Academic literature on the topic 'Modified strength criterion'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Modified strength criterion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Modified strength criterion"
1
ZHANG, Qiang, Shuilin WANG, Xiurun GE, and Hongying WANG. "Modified Mohr-Coulomb strength criterion considering rock mass intrinsic material strength factorization." Mining Science and Technology (China) 20, no. 5 (2010): 701–6. http://dx.doi.org/10.1016/s1674-5264(09)60266-0.
Full text
2
Zheng, Yonglai, and Shuxin Deng. "Failure Probability Model considering the Effect of Intermediate Principal Stress on Rock Strength." Mathematical Problems in Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/960973.
Full textAbstract:
A failure probability model is developed to describe the effect of the intermediate principal stress on rock strength. Each shear plane in rock samples is considered as a micro-unit. The strengths of these micro-units are assumed to match Weibull distribution. The macro strength of rock sample is a synthetic consideration of all directions’ probabilities. New model reproduces the typical phenomenon of intermediate principal stress effect that occurs in some true triaxial experiments. Based on the new model, a strength criterion is proposed and it can be regarded as a modified Mohr-Coulomb criterion with a uniformity coefficient. New strength criterion can quantitatively reflect the intermediate principal stress effect on rock strength and matches previously published experimental results better than common strength criteria.
3
Xiao, Yang, HanLong Liu, and Robert Y. Liang. "Modified Cam-Clay model incorporating unified nonlinear strength criterion." Science China Technological Sciences 54, no. 4 (2011): 805–10. http://dx.doi.org/10.1007/s11431-011-4313-4.
Full text
4
Yang, Yugui, Feng Gao, and Yuanming Lai. "Modified Hoek?Brown criterion for nonlinear strength of frozen soil." Cold Regions Science and Technology 86 (February 2013): 98–103. http://dx.doi.org/10.1016/j.coldregions.2012.10.010.
Full text
5
Zhang, Jian Yu, Rui Bao, and Bin Jun Fei. "Modified Swift Criteria for Residual Strength of Multiple Site Damage Structure." Key Engineering Materials 417-418 (October 2009): 881–84. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.881.
Full textAbstract:
As more aircrafts reach or exceed their design life, it is becoming very important to research multiple cracks damage, especially the multiple site damage (MSD) in order to re-evaluate their service life and damage tolerance/durability performance. The existing of MSD may remarkably reduce the residual strength of an aerospace structural component than those with a singe lead crack. This study investigated the residual strength of aluminum alloy sheet with MSD through three types of aluminum specimens test. Aluminum panels with bare collinear constant diameter holes were chosen as specimens. After some constant amplitude tension-tension load cycles, the MSD were found in these specimens since there were multiple fatigue cracks emanating from the saw cuts of holes. The residual strength was recorded as the maximum load when every specimen was subjected to monotonically increasing tensile load until failure occurred. In different failure prediction criteria that were often used in engineering in order to evaluate the accuracy of these criteria, Swift criterion (ligament yield) criterion got more accurate prediction results than other criteria. Although Swift criterion was more accurate than some other criteria, its error was still big for some specimens. Two modified approaches were proposed in order to get more accurate and appropriate failure criterion for MSD structure.
6
Wang, Yalei, Jinming Xu, Junshuai Xu, and Chuanjiang Zhong. "Estimation of Rock Burst Grades Using Rock Mass Strength." Advances in Civil Engineering 2020 (July 18, 2020): 1–14. http://dx.doi.org/10.1155/2020/2517459.
Full textAbstract:
The traditional rock burst estimation method is usually based on the σc (rock strength) in practice, while the actual occurrence of rock burst depends more on the structure and strength of the rock mass. In this work, the actual rock bursts occurred in a railway tunnel project in Western China, and the σcm (rock mass strength) was calculated by the generalized Hoek–Brown criterion. According to the actual situation of rock bursts, a modified rock burst estimation criterion using the ratio of σcm to σmax (maximum geostress) was proposed. The influence of randomness on the reliability of rock burst estimation criterion was considered. The estimation results based on the traditional and modified method were furthermore compared with those of the actual rock bursts. The results show that σcm calculated by the generalized Hoek–Brown criterion may be considered well in the rock type and strength, construction condition, and structure features of the rock mass; the estimation results of rock burst using the ratio of σc to σmax are quite different from the actual situation, while those using the ratio of the σcm to σmax coincided relatively with the actual rock bursts; the ratios of σcm to σmax, which are greater than 0.167, 0.066 to 0.167, 0.012 to 0.066, and less than 0.012, are corresponded to the slight, medium, strong, and violent grades of the rock bursts, respectively; the randomness of data selection has certain influence on the rock burst estimation criterion, but the variation range is small; the modified estimation criterion of rock burst proposed in this work has a good reliability. The results presented herein are important for tunnel construction and the prevention of rock burst in the high geostress areas.
7
Liao, Mengke, Yuanming Lai, and Chong Wang. "A strength criterion for frozen sodium sulfate saline soil." Canadian Geotechnical Journal 53, no. 7 (2016): 1176–85. http://dx.doi.org/10.1139/cgj-2015-0569.
Full textAbstract:
Salt content has been proven to be an important influencing factor on the mechanical properties of frozen saline soils, whose strength criterion is different from that of unfrozen saline soils or frozen soils without salts. In this paper, a series of conventional triaxial tests are carried out for frozen saline soils with sodium sulfate at a temperature of –6 °C. A strength criterion of the frozen saline soils, including the influence of salt content, is established by using the generalized nonlinear strength theory. Based on conventional triaxial test results, a modified hydrostatic pressure expression is proposed according to the critical strength function of the modified Cam clay model in the meridian plane. The influence of salt content on the shear strength of the frozen saline soils is investigated according to their freezing temperature curves as well as the formation of salt and ice crystals. The relationship between salt content and friction angle is analyzed. The proposed strength criterion of frozen saline soil is proved to be reliable by extrusion elongation triaxial tests. This criterion can reasonably reflect the major nonlinear strength characteristics of frozen saline soils, including the influences of change in salt content, pressure melting, and ice crushing.
8
JOHN, H. BRIGHTON ISAAC, and T. CHRISTOPHER. "Fracture strength evaluation of titanium alloys using modified average stress criterion." Transactions of Nonferrous Metals Society of China 23, no. 4 (2013): 1072–79. http://dx.doi.org/10.1016/s1003-6326(13)62568-6.
Full text
9
Deng, Xianghui, Yuncai Wang, Rui Wang, Daohong Xia, and Zhiqing Zhao. "Application of Modified Hoek–Brown Strength Criterion in Water-Rich Soft Rock Tunnel." Geofluids 2021 (June 7, 2021): 1–12. http://dx.doi.org/10.1155/2021/5552791.
Full textAbstract:
When a tunnel is excavated in the water-rich soft rock stratum, the strength of the soft rock is greatly reduced due to the seepage of groundwater. The condition may result in engineering accidents, such as large deformation, limit invasion, and even local collapse of the tunnel. Therefore, it is very important to research the stability of the surrounding rock in the water-rich soft rock tunnel. The water-rich disturbance factor considering the seepage influence of groundwater and blasting disturbance is proposed, and the generalized Hoek–Brown strength criterion is modified on the basis of the immersion softening test of soft rock. In accordance with the classical elastic–plastic mechanics theory, the stress, strain, and displacement calculation formulas of the tunnel surrounding rock are derived. The displacement of tunnel surrounding rock is analyzed using the derived formula and the modified Hoek–Brown strength criterion and then compared with the measured value. Results show that the displacement of surrounding rock, which is calculated by modified Hoek–Brown strength criterion considering water-rich disturbance factor and the displacement calculation formula, is close to the measured deformation of surrounding rock in water-rich soft rock tunnel, and the error is small. Therefore, the modified Hoek–Brown strength criterion can be applied to the water-rich soft rock tunnel, and the derived displacement calculation formula can accurately calculate the deformation of tunnel surrounding rock. It is of great significance to the study of surrounding rock stability of water-rich soft rock tunnel.
10
Wang, Shyh-Jen, and Marvin W. Dixon. "A New Criterion for Positive Mean Stress Fatigue Design." Journal of Mechanical Design 119, no. 1 (1997): 135–37. http://dx.doi.org/10.1115/1.2828776.
Full textAbstract:
The modified Findley line is proposed by using ultimate strength and endurance limit as parameters to obtain a good initial approximation of an acceptable design. Comparing with experimental data, the modified Findley line could be a strong candidate for fatigue design criterion for parts made of a nonferrous materials, and be conservative for ferrous material parts.
Dissertations / Theses on the topic "Modified strength criterion"
1
Жигилій, Дмитро Олексійович, Дмитрий Алексеевич Жигилий та Dmytriy Oleksiyovych Zhyhyliy. "Конструкційна міцність комбінованих балонів високого тиску". Thesis, Сумський державний університет, 2010. http://essuir.sumdu.edu.ua/handle/123456789/3775.
Full textAbstract:
Дисертація на здобуття вченого ступеня кандидата технічних наук за фахом 05.02.09 – динаміка і міцність машин. – Сумський державний університет, Суми 2010.
На основі дискретно-структурної теорії анізотропних пластин і оболонок розроблена методика розв’язання геометрично нелінійних контактних задач при розрахунку на міцність багатошарових анізотропних пластин і оболонок з урахуванням як ідеального, так і неідеального контакту між шарами. Отримано розв’язок широкого класу контактних задач, виявлені основні закономірності зміни напруженого стану і контактного тиску в зоні локальних ділянок непроклею або розшарувань. Вивчений вплив структурної неоднорідності шаруватого матеріалу на макрорівні із застосуванням алгоритму поетапного навантаження і застосування того або іншого варіанта запропонованих розрахункових моделей багатошарової конструкції. Перехід від одного варіанта розрахункової моделі до іншого визначається умовами міцності композиту в точках поверхні сполучення найбільш навантажених шарів конструкції. З метою оцінки достовірності основних положень і результатів роботи проведені експериментальні дослідження і отримано числові розв’язки тестових задач. На основі методу переміщень розроблена методика розрахунку конструкційної міцності і несучої здатності оболонок обертання складної форми з шаруватою структурою матеріалу. Вивчені конструкційна міцність і несуча здатність комбінованого балона високого тиску, що складається із склопластикової несучої оболонки, захищеної з зовнішнього боку металевою оболонкою.
При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/3775<br>Диссертация на соискание учёной степени кандидата технических наук по специальности 05.02.09 – динамика и прочность машин. – Сумский государственный университет, Сумы 2010.
На основе дискретно-структурной теории анизотропных пластин и оболочек разработана методика решения геометрически нелинейных контактных задач при расчёте на прочность многослойных анизотропных пластин и оболочек с учетом как идеального, так и неидеального контакта между слоями. Получено решение широкого класса контактных задач, выявлены основные закономерности изменения напряженного состояния и контактного давления в зоне локальных участков непроклеиваний или расслоений. Изучено влияние структурной неоднородности слоистого материала на макроуровне с применением алгоритма поэтапного нагружения и применения того или иного варианта предлагаемых расчетных моделей многослойной конструкции. Переход от одного варианта расчетной модели к другому определяется условиями прочности композита в точках поверхности сопряжения наиболее нагруженных слоев конструкции. С целью оценки достоверности основных положений и результатов работы проведены экспериментальные исследования и получено численное решение тестовых задач. На основе метода перемещений разработана методика расчета конструкционной прочности и несущей способности оболочек вращения сложной формы со слоистой структурой материала. Изучены конструкционная прочность и несущая способность комбинированного баллона высокого давления, состоящего из несущей стеклопластиковой оболочки, защищенной с внешней стороны металлической оболочкой.
При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/3775<br>Thesis for a Candidate degree in Technical Science in speciality 05.02.09 - dynamics and strength of machines. – Sumy State University, Sumy, 2010.
Based on discrete-structural theory of anisotropic plates and shells, methodology of geometrically nonlinear contact problem solving is developed. This problem appears during a strength design of multi-layered anisotropic plates and shells with a glance to both ideal and nonideal contact between layers. Solutions of wide class of contact problems are found. The basic mechanism of deflected mode and contact pressure changes in the area of starved spots and delaminations is revealed. The influence of structure inhomogeneity of multilayer material is studied at the macrolevel with the use of algorithm of stage-by-stage loading and choosing of one or another variant of the offered multilayered structure calculation models. An adoption of one calculation model to another one is determined by the terms of composites strength in the junction surface points of the most loaded layers of the construction. Experimental researches are led and numerical solving of the test problems is got for conceptual issues and efforts authenticity estimation. The methodology of structural strength and load-carrying ability calculation of difficult form layered rotation shells based on deflection method is offered. Structural strength and load-carrying ability of the hybrid high-pressure balloon are studied. This combined high-pressure cylinder consists of load-bearing glass-fibre plastic shell and external protective metal shell.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3775
Books on the topic "Modified strength criterion"
1
Doruk, Piril. Analysis of the laboratory strength data using the original and modified Hoek-Brown failure criteria. National Library of Canada = Bibliothèque nationale du Canada, 1991.
Find full textBook chapters on the topic "Modified strength criterion"
1
da Fontoura, Sergio A. B. "Lade and Modified Lade 3D Rock Strength Criteria." In The ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 2007-2014. Springer International Publishing, 2012. http://dx.doi.org/10.1007/978-3-319-07713-0_23.
Full text
2
Prasad, Kanika, and Rishi Dwivedi. "Application of Modified Similarity-Based Method for Cotton Fiber Selection." In Advances in Environmental Engineering and Green Technologies. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8579-4.ch007.
Full textAbstract:
In today's business environment, sustainability is one of the most significant issues that organizations needs to deal with. Fiber choice is often the initial stride that designers and product developers will consider in minimizing the ecological impact of a garment while achieving sustainability. Cotton fiber, whether alone or blended with some other fiber, is being extensively used in textile industries. However, the selection of optimal cotton fiber depends on its several properties like length, strength, fineness, length uniformity, short fiber content, etc., thus making this selection process s multi-criteria decision-making problem. Thus, for the first time, this chapter examines the applicability and feasibility of a modified similarity-based approach for selection of cotton fiber which in turn assists in achieving sustainable design characteristics. Two illustrative examples from past researches and one existing cotton fiber selection problem of a small textile organization are solved applying the adopted method to validate its veracity and robustness.
Conference papers on the topic "Modified strength criterion"
1
Bineshian, Hossein, and Zahra Bineshian. "Prediction of Triaxial Compressive Strength of Geomaterials Based on a Failure Criterion." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83036.
Full textAbstract:
Ramamurthy et al strength criterion is applicable only for compression. Tensile strength and unconfined compressive strength cannot be calculated by the criterion. Ramamurthy et al criterion contains two parameters as inherent constants of geomaterials that are known as B and α. A popular method to predict the strength by a certain criterion is using the proposed values for the criterion’s parameters, authors in this paper suggested suitable practical values for the parameters and a precise equation for B for a wide range of geomaterials. Also especial consideration has been pertained for soft geomaterials to calculate the parameters for different conditions of weak planes and loading direction. Moreover authors have presented linear conversion and nonlinear regression model for Ramamurthy et al criterion to extract the mathematical coefficients and the strength criterion’s parameters. Using these parameters for seabed geomaterials will present a fast, useful and credible prediction for the compressive strength by this modified strength criterion.
2
Khosravanian, Rasool, and Bernt Sigve Aadnøy. "Uncertainty Evaluation of Wellbore Stability Using Comparative Rock Strength Criterions." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18052.
Full textAbstract:
Abstract The requirement of uncertainty analysis has shifted the transformation of sensitivity analysis from the deterministic area to the stochastic area.Geomechanical wellbore integrity problems during drilling operation can occur due to wellbore shear failure or tensile failure. To guarantee wellbore integrity, breakout and fracture geomechanical analysis is essential to estimate the Safe Mud Weight Window (SMWW). Wellbore stability problems causes many challenges in a drilling operation, such as pipe sticking, wellbore collapse, fluid loss and poor cement jobs. A drilling engineer must minimize the risk of these problems, however, there is a considerable uncertainty of different parameters such as geomechanical rock properties of drilled formation, and, data and parameters gathering are often incomplete. This uncertainty of main parameters have impact on the resulting SMWW.This paper perform an uncertainty evaluation of wellbore stability and its effect on the optimum interval of SMWW. The SMWW Uncertainty Evaluation of Wellbore Stability assessment for two failure criteria are compared, Mohr-Coulomb and Modified Lade criterion. We apply Monte Carlo simulations to investigate the uncertainty of the models and we do a sensitivity analysis and confidence level analysis. The paper will show the advantage of including uncertainty evaluation when determining the optimum SMWW window, as opposed to classical deterministic analysis. A case study is presented to draw a perfect understanding of the foundation of the MCS approach with practical and good results. It confirmed the capability of the proposed approach in solving such a strong-nonlinear, complex real problem.
3
Shih, Hua-Chu, and Taylor Gambon. "An Empirical Stretch Bending Failure Criterion for AHSS." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71722.
Full textAbstract:
The failure mechanism in stretch bending over a small die radius for Advanced High Strength Steels (AHSS), commonly referred as “shear fracture”, has rendered the Forming Limit Diagrams (FLD) fail to predict it based on the initiation of a localized neck. As shown in previous studies using a Stretch-Forming Simulator (SFS) and Bending Under Tension (BUT) test, shear fracture depends not only on the radius-to-thickness (R/T) ratio but also on the tension/stretch level applied to the sheet during bending. Although the stress-base empirical fracture limit criterion was developed for various AHSS grades, the fracture limit was not well implemented in the computer simulations to predict stretch bending fracture. In this paper, the new developed experimental analysis is conducted on the modified bending under tension test to further investigate the stretch bending fracture mechanism under the production die condition. Various AHSS grades including DP590, DP780, DP980 and DP1180 are included in the study. Based on numerous experimental results, the maximum shear stress at failure, the thinning strain and strain gradient across the die radius are obtained for all test materials. Results demonstrate that the presence of the large strain gradient is the cause for fracture in stretch bending AHSS over a small die radius. The maximum shear stress at failure and the limit thinning strain on the die radius in the stretch bending condition are determined and used as the new fracture criteria, which can be easily implemented in the computer simulations.
4
Chen, Jianqiao, Xiangyang Wang, and Cheng Luo. "Reliability Analysis of FRP Laminated Plates With Initial Imperfection." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1344.
Full textAbstract:
In this paper, a probabilistic progressive failure analysis method is applied to estimating the reliability of a simply supported laminated composite plate with an initial imperfection under bi-axial compression load. The initial imperfection and the strength parameters are considered as random variables. Ply-level failure probability is evaluated by the first order reliability method (FORM) together with the Tsai-Wu strength criterion and Tan criterion. Current stresses in the laminated structure are calculated by classical lamination theory with the stiffness being modified based on the last step ply failure. Probabilistieally dominant ply-level failure sequences leading to overall system failure are identified by branch and bound method. The system failure probability is estimated through the union of significant failure sequences. A numerical example is presented to demonstrate the methodology proposed. Parameter studies show that the deviation of the initial imperfection and strength parameters largely influence the system reliability.
5
McDonald, Brodie, Shannon Ryan, Stephen J. Cimpoeru, Nathan Edwards, and Adrian Orifici. "Modelling the Fracture of High-Hardness Armour Steel in Taylor Rod-on-Anvil Experiments." In 2019 15th Hypervelocity Impact Symposium. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/hvis2019-041.
Full textAbstract:
Abstract A series of Taylor rod-on-anvil experiments have been performed to validate the predicted impact velocity fracture threshold and fracture mode of a high hardness armour steel (HHA) obtained through explicit finite element simulations. Experimentally, the rods exhibited principal shear failure, a condition that can be closely linked to adiabatic shear band (ASB) formation in high strength steel. Using a stress triaxiality and Lode angle dependent failure strain criterion (Basaran 3D fracture locus), calibrated from quasi-static mechanical characterisation tests, the simulations were unable to predict the onset of fracture observed in experiments. As such, a strength-fading criterion is proposed using a phenomenological description to capture the loss of load-carrying capacity resulting from ASB formation. The ASB criterion is based on an exponential fit to experimentally-observed instability strains measured at different average stress triaxialities in a series of tests on inclined cylindrical and modified flat-hat specimens. With the prediction of ASB formation the material strength is reduced to model the thermal softening experienced in the shear band, and fracture of the material (in the form of element erosion) remains controlled by the Basaran fracture model. Incorporating the ASB-based criterion, the numerical models were found to accurately predict both the impact velocity fracture threshold, as well as the general appearance of the observed principal shear fracture. The proposed criterion enables the effects of ASB formation to be captured in an impact simulation with little increase in computational cost.
6
Swankie, Troy, Vinod Chauhan, Robert Owen, Robert Bood, and Geoffrey Gilbert. "Assessment of the Remaining Strength of Corroded Small Diameter (Below 6”) Pipelines and Pipework." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90401.
Full textAbstract:
Internal and external corrosion damage is a major cause of pipeline failures worldwide. When corrosion features in pipelines are detected by in-line inspection (ILI), a decision whether to replace, repair or accept and monitor must be made. Extensive experimental and numerical work has been undertaken to develop methods for assessing the remaining strength of corroded transmission pipelines. Common methods used by the pipeline industry include ASME B31G, modified ASME B31G and LPC. These methods are semi-empirical and have been developed using a modified version of a toughness independent ductile failure criterion for pressurized pipes containing axially orientated surface breaking defects. The validity range of these models is dominated by large diameter (10 to 48″), thin walled, low grade (API 5L grade A to X65) and low yield to tensile ratio line pipe. Smaller diameter (not greater than 6″), thick walled pipelines and pipework located, for example, at above ground installations, compressor and pressure reduction stations are very common. The use of ASME B31G, modified ASME B31G or LPC may not be appropriate when assessing the remaining strength of small diameter pipelines and pipework. No alternative methods are available in the public domain and hence a program of work was undertaken to derive appropriate defect acceptance limits by conducting a series of full-scale burst tests on small diameter pipe with simulated corrosion defects. It was concluded that the LPC method gave the most accurate prediction of failure pressure when compared with the results of the full-scale tests, and the most conservative predictions of failure pressure were obtained using the ASME B31G method.
7
Sasihithlu, Karthik, and Arvind Narayanaswamy. "Effect of Curvature on Near-Field Radiative Transfer: The Modified Proximity Approximation." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75163.
Full textAbstract:
Near-field radiative transfer between two spheres can be computed using Rytov’s theory of fluctuational electrodynamics in which the strength of electromagnetic sources is related to temperature through the fluctuation-dissipation theorem, and the resultant energy transfer is described using an expansion of the dyadic Green’s function of the vector Helmholtz equation in a series of vector spherical waves. We show that when electromagnetic surface waves are active at a frequency the number of vector spherical waves required for convergence is proportional to Rmax/d when d/Rmax → 0, where Rmax is the radius of the larger sphere, and d is the smallest gap between the two spheres. Using this criterion, we show that the surface polariton mediated near–field thermal radiative conductance between two spheres of equal radii R scales as R/d as d/R → 0. We also propose a modified form of the proximity approximation to predict near–field radiative transfer between curved objects from simulations of radiative transfer between parallel surfaces.
8
Ruggieri, Claudio, Fernando F. Santos, Mitsuru Ohata, and Masao Toyoda. "A Micromechanics Approach to Assess Ductile Crack Initiation in Damaged Pipelines." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1993.
Full textAbstract:
This study explores the capabilities of a computational cell framework into a 3-D setting to model ductile fracture behavior in tensile specimens and damaged pipelines. The cell methodology provides a convenient approach for ductile crack extension suitable for large scale numerical analyses which includes a damage criterion and a microstructural length scale over which damage occurs. Laboratory testing of a high strength structural steel provides the experimental stress-strain data for round bar and circumferentially notched tensile specimens to calibrate the cell model parameters for the material. The present work applies the cell methodology using two damage criterion to describe ductile fracture in tensile specimens: (1) the Gurson-Tvergaard (GT) constitutive model for the softening of material and (2) the stress-modified, critical strain (SMCS) criterion for void coalescence. These damage criteria are then applied to predict ductile cracking for a pipe specimen tested under cycling bend loading. While the methodology still appears to have limited applicability to predict ductile cracking behavior in pipe specimens, the cell model predictions of the ductile response for the tensile specimens show good agreemeent with experimental measurements.
9
Pan, Yi, and Assimina A. Pelegri. "Numerical Test Method for Random Chopped Fiber Composites." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-40693.
Full textAbstract:
A two-scale approach for numerical determination of composite material constants using a finite element model is developed. A representative volume element is numerically generated using a modified sequential adsorption algorithm. To determine the strength of the composite material, progressive material degradation models are adopted for the matrix, fiber and the fiber/matrix interface. The epoxy resin is modeled with a modified von Mises criterion in which the effect of hydrostatic stress on yield is accounted for. The resin’s elastic constants degrade with increasing loading application. The glass fiber is modeled as an isotropic material whose failure is governed by the maximum strain criterion. A traction-separation type cohesive zone model is applied at the fiber/matrix interface. Validation of the presented model is achieved by comparing numerical simulations with experimental data. The effective material constants that have been homogenized by the numerical test approach can be applied for future structural analysis.
10
Seo, Yun-Ho, and Chong-Won Lee. "A New Frequency-Speed Diagram Weighted With Strength of Modes in Rotating Machinery." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50855.
Full textAbstract:
The coincidence of operating speed and critical speed must be avoided in the design of a rotor system. If the rotor system has various critical speeds as well as many modes, the determination of dangerous modes is a first step of the design stages. In this paper, the use of a new frequency-speed diagram that displays the significance of modes in order to help the design and analysis of a rotor system is suggested. The diagram is a modified version of a waterfall chart. The method graphically shows the magnitude of the forced responses by the directional frequency response matrices in accordance with operating speed because the responses are the most important criterion to determine significance of modes. In addition, because the excitation force of a rotor system such as mass unbalances is not known before the completion of manufacturing, the concept of summation of matrix norms, which is more conservative than conventional H∞ norm, is used in order to consider the worst of the worst case. A simple rotor system and a real generator system, which has both anisotropy and asymmetry, are demonstrated for usefulness of the proposed diagrams. The information of the diagram is then used to analyze the dynamic characteristics of the generator system.
Reports on the topic "Modified strength criterion"
1
Becker, Peter J. Using the Light Weight Deflectometer for Performance-Based Quality Assurance Testing of Cement Modified Subgrades. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317304.
Full textAbstract:
This report documents the findings from SPR-4230 (Alternative Quality Assurance Methods for Compacted Subgrade). The main objective of SPR-4230 involved establishing performance-related quality assurance (QA) test methods for pavement subgrade construction. Because INDOT generally prefers specifying subgrade treatment type IBC (i.e., 14-in. cement modified subgrade), this study focused on performance-based QA test methods for constructing cement modified subgrade. Moreover, INDOT prefers using light weight deflectometer (LWD) for chemically modified subgrade construction acceptance, so this study aimed to use LWD deflection measurements as performance-related construction acceptance criteria. A laboratory study was performed to relate LWD deflections with resilient modulus that is the key subgrade performance-related parameter in pavement design. In addition, LWD deflections were related with unconfined compressive strength increase that is the key parameter in chemical soil modification mix design. A rigorous field study consisting of LWD testing and falling weight deflectometer (FWD) testing at INDOT new pavement construction sites was conducted to verify the laboratory developed relationship. Recommendations for implementing results of this study into cement modified subgrade construction acceptance is provided, as are recommendations for future research.
2
Quality Assurance in HECA Colleges During the COVID-19 Pandemic: A Mixed Methods Analysis through the lens of QQI’s Core Criteria. Higher Education College's Assocation (HECA), 2022. http://dx.doi.org/10.22375/hqf.tos22.
Full textAbstract:
The National Forum’s 2020 Network and Discipline Fund was launched in November 2020 and focuses on Shared Solutions to Common Challenges. Its overarching aim is to support networks and discipline groups to work together to respond proactively to identified challenges in teaching and learning in higher education, including those that have come to light through the sudden move to online/remote teaching and learning. The National Forum’s 2020 Network and Discipline Fund, drawing on the Higher Education Colleges’ Association (HECA) members’ experience, provided the HECA Academic Quality Enhancement Forum(HAQEF) with opportunities to strengthen its networks and discipline group, support their efforts to enhance teaching and learning, and produce useful insights and resources into the application of quality assurance of blended and online learning. In the pandemic period, many colleges were forced to change from a face-to-face delivery model of education and training to an online format of delivery. This disruption meant that assumptions about and plans for how the courses were to be delivered and managed had to be rapidly reviewed. With government pronouncements advising all staff to work from home where possible, the majority of internal roles and processes of colleges were also affected. The quality assurance (QA) policies, processes and procedures that were developed by colleges had to be modified to reflect this change in circumstances. This document reports on the results of a mixed methods study of QA developments that came about as a result of the initial changes enforced by the pandemic and the move to working from home. It also looked at what was learned about the management of quality in this sector during this time. Data was collected by HAQEF via a survey of QA personnel from the member colleges of HECA and follow up interviews. The survey consisted of 11 questions, one for each Core Area of Quality, as set out in the QQI Core QA Guidelines (2016). The questions asked for reflections on each provider’s experience of managing this aspect of QA, what resources or instances of good practice they could share with practitioners and which stakeholders were involved in this adaptation. The interviews asked about the measures that were undertaken to adapt QA processes in the pandemic period and what challenges could be reported from this adaptation. The report is divided into 11 chapters, with each chapter centred on a discussion of one Core Area of Quality as set out in the QQI Core QA Guidelines. An overview of the core area is developed, followed by a commentary on common experiences of the group in this area. Most sections conclude with resources, volunteered by member colleges of HECA, that was rated as useful in how the cohort navigated the management of QA in this core area.