using two-span and short batten tests undertaken using roof battens made at the university workshop. Based on the test results, a suitable modification factor was recommended for use with the pull-through capacity equation presented in the current Australian (AS/NZS 4600: 2005) and American (AISI S100: 2012) cold-formed steel standards to accurately determine the pullthrough failure loads of roof battens.
The main and extensive experimental study was then undertaken using two-span and short batten tests to examine the pull-through failures of roof battens. The tests were conducted to investigate the effects of many critical parameters such as screw fastener tightening, batten height, web angle, steel grade, batten thickness, screw fastener head size, screw fastener location, batten bottom flange width, underside and edge details of the screw fastener head, and screw fastener types on the roof batten pull-through failure behaviour and capacity. Since the test results showed that the pull-through failure behaviour of high strength and low strength steel roof battens significantly differed from each other due to the differences in ductility, two new design rules and relevant capacity reduction factors were developed to accurately determine the design pull-through capacities of roof battens.
The finite element models of both two-span batten and short batten test specimens were modelled and analysed using ABAQUS software. A suitable failure criterion was developed based on constitutive model inputs and employed in the finite element analyses to accurately predict the initiation of pull-through failures of thin steel roof battens associated with the tearing fracture of bottom flange around the screw fastener head edge. The finite element models were validated using the test results, and additional parametric studies were conducted to investigate the parameters which were not considered in the experimental study due to their lower importance on pullthrough failure behaviour and capacity of roof battens. A large pull-through capacity data base was developed using the pull-through failure loads obtained from the tests and finite element analyses. Suitable design rules were then developed using them and finally recommended with suitable capacity reduction factors for the accurate determination of the design pull-through capacities of thin-walled steel roof battens.
This study also investigated the strengthening methods recommended by the roof batten manufacturers and builders and showed that they are inadequate to provide a significant improvement based on the governing pull-through failures of roof battens.
A reliable strengthening method using overlapping short battens as brackets at the supports was recommended and a series of roof batten tests was conducted using two-span batten tests and two types of industrial roof battens. The test results confirmed the adequacy of the proposed strengthening method.
Suitable fragility curves were developed using detailed probabilistic analyses and Monte Carlo simulations based on the governing pull-through failures of thin steel roof battens to predict the likely level of roof damages to a large community for a given wind speed. The pull-through failure behaviour of roof battens was examined by defining eight different cases that are likely to occur during high wind events (for example, with and without dominant openings) and developing relevant fragility curves. The effects of using different batten span and spacing were also investigated using fragility curves. Fragility curves were also used to evaluate the enhancement level that could be achieved with the proposed strengthening method.
In summary, this research study has developed suitable test, design and strengthening methods and fragility curves for thin steel roof battens subject to localised pullthrough failures under high wind uplift loads.
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Zambrano, Orlando. "Error-in-variables for failure criteria applied to the near -wellbore region." Texas A&M University, 2003. http://hdl.handle.net/1969.1/196.
Full textAbstract:
The development of a methodology to improve the parametric representation of the failure criteria used to characterize rock strength of a reservoir rock in the near-wellbore region is the focus of this study. We adopted a statistical method, so-called error-in-variables (EIV), to take into account experimental errors in all of the measured variables. The proposed methodology is employed to obtain the parameters of the failure envelope (2D criteria) from experimental data in the following cases:
When the experimental data are used directly to determine the failure envelope in the Mohr plane. When a failure envelope is first obtained in the principal-stress plane and then transformed into the Mohr plane using Computer Algebra. When the presence of pore fluid requires the consideration of effective stresses. When the brittle-ductile transition requires special form of the envelope (cap models) Using generalization of previously developed methods, we employed EIV methods to obtain the parameters of a failure surface in the principal-stress space (3D criteria).The basic hypothesis of this work is that the EIV method provides a better representation of failure criteria than the previous methodology. The basic application of any failure criterion is to determine whether a certain stress state will or will not lead to failure. A parametric representation is considered better than another if the likelihood of obtaining the wrong answer is less than in the other case. Therefore, the best representation (within a certain family of envelopes or surfaces) is the one minimizing the objective function, which is nothing else but the likelihood of this wrong answer. To test the basic hypothesis of this work, I compared the objective function (likelihood of erroneous decision) calculated with parametric representations obtained by various methods. To achieve this I evaluated a well-documented, published set of experimental data, for which failure envelopes have been fitted by other methods. This work is limited to the processing of data obtained in experiments conducted in homogenous, isotropic rock at isothermal conditions. Sedimentary rocks such as sandstone are the focus of this study because of their importance in near-wellbore reservoir rock stability problems. Nevertheless, the methodology developed in this work is not limited to this type of rock.
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Le, Pavic Jérémy. "Méthodologie de dimensionnement d’un assemblage collé pour application aérospatiale." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2018. http://www.theses.fr/2018ENTA0001/document.
Full textAbstract:
Les lanceurs spatiaux sont des structures complexes associant une multitude de composants. L’assemblage de ces éléments doit répondre à un niveau de performance élevé. Le collage structural demeure un bon candidat en raison des nombreux avantages qu’il présente. Cependant, cette technologie montre des inconvénients. En raison des changements brusques de géométrie et de propriétés matériaux, des concentrations de contraintes apparaissent aux extrémités du joint de colle. Ce phénomène appelé effets de bords est néfaste pour la tenue mécanique de l’assemblage collé. La présence des effets de bords exclut l’utilisation de critères en contrainte utilisés classiquement. Le dimensionnement d’assemblages collés requiert des outils fiables prenant en compte ces effets de bords. Dans cette étude, un modèle de ruine incrémentale, associant une approche en contrainte et en énergie, est utilisé. L’utilisation de cet outil dans un cadre industriel, impose de répondre aux besoins d’un Bureau d’Études, notamment en termes de coût de calculs. Afin de le diminuer, une implémentation semi-analytique, est tout d’abord développée. Puis, une seconde méthode d’implémentation, basée sur la méthode des Eléments Finis, permet une prévision plus précise de la ruine d’un assemblage. La pertinence de ces deux approches a été vérifiée pour plusieurs configurations de joints collés. Des campagnes d’essais, destinées à confronter les résultats expérimentaux aux prévisions numériques, ont été réalisées. Dans le cadre de ce travail, un montage de collage et d’essai pour assemblages tubulaires a en particulier été développé. L’objectif du pré-dimensionnement est d’identifier une zone d’intérêt dans l’ensemble du domaine d’étude. Aussi, une étude paramétrique peut être requise afin de réaliser cette tâche. Afin de réduire le coût de calcul, une méthode d’interpolation spatiale appelée Krigeage a été mise en œuvre, et permet la construction efficace d’une surface de réponseSpace Launchers are complex structures composed of a large number of elements. The assembling of these components must show a high level of reliability. The use of adhesive bonding technology is an interesting solution since it presentsseveral assets compared to “classical” joint techniques (such as riveting, bolting and welding), mainly because it can help to construct lighter and less energy consuming systems However„ the implementation of adhesives also has somedrawbacks. Due to the strong variations of geometrical and material properties, stress concentrations appear at the extremities of the joint. This phenomenon; called edge effects; has a great influence on the failure of the bond. As a result, the simple use of a classical stress or energetic criteria is not appropriate to predict the fracture of such structures. Therefore, it is obvious that the design of bonded assemblies requires reliable tools to take the edge effects into account. In this work an incremental failure model, which combines the stress and energetic criteria, is used. In order to decrease the computational cost, a semi-analytical application of this model is proposed. This is intended to make the approach more interesting to be implemented in an industrial environment. The accuracy of the prediction of the failure load is enhanced by means of the Finite Element method. The reliability of both the semi-analytical and Finite Element approaches is verified by comparing the model predictions with experimental data issued from double-notched Arcan and tubular specimen geometries. The aim of the pre-design phase is to identify the critical area in the whole range of the application of the studied geometry. Therefore, the realization of a parametric study is required in order to build a response surface. In the present study, this has been achieved by means of spatial interpolation using the Kriging model
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Gearing, Brian P. (Brian Paul) 1972. "Constitutive equations and failure criteria for amorphous polymeric solids." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/17543.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (v. 2, p. 104-109).
Anand & Gurtin (2002) have recently developed a continuum theory for the elastic-viscoplastic deformation of amorphous solids. Their theory is motivated by and builds on the work of Parks, Argon, Boyce, Arruda, and their co-workers (e.g. Boyce et al., 1988; Arruda & Boyce, 1993) on modeling the plastic deformation of amorphous polymers. The theory of Anand & Gurtin (2002) carefully accounts for restrictions placed on constitutive assumptions by frame-indifference and by a new mathematical definition of an amorphous material based on the notion that the constitutive relations for such materials should be invariant under all rotations of the reference configuration and, independently, all rotations of the relaxed configuration. Also, they explicitly account for the dependence of the Helmholtz free energy on the plastic deformation in a thermodynamically consistent manner, a dependence which leads directly to a backstress in the underlying flow rule. In addition to the standard kinematic and stress variables, their theory contains two internal variables: a variable s > 0 that represents an isotropic intermolecular resistance to plastic flow; and an unsigned variable 7 that represents the local free-volume. In this thesis, we extend the work of Anand & Gurtin (2002) to model the deformation and fracture response of amorphous glassy polymers which exhibit both a ductile mechanism of fracture associated with large plastic stretches and subsequent chain scission and a brittle mode of fracture.
(cont.) For polymers such as polycarbonate (PC), the brittle fracture mode is characterized by a mechanism of elastic cavitational failure, which results in cleavage-type fracture similar to that observed in brittle fracture of metals. In contrast, polymers such as polymethylmethacrylate (PMMA) and polystyrene (PS) exhibit a brittle mode of fracture characterized by craze initiation, flow, and breakdown. To model crazing, we introduce a continuum constitutive relation which contains the three ingredients of crazing - initiation, widening, and breakdown - in a suitable statistically-averaged sense. We allow for local inelastic deformation due to shear yielding in possible concurrence with that due to crazing, and introduce a craze initiation criterion based on the local maximum principal tensile stress reaching a critical value which depends on the local mean normal stress. After crazing has initiated, our continuum model represents the transition from shear-flow to craze-flow by a change in the viscoplastic flow rule, in which the dilational inelastic deformation associated with craze-plasticity is taken to occur in the direction of the local maximum principal stress. Finally, for situations in which the local maximum tensile stress is positive, craze-breakdown and fracture is taken to occur when a local tensile plastic craze strain reaches a critical value. We apply our model to the techologically important polymer, polymethylmethacrylate ...
by Brian Paul Gearing.
Ph.D.
47
Yanik, Yasar. "Quantification of parametric uncertainties effects in structural failure criteria /." Ilha Solteira, 2019. http://hdl.handle.net/11449/182040.
Full textAbstract:
Orientador: Samuel SilvaResumo: Critérios de falhas realizam a predição de circunstâncias nas quais materiais sólidos estão sobre ação de carregamentos externos. As teorias de falhas são conhecidas como diferentes critérios de falhas, como von Mises e Tresca, os quais são os mais famosos para determinados materiais. Além disso, esta dissertação de mestrado pretende mostrar a comparação entre os critérios de falha de Tresca e von Mises, levando em conta incertezas subjacentes nas equações constitutivas e na análise de tensão. Para exemplificar acomparação,algumassimulaçõessãorealizadasusandoumaplacasimples,umproblema de deflexão simples,e a estrutura de um carro do formula SAE. Devido à complexidade deste sistema, diferentes tipos de etapas probabilísticas são utilizadas, como o método de superfície de resposta e a correlação de parâmetros. Os resultados mostram que várias variáveis aleatórias de entrada afetam em maneiras diferentes as variáveis aleatórias de saída e que não há uma diferença grande entre os critérios de falha de von Mises e Tresca quando incertezas são assumidas na formulação para a análise de tensão.
Abstract: Failure theory is the investigation of predicting circumstances under which solid materials under the processing of external loads. The theories of failure are known as different failure criteria such as von Mises and Tresca which are the most famous of these for certain materials. Additionally, this master dissertation intends to show a comparison between Tresca and von Mises failure criterions, taking into account the underlying uncertainties in the constitutive equations and stress analysis. In order to exemplify the comparison, some numerical simulations are performed using a simple plate, simple deflection problem and a frame of the formula car. Due to the complexity of frame of the formula car, different kind of probabilistic steps are used as a response surface method and parameters correlation. Results show that several random input variables effect the random output variables in various ways, and there is no such a big difference between the von Mises and Tresca failure criterions when uncertainties are assumed in the formulation for stress analysis.
Mestre
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Xu, Longfei. "Mechanical behaviour of compacted earth with respect to relative humidity and clay content : experimental study and constitutive modelling." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSET005/document.
Full textAbstract:
La terre compactée est considérée comme un mélange granulaire dans lequel l'argile joue un rôle de liant mais cette dernière exhibe une forte interaction avec l'eau. Pendant la durée de vie en service, la terre compactée est soumise aux changements de l’humidité relative. En raison de ces changements des conditions ambiantes perpétuels, la teneur en eau dans la terre varie, impactant leur performance mécanique. Le présent travail a ainsi pour but d’étudier l’impact de l’humidité relative et de la teneur d'argile sur le comportement mécanique de la terre compactée. Il se réalisera au travers d’études expérimentales et d'une modélisation constitutive. Dans la première partie de cette thèse, quatre terres régionales de provenances et de teneurs d'argile différentes sont identifiées. Une étude comparative a été réalisée entre le double compactage statique et le compactage dynamique. En parallèle, trois types d'essais spécifiques : essais de succion par la méthode de papier-filtre, essais de retrait et essais d'absorption d'eau, ont été menés pour donner des indications préliminaires quant aux effets d'interaction entre l'eau et l'argile. Dans la deuxième partie, l’impact de l’humidité relative et de la teneur d'argile sur le comportement de cisaillement a été étudié, prenant en compte des cycles de chargement-déchargement. En adoptant une définition particulière de la contrainte effective de Bishop, il a également été observé que les états de rupture dans le plan (p'-q) pour tous les échantillons sont alignés approximativement à une ligne droite unique passant par l'origine, quelque soit la succion et la pression de confinement. Sur la base des résultats expérimentaux, un nouveau modèle constitutif a été développé pour la simulation du comportement mécanique de la terre compactée. Ce nouveau modèle a ainsi été formulé dans la cadre de la mécanique de l'endommagement des milieux continus et de la théorie de Bounding Surface PlasticityCompacted earth is regarded as a granular mixture in which clay plays a role of binder but it also exhibits an important interaction with water. During their service life, compacted earth can be subject to large changes in relative humidity. Those perpetual changes of environmental conditions induce continuous changes of water content of the earth that impact significantly its mechanical performances. The present work aimes at studying the mechanical behavior of compacted earth with respect to relative humidity and clay content. It involves an extensive experimental study and a constitutive modelling. In the first part of this thesis, four kinds of local earth are identified with different clay contents. A comparison of compaction method was then conducted between a double static compaction and dynamic compaction. Three types of specific tests: suction test by filter paper method, shrinkage test and sorption-desorption test were carried out, thereby providing a preliminary insight on the interaction effects between clay and water. In the second part, the impact of clay and moisture contents on the shear behavior of compacted earth was investigated taking into account loading-unloading cycles. Adopting a particular definition of Bishop's effective stress, failure states of all samples were observed to lie approximately on a unique failure line crossing the origin in the (p'-q) plane regardless of matric suction and confining pressure. Finally, based on the above experimental results, a new constitutive model was proposed, based on the theories of Bounding Surface Plasticity and continuum damage mechanics, aiming to simulate mechanical behaviour of compacted earth
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Prakhya, Ganga Kasi Viswanadha. "Ferrocement structures : constitutive relations, non-linear finite element analysis, and analogy with reinforced concrete." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292241.
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Pyiypchuk, Mariya, Lldiia Dziuba, Ihor Rebezniuk, Oksana Chmyr, and Mykhailo Burdiak. "Modeling Parametric Failures of Woodworking Machines According to the Technological Precision Criterion." Thesis, Inter Grabchenko's International Conference t y *-* t y -t on Advanced Manufacturing Processes “ " “ http://interpartner.odessa.ua Partner, 2021. https://sci.ldubgd.edu.ua/jspui/handle/123456789/9943.
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