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Necking
About: Necking is a research topic. Over the lifetime, 5280 publications have been published within this topic receiving 113945 citations.
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TL;DR: In this paper, a model to represent ductile failure controlled by nucleation, growth and coalescence of materials whose irreversible deformation is controlled by several plastic or viscoplastic deformation mechanisms is presented.
84 citations
TL;DR: The thermal oxidation of polypropylene films (100 μm) in air at 90°C was studied by IR spectroscopy, rheometry at 210°C and tensile testing.
83 citations
TL;DR: In this article, the authors used the optical strain measuring system ARAMIS to validate existing failure models used in finite element (FE) simulations in terms of dependence on length scale and strain state, and the failure criteria that were verified against the tests were chosen among those available in the FE software Abaqus and the Bressan-Williams-Hill (BWH) criterion proposed by Alsos et al.
83 citations
TL;DR: In this paper, a phenomenological plasticity model is proposed, in which a smooth yield surface for an anisotropic solid is combined with a vertex-type plastic flow rule, and the model is tested on predictions of the onset of necking in biaxially stretched metal sheets.
Abstract: An abrupt strain path change has recently been used to determine the shape of the subsequent yield surface near a current loading point. Both polycrystal plasticity calculations and experiments have shown non-normality of plastic flow, with a vertex-type response on the apparently smooth yield surface. The physical reason for this observation is carefully discussed in the paper, with particular emphasis on the fact that the prediction appears in spite of the normality rule built into each slip system of the crystal plasticity model. To represent the observed non-linear material response, a phenomenological plasticity model is proposed, in which a smooth yield surface for an anisotropic solid is combined with a vertex-type plastic flow rule. As plastic instability results are particularly sensitive to accurate modeling of material response under abrupt stress path change, the material model is tested on predictions of the onset of necking in biaxially stretched metal sheets. It is shown that the phenomenological plasticity model gives a good approximation of critical strains predicted by direct application of the Taylor polycrystal plasticity model.
83 citations
TL;DR: In this paper, a finite element model and an associated algorithm are developed for the analysis of the thermomechanical coupling in the necking process of a bar in an uniaxial tension test.
Abstract: SUMMARY The necking process of a bar in an uniaxial tension test is influenced by the heat production due to inelastic deformations. Thus, for an analysis of this problem the thermomechanical coupling has to be considered. A finite element model and an associated algorithm are developed for this purpose. This computational tool allows the study of adiabatic processes as well as processes with heat flux. The analysis of the necking process of a perfectly cylindrical specimen shows that, in contrast to isothermal and adiabatic cases, no bifurcation occurs in the case where heat flux is considered. 1. INTRODUCTION A variety of experimental, analytical and numerical investigations have lead to a basic under- standing of the mechanisms pertaining to the diffuse necking process in a circular ductile bar tensile test. A number of papers have been published in which numerical simulations of this phenomenon within the framework of classical elastoplasticity can be found, see e.g. Chen6 or Needleman. Any advanced simulation of the necking problem should consider the fact that heat production due to dissipated mechanical work in plastic deformations will lead to temperature changes in the specimen when the test is performed at finite rates. In the context of a pure adiabatic process the associated bifurcation loads of cylindrical specimen has been investigated by Bruhns and Mielniczuk. Several numerical concepts for coupled thermomechanical processes have been developed in Argyris and Doltsinis2 and Argyris
83 citations