A Critical Reexamination of Classical Metal Plasticity

Abstract

early work on flow and fracture in the presence of hydrostatic pressure showed no systematic effect on strain hardening. This experimental observation led to the conclusions that yielding does not depend on hydrostatic stress and that the yielded material is incompressible. Classical plasticity theory was largely built on these observations. New experiments and nonlinear finite element analyses of 2024-T351 aluminum notched round bars has quantified the effect of hydrostatic tensile stresses on yielding. Nonlinear finite element analyses using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions was performed. The von Mises results overestimated experimental loaddisplacement curves by 10-65 percent. The Drucker-Prager results essentially matched the experimental results. The only additional data requirement for the Drucker-Prager yield function is the compressive yield strength.

Some applications of Burzyński yield condition in metal plasticity

“…4 6 show the load displacement curves obtained in numerical situation using the Burzyń ski paraboloid model for dif ferent values of the strength differential factor k:k = 1, 1.06, 1.1 and 1.2. These results are compared with the experimentally ob served behaviour of the specimen [6].…”

“…These properties, including the Young Modulus E and Poisson's ratio m constants, are listed in Table 1. A compression test were also con ducted by Wilson [6], and the resulting r C 0 is given in Table 1. The geometry and dimension details of the notched round bar specimens are given in Fig.…”

“…The material considered is the 2024 T351 aluminum alloy. The true stress true strain material characteristc ðr T Y eÞ obtained from uniaxial tensile tests [6] follows the Ramberg Osgood power law hardening relationship:…”

“…Simulation of tests on notched tensile specimens of 2024 T3 aluminum alloy [6] In order to analyse the behaviour of the proposed model and the integration algorithm, different tensile tests performed experimen tally by Wilson [6] were simulated. The material considered is the 2024 T351 aluminum alloy.…”

“…The computations were compared with the experimental data and the results of numerical calculations made with the application of the Drucker Prager yield condition presented in [6]. Also, the experimental data obtained by Iyer and Lissenden [12] for the polycrystalline nickel base alloy Inconel 718, which reveals the strength differential effect, were applied.…”