Topic
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, the authors developed a micro-mechanical framework for the whole coalescence regime, which is defined by a set of constitutive equations including a closed form of the yield surface along with appropriate evolution laws for void shape and ligament size.
Abstract: Significant progress has been recently made in modelling the onset of void coalescence by internal necking in ductile materials The aim of this paper is to develop a micro-mechanical framework for the whole coalescence regime, suitable for finite-element implementation The model is defined by a set of constitutive equations including a closed form of the yield surface along with appropriate evolution laws for void shape and ligament size Normality is still obeyed during coalescence The derivation of the evolution laws is carefully guided by coalescence phenomenology inferred from micromechanical unit-cell calculations The major implication of the model is that the stress carrying capacity of the elementary volume vanishes as a natural outcome of ligament size reduction Moreover, the drop in the macroscopic stress accompanying coalescence can be quantified for many initial microstructures provided that the microstructure state is known at incipient coalescence The second part of the paper addresses a more practical issue, that is the prediction of the acceleration rate δ in the Tvergaard–Needleman phenomenological approach to coalescence For that purpose, a Gurson-like model including void shape effects is used Results are presented and discussed in the limiting case of a non-hardening material for different initial microstructures and various stress states Predicted values of δ are extremely sensitive to stress triaxiality and initial spacing ratio The effect of initial porosity is significant at low triaxiality whereas the effect of initial void shape is emphasized at high triaxiality
274 citations
TL;DR: In this article, the authors used a video-controlled testing system to determine the evolution of volume strain in polyethylene terephtalate (PET) and high-impact polystyrene (HIPS) by measuring in real time the three principal strain components in a small volume element, while the specimens are deformed under uniaxial tension at constant true strain rate.
273 citations
TL;DR: In this paper, a simplified analytical model is presented, which reveals that a preexisting geometric imperfection can grow from the outset of deformation, even while the load rises.
269 citations
TL;DR: In this paper, it was shown that the modulus of many polymers is much reduced by strain and the consequent downward bending of the stress-strain curve leads to mechanical instability and so causes a neck to form.
264 citations
TL;DR: In this article, a micromechanics model based on the theoretical framework of plastic localization into a band introduced by Rice is developed, which consists of a planar band with a square array of equally sized cells, with a spherical void located in the centre of each cell.
256 citations