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 article, the authors focus on the loading rate of the region bounded by a ring of maximum thinning referred to here as the crown, which is associated with the onset of a rapid rate of thinning under falling crown load.
Abstract: Criteria for diffuse and local necking in sheet metals stretched over a hemispherical punch have been developed. During stretching, a peak develops in the distribution of strain across the dome. This peak is a ring of thinned material around the pole which moves outward radially with continued deformation. The present approach essentially focuses on the loading rate of the region bounded by this ring of maximum thinning referred to here as thecrown. While diffuse instability is identified with a vanishing rate of crown loading, local necking is associated with the onset of a rapid rate of thinning under falling crown load. The principal surface strains were measured from incremental stretching of several different materials and time dependent constitutive relations were used to predict the instability strains. Such predictions agree with experimentally observed forming limits defined by the onset of visible necking and provide an understanding of the failure of biaxially stretched sheets deformed by a rigid punch. Since no satisfactory plasticity analyses have been developed to predict the strain distribution during punch stretching, the empirical input to the present instability criterion is required.
109 citations
TL;DR: In this article, a freestanding Cu/Nb multilayers with equal individual layer thickness of 40nm were tested in tension and the material exhibits a flow stress of 1.55 GPa and elongation to failure of 3.4%.
109 citations
TL;DR: In this paper, the authors used a rate-sensitive polycrystal plasticity model together with the Marciniak-Kuczynski approach for the computation of forming limit diagrams (FLDs).
Abstract: This paper is concerned with the computation of forming limit diagrams (FLDs) using a rate-sensitive polycrystal plasticity model together with the Marciniak–Kuczynski approach. Sheet necking is initiated from an initial imperfection in terms of a narrow band. The deformations inside and outside the band are assumed to be homogeneous and conditions of compatibility and equilibrium are enforced across the band interfaces. Thus, the polycrystal model needs only to be applied to two polycrystalline aggregates, one inside and one outside the band. Each grain is modelled as an FCC crystal with 12 distinct slip systems. The response of an aggregate comprised of many grains is based on an elastic–viscoplastic Taylor‐type polycrystal model developed by Asaro and Needleman (1985). The effects of initial imperfection intensity and orientation, initial distribution of grain orientations, crystal elasticity, strain rate sensitivity, single slip hardening and latent hardening on the FLD are discussed in detail. The predicted FLD is compared with experimental data for an aluminium alloy sheet.
108 citations
TL;DR: In this article, an implicit approach for the incremental analysis of planar anisotropic elasto-plastic sheet forming processes was developed based on the incremental deformation theory of plasticity.
108 citations
107 citations