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Dissertations / Theses on the topic 'Bending mechanics'
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1
Hua, Meng. "The mechanics of continuous roller bending of plates." Thesis, Aston University, 1986. http://publications.aston.ac.uk/11862/.
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This research initiates a study of the mechanics of four roll plate bending and provides a methodology to investigate the process experimentally. To carry out the research a suitable model bender was designed and constructed. The model bender was comprehensively instrumented with ten load cells, three torquemeters and a tachometer. A rudimentary analysis of the four roll pre-bending mode considered the three critical bending operations. The analysis also gave an assessment of the model bender capacity for the design stage. The analysis indicated that an increase in the coefficient of friction in the contact region of the pinch rolls and the plate would reduce the pinch resultant force required to end a plate to a particular bend radius. The mechanisms involved in the four roll plate bending process were investigated and a mathematical model evolved to determine the mechanics of four roll thin plate bending. A theoretical and experimental investigation was conducted for the bending of HP30 aluminium plates in both single and multipass bending modes. The study indicated that the multipass plate bending mechanics of the process varied according to the number of bending passes executed and the step decrement of the anticipated finished bend radius in any two successive passes (i.e. the bending route). Experimental results for single pass bending indicated that the rollers normally exert a higher bending load for the steady-continous bending with the pre-inactive side roll oper?tive. For the pre-bending mode and the steady-continous bending mode with the pre-active side roll operative, the former exerted the higher loads. The single pass results also indicated that the force on the side roll, the torque and power steadily increased as the anticipated bend radius decreased. Theoretical predictions for the plate internal resistance to accomplish finished bend radii of between 2500mm and 500mm for multipass bending HP30 aluminium plates, suggested that there was a certain bending route which would effectively optimise the bender capacity.
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Lazim, Duraid. "Springback in draw-bending on aerospace alloys." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79244.
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The springback phenomenon was studied by a series of draw-bend tests. These tests were done by varying the blankholding pressure with different lubrication conditions, and with different transverse anisotropy directions. The purpose is to find the forming loads, the thickness changes and the springback angles. It has been found that the springback angle after unloading depends on the amount of blankholding pressure, the material properties, and the tool geometry. Increasing the blankholding pressure almost eliminates the springback if the tensile stress caused by the blankholding pressure reaches the yield in the material. To compliment the experiments, a theoretical model has been developed by calculating the tensile strain developed from applying the blankholding pressure. This strain then was considered in finding the total bending moment.
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Lahey, Timothy. "Modelling Hysteresis in the Bending of Fabrics." Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/941.
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This thesis presents a model of fabric bending hysteresis. The hysteresis model is designed to reproduce the fabric bending measurements taken by the Kawabata Evaluation System (KES) and the model parameters can be derived directly from these property measurements. The advantage to using this technique is that it provides the ability to simulate a continuum of property curves. Results of the model and its components are compared and constrasted with experimental results for fabrics composed of different weaves and yarn types. An attempt to incorporate the bending model as part of a fabric drape simulation is also made.
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Ridge, I. M. L. "Bending-tension fatigue of wire rope." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315486.
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Corrales, Tomas P. [Verfasser]. "Local dynamics and bending mechanics of mesostructured materials / Tomas P. Corrales." Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1045264318/34.
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Derian, Edward J. "Large deformation dynamic bending of composite beams." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45678.
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The large deformation response of composite beams subjected to a
dynamic axial load was studied. The beams were loaded with a moderate
amount of eccentricity to promote bending. The study was primarily
experimental but some finite element results were obtained. Both the
deformation and the failure of the beams were of interest. The static
response of the beams was also studied in order to determine the
difference between the static and dynamic failure. Twelve different
laminate types were tested. The beams tested were 23 in. by 2 in. and
generally 30 plies thick. The beams were loaded dynamically with a
gravity-driven impactor traveling at 19.6 ft./sec. and quasi-static
tests were done on identical beams in a displacement controlled
manner. For laminates of practical interest, the failure modes under
static and dynamic loadings were identical. Failure in most of the
laminate types occurred in a single event involving 40% to 50% of the
plies. However, failure in laminates with 30° or 15° off axis plies occurred in several events. All laminates exhibited bimodular
properties. The compressive flexural moduli in some laminates was
measured to be 1/2 the tensile flexural modulus. No simple relationship
could be found among the measured ultimate failure strains of the
different laminate types. Using empirically determined flexural
properties, a finite element analysis was reasonably accurate in
predicting the static and dynamic deformation response.Master of Science
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Vandenbossche, Sacha. "Prediction of paperboard thickness and bending stiffness based on process data." Thesis, KTH, Hållfasthetslära (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-258827.
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Bending stiness is one of the most important mechanical properties in paperboard making,giving rigidity to panels and boxes. This property is currently only possible to measure bydestructive measure o the production line. The current quality control method is decient byassuming a non-realistic consistency of the paperboard properties along the machine direction.The objective of this thesis is to predict the thickness and bending stiness of the nal boardsfrom process data.Two modelling approaches are used: the rst model calculates the bending stiness from acalculated thickness, while the other one uses the measured baseboard thickness. Both modelsuse common inputs such as material properties and grammage measurement. The grammage istaken from the online baseboard measurement. The material properties come from laboratorymeasurements and assumptions. It is assumed that the density ratio between the outer andmiddle plies is constant for all product lines, at all times. The TSI of each ply is dened fromtensile testing experiments and nominal bending stiness. It is also assumed that the coatingdoes not contribute to bending stiness. The two models use equations based on laminatetheory assuming orthotropic layers and neglecting the interlaminar shear forces. The modelsuse data of two dierent natures: i.e. laboratory data and online data. Laboratory data is usedas a comparative to evaluate the models' performance of calculated values from online data.The results show various levels of prediction accuracy for dierent paperboard grades. Theaverage thickness predictions are all underestimations within a 5% error while the bendingstiness estimations vary much more from product to product; varying from 9% underestimationto 32% overestimation. The bending stiness prediction for CD is consistently higher thanfor MD for both models. Most product lines have better results with the calculated thickness,approach 1. The calculated thickness is always underestimated and bending stiness is overestimated,hence the better results with the rst approach.The most important conclusion from the models' results is the spread of laboratory measurements,when compared to the predicted values. The large variation most likely comes fromproduction, implying inconsistencies in the manufacturing process that are not accounted forby the models. These modelling approaches have failed to capture the production variationsbecause of the lack of input parameters.
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Kuriakose, Sunil. "Analysis of damage in composite laminates under bending." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12054.
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Olofsson, Kenneth. "Non destructive testing of paper products and tubes using transient bending waves." Licentiate thesis, Luleå tekniska universitet, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17165.
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Amany, Aya Nicole Marie. "Characterization of shear and bending stiffness for optimizing shape and material of lightweight beams." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112553.
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Optimized slender and short-thick beams are used in building, aircraft and machine structures to increase performance at a lower material cost. A previous work proposes an optimum shape, material and size selection model to design lightweight slender beams under pure bending. In short-thick beams, the transverse shear effects are no longer negligible and impact the choice of the optimum shape. This work extends such an optimum selection model to consider both slender and short-thick beams, by formulating the total beam stiffness design requirement as a combination of shear and bending stiffness. Selection charts are developed to show the impact of design variables, such as shape, size, material and slenderness, on the total beam stiffness. The model of total beam stiffness is validated against computational results from finite element analyses of beam models. A case study demonstrates the use of the selection charts to compare the performance of beams at the conceptual design stage.
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Forties, Robert A. "Applications of statistical mechanics to nucleic acids." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1311022751.
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Veldhuizen, Todd. "Grid Filters for Local Nonlinear Image Restoration." Thesis, University of Waterloo, 1998. http://hdl.handle.net/10012/943.
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A new approach to local nonlinear image restoration is described, based on approximating functions using a regular grid of points in a many-dimensional space. Symmetry reductions and compression of the sparse grid make it feasible to work with twelve-dimensional grids as large as 2212. Unlike polynomials and neural networks whose filtering complexity per pixel is linear in the number of filter co-efficients, grid filters have O(1) complexity per pixel. Grid filters require only a single presentation of the training samples, are numerically stable, leave unusual image features unchanged, and are a superset of order statistic filters. Results are presented for additive noise, blurring, and superresolution.
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Huang, Shuo. "A Fast Multipole Boundary Element Method for the Thin Plate Bending Problem." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368026582.
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Ahmadi-Brooghani, S. Y. "Application of the dual boundary element method to linear elastic fracture mechanics of plate-bending problems." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284777.
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Miller, Douglas Dwight. "Stress intensity factors for circumferential part-through cracks from holes in hollow cylinders subjected to tension and bending loads." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16055.
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van, Heiningen Jan Adam. "Optical tweezers electrophoresis with applications to micro-fluidic velocimetry, nano-tube bending mechanics, and polymer adsorption dynamics." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96677.
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Polymer adsorption and desorption onto micro-spheres, and the micromechanics of single polymeric nanotubes were investigated using optical tweezers.In parallel-plate micro-channels, frequency-dependent apparent micro-sphere electrophoretic mobilities were measured in various sodium chloride and calcium chloride electrolytes, and channel gap ocations. The apparent electrophoretic mobility reflects anomalous electro-osmotic flow (EOF) dynamics, which are present in compliant parallel-plate micro-channels. At limiting high and low frequencies, the EOF dynamics are those of an open and closed channel, respectively.Using optical tweezers electrophoresis (OTE), electrophoretic mobilities of single silica micro-spheres were measured during poly(ethylene oxide) adsorption and desorption. For neutral polymers, the electrophoretic mobility is a sensitive measure of adsorbed polymer hydrodynamic layer thickness. However, at the position of zero-EOF in closed parallel-plate channels, transient EOF artifacts are observed when polymers adsorb on channel walls. Such artifacts are reduced when polymers flow parallel to the electric field in parallel-plate micro-channels. In this polymer-flow configuration, low-frequency apparent electrophoretic mobilities reflect intrinsic particle mobility dynamics. Polymer hydrodynamic layer thickness and adsorbed amounts were calculated from electrophoretic mobilities using electrokinetic models and calculated equilibrium layer profiles. The growth of the hydrodynamic layer thickness reflects polymer reptation and diffusion through initially adsorbed layers, limited by polymer reconformation dynamics. Desorption kinetics were faster than expected by local equilibrium models.The bending of polymer composite nanotubes was investigated in various transverse hydrodynamic flows using multiple optical tweezers. Directed assembly of latex beads to a single nanotube was undertaken, and two of these beads were used as handles for the nanotube bending experiments. The calculated nanotube Young's moduli were in agreement with macroscale continuum models for the bulk materials.L'adsorption et la désorption de polymères sur des micro-sphères, ainsi que la micromécanique de nanotubes polymériques uniques, ont été étudiées à l'aide de pinces optiques.Dans les canaux à plaques parallèles, d'apparentes mobilités électrophoretiques de micro-sphères, dépendantes de la fréquence, ont été mesurées dans diverses concentrations d'électrolytes de chlorure de sodium et de chlorure de calcium, ainsi que dans divers sites d'instercices de canaux. La mobilité électrophorétique apparente reflète une dynamique d'écoulement électro-osmotique (EOF) anormale, laquelle est présente dans les micro-canaux à plaques parallèles souples. Aux limites de fréquences élevées et basses, les dynamiques d'EOF sont celles de canaux ouverts et fermés, respectivement. Les mobilités électrophorétiques des particules simples de silice ont été mesurées pendant l'adsorption et la désorption de poly(oxyde d'éthylène) en utilisant l'électrophorèse avec pinces optiques (OTE). Pour les polymères neutres, la mobilité électrophorétique est une mesure sensible à l'épaisseur hydrodynamique de couches de polymères adsorbés. Cependant, à la position de zéro-EOF dans les canaux fermés à plaques parallèles, on observe des artefacts d'EOF lorsque les polymères adsorbent aux murs des canaux. Ces artefacts sont réduits lorsque les polymères coulent parallèlement au champ électrique dans les micro-canaux à plaques parallèles. Dans cette configuration de l'écoulement de polymères, les mobilités électrophorétiques de basse fréquence apparentes reflètent des dynamiques de mobilité de particules intrinsèques. L'épaisseur hydrodynamique des couches de polymères et les montants adsorbés ont été calculés à partir des mobilités électrophorétiques à l'aide de modèles électrokinétiques et des profils de couches d'équilibre calculés. La croissance de l'épaisseur hydrodynamique des couches reflète la reptation et la diffusion des polymères au travers des couches initialement adsorbées, limitées par la dynamique de reconformation de polymères. La cinétique de désorption était plus rapide que celle prévue par les modèles d'équilibre local. Le recourbement des nanotubes de polymères composés a été étudié dans divers écoulements hydrodynamiques transversaux à l'aide de pinces optiques multiples. Le rassemblement des perles de latex dirigé à un simple nanotube a été entrepris, et deux de ces perles ont été employées en tant que poignées pour les expériences de recourbement de nanotubes. Les modules de Young calculés des nanotubes étaient en accord avec les modèles de continuum macroscopiques pour les matériaux en vrac.
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Scott-Emuakpor, Onome Ejaro. "Development of a novel energy-based method for multi-axial fatigue strength assessment." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196280356.
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Lynam, Thomas. "Exploitation of Redundant Inverse Term Frequency for Answer Extraction." Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/1190.
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An automatic question answering system must find, within a corpus,short factual answers to questions posed in natural language. The process involves analyzing the question, retrieving information related to the question, and extracting answers from the retrieved information. This thesis presents a novel approach to answer extraction in an automated question answering (QA) system. The answer extraction approach is an extension of the MultiText QA system. This system employs a question analysis component to examine the question and to produce query terms for the retrieval component which extracts several document fragments from the corpus. The answer extraction component selects a few short answers from these fragments. This thesis describes the design and evaluation of the Redundant Inverse Term Frequency (RITF) answer extraction component. The RITF algorithm locates and evaluates words from the passages that are likely to be associated with the answer. Answers are selected by finding short fragments of text that contain the most likely words based on: the frequency of the words in the corpus, the number of fragments in which the word occurs, the rank of the passages as determined by the IR, the distance of the word from the centre of the fragment, and category information found through question analysis. RITF makes a substantial contribution in overall results, nearly doubling the Mean Reciprocal Rank (MRR), a standard measure for evaluating QA systems.
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田中, 啓介, Keisuke TANAKA, 義明 秋庭, Yoshiaki AKINIWA, 泰樹 北, Yasuki KITA, 永次 佐藤, and Eiji SATO. "多孔質セラミックスの切欠き破壊強度のR曲線法による評価." 日本機械学会, 2003. http://hdl.handle.net/2237/9143.
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Cil, Kursad. "Free Flexural (or Bending) Vibrations Analysis Of Doubly Stiffened, Composite, Orthotropic And/or Isotropic Base Plates And Panels (in Aero-structural Systems)." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/2/1062256/index.pdf.
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In this Thesis, the problem of the Free Vibrations Analysis of Doubly Stiffened Composite, Orthotropic and/or Isotropic, Base Plates or Panels (with Orthotropic Stiffening Plate Strips) is investigated. The composite plate or panel system is made of an Orthotropic and/or Isotropic Base Plate stiffened or reinforced by adhesively bonded Upper and Lower Orthotropic Stiffening Plate Strips. The plates are assumed to be the Mindlin Plates connected by relatively very thin adhesive layers. The general problem under study is considered in terms of three problems, namely Main PROBLEM I Main PROBLEM II and Main PROBLEM III. The theoretical formulation of the Main PROBLEMS is based on a First Order Shear Deformation Plate Theory (FSDPT) that is, in this case, the Mindlin Plate Theory. The entire composite system is assumed to have simple supports along the two opposite edges so that the Classical Levy's Solutions can be applied in that direction. Thus, the transverse shear deformations and the rotary moments of inertia of plates are included in the formulation. The very thin, yet elastic deformable adhesive layers are considered as continua with transverse normal and shear stresses. The damping effects in the plates and the adhesive layers are neglected. The sets of the systems of equations of the Mindlin Plate Theory are reduced to a set of the Governing System of First Order Ordinary Differential Equations in the state vector form. The sets of the Governing System for each Main PROBLEM constitute a Two-Point Boundary Value Problem in the y-direction which is taken along the length of the plates. Then, the system is solved by the Modified Transfer Matrix Method (with Interpolation Polynomials and/or Chebyshev Polynomials)which is a relatively semi-analytical and numerical technique. The numerical results and important parametric studies of the natural modes and the corresponding frequencies of the composite system are presented.
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Jin, Hui, and Hao Wu. "Finite Element Modelling of Fracture in dowel-type timber connections." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-34783.
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Dowel-type steel to timber connections are commonly used in timber structure. The load carrying capacity and the stress distribution within the connection area are complicated and the failure behavior of a connection depends on many parameters. The main purpose of this thesis was to verify, using the data obtained from previous experiments, the conventional design method of European Code 5(EC5) (hand calculation) for dowel type joints subjected to pure bending moment and other alternative design methods based on the finite element method (FEM) including the use of the mean stress approach and the extended finite element method (XFEM). Finite element models were created in the software ABAQUS. The models were then used to predict the load bearing capacity and compare this to the experimental results. In addition parametric studies were performed with modifications of material properties and other parameters. The closest prediction in relation to the test results was obtained using XFEM where the predicted capacity was 3.82% larger than the experimental result. An extension of the mean stress method going from a 2D-formulation to a 3D-formulation was verified as well. A general conclusion drawn from this work is that the numerical modelling approaches used should also be suitable for application to complex connections and situations involving other loading situations than pure tension.
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Wang, Chuantao. "Mechanics of Bending, Flanging, and Deep Drawing on a Computer-Aided Modeling System for Predictions of Strain, Fracture, Wrinkling, and Springback in Sheet Metal Forming." Connect to resource, 1993. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1220463525.
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Perkins, John T. "ANALYTICAL STRIP METHOD FOR THIN CYLINDRICAL SHELLS." UKnowledge, 2017. http://uknowledge.uky.edu/ce_etds/57.
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The Analytical Strip Method (ASM) for the analysis of thin cylindrical shells is presented in this dissertation. The system of three governing differential equations for the cylindrical shell are reduced to a single eighth order partial differential equation (PDE) in terms of a potential function. The PDE is solved as a single series form of the potential function, from which the displacement and force quantities are determined. The solution is applicable to isotropic, generally orthotropic, and laminated shells. Cylinders may have simply supported edges, clamped edges, free edges, or edges supported by isotropic beams. The cylindrical shell can be stiffened with isotropic beams in the circumferential direction placed anywhere along the length of the cylinder. The solution method can handle any combination of point loads, uniform loads, hydrostatic loads, sinusoidal loads, patch loads, and line loads applied in the radial direction. The results of the ASM are compared to results from existing analytical solutions and numerical solutions for several examples; the results for each of the methods were in good agreement. The ASM overcomes limitations of existing analytical solutions and provides an alternative to approximate numerical and semi-numerical methods.
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Luca, Matthieu. "Quality Timber Strength Grading : A prediction of strength using scanned surface grain data and FE-analyses." Thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-14037.
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Pasha, Hasan G. "Estimation of Static Stiffnesses from Free Boundary Dynamic (FRF) Measurements." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416569956.
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Roselin, Mattias. "Utveckling av ett z-160 entresolpan." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-41410.
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A mezzanine is an extra floor which is used to be able to use more area both below and above the mezzanine plane. The Mezzanine is used in many various places, but this thesis is focusing on a mezzanine which will be used in in warehouses. A mezzanine concept is designed to fulfill a need within Brännhylte lagersystems AB, which is a mezzanine plane with Z-160 beams as a main component. A requirement specification is developed to help understanding what requirement the mezzanine should fulfill. With the help of the requirement specification a mezzanine concept is developed which fulfill these requirements. Because the mezzanine will have to withstand a lot of forces from different loads and people walking on it therefore it must be steady and secure. The maximum forces when the mezzanine reaches its maximum bending limit of beam length divided by 400 is calculated. This information can be used in the future to adapt the mezzanine depending on what weight it needs be able to withstand.Ett entresolplan är ett extra våningsplan som man kan montera upp för att utnyttja mer yta både under och över entresolplanet. En entresol används på många olika platser, detta examensarbete fokuserar dock på ett entresolplan som kommer att användas i lagerlokaler. Ett entresolkoncept designades för att uppfylla ett behov ifrån Brännhylte lagersystems AB som ville ha ett entresolplan som använder sig utav Z-160 balkar som huvudkomponent. En kravspecifikation utvecklades för att få konkreta uppgifter vad som skulle uppnås med entresolen. Med hjälp av kravspecifikationen utvecklades ett entresolkoncept som uppfyller dessa krav. Eftersom entresolen kommer att utsättas för massa olika vikter under användning samt att människor ska kunna gå på den så är den tvungen att vara tillräcklig stadig för att kunna användas säkert. Därför analyserades den maximala kraften som entresolplanet kan klara av innan den når sin nedböjningsgräns som är balklängden delat på 400. För att den informationen ska kunna användas i framtiden och för att kunna anpassa entresolen utifrån hur mycket vikt man vill att den ska klara av.
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Karasin, Abdulhalim. "An Improved Finite Grid Solution For Plates On Generalized Foundations." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604697/index.pdf.
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In many engineering structures transmission of vertical or horizontal forces to the foundation is a major challenge. As a first approach to model it may be assumed that the foundation behaves elastically. For generalized foundations the model assumes that at the point of contact between plate and foundation there is not only pressure but also moments caused by interaction between the springs. In this study, the exact stiffness, geometric stiffness and consistent mass matrices of the beam element on two-parameter elastic foundation are extended to solve plate problems. Some examples of circular and rectangular plates on two-parameter elastic foundation including bending, buckling and free vibration problems were solved by the finite grid solution. Comparison with known analytical solutions and other numerical solutions yields accurate results.
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Haynes, Robert Andrew. "Hygrothermally stable laminated composites with optimal coupling." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34671.
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This work begins by establishing the necessary and sufficient conditions for hygrothermal stability of composite laminates. An investigation is performed into the range of coupling achievable from within all hygrothermally stable families. The minimum number of plies required to create an asymmetric hygrothermally stable stacking sequence is found to be five. Next, a rigorous and general approach for determining designs corresponding to optimal levels of coupling is established through the use of a constrained optimization procedure. Couplings investigated include extension-twist, bend-twist, extension-bend, shear-twist, and anticlastic. For extension-twist and bend-twist coupling, specimens from five- through ten-ply laminates are manufactured and tested to demonstrate hygrothermal stability and achievable levels of coupling. Nonlinear models and finite element analysis are developed, and predictions are verified through comparison with test results. Sensitivity analyses are performed to demonstrate the robustness of the hygrothermal stability and couplings to deviations in ply angle, typical of manufacturing tolerances. Comparisons are made with current state-of-the-art suboptimal layups, and significant increases in coupling over previously known levels are demonstrated.
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Quesada, Díaz Raquel. "Horseshoe Bending Machine : Bending Mechanism." Thesis, Högskolan i Skövde, Institutionen för teknik och samhälle, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-9432.
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Horseshoes are manufactured metal plates developed in an extensive assortment of materials and shapes and their main function is to protect the horse’s hooves and legs against abrasion and rupture. After a certain period of time the horseshoes are lost, worn out, or the hoof needs to be treated. Horseshoeing is a repetitive time consuming process for the farrier who has to heat the horseshoe inside a forge until it reaches the required temperature and shape it with a hammer until it fits perfectly to the horses’ hoof. The main goal of this project is to develop a horseshoe bending machine able to shape the horseshoe so its shape fits perfectly the horse’s hoof. The calculation of the bending force needed to be applied to the horseshoe in order to provoke a plastic deformation will be done with Euler-Bernoulli beam theory. The bending force is then used to design and dimension each element of the bending mechanism so that it may be able to resist the stresses and prevent the parts from collapsing during its working life span. A study of the springback effect will be done followed by the analysis of the hertzian contact stresses between the rollers and the horseshoe. In addition, a clamping system is selected to constrain the movements of the horseshoe during the bending process. This machine will reduce the final user’s horse maintenance costs at the same time that makes the fitting process easier and less demanding, which will improve the farrier’s working life span and quality.
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Robertson, Galen Charles. "Quantification of Skeletal Phenotype Using Micro-CT and Mechanical Testing." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4874.
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With the vast array of genetically altered (knockout) mice becoming available there is a need for quantitative, repeatable, and efficient methodologies to characterize the phenotypic consequences of knocking out specific genes. Since knockout animals often have the ability to compensate for a single missing gene, it is important to examine the structural, material and morphological properties to obtain a thorough understanding of the changes occurring. For this project, femurs of knockout mice were first scanned using microcomputed tomography (micro-CT) to obtain high-resolution images of the trabecular bone in the distal femur, as well as cortical bone in the mid-diaphysis. After scanning, the femurs were tested to destruction in four-point bending at the mid-diaphysis about the medial lateral axis of the femur. These methodologies allowed quantification of (1) morphologic properties such as bone volume fraction, trabecular properties and 2nd moment of the area (2) structural properties such as stiffness, maximum load at failure, and post yield deformation and (3) material properties such as bone mineral density, elastic modulus and yield strength.
As part of two independent studies, two different knockout mice, cyclooxygenase-2 (COX-2 -/-) and Apolipoprotein E (APOE -/-), were examined for structure-function relationships using these methodologies. COX-2 knockout mice were found to have decreased mineral content in their femurs, and increased post yield deformation. APOE knockout mice at 10 weeks of age had decreased bone mass and structural properties. However, by 40 weeks of age APOE deficient mice caught up to and exceeded the structural properties and bone mass of their wild type counterparts.
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Döbrich, Oliver, Thomas Gereke, Olaf Diestel, Sybille Krzywinski, and Chokri Cherif. "Decoupling the bending behavior and the membrane properties of finite shell elements for a correct description of the mechanical behavior of textiles with a laminate formulation." Sage, 2014. https://tud.qucosa.de/id/qucosa%3A35608.
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Drape simulation of textiles is a field of research, which is known in the clothing sector for a long time. The ongoing development of high-performance composites made of textile reinforcements and matrix materials focus the interests on a serial production in many industrial sectors, such as aviation and automotive industries. Challenges occur mainly in the serial production technologies and in supplying concepts for the preform architecture and shape. Research aims on the acceleration of preform manufacturing and the reduction of expensive pretests. Numerical simulation models can help to improve the composite development chain with structure and process simulation. A special challenge in drape modeling is the bending behavior of textiles. This study introduces a novel approach for modeling single textile layers as laminates to gain a correct mechanical behavior, where all deformation mechanisms are uncoupled. The implementation in the finite element software LS-DYNA® is described. An algorithm is introduced which provides the membrane stiffness for each layer of a laminate to fit the measured cantilever bending stiffness of textiles in every bending direction and bending side. The calculated parameters for the laminate formulation result in the requested bending stiffness for the textile layer. The cantilever bending stiffness can be used directly for dimensioning the model.
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De, Vittorio Giancarlo. "Crack measurements in structural concrete with D.I.C. system and validation of a tensile constitutive law." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2048/.
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Compared with other mature engineering disciplines, fracture mechanics of concrete is still a developing field and very important for structures like bridges subject to dynamic loading. An historical point of view of what done in the field is provided and then the project is presented. The project presents an application of the Digital Image Correlation (DIC) technique for the detection of cracks at the surface of concrete prisms (500mmx100mmx100mm) subject to flexural loading conditions (Four Point Bending test). The technique provide displacement measurements of the region of interest and from this displacement field information about crack mouth opening (CMOD) are obtained and related to the applied load. The evolution of the fracture process is shown through graphs and graphical maps of the displacement at some step of the loading process. The study shows that it is possible with the DIC system to detect the appearance and evolution of cracks, even before the cracks become visually detectable.
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Guo, Shu. "Experimental and Numerical Investigations on the Durability and Fracture Mechanics of the Bonded Systems for Microelectronics Application." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28743.
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Water-assisted crack growth at an epoxy/glass interface was measured as a function of applied strain energy release rate, G, and temperature using a wedge test geometry. The specimens consist of two glass plates bonded with a thin layer of proprietary epoxy adhesive. The crack fronts along the epoxy/glass interfaces were measured using an optical stereomicroscope. The relationship between G and the debonding rate, v, can be measured using this method, and the threshold value of strain energy release rate, Gth, can be determined from the measured data. Two types of testing procedures were conducted in this study: ex situ, i.e., pre-conditioned wedge tests and in situ ones, in which wedges were applied before the specimens were submerged into water. A preliminary model was developed based on the thermal activation barrier concept, and allows the prediction of Gth for the temperatures beyond the testing region.
Changes in interfacial strain energy release rate caused by thermal residual stresses in a triple-layered specimen were analyzed in Chapter Three. The method is based on linear elastic fracture mechanics and simple beam theory. The curvature of a bimaterial strip was chosen to characterize the residual stress in the specimen, and the strain energy release rate, caused by both tensile and compressive residual stresses in the adhesive, was derived for an asymmetric double cantilever beam (ADCB) geometry. The contribution of the thermal residual and mechanical stress to the global energy release rate was analyzed. The thermally induced energy release rate, GT, is found to be independent of crack length, but is a function of residual stress level and geometric and material parameters of the specimen.
The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail in Chapter Four. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen's deflection if it experiences plate behavior under small loads. However, this effect diminishes when membrane behavior is dominant.
The mechanics of a single-lap joint with different boundary conditions subjected to tensile loading are investigated. Closed-form solutions are obtained for a specimen configuration considering different clamping methods. Based on the approach pioneered by Goland and Reissner, the solutions reported in this paper provide a simple but useful way to understand the effects of boundary conditions on this test geometry. The solutions in this study suggest that different grip configurations mainly affect the response of the specimens if the grip position is close to the joint edge or the loads are small. Generally, the influence caused by different gripping methods is only limited to the boundary region, and the behavior of the joint part subjected to tensile loading is almost the same as that for a simply-supported case.Ph. D.
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Pereira, Júnior Wanderlei Malaquias. "Análise numérica de estruturas de concreto com fibras utilizando mecânico do dano." Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/4377.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The work is a contribution to the mechanical numerical modeling of concrete structures with steel fibers using constitutive models based on Damage Mechanics behavior. The same, presents the formulation of a model proposed Damage admits that the concrete as initially isotropic elastic material, but with the evolution of the damage process, the material exhibits plastic deformations, anisotropy and bimodularidad induced damage. The incorporation of fibers in the modeling is performed through a homogenization procedure. The constitutive model for the concrete as well as the homogenization technique for dealing with the case of fiber concrete are implemented on a structural analysis program bar finite element laminated in layers. The parametric identification of the constitutive model together with the proposed homogenization is carried out using experimental results from the literature. Finally, numerical analysis of reinforced concrete beams reinforced with steel fibers and subjected to bending are conducted to assess the applicability of the constitutive model considered in this work. An attempt is thus contribute to the study of the deformation of fibrous concrete beams in service, in order to aggregate results and discussions in a future proposal of Brazilian technical standard for this type of structure.
O trabalho trata de uma contribuição à modelagem numérica do comportamento mecânico de estruturas de concreto com fibras de aço utilizando modelos constitutivos baseados na Mecânica do Dano. O mesmo, apresenta a formulação de um modelo de Dano proposto que admite o concreto como material inicialmente isótropo e elástico, mas com a evolução do processo de danificação o material exibe deformações plásticas, anisotropia e bimodularidade induzidas pelo dano. A incorporação das fibras na modelagem é efetuada através de um procedimento de homogeneização. O modelo constitutivo para o concreto, assim como a técnica de homogeneização para tratar do caso do concreto com fibras são implementados em um programa para análise de estruturas de barras com elementos finitos estratificados em camadas. A identificação paramétrica do modelo constitutivo, juntamente com a proposta de homogeneização, é realizada utilizando resultados experimentais encontrados na literatura. Por fim, análises numéricas de vigas de concreto armado reforçado com fibras de aço e sujeitas à flexão são conduzidas no sentido de avaliar a aplicabilidade do modelo constitutivo tratado neste trabalho. Procura-se, assim, contribuir para o estudo da deformabilidade de vigas de concreto fibroso em serviço, com o intuito de agregar resultados e discussões numa futura proposta de norma técnica brasileira para este tipo de estrutura.
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Majeed, Moiz, and Teja Geesala Rahitya Venkata. "Characterization of thin laminate interface by using Double Cantilever Beam and End Notched Flexure tests." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20852.
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This thesis is intended to identify the mode I and mode II fracture toughness to characterize the thin laminate interface by using the Double Cantilever Beam test (DCB) and End Notched Flexure test (ENF). This study’s thin laminate was Polyethylene Terephthalate and Low-Density Polyethylene (PET-LDPE), which is mostly used by packaging industries in the manufacturing of packages to store liquid food. As PET-LDPE film is very flexible and difficult to handle, DCB and ENF tests cannot be performed directly so, sheet metal (Aluminium) was used as carrier material. PET-LDPE film is placed between two aluminum plates to reduce the flexibility and perform the tests. Therefore, the Aluminium plate was also studied to find the constitutive parameters (young’s modulus (E) and mixed hardening parameters (Plastic properties)) under the tensile test and three-point bending test. From the test response, energy release rate calculation has been done for different Pre-crack lengths to validate the DCB and ENF experimental setup, study the different Pre-crack lengths, and characterize the laminate interface. Finite Element simulation (FE simulation) for those tests were carried out in AbaqusTM2020. When needed, the force versus displacement response from FE simulation was optimized against experimental response to find the required constitutive parameters (Young’s modulus, Hardening parameters, and PET-LDPE material properties). Implementing of optimization algorithm and automated simulation has been done with the help of MATLAB code. In contrast, MATLAB works as a server, and Abaqus works as a client and connected two interfaces to run the optimization. The results obtained from experiments and FE simulations were compared to the results found in the literature.
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Palecanda, Krishna Suraj Appachu. "Analysis and prediction of springback – 3 point bending and U-bending." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440153425.
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Arun, Sutham. "Finite element modelling of fracture & damage in austenitic stainless steel in nuclear power plant." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/finite-element-modelling-of-fracture-and-damage-in-austenitic-stainless-steel-in-nuclear-power-plant(031e5ceb-b3b5-4499-8094-dbe362e27ff7).html.
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The level of residual stresses in welded components is known to have a significant influence on their failure behaviour. It is, therefore, necessary to understand the combined effect of mechanical loading and residual stresses on the ductile fracture behaviour of these structures in order to provide the accurate structural safety assessment. Recently, STYLE (Structural integrity for lifetime management-non-RPV component) performed a large scale bending test on a welded steel pipe containing a circumferential through-thickness crack (the MU2 test). The purpose of this test is to study the impact of high magnitude weld residual stresses on the initiation and growth of cracks in austenitic stainless steels. This research presents the simulation part of the STYLE project which aims to develop the finite element model of MU2 test in ABAQUS to enhance the understanding and ability to predict the combined influence of mechanical loading and residual stresses on the ductile fracture behaviour of nuclear pressure vessel steels. This research employs both fracture mechanics principles (global approach) and Rousselier damage model (local approach) to study this behaviour including crack initiation and growth. In this research, the Rousselier model was implemented into ABAQUS via the user defined subroutines for ABAQUS/Standard and ABAQUS/Explicit modules, i.e. UMAT and VUMAT. The subroutines were developed based on the integration algorithm proposed by Aravas and Zhang. The validation of these subroutines was checked by comparing the FE results obtained from the implementation of these subroutines with the analytical and other benchmark solutions. This process showed that UMAT and VUMAT provide accurate results. However, the UMAT developed in this work shows convergence problems when the elements start to fail. Hence, only VUMAT was used in the construction of the finite element model of the MU2 test. As mentioned above, the results obtained from both fracture mechanics approach and Rousselier model are compared with the experimental data to validate the accuracy of the model. The results shows that both fracture mechanics approach and the Rousselier model predict similar final crack shapes which correspond closely to the test results in south direction. The other conclusions about the influence of residual stress on ductile fracture obtained from this work are also summarized in this thesis.
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Mjali, Kadephi Vuyolwethu. "Laser bending of commercially pure grade 2 titanium alloy plates: mechanisms analysis and characterisation of mechanical properties." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1021147.
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The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
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Mjali, Kadephi Vuyolwethu. "Mechanisms, analysis and characterisation of mechanical properties of laser formed commercially pure grade 2 titanium alloy plates." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1021083.
Full textAbstract:
The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
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Kubista, Kevin Dean. "Local measurements of cyclotron states in graphene." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39592.
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Multilayer epitaxial graphene has been shown to contain "massless Dirac fermions" and is believed to provide a possible route to industrial-scale graphene electronics. We used scanning tunneling microscopy (STM) and spectroscopy (STS) in high magnetic fields to obtain local information on these fermions. A new STS technique was developed to directly measure graphene's energy-momentum relationship and resulted in the highest precision measurement of graphene's Dirac cone. STS spectra similar to ideal graphene were observed, but additional anomalies were also found. Extra peaks and an asymmetry between electron and hole states were shown to be caused by the work function difference between the Iridium STM tip and graphene. This tip effect was extracted using modeled potentials and performing a least square fit using degenerate perturbation theory on graphene's eigenstates solved in the symmetric gauge. Defects on graphene were then investigated and magnetic field effects were shown to be due to a mixture of potential effect from defects and the tip potential. New defect states were observed to localize around specific defects, and are believed to interact with the STM tip by Stark shifting in energy. This Stark shift gives a direct measurement of the capacitive coupling between the tip and graphene and agrees with the modeled results found when extracting the tip potential.
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Viszlay, Viliam. "Ohýbaná tělesa: Numerická podpora v software ANSYS." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240183.
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The aim of the thesis is the investigation of fracture-mechanics parameters on specimens made of quasi-brittle materials. The principles of two-parameter fracture mechanics are used. Couple of numerical simulations were done and their outputs are used for two main analysed specimen geometries. For simulations the finite element method software ANSYS is used. In the first part, the thesis focuses on bended specimens. The influence of different geometric parameters on fracture mechanics behaviour of cracked specimen is investigated. For model calibration the outputs of other authors are used. In the second part the specimens for modified compact-tension test (CT test) are analysed. Similar to the first part, the influence of geometric parameters of the specimen (in this case, the specimen size) on fracture mechanics parameters were investigated. The modified CT test was derived from CT test which is commonly used for metal materials testing as the suitable geometry for cement-based composite materials testing. The outputs of both parts are calibration polynomials, which are expressions obtained for different specimen geometries, giving the value of fracture mechanics parameter as the function of specimen geometry. As the example, calibration curves are used to obtain fracture toughness of tested material using the outputs from recent experiment.
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Raheem, Hassan Hassan [Verfasser]. "Plasto-Mechanical Model of Tube Bending in Rotary Draw Bending Process / Hassan Raheem Hassan." Aachen : Shaker, 2017. http://d-nb.info/1138178209/34.
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Amireghbali, Aydin. "Elastic Analysis Of A Circumferential Crack In An Isotropic Curved Beam Using Modified Mapping-collocation Method." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615675/index.pdf.
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The modified mapping-collocation (MMC) method is applied to analyze a circumferential
crack in an isotropic curved beam. Based on the method a MATLAB code was developed to
obtain the stress field. Incorporating the stress correlation technique, the opening and sliding
fracture mode stress intensity factors (SIF)s of the crack for the beam under pure bending
moment load case are calculated.
The MMC method aims to solve two-dimensional problems of linear elastic fracture mechanics
(LEFM) by combining the power of analytic tools of complex analysis (Muskhelishvili
formulation, conformal mapping, and extension arguments) with simplicity of applying the
boundary collocation method as a numerical solution approach.
Qualitatively, a good agreement between the computed stress contours and the fringe shapes
obtained from the photoelastic experiment on a plexiglass specimen is observed. Quantitatively,
the results are compared with that of ANSYS finite element analysis software. The
effect of crack size, crack position and beam thickness variation on SIF values and mode
mixity is investigated.
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Didier, Jérôme. "Etude du comportement au flambage des coques cylindriques multicouches métal/matériau mousse sous chargements combinés pression interne/cisaillement/flexion." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0069/document.
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De nombreuses structures spatiales telles que les lanceurs sont équipées d’une mousse de protection thermique. Cette couche de matériau extrêmement léger présente d’excellentes propriétés d’isolation thermique mais des caractéristiques mécaniques très faibles. Il est ici proposé d’analyser le comportement au flambage de ce type de construction où une fine et légère structure, coque cylindrique en aluminium avec un ratio R/t de 665, est recouverte par une épaisse couche de mousse de faible densité. Afin d'évaluer l'effet du comportement au flambage de ce type de coque multicouche, des essais expérimentaux et numériques sont réalisés sur des cylindres faiblement pressurisés soumis à du cisaillement et de la flexion. Ce cas de charge représente la configuration « cas sol », d’un lanceur sur le pas de tir, dans l’attente du lancement, et soumis à des charges mécaniques extrêmes générées par le ventMany space structures such as launchers are equipped with a thermal foam protection barrier. This layer, of extremely light material generally exhibits excellent properties of heat insulation but very weak mechanical characteristics. This study is devoted to the analysis of the buckling behavior of this hybrid wall construction where the skin of a very thin light-weight structure, an aluminum cylindrical shell with an R/t ratio of about 665, is coated with a thick layer of foam with a low material density. To gauge the effect on the buckling behavior of this kind of multilayered shells, experimental and numerical tests are conducted on slightly pressurized cylindrical shells submitted to shear load. This load configuration represents the case of a rocket on the launching pad, waiting to be launched, and submitted to mechanical loads induced by the wind
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Kaczmarek, Adam S. "Sensing bending in a compliant biomimetic fish." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36753.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 34).
This thesis examines the problem of sensing motion in a compliant biomimetic device. Specifically, it will examine the motion of a tail in a biomimetic fish. To date, the fish has been an open-loop system, the motion of the tail only controlled by the input to a servo motor. By sensing the motion of the tail, a closed loop system can be implemented to control the motion. In order to determine the best sensor to use, a number of options were examined. We decided to use foil bend sensors. The silicone used in the prototype was too compliant and therefore the sensors did not bend at a magnitude great enough to provide sufficient information about the bending of the tail. Upon further development and use of the sensors in stiffer silicones, they could be used in a closed loop system.
by Adam S. Kaczmarek.
S.B.
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OLARD, François. "COMPORTEMENT THERMOMÉCANIQUE DES ENROBÉS BITUMINEUX À BASSES TEMPÉRATURES. Relations entre les propriétés du liant et de l'enrobé." Phd thesis, INSA de Lyon, 2003. http://tel.archives-ouvertes.fr/tel-00006050.
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Cette thèse s'inscrit dans le cadre d'une collaboration entre l'Ecole Nationale des TPE et les entreprises routières APPIA et EUROVIA. La société pétrolière TOTAL a également été associée à l'étude. Ce travail traite de l'analyse du comportement thermo-mécanique des enrobés bitumineux aux températures basses et intermédiaires et vise à mettre en évidence les relations entre les propriétés des liants et des enrobés. Un large travail expérimental de laboratoire a été réalisé en vue de répondre à ces deux objectifs. Il s'agit notamment de mieux cerner les critères existants de caractérisation des liants, voire d'en proposer de nouveaux, en relation avec le comportement en place des enrobés.Après une étude bibliographique sur la rhéologie et les propriétés thermo-mécaniques des bitumes, des mastics et des enrobés bitumineux, le travail expérimental mené aussi bien dans le domaine des petites déformations que des grandes déformations, est exposé.
Le comportement à basse température des bitumes a été évalué avec trois tests fondamentaux largement répandus : i)l'essai de module complexe, ii)l'essai de fluage au BBR, iii)l'essai de traction directe SHRP à vitesse de déformation constante et températures constantes. En outre, un nouvel essai de fissuration, consistant en un essai de flexion trois points sur éprouvettes de bitume préentaillées, a été développé à l'ENTPE. Les paramètres de ténacité et d'énergie de rupture des bitumes à basses températures ont pu être déterminés en utilisant les hypothèses de la MLR (Mécanique Linéaire de la Rupture).
Le comportement thermo-mécanique des enrobés bitumineux à basse température a été étudié en réalisant i)des essais de module complexe, ii)des mesures du coefficient de dilatation-contraction thermique, iii)des essais de traction à vitesses de déformation constantes, iv)ainsi que des essais de retrait thermique empêché.
Tout d'abord, des liens pertinents entre les propriétés des liants et des enrobés, et des caractéristiques suffisamment discriminantes au regard des propriétés à basse température des enrobés ont été mis en évidence. Ensuite, l'analyse a consisté à effectuer un travail de modélisation du comportement des liants et des enrobés, en petites et grandes déformations.
Un modèle rhéologique monodimensionnel, qui consiste en une généralisation du modèle analogique de Huet-Sayegh, a été développé dans le domaine des petites déformations. Ce modèle, appelé modèle “2S2P1D”, permet de simuler correctement à la fois le comportement visco-élastique linéaire des bitumes et celui des enrobés bitumineux. A partir de ce modèle, une transformation originale –indépendante du modèle– permettant de prédire le module complexe de l'enrobé à partir de celui du liant est proposée, puis validée.
Enfin, la dernière partie de cette thèse est consacrée à la loi généralisée monodimensionnelle “DBN” (Di Benedetto-Neifar) à partir de laquelle un programme a été développé sur l'interface Visual Basic du logiciel Excel. Ce programme constitue un outil simple de prévision du comportement de l'enrobé bitumineux sous diverses sollicitations (mécaniques et/ou thermiques). Ce modèle rhéologique permet de faire le lien entre les petites et les grandes déformations. Des simulations d'essais de traction à vitesses de déformation constantes, ainsi que des simulations d'essais de retrait thermique, monotones ou cycliques, sont enfin présentées.
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Iosilevich, Alexander G. "An analysis of finite elements for plate bending problems." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38152.
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Hale, Michael Bruce. "Dynamic analysis and control of a roll bending process." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/35332.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 122-124.
by Michael Bruce Hale.
M.S.
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Harris, David L. S. M. Massachusetts Institute of Technology. "Characterization of Nb₃Sn superconducting strand under pure bending." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33899.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. [247]-252).
Characterizing the strain-dependent behavior of technological Nb₃Sn superconducting strand has been an important subject of research for the past 25 years. Most of the effort has focused on understanding the uniaxial tension and compression effects and applying this information to improve predictive scaling laws which are used for superconducting magnet design. However, the strain state of the strand in an actual magnet winding is often a complicated combination which includes uniaxial tension or compression, bending, and transverse compression. A bending mechanism was designed and used to characterize the bending strain behavior of two different types of Nb₃Sn superconducting strand at 4.2K in a magnetic field. Results showed that the critical current of the strand increased up to an applied bending strain between 0.2-0.3% and then decreased with continued applied strain.
by David L. Harris.
S.M.
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Khan, Md Mahfujul H. "IMPACT PERFORMANCE AND BENDING BEHAVIOR OF COMPOSITESANDWICH STRUCTURES IN COLD TEMPERATURE ARCTIC CONDITION." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1580471034677078.
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