Tesis sobre el tema "Shear Failure"
Siga este enlace para ver otros tipos de publicaciones sobre el tema: Shear Failure.
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores tesis para su investigación sobre el tema "Shear Failure".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore tesis sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Nie, Xin. "Failure mechanism of rolling shear failure in cross-laminated timber". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55299.
Texto completoResumen
Wood as building material is gaining more and more attention in the 21st century due to its positive attributes such as light weight, renewability, low carbon footprint and fast construction period. Cross-laminated timber (CLT), as one of the new engineered wood products, requires more research emphasis since its mechanical performance can allow CLT to be utilized in massive timber structures. This thesis focuses on revealing one of the key failure mechanisms of CLT, which is usually referred to as the rolling shear failure. The scientific research conducted in this thesis combined both analytical modelling and experimental material testing. The stresses in CLT cross-layers obtained from a finite-element model were analyzed to differentiate various failure modes possible. Tension perpendicular to grain stress was found to cause cross-layer failure in combined with the rolling shear stress. Experimentally, specimens prepared from 5-layer CLT panels were tested under center-point bending condition. Detailed failure mechanism of CLT cross-layers were recorded with high speed camera to capture the instant when initial failure happened. It is evident that some of the specimens failed in tension perpendicular to grain which verified the modelling results. Variables such as the rate of loading and the manufacturing clamping pressure were designed in experiments to compare their influence to the failure of CLT specimens. In this research, the failure of CLT cross-layer was updated to a combined consequence of both rolling shear stress and tension perpendicular to grain stress. Future research topics and product improvement potentials were given by the end of this thesis.Forestry, Faculty of
Graduate
2
Chana, Palvinder Singh. "Shear failure of reinforced concrete beams". Thesis, University College London (University of London), 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282869.
Texto completo
3
Raischel, Frank. "Fibre models for shear failure and plasticity". [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29619.
Texto completo
4
Johnsson, Helena. "Plug shear failure in nailed timber connections : avoiding brittle and promoting ductile failures /". Luleå : Univ, 2004. http://epubl.luth.se/1402-1544/2004/03.
Texto completo
5
Li, Xu Dong. "Simulation of Progressive Shear Failure in Railway Foundation". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41498.
Texto completoResumen
Railways are one of the largest transportation networks in the world that play an important role in the mass transportation of both the passengers and freight. The speed of trains and as well as the axial load carrying capacity have been increasing significantly during the past few decades to keep in pace with the population and economy growth and to compete with other modes of transportation such as the road, air and water transportation system. Billions of dollars are spent annually for maintenance of rail tracks in the world. The efficient and optimum use of these funds is a challenging task that demands innovative and cutting edge technologies in railway engineering.
The railway subgrade is an important part of railway foundation and should be capable of providing a suitable base supporting the ballast and subballast to accommodate the stresses due to traffic loads without failure or excessive deformation. The progressive shear failure is a well-known and age old challenging problem for railways over the world for centuries. The subgrade of railway track which typically constitutes of fine-grained material tends to fail through the accumulation of soil movements up- and sideward developing a path for the least resistance along which progressive shear failure occurs under repeated train-induced loads and due to the effects of climate factors. To-date, limited number of studies have addressed failure mechanism associated with the progressive shear failure, especially using the mechanics of unsaturated soils.
In this thesis, a novel and first of its kind, Visual Basic program developed in AutoCAD environment based on Mohr-Coulomb failure criteria and unsaturated soil mechanics theory. This program is capable of taking account of the influence of matric suction and simulate progressive shear failure in the subgrade under moving train. Simulation results suggest several parameters that include stress distribution, matric suction, cohesion, coefficient of lateral earth pressure at rest, and coefficient of residual friction as well as the angle of internal friction have a significant effect on the progressive shear failure and the shape of failure planes in the subgrade. The progressive shear failure in subgrade can be reduced by increasing matric suction, cohesion, coefficient of lateral earth pressure at rest, and coefficient of residual friction as well as the angle of internal friction, and optimizing combination of these parameters.
The simulation results suggest the progressive shear failure can be well simulated with the Mohr-Coulomb failure criteria. Several suggestions are made for railway subgrade construction and maintenance based on the results of this study.
6
Zhang, Xuesong y n/a. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion". Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051104.153239.
Texto completoResumen
Failure criteria play a vital role in the numerical analysis of reinforced concrete structures. The current failure criteria can be classified into two types, namely the empirical and theoretical failure criteria. Empirical failure criteria normally lack reasonable theoretical backgrounds, while theoretical ones either involve too many parameters or ignore the effects of intermediate principal stress on the concrete strength. Based on the octahedral shear stress model and the concrete tensile strength under the state of triaxial and uniaxial stress, a new failure criterion, that is, the simplified unified strength theory (UST), is developed by simplifiing the five-parameter UST for the analysis of reinforced concrete structures. According to the simplified UST failure criterion, the concrete strength is influenced by the maximum and intermediate principal shear stresses together with the corresponding normal stresses. Moreover, the effect of hydrostatic pressure on the concrete strength is also taken into account. The failure criterion involves three concrete strengths, namely the uniaxial tensile and compressive strengths and the equal biaxial compressive strength. In the numerical analysis, a degenerated shell element with the layered approach is adopted for the simulation of concrete structures. In the layered approach, concrete is divided into several layers over the thickness of the elements and reinforcing steel is smeared into the corresponding number of layers of equivalent thickness. In each concrete layer, three-dimensional stresses are calculated at the integration points. For the material modelling, concrete is treated as isotropic material until cracking occurs. Cracked concrete is treated as an orthotropic material incorporating tension stiffening and the reduction of cracked shear stiffness. Meanwhile, the smeared craclc model is employed. The bending reinforcements and the stirrups are simulated using a trilinear material model. To verify the correctness of the simplified UST failure criterion, comparisons are made with concrete triaxial empirical results as well as with the Kupfer and the Ottosen failure criteria. Finally, the proposed failure criterion is used for the flexural analysis of simply supported reinforced concrete beams. Also conducted are the punching shear analyses of single- and multi-column-slab connections and of half-scale flat plate models. In view of its accuracy and capabilities, the simplified UST failure criterion may be used to analyse beam- and slab-type reinforced concrete structures.
7
Zhang, Xuesong. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365777.
Texto completoResumen
Failure criteria play a vital role in the numerical analysis of reinforced concrete structures. The current failure criteria can be classified into two types, namely the empirical and theoretical failure criteria. Empirical failure criteria normally lack reasonable theoretical backgrounds, while theoretical ones either involve too many parameters or ignore the effects of intermediate principal stress on the concrete strength. Based on the octahedral shear stress model and the concrete tensile strength under the state of triaxial and uniaxial stress, a new failure criterion, that is, the simplified unified strength theory (UST), is developed by simplifiing the five-parameter UST for the analysis of reinforced concrete structures. According to the simplified UST failure criterion, the concrete strength is influenced by the maximum and intermediate principal shear stresses together with the corresponding normal stresses. Moreover, the effect of hydrostatic pressure on the concrete strength is also taken into account. The failure criterion involves three concrete strengths, namely the uniaxial tensile and compressive strengths and the equal biaxial compressive strength. In the numerical analysis, a degenerated shell element with the layered approach is adopted for the simulation of concrete structures. In the layered approach, concrete is divided into several layers over the thickness of the elements and reinforcing steel is smeared into the corresponding number of layers of equivalent thickness. In each concrete layer, three-dimensional stresses are calculated at the integration points. For the material modelling, concrete is treated as isotropic material until cracking occurs. Cracked concrete is treated as an orthotropic material incorporating tension stiffening and the reduction of cracked shear stiffness. Meanwhile, the smeared craclc model is employed. The bending reinforcements and the stirrups are simulated using a trilinear material model. To verify the correctness of the simplified UST failure criterion, comparisons are made with concrete triaxial empirical results as well as with the Kupfer and the Ottosen failure criteria. Finally, the proposed failure criterion is used for the flexural analysis of simply supported reinforced concrete beams. Also conducted are the punching shear analyses of single- and multi-column-slab connections and of half-scale flat plate models. In view of its accuracy and capabilities, the simplified UST failure criterion may be used to analyse beam- and slab-type reinforced concrete structures.Thesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
Full Text
8
Zhou, Guolin y 周國林. "Complete stress-strain behavior for shear failure of rocks". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B42575679.
Texto completo
9
Zhou, Guolin. "Complete stress-strain behavior for shear failure of rocks". Click to view the E-thesis via HKUTO, 1999. http://sunzi.lib.hku.hk/hkuto/record/B42575679.
Texto completo
10
Nazir, Shahid. "Studies on the failure of unreinforced masonry shear walls". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/82792/1/Shahid_Nazir_Thesis.pdf.
Texto completoResumen
This thesis aims at studying the structural behaviour of high bond strength masonry shear walls by developing a combined interface and surface contact model. The results are further verified by a cost-effective structural level model which was then extensively used for predicting all possible failure modes of high bond strength masonry shear walls. It is concluded that the increase in bond strength of masonry modifies the failure mode from diagonal cracking to base sliding and doesn't proportionally increase the in-plane shear capacity. This can be overcome by increasing pre-compression pressure which causes failure through blocks. A design equation is proposed and high bond strength masonry is recommended for taller buildings and/ or pre-stressed masonry applications.
11
Lee, Jaeman. "Flexural and Shear Failure Mechanisms of Precast/Prestressed Concrete Members". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174917.
Texto completo
12
Baptist, Olu. "Powder cohesion and stick-slip failure in a shear cell". Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843467/.
Texto completoResumen
The overriding aim of this project is to gain an understanding of the flowability of powders. Industrial interest for this study was provided by Centura Foods, U.K. who supplied three samples for study. These powder samples are starch, maltodextrin and hydrolysed vegetable protein (HVP). The first half of this project addresses the influence of adsorbed moisture on the flowability of these powders with strong emphasis on the value of cohesion. There is evidence in the literature suggesting that the prevailing relative humidity has an influence on powder cohesion. The general trend indicates an increase in cohesion with an increase in relative humidity. Some attempts have been made in the literature to relate this humidity dependence to powder properties notably the propensity for water sorption. Material characterisation studies revealed the morphological and surface characteristics of the samples through Scanning Electron Microscopy (SEM). It revealed the angular and amorphous appearances of the maltodextrin and HVP particles respectively. The starch particles appear to have distinct groups of larger and smaller particles. The larger particles are ellipsoidal and the smaller particles are near perfectly spherical. Water sorption studies using a gravimetric analyzer showed that the starch and maltodextrin powders had on average 19 and 25 % mass increase respectively when subjected to a relative humidity change from 0 % to 90 %. However, the HVP powders had the largest percentage mass uptake of over 100 %. This was supported by in-situ humidity microscopy results that showed significant swelling with dissolution when exposed to saturated air. Comparatively but to a lesser degree, similar behaviour was observed for maltodextrin powders. Starch particles also exhibited swelling under saturation conditions. Powder flowability studies were carried out using a Jenike-type shear cell. Commissioning of the shear cell was conducted using limestone powders. Measurements were carried out at dry, ambient and saturated conditions. This was facilitated by a newly designed in-situ humidity control system. Values of cohesion were obtained by constructing a family of yield loci for each material. HVP powders showed a significant increase in cohesion with humidity. Maltodextrin and starch powders showed no significant change in cohesion with humidity. However, both powders were more difficult to stir with changes to the relative humidity thereby highlighting that the shear cell in this study is not sensitive enough to detect the changes in fiowability. The phenomenon of stick-slip failure was observed for starch at all humidities, and for maltodextrin but only at 0 %RH. Published information implies that stick-slip behaviour is linked to the rate of stored elastic energy and frictional dissipation. A study of stick-slip observed with starch powder was conducted under four levels of consolidation over four different velocities. A mathematical model has been applied which describes the various stages of stick-slip and consequently identifying the parameters that influence stick-slip. A comparison of the model with experimental values highlighted the effectiveness of the model. Results from this study identified the levels of consolidation and drive velocities as the governing parameters influencing stick-slip, with the level of consolidation argued to have a greater impact. It was anticipated that the study would identify conditions to eliminate stick-slip. Although this was not achieved, the study however presents O, a measureable which represents the extent of stick-slip. On this basis, stick-slip is argued to be minimized under a combination of high consolidation loads and velocities. The study has identified possible areas for future work. Firstly, some irregular trends were observed when comparing some results under the two intermediate consolidation levels (4 kN/m2 and 12.5 kN/m2). It is possible to further investigate stick-slip failure with smaller increments to the level of consolidation. It is possible to add to the work done in this study by investigating the effects of higher consolidation and velocities and testing on other materials. Finally, a parallel study repeating the work done in this study (and incorporating the proposed ideas for future work) using a different type of shear tester remains a good candidate for research.
13
Barsoum, Imad. "Ductile failure and rupture mechanisms in combined tension and shear". Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4064.
Texto completo
14
Diangha, Maurice Nkinyam Boh. "Punching shear modes of failure in impacted reinforced concrete beams". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245559.
Texto completo
15
Kuang, Jun Shang. "Punching shear failure of concrete slabs with compressive membrane action". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240241.
Texto completo
16
Kaneko, Yoshio. "Modelling of shear-off failure of concrete : fracture mechanics approach". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13200.
Texto completo
17
Salim, Wijaya. "Punching shear failure in reinforced concrete slabs with membrane restraint". Thesis, University of Bristol, 2006. http://hdl.handle.net/1983/e2a8f32a-0fc2-40ee-8183-a9100122e429.
Texto completo
18
Fan, Dongliang Fan. "Lap-shear test: from “Kendall’s steady peeling” to “catastrophic failure”". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1523316028088973.
Texto completo
19
Oluwabusi, Oludare E. "Assessing the In-plane Shear Failure of GFRP Laminates and Sandwich Structures". University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544528074090494.
Texto completo
20
Hayward, Benjamin James. "Investigation of road base shear strains using in-situ instrumentation". Thesis, University of Canterbury. Civil Engineering, 2006. http://hdl.handle.net/10092/1164.
Texto completoResumen
The large majority of New Zealand's road network is constructed from thin surfaced unbound flexible pavements where a granular layer provides the main structural strength of the pavement. The current New Zealand empirical design theory states that permanent deformation should largely be attributed to the subgrade and that shape loss in the granular layers is simply a consequence of a previously deformed subgrade. However, recent research and field trials have indicated that basecourse shear strains may be a large contributor to rutting in unbound granular layers. The purpose of this investigation was to determine whether the shear strains induced under heavy vehicle loads can be accurately measured using in-situ induction coils and whether the shear strains are related to permanent pavement deformation. In this investigation a rosette configuration of free floating induction coils was designed to measure principal basecourse shear strains. The principal strains were then used to construct Mohr's circle of strain in order to calculate the maximum shear strain occurring in the granular layer. The rosettes were installed in two full scale test pavements at the Canterbury Accelerated Pavement Testing Indoor Facility (CAPTIF). The pavements were loaded with an 8 tonne dual wheel axle load for 1 million and 600,000 load applications respectively and strain and rut depth testing occurred periodically throughout the test life. The research showed that the rosette coil arrangement was a feasible and accurate device for measuring in-situ shear strains in granular pavement layers. Finite element modelling confirmed the accuracy of the system. The results from the two CAPTIF pavements showed that there was a strong linear relationship between the magnitude of the basecourse shear strain and the rut depth at the end of the post construction compaction period. The investigation also showed that shear strain magnitudes in the region of 5000µƐ result in rapid shear failure in the granular layer. In addition, after the post construction compaction period had finished, the rate of change of shear strain was proportional to the rate of change of rut development. The results indicated that there was approximately a 4:1 ratio between the rate of change in rut depth and the rate of change in shear strain after the initial post construction period. Investigations into the effect of load magnitude on the magnitude of the basecourse shear strain showed that a linear relationship existed between the two parameters. Further to this, load location testing revealed that for a dual wheel configuration, 50mm of lateral wheel variation either side of a point of interest was the maximum allowable movement that would result in similar strain measurements. The research highlighted the dominance of the longitudinal tensile strain and shear strain over the vertical compressive strain within granular layers. As a result, these pavement responses should be considered in further granular pavement research in addition to the commonly used vertical compressive strains.
21
Kara, Emre. "A Numerical Study On Block Shear Failure Of Steel Tension Members". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606359/index.pdf.
Texto completoResumen
Block shear is a limit state that should be accounted for during the design of the steel tension members. This failure mechanism combines a tension failure on one plane and a shear plane on a perpendicular plane. Although current design specifications present equations to predict block shear load capacities of the connections, they fail in predicting the failure modes. Block shear failure of a structural connection along a staggered path may be the governing failure mode. Code treatments for stagger in a block shear path are not exactly defined. A parametric study has been conducted and over a thousand finite element analyses were performed to identify the parameters affecting the block shear failure in connections with multiple bolt lines and staggered holes. The quality of the specification equations were assessed by comparing the code predictions with finite element results. In addition, based on the analytical findings new equations were developed and are presented herein.
22
Pani´c, Nebojsa. "High strain rate-induced failure in steels at high shear strains". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/MQ45106.pdf.
Texto completo
23
Minnaar, Karel. "Comparison and analysis of dynamic shear failure behavior of structural metals". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/16340.
Texto completo
24
Kunieda, Minoru, Naoshi Ueda, Yoshihito Yamamoto, Hikaru Nakamura y Yasar Hanifi Gedik. "Effect of Stirrups on the Shear Failure Mechanism of Deep Beams". 日本コンクリート工学会, 2012. http://hdl.handle.net/2237/20960.
Texto completo
25
Barragán, Bryan Erick. "Failure and toughness of steel fiber reinforced concrete under tension and shear". Doctoral thesis, Universitat Politècnica de Catalunya, 2002. http://hdl.handle.net/10803/5905.
Texto completoResumen
La tesis se enmarca en la caracterización, a nivel material, de la fractura del hormigón reforzado con fibras de acero (SFRC) bajo solicitaciones de tracción y cortante, y sobre la determinación de parámetros que representan la tenacidad del material sometido a esos dos modos de carga. Asimismo, se han realizado ensayos hasta rotura por cortante de elementos estructurales a escala real, los cuales se han analizado utilizando formulaciones existentes en distintos códigos de diseño.El comportamiento a tracción uniaxial del hormigón reforzado con fibras de acero se caracteriza utilizando cilindros entallados, elaborados con hormigones de resistencia normal y alta, con y sin fibras de acero. La metodología se extiende también para testigos extraídos de elementos de mayor tamaño. Los resultados se utilizan para definir parámetros de tenacidad y resistencia equivalentes de post-pico utilizables para representar el comportamiento del material y para un posible diseño estructural. Además, se desarrolla un estudio paramétrico experimental, que considera diferentes variables del ensayo y forma de probetas, para definir una configuración confiable del ensayo. Se analizan los modos de rotura observados y se evalúa la respuesta tensión-ancho de fisura. Asimismo, se propone una relación tensión-apertura de fisura característica para el diseño y análisis estructural. El comportamiento a tracción uniaxial se compara también con el de flexión y tracción por compresión diametral.
La fractura por cortante se estudia a nivel material, en hormigones de resistencia normal y alta, con y sin fibras de acero, utilizando la configuración de cortante directo denominada push-off. Se analizan el modo de rotura y la respuesta tensión-desplazamiento. Además, se definen parámetros basados en la tenacidad y tensiones equivalentes de cortante para una posible utilización en el diseño estructural.
Con el fin de obtener resultados que validen la utilización de las fibras de acero como refuerzo de cortante y al mismo tiempo estudiar la fractura por cortante a nivel estructural, se han realizado ensayos a escala real sobre vigas de sección rectangular y en T. Se analizan las respuestas carga-flecha y carga-ancho de fisura de vigas rectangulares de hormigón reforzado con fibras de acero variando su altura y de vigas T variando las dimensiones del ala. Los resultados obtenidos experimentalmente se utilizan para verificar la aplicabilidad de los métodos de diseño existentes en el caso del hormigón reforzado con fibras de acero. Además, se presenta una propuesta para el diseño a cortante basada en la respuesta tensión-desplazamiento relativo obtenida a partir del ensayo push-off de cortante directo.
The thesis deals with the characterization of the failure of steel fiber reinforced concrete (SFRC) in tension and shear, on the material level, and the determination of parameters that represent the toughness in these two modes of failure. Tests have been performed on large-scale beams failing under shear failure, which have been analyzed using existing design code formulas. The toughness parameters determined from the material are used in the design against such failure.
The uniaxial tensile behavior of SFRC is characterized using notched cylinders of normal and high strength concretes, with and without steel fibers. The methodology is also extended to cores extracted from large elements. Results are used to define toughness parameters and equivalent post-peak strengths to be used for representing the material behavior and for possible structural design. Furthermore, a parametric study considering different test variables and specimen shape is carried out in order to define a reliable test configuration. The observed modes of failure are analyzed and the stress-crack width response is evaluated. Also, a characteristic stress-crack width response is proposed for structural analysis and design. The uniaxial tension behavior is also compared with that of flexural and splitting-tension.
The shear failure is studied using the direct shear push-off test configuration, in normal and high strength concretes with and without steel fibers. The mode of failure and the stress-slip and stress-crack opening responses are analyzed. Toughness parameters and equivalent shear strengths based on the test results are defined for structural design.
In order to provide results for validating the use of steel fibers as shear reinforcement and for studying shear failure at the structural level, full-scale tests on rectangular and T-beams were performed. The load-deflection and load-crack width responses are analyzed and compared with results of plain concrete beam tests. The experimentally-obtained results are used to evaluate the applicability of existing design methods for steel fiber reinforced concrete. Furthermore, a proposal for shear design based on the shear stress versus slip relationship from the push-off shear test is presented.
26
Swaminathan, Palanivel. "Numerical study of the occurrence of adiabatic shear banding without material failure". Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3750.
Texto completoResumen
Segmented chips that arise as a result of formation of adiabatic shear bands are common in high-speed machining of harder alloys. Analytical models describing the mechanics of segmented chip formation have been developed, and these models do not assume or require failure in the material. Most of the finite element (FE) studies of segmented chip formation in the literature always include failure in the material. This thesis presents a numerical study of the occurrence of adiabatic shear banding without material failure. Here, the mechanical properties of hardened 4340 steel was used as a base line, and Johnson and Cook material model for this material were modified to make the material more prone to shear banding. Simulations were performed in two different commercial FE packages: ABAQUS/Explicit and LS-DYNA. The arbitrary Lagrangian-Eulerian (ALE) approach in ABAQUS/Explicit showed shear banding when mass scaling factor was 100. The same simulation did not show shear banding once the mass scaling was removed. Also, the simulations with accelerated thermal softening kept crashing; likely due to the onset of shear banding causing too much mesh distortion. Since steady state was not achieved with any of these simulations, it is hard to say exactly how the intensity of shear banding changes with material properties.
Finite element studies in the recent literature, where researchers have shown shear banding through strain softening without material failure using the updated Lagrangian approach, were repeated with ALE in ABAQUS. With the reduction in the parameter controlling the curvature based mesh refinement, shear banding has been successfully simulated in ABAQUS. ALE approach in ABAQUS did not produce the same chip geometry shown in literature because the simulations failed since the mesh was not able to reform to
vii
a large extent and produce concave shapes as we see in serrated chips. Mass scaling with a factor of 100 did not affect the result. It should be noted that the strain seems to diffuse with the increase in the element size. So, smaller elements are needed to better capture the strains along the PSZ.
Lagrangian analysis with a parting-layer approach in LS-DYNA showed shear banding for different plastic properties of the material and no shear banding for others. Observations of the effect of different material and mesh parameters on the shear banding intensity have been made from the simulations and future research are proposed.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering.
27
Chui, Clarence 1970. "Interface failure under local normal and shear stress conditions : initiation and propagation". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11779.
Texto completo
28
Sarzynski, Melanie Diane. "Carbon foam characterization: sandwich flexure, tensile and shear response". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/55.
Texto completoResumen
The focus of this research is characterizing a new material system composed of carbon and graphite foams, which has potential in a wide variety of applications encompassing aerospace, military, offshore, power production and other commercial industries. The benefits of this new material include low cost, light weight, fire-resistance, good energy absorption, and thermal insulation or conduction as desired. The objective of this research is to explore the bulk material properties and failure modes of the carbon foam through experimental and computational analysis in order to provide a better understanding and assessment of the material for successful design in future applications. Experiments are conducted according to ASTM standards to determine the mechanical properties and failure modes of the carbon foam. Sandwich beams composed of open cell carbon foam cores and carbon-epoxy laminate face sheets are tested in the flexure condition using a four point setup. The primary failure mode is shear cracks developing in the carbon foam core at a critical axial strain value of 2,262 με. In addition to flexure, the carbon foam is loaded under tensile and shear loads to determine the respective material moduli. Computational analysis is undertaken to further investigate the carbon foam's failure modes and material characteristics in the sandwich beam configuration. Initial estimates are found using classical laminated plate theory and a linear finite element model. Poor results were obtained due to violation of assumptions used in both cases. Thus, an additional computational analysis incorporating three dimensional strain-displacement relationships into the finite element analysis is used. Also, a failure behavior pattern for the carbon foam core is included to simulate the unique failure progression of the carbon foam on a microstructure level. Results indicate that displacements, strains and stresses from the flexure experiments are closely predicted by this two parameter progressive damage model. The final computational model consisted of a bond line (interface) study to determine the source of the damage initiation, and it is concluded that damage initiates in the carbon foam, not at the bond line.
29
O'Connor, Bernard. "High strain deformation and ultimate failure of HIPS and ABS polymers". Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245417.
Texto completo
30
Umberger, Pierce David. "Modeling the High Strain Rate Tensile Response and Shear Failure of Thermoplastic Composites". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23846.
Texto completoResumen
The high strain rate fiber direction tensile response of Ultra High Molecular Weight Polyethylene (UHMWPE) composites is of interest in applications where impact damage may occur. This response varies substantially with strain rate. However, physical testing of these composites is difficult at strain rates above 10^-1/s. A Monte Carlo simulation of composite tensile strength is constructed to estimate the tensile behavior of these composites. Load redistribution in the vicinity of fiber breaks varies according to fiber and matrix properties, which are in turn strain rate dependent. The distribution of fiber strengths is obtained from single fiber tests at strain rates ranging from 10^-4/s to 10^-1/s and shifted using the time-Temperature Superposition Principle (tTSP) to strain rates of 10^-4/s to 10^6/s. Other fiber properties are obtained from the same tests, but are assumed to be deterministic. Matrix properties are also assumed to be deterministic and are obtained from mechanical testing of neat matrix material samples. Simulation results are compared to experimental data for unidirectional lamina at strain rates up to 10^-1/s.
Above 10^-1/s, simulation results are compared to experimental data shifted using tTSP. Similarly, through-thickness shear response of UHMWPE composites is of interest to support computational modeling of impact damage. In this study, punch shear testing of UHMWPE composites is conducted to determine shear properties. Two test fixtures, one allowing, and one preventing backplane curvature are used in conjunction with finite element modeling to investigate the stress state under punch shear loading and the resulting shear strength of the composite.Ph. D.
31
Ngekpe, B. E. "Punching shear failure of reinforced concrete flat slabs supported on steel edge column". Thesis, Coventry University, 2016. http://curve.coventry.ac.uk/open/items/5f0f9112-1838-448f-a245-cacc0bc3a9f5/1.
Texto completoResumen
This study examines punching shear failure at edge supported flat slab. Due to the significant dearth of research on punching shear at edge steel column, this study focuses on the design and performance of a novel shearhead system proposed for edge connection. By considering multi-stage processes and parameters that influence punching shear failure, both numerical and experimental studies were adopted. Firstly linear finite element analysis was employed to study the relationship between the continuous structure and the representative specimen; in order to support decisions on boundary conditions that create the similitude. A nonlinear (NLFEA) model was proposed where various concrete material constitutive models were compared and contrasted. The Total Strain crack model was adopted on the ground that it accounts for the tensile strength of cracked concrete which was ignored in previous theoretical model that lead to poor prediction of punching shear. By considering the appropriate material constitutive model for concrete and steel, material parameters, appropriate modelling scheme capable of predicting punching shear was formulated. The adopted modelling scheme was validated using previous research work. Numerical results reveal that punching shear is influenced most significantly by concrete tensile strength, fracture energy. The shearhead assembly was design with using ACI318-05 and Newzealand codes recommendations with some modifications. These are only codes that provide design guidance on shearhead. Experimental and numerical results show that the shearhead contributes appreciably to punching shear capacity of the edge connection. Various design codes on punching shear were compared; Eurocode 2 provides a good prediction of punching shear at edge support; which correlate well with experimental result. Hence, it was adopted to propose an equation for punching shear for edge connection with shearheads. Most importantly, appropriate design guidance and analytical equation have been proposed for shearhead connection. The design guidance and equation would enable practising Engineers to design shearheads without going through the rigor of experimental or numerical investigation. This study has contributed appreciably to the applicability of steel column in flat slab construction.
32
Karaca, Erdem 1976. "FRP strengthening of RC beams in flexure and shear : failure modes and design". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/84785.
Texto completo
33
Petkune, Natalja. "Investigating behaviour and failure modes of FRP and hybrid steel/FRP shear walls". Thesis, Kingston University, 2016. http://eprints.kingston.ac.uk/37873/.
Texto completoResumen
The behaviour of steel shear walls has been investigated for several decades. They have been used in a number of high rise buildings as a primary lateral loading system. Steel shear walls have significant advantages in terms of their light weight, high stiffness and energy absorption in comparison with other structural systems. Hybrid structural elements are becoming popular in thin walled structures, sandwich panels and shear walls. Hybrid shear walls (HSW) are an innovative structural lateral load resisting system. In this thesis HSW are defined as consisting of steel framed elements and steel infill plates laminated with fibre reinforced polymers (FRP) material. By reducing out-of-plane deformations of the infill plate and increasing energy absorption capacity, such systems have the potential to provide highly effective structural solution. The aim of this PhD project was to conduct experimental studies and investigate the behaviour of steel framed shear walls with steel, hybrid (steel/CFRP and steel/GFRP) and pure FRP (glass FRP and carbon FRP) infill plates. Medium scale specimens with dimensions of approximately 1 m width and 1 m height were tested under displacement controlled cyclic sinusoidal loading with amplitudes increasing from 0.2 mm to 35 mm in accordance to the ATC-24 protocol. Analysis of the behaviour of specimens was done predominately via comparing load values and energy absorption. Analysis of the results has shown that hybrid steel and FRP specimens have higher stiffness in comparison to the control steel specimen and a higher energy absorption capacity. Additional analysis performed was that of specific energy absorption to weight, the importance of the surface of connections between primary fish plates elements and infill plates and the strengthening of damaged specimens.
34
Wilhelm, Maximilian Felix, Uwe Füssel, Thomas Richter, Matthias Riemer y Martin Foerster. "Analysis of the shear-out failure mode for CFRP connections joined by forming". Sage, 2015. https://tud.qucosa.de/id/qucosa%3A35782.
Texto completoResumen
In this paper, we look at the shear-out failure of carbon fiber reinforced plastics connections in the automotive industry. Contrary to the aircraft industry, the boundary conditions of automotive applications favor this failure mode strongly. Moreover, the use of other joining technologies than that used in the aircraft industry, such as joining by forming, leads to new challenges. The different influences, typical for joining by forming, on ultimate shear-out strength were first investigated separately and then transferred and validated on connections related to praxis by an analytical model. Special attention was given to effects that resulted from oversized pre-holes, acting clamping forces, and the reduced quality of the laminates in the immediate vicinity of the joint due to the joining process.
35
Dahlem, Emilie. "Characterisation of refractory failure under combined hydrostatic and shear loading at elevated temperatures". Limoges, 2011. https://aurore.unilim.fr/theses/nxfile/default/dfd9d04c-9d0f-4489-a364-f7ffe7a40e0c/blobholder:0/2011LIMO4051.pdf.
Texto completoResumen
In many industrial applications, combination of compressive and shear loads will act on refractory linings. Therefore the prediction of lining failure requires the knowledge of the multiaxial behaviour of the refractory materials under service conditions. In order to take into account those aspects in modelling, Drucker-Prager criterion is often used to describe the mechanical behaviour of granular materials. It applies a linear dependency of the shear strength on the hydrostatic pressure. Therefore the Drucker-Prager failure line requires the knowledge of two essential parameters which should be determined experimentally: the cohesion (d) representing the failure shear stress without any hydrostatic pressure, and the friction angle (β) defining the increase of the failure shear stress with hydrostatic pressure. For several materials experimental data are available in literature, especially in the field of geology or civil engineering. But, unfortunately characterization techniques applied so far are operating at ambient temperature only. For refractories, cohesion and friction angle have also to be determined at elevated temperature (up to e. G. 1500°C). A simple adaptation of available experimental devices, developed for room temperature measurements, to elevated temperatures is not possible. The present work proposes a new approach to carry out such measurements in the case of refractory materialsDans de nombreuses applications industrielles, les matériaux réfractaires subissent des contraintes combinées de compression et de cisaillement pouvant entrainer la rupture du matériau. La prédiction de la rupture du revêtement réfractaire nécessite alors la connaissance du comportement multiaxial des matériaux réfractaires dans ces conditions d’utilisation. Afin de tenir compte de ces aspects dans la modélisation numérique, le critère de Drucker-Prager est souvent utilisé pour décrire le comportement mécanique des matériaux granulaires. En effet, le critère de Drucker-Prager correspond à une approche simple qui permet de décrire la dépendance de la contrainte à rupture en cisaillement en fonction de la pression hydrostatique. Néanmoins, l’utilisation de ce critère nécessite la connaissance de deux paramètres essentiels qui doivent être déterminés expérimentalement : la cohésion (d) traduisant la contrainte à la rupture en cisaillement sans pression hydrostatique appliquée, et l’angle de frottement (β) traduisant l’évolution de cette contrainte à rupture lorsque la pression hydrostatique augmente. De nombreux travaux expérimentaux sur ce type de caractérisation sont disponibles dans la littérature, en particulier dans le domaine de la géologie ou du génie civil. Mais, malheureusement, tous ces travaux traitent de techniques de caractérisation fonctionnant à température ambiante. Dans notre cas, la cohésion et l’angle de frottement doivent aussi être déterminés à haute température (jusqu’à 1500°C). La transposition à haute température des dispositifs développés pour des mesures à température ambiante, est tout simplement impossible. Ce travail propose donc une nouvelle approche pour réaliser de telles mesures dans le cas des matériaux réfractaires
36
Haidar, Mohamed. "Modelling of failure mechanisms for corrugated board". Thesis, KTH, Hållfasthetslära (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176010.
Texto completoResumen
The present work describes the construction of a semi-analytical model for prediction of buckling loads in simply supported corrugated paperboard panels. The model accounts for transverse shear, due to the weakness of the core in such plates compared to the facings. This was done utilizing energy relations and rst order transverse shear. The panel was homogenised using laminate theory. A detailed model using FEM was derived in order to validate the predictive capabilities of the analytical model. Experimental testing was performed to estimate the accuracy of both theoretical models, and assess the limitation of the analytical model. All modes of analysis showed good agreement for cubic boxes. Further investigation into expanding the scope of the analytical model was carried out and commented on.
37
Nedele, Martin Rolf. "Micromechanical modelling of unidirectional composites subjected to external and internal loadings". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336828.
Texto completo
38
Junaideen, Sainulabdeen Mohamed. "Failure of saturated sandy soils due to increase in pore water pressure". Thesis, Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B30708540.
Texto completo
39
Bell, A. P. "Finite element analysis of shear band failure with particular reference to circular plate impact". Thesis, City University London, 1989. http://openaccess.city.ac.uk/7410/.
Texto completoResumen
This thesis addresses the problem of the numerical simulation of the shear band or 'plugging' mode of failure in metallic solids. Particular reference is made to the normal impact between blunt projectiles and circular plates of thin to intermediate thickness. The thesis presents a two dimensional axisymmetric and plane strain finite element computer program related to the Lagrangian reference frame. A four node element with one point quadrature and associated stabilisation is utilised, and is shown to be superior to standard isoparametric implementations when applied within an explicit time integration scheme. Finite deformation capabilities are included, together with material nonlinearity in the form of a von Mises elastic-plastic model. The algorithms used in this work are dictated to a large degree by the emphasis which is placed upon efficiency, although this is not at the expense of accuracy. Numerical stability in the presence of severe stress gradients is achieved through the use of an artificial viscosity scheme. The impact conditions along the contacting interface are governed by the use of a penalty-based slideline technique which permits arbitrarily large relative deformations of the contact surfaces. With the foregoing numerical basis, the penalty-based slideline technique has been extended in this work to facilitate the discrete modelling of the fracture process present during plugging. The computational model has been embedded within the LUSAS finite element system which provides extensive pre and post processing facilities. A detailed discussion of the problems involved in the solution of high velocity impact calculations is given, together with an assessment of the effects of several material related parameters on the solution. several numerical comparisons with experimental evidence are also performed to indicate the effectiveness of the method. Finally, relevant conclusions have been made and suggestions for further study are provided.
40
Chen, Yiyu. "Non-linear finite element analysis of certain shear failure mechanisms in reinforced concrete beams". Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/68.
Texto completo
41
Williams, Scott A. "Numerical Analysis of Reinforced Masonry Shear Walls Using the Nonlinear Truss Approach". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25219.
Texto completoResumen
Reinforced masonry (RM) shear walls are a common lateral load-resisting system for building structures. The seismic design guidelines for such systems are based on relatively limited experimental data. Given the restrictions imposed by the capabilities of available experimental equipment, analytical modeling is the only means to conduct systematic parametric studies for prototype RM wall systems and quantify the seismic safety offered by current design standards. A number of modeling approaches, with varying levels of complexity, have been used for the analysis of reinforced concrete (RC) and masonry wall structures. Among the various methods, the truss analogy is deemed attractive for its conceptual simplicity and excellent accuracy, as indicated by recent studies focusing on RC walls.
This thesis uses an existing modeling method, based on nonlinear truss models, to simulate the behavior of fully grouted reinforced masonry shear walls. The modeling method, which was originally created and used for RC walls, is enhanced to capture the effect of localized sliding along the base of a wall, which may be the dominant mode of damage for several types of RM walls. The truss modeling approach is validated with the results of quasi-static cyclic tests on single-story isolated walls and dynamic tests on a multi-story, three-dimensional wall system. For the latter, the truss model is found to give similar results to those obtained using a much more refined, three-dimensional finite element model, while requiring a significantly smaller amount of time for the analysis.
Finally, truss models are used for the nonlinear static analysis of prototype low-rise walls, which had been analyzed with nonlinear beam models during a previous research project. The comparison of the results obtained with the two modeling methods indicates that the previously employed beam models may significantly overestimate the ductility capacity of RM squat walls, due to their inability to accurately capture the shear-flexure interaction and the effect of shear damage on the strength of a wall.Master of Science
42
Pei, Shuangxi. "An investigation into the punching shear failure in R.C. waffle slabs subjected to concentrated load". Thesis, University of Abertay Dundee, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240614.
Texto completo
43
Aliamiri, Sara. "Prediction of premature failure load in FRP or steel plated RC beams". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13631.
Texto completo
44
Isabell, Eriksson y Niklas Karlsson. "Non-Linear Assessment of a Concrete Bridge Slab Loaded to Failure". Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188900.
Texto completoResumen
This thesis covers an investigation regarding the failure in the bridge slab of Gruvvägsbron, which was the result of the full scale test that the bridge was subjected to prior to demolition. Using the non-linear finite element software ATENA 3D, a model of the bridge was assembled, with the purpose to attempt to reenact the test procedure and realistically capture the failure load and behaviour. This in order to be able to conclude what kind of failure that occurred. The initial part of this thesis presents a summary of a conducted literature study, which aims to give deeper knowledge regarding the linear shear and punching shear phenomena and their respective failure mechanisms, and how they are applied on bridge slabs. Furthermore, the shear capacity of the bridge was calculated according to current design codes. A parameter study was conducted on the model, which initially showed a over-stiff response. The aim of this was to study the influence of key variables on the outcome of the analysis, and hopefully get closer to the failure load acquired inthe experiment. From the studied parameters, it was observed that a combined reduction of the tensile strength and fracture energy, together with a low fixed crack coefficient had the largest influence on the outcome of the analysis. It was also observed that the location of the failure and failing load was dependant on how the loading was applied to the model, i.e. via load control or deformation control. The final model failed at a load which surpassed the actual failure load by 10.5%. The mode of failure obtained in all the analyses were the result of a large shear crack propagating from the edges of the loading plate, through the slab to the slab/girder-intersection. This indicates that the type of failure that occurred was primarily due to a linear shear mechanism with a secondary punching effect. The design values calculated by keeping with the current codes resulted in too conservative values when compared to the obtained failure load from the experiment. This proves the difficulty in regarding the internal force distribution in slab struc-tures as well as the shear carrying width, which from the analysis were found to be larger than that obtained from the code.Denna uppsats behandlar en utredning gällande brottet i plattan på Gruvvägsbron, som var resultatet av det fullskaletest som bron utsattes för innan rivning. Med hjälp av den icke-linjära finita element-programvaran ATENA 3D skapades en modell avbron, med syfte att på ett realistiskt sätt försöka återskapa experimentet och fånga brons verkliga beteende. Detta för att således kunna dra slutsatser angående brottets natur. Den första delen av denna uppsats innehåller en sammanfattning av en utförd litteraturstudie, som ämnar ge en ökad förståelse angående fenomenen skjuvning och genomstansning, tillsammans med olika brottmekanismer relaterade till dessa. Vidare har brons motstånd mot skjuv- och genomstansningbrott beräknats enligt rådande normer. En parameterstudie utfördes på modellen, då den ursprungligen uppvisade ett överstyvt beteende. Syftet med detta var att studera nyckelparametrars påverkan på analysens resultat, och eventuellt komma närmare den verkliga brottlasten i experimentet. Av de studerade parametrarna observerades att en samtida reduktion av draghållfasthet och brottenergi, samt ett lågt värde på den så kallade "fixedcrack"-koefficienten gav störst inverkan på resultatet. Vidare observerades att brottets lokalisering och brottlasten var beroende av hur lasten påfördes modellen, dvs genom last- eller deformationsstyrning. Den slutgiltiga modellen gick till brott vid en last som översteg den verkliga brottlasten med 10.5%. Brottet som skedde var i samtliga analyser resultatet av en skjuvspricka som sträckte sig från kanten av lastplattan, genom plattan, ner till mötet mellan platta och balk. Detta indikerar att den typ av brott som skedde var ett primärt skjuvbrott med en sekundär stanseffekt. Lastvärdena beräknade enligt rådande normer tycks vara för konservativa, om jämförelse görs med lasten som uppnåddes i experimentet. Detta visar på svårigheten i att bedöma den inre kraftspridningen i plattor, och även dess skjuvbärande bredd, då analysen visade att denna var betydligt större än vad som ges i koden.
45
Love, Bryan Matthew. "Multiscale Analysis of Failure in Heterogeneous Solids Under Dynamic Loading". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29650.
Texto completoResumen
Plane strain transient finite thermomechanical deformations of heat-conducting particulate composites comprised of circular tungsten particulates in nickel-iron matrix are analyzed using the finite element method to delineate the initiation and propagation of brittle/ductile failures by the nodal release technique. Each constituent and composites are modeled as strain hardening, strain-rate-hardening and thermally softening microporous materials. Values of material parameters of composites are derived by analyzing deformations of a representative volume element whose minimum dimensions are determined through numerical experiments. These values are found to be independent of sizes and random distributions of particulates, and are close to those obtained from either the rule of mixtures or micromechanics models.
Brittle and ductile failures of composites are first studied by homogenizing their material properties; subsequently their ductile failure is analyzed by considering the microstructure. It is found that the continuously varying volume fraction of tungsten particulates strongly influences when and where adiabatic shear bands (ASB) initiate and their paths. Furthermore, an ASB initiates sooner in the composite than in either one of its constituents.
We have studied the initiation and propagation of a brittle crack in a precracked plate deformed in plane strain tension, and a ductile crack in an infinitely long thin plate with a rather strong defect at its center and deformed in shear. The crack may propagate from the tungsten-rich region to nickel-iron-rich region or vice-a-versa. It is found that at the nominal strain-rate of 2000/s the brittle crack speed approaches Rayleigh's wave speed in the tungsten-plate, the nickel-iron-plate shatters after a small extension of the crack, and the composite plate does not shatter; the minimum nominal strain-rate for the nickel-iron-plate to shatter is 1130/s. The ductile crack speed from tungsten-rich to tungsten-poor regions is nearly one-tenth of that in the two homogeneous plates. The maximum speed of a ductile crack in tungsten and nickel-iron is found to be about 1.5 km/s.
Meso and multiscale analyses have revealed that microstructural details strongly influence when and where ASBs initiate and their paths. ASB initiation criteria for particulate composites and their homogenized counterparts are different.Ph. D.
46
Ekesiöö, Anton y Andreas Ekhamre. "Safety formats for non-linear finite element analyses of reinforced concrete beams loaded to shear failure". Thesis, KTH, Betongbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231087.
Texto completoResumen
There exists several different methods that can be used to implement a level of safety when performing non-linear finite element analysis of a structure. These methods are called safety formats and they estimate safety by different means and formulas which are partly discussed further in this thesis. The aim of this master thesis is to evaluate a model uncertainty factor for one safety format method called the estimation of coefficient of variation method (ECOV) since it is suggested to be included in the next version of Eurocode. The ECOV method will also be compared with the most common and widely used safety format which is the partial factor method (PF). The first part of this thesis presents the different safety formats more thoroughly followed by a theoretical part. The theory part aims to provide a deeper knowledge for the finite element method and non-linear finite element analysis together with some beam theory that explains shear mechanism in different beam types. The study was conducted on six beams in total, three deep beams and three slender beams. The deep beams were previously tested in the 1970s and the slender beams were previously tested in the 1990s, both test series were performed in a laboratory. All beams failed due to shear in the experimental tests. A detailed description of the beams are presented in the thesis. The simulations of the beams were all performed in the FEM- programme ATENA 2D to obtain high resemblance to the experimental test. In the results from the simulations it could be observed that the ECOV method generally got a higher capacity than the PF method. For the slender beams both methods received rather high design capacities with a mean of about 82% of the experimental capacity. For the deep beams both method reached low design capacities with a mean of around 46% of the experimental capacity. The results regarding the model uncertainty factor showed that the mean value for slender beams should be around 1.06 and for deep beams it should be around 1.25.
47
Otaki, Takeshi. "SIZE EFFECTS IN SHEAR FAILURE OF REINFORCED CONCRETE BRIDGE COLUMNS - FULL SCALE TEST AND ANALYTICAL EVALUATION". Kyoto University, 2001. http://hdl.handle.net/2433/150668.
Texto completo
48
Saum, Keith L. "Targeting Endothelial Kruppel-like Factor 2 (KLF2) in Arteriovenous Fistula Maturation Failure". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269382206163.
Texto completo
49
Lear, Matthew Houck. "Numerical Simulation of Adiabatic Shear Bands and Crack Propagation in Thermoviscoplastic Materials". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27196.
Texto completoResumen
Plane strain deformations of an elastoplastic material are studied using numerical methods. In the first chapter, a meshless formulation of the static small strain elastic-plastic problem is formulated using the meshless local Petrov-Galerkin method. The code is validated against the small strain plasticity routines in the commercial finite element code ABAQUS for two basic configurations with loading, unloading, and reloading. The results are found to agree within 5%. The validated code is then used to analyze the stress intensity factor (SIF) in a double edge-cracked plate. Deformations of the plate are studied both with and without exploiting the symmetry conditions. The penalty method is used to enforce the essential boundary condition in the former case. When analyzing the deformations of the entire plate, the diffraction method is employed in order to introduce the discontinuity in the displacement field across the crack faces. The log-log and a higher order extrapolation technique due to Dally and Berger (1996) are used to calculate the SIF. It is found that the penalty method was inadequate to enforce the essential boundary conditions in the vicinity of the crack tip and that in this region the deformations were oscillatory. Consequently, the SIF calculation using the higher order technique was not accurate. It is also found that for a small plastic zone (3% of the cracked length) the SIFs do not differ significantly from their values for the corresponding linear elastic problem.
In the second chapter, a finite element formulation of the dynamic deformations of a micro-porous thermoviscoplastic solid is formulated. The heat conduction in a material is assumed to be governed by a hyperbolic heat equation; thus thermal and mechanical waves propagate with finite speeds. The formation and propagation of an adiabatic shear band (ASB) inplane strain tensile deformations is studied for eleven materials. The ASB is assumed to form when the maximum shear stress has been reduced to 80% of its peak value at a point and it is deforming plastically. The materials are ranked according their susceptibility to the formation of an ASB. A parametric study of the effect of the initial defect strength where the defect is assumed through an initially inhomogeneous distribution of porosity, the thermal conductivity, the thermal wave speed, and the applied strain-rate upon the ASB initiation and propagation is conducted. It is found that the susceptibility ranking for this configuration differs somewhat from that previously found for simple shear and torsion of thin-walled tubes. It is also found that thermal conductivity influences ASB initiation and propagation only for materials with large values of · and that for such materials an adiabatic model may not be adequate. The effects of initial defect strength and the nominal strain-rates are both found to be consistent with simple shearing studies except that the ASB propagation speed was found to decrease with increasing nominal strain-rate. It is found that the criterion employed for ASB initiation accurately predicts the onset of the collapse of the total axial load applied to the body.
In the final chapter, the formulation from the previous chapter is modified to permit the formation and propagation of brittle and ductile fracture. Deformations of the impact loaded double edge-crack specimen of Kalthoff and Winkler (1987) are studied. The brittle to ductile failure mode transition with increasing impact speed was found. Previous studies have focused on identifying the transition speed and did not allow for crack propagation. In this study, crack propagation is achieved through a nodal release algorithm and interpenetration of the crack surfaces is prevented using stiff-spring contact elements. Brittle fracture is assumed to occur when the maximum tensile principal stress achieves a critical value and the ductile fracture is assumed to occur when the effective plastic strain reaches a critical value. It is found that the transition speed for 4340 steel is approximately 54 m/s. For the brittle failure, the stress field is found to be significantly modified by the propagating crack and in the vicinity of the propagating crack the field is mode-I dominant. The crack formed through brittle fracture is found to completely propagate through the plate. For the ductile failure, the distribution of effective plastic strain about the crack tip is not significantly altered by the formation of the crack. The temperature rise in the vicinity of the ductile crack is found to be approximately 45% of the melting temperature of the material.Ph. D.
50
Herrero, Javier. "Buckling, postbuckling and progressive failure analysis of hybrid composite shear webs using a continuum damage mechanics model". Diss., Wichita State University, 2007. http://hdl.handle.net/10057/1488.
Texto completoResumen
This dissertation presents an innovative analysis methodology to enhance the design of composite structures by extending their work range into the postbuckling regime. This objective is accomplished by using the numerical simulation capabilities of nonlinear finite element analysis combined with continuum damage mechanics models to simulate the onset of failure and the subsequent material properties degradation. A complete analysis methodology is presented with increasing levels of complexity. The methodology is validated by correlation of analytical results with experimental data from a set of hybrid carbon/epoxy glass/epoxy composite panels tested under shear loading using a picture frame fixture.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
"December 2007."