von Mises yield criterion

About: von Mises yield criterion is a research topic. Over the lifetime, 4374 publications have been published within this topic receiving 82642 citations. The topic is also known as: Von Mises stress.

Semi-analytical postbuckling and strength analysis of arbitrarily stiffened plates in local and global bending

Abstract: A semi-analytical method for pre- and postbuckling analysis of imperfect plates with arbitrary stiffener arrangements, subjected to in-plane biaxial and shear loading, is presented. By using large deflection theory in combination with the Rayleigh–Ritz approach on an incremental form, the method is able to trace both local and global equilibrium paths. Ultimate strength predictions are made using the von Mises’ yield criterion applied to the membrane stresses as collapse criterion. A Fortran computer program based on the presented theory is developed and computed results are verified by comparisons with nonlinear finite element analysis. Relatively high numerical accuracy is achieved with small computational efforts. The method is therefore suited also for design optimisation and reliability studies.

Pre-buckling and post-buckling failure at web-flange junction of pultruded GFRP beams

Abstract: Separation at the web-flange junction is a common failure mode of pultruded glass fiber-reinforced (GFRP) beams subjected to bending. The causes of this separation appear to depend on the presence of lateral supports to prevent lateral buckling. To clarify the driving mechanisms, four-point bending experiments were carried out on pultruded GFRP girders. Lateral buckling was prevented by using lateral supports. Web-flange separation failure due to exceeding the shear strength was observed before any buckling was seen. Furthermore, nonlinear FEA was performed to identify the critical stress states of GFRP beams from the research literature, without any lateral supports in the post-buckling phase. In this case, based on numerical calculation, the critical stress states and their locations depended significantly on the shape of initial imperfections. The ultimate loads, with or without lateral supports, were predicted by a modified von Mises criterion applied to the stress states at the web-flange junction.

Finite-element analysis on wafer-level CMP contact stress: reinvestigated issues and the effects of selected process parameters.

Abstract: Contact stress uniformity is a key issue for the performance of wafer-level chemical–mechanical planarization (CMP) and has been extensively studied during the past two decades. However, contact-stress-related issues are not consistently presented in the literature. In addition, a number of topics remain to be addressed in wafer-level contact analysis. The objective of this article is in twofold. First, it aims to provide a more detailed discussion and stress analysis of the inconsistent issues, including the definition of CMP uniformity, the stress indicator, and the effect of carrier films. Second, contact stress analyses of several important but rarely touched problems are also investigated. Topics to be investigated include: the effects of material hyperelasticity, the effects of a grooved pad, the effects of wafer warpage due to residual stress, and finally the possible advantages of a multizone loading manner. For the first category, this work proposes a new definition of CMP uniformity based on the width of the relatively flat zone. In addition, the contact stress distribution in terms of both von Mises and normal stress are also investigated and their relationship is qualitatively established. Furthermore, the importance of the carrier films is reinvestigated, and the conclusion indicates that their importance is not as significant as previously reported. The hyperelasticity of pad material primarily affects the pad deformation. The presence of pad grooves results in a net increase of contact stress, but the global tendency is unchanged. A warped wafer significantly reduces the contact stress uniformity. By contrast, the multizone loading manner can effectively improve the uniformity of stress distribution. Finally, the stress analyses presented are integrated with a graphic user interface to form a CMP computer-aided design system for further applications. The issues addressed and the conclusions obtained are important for improvement of CMP performance.

Stress and Strain in Silicon Electrode Models

Abstract: Author(s): Higa, K; Srinivasan, V | Abstract: While the high capacity of silicon makes it an attractive negative electrode for Li-ion batteries, the associated large volume change results in fracture and capacity fade. Composite electrodes incorporating silicon have additional complexity, as active material is attached to surrounding material which must likewise experience significant volume change. In this paper, a finite-deformation model is used to explore, for the first time, mechanical interactions between a silicon particle undergoing lithium insertion, and attached binder material. Simulations employ an axisymmetric model system in which solutions vary in two spatial directions and shear stresses develop at interfaces between materials. The mechanical response of the amorphous active material is dependent on lithium concentration, and an equation of state incorporating reported volume expansion data is used. Simulations explore the influence of active material size and binder stiffness, and suggest delamination as an additional mode of material damage. Computed strain energies and von Mises equivalent stresses are in physically-relevant ranges, comparable to reported yield stresses and adhesion energies, and predicted trends are largely consistent with reported experimental results. It is hoped that insights from this work will support the design of more robust silicon composite electrodes.