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Application of Modified Mohr-Coulomb Necking Locus with Forming Severity Concept to Predict Metal Sheets Necking under Nonlinear Strain Path

Yuanli Bai (University of Central Florida), Tomasz Wierzbicki (MIT)

Instability in Solids and Structures

Mon 4:20 - 5:40

Barus-Holley 190

A concept of “cumulative forming severity” was introduced by Bai and Wierzbicki to consider metal sheet necking under complex loading histories. In this presentation, an idea of necking locus in the 2D space of stress triaxiality and equivalent strain to necking was investigated, which use a similar equation to the modified Mohr-Coulomb (MMC) fracture locus. The necking locus is defined under the assumption of proportional loading conditions. Comparative study shows that the MMC necking locus has similar capability as that of analytical solutions from Hill's and Stoeren-Rice. The proposed necking locus is extended to describe necking anisotropy using linear transformation applied to the plastic strain tensor. Necking test data under nonlinear strain paths of aluminum alloy 6111-T4 and aluminum-killed sheet steel found in the literatures are revisited by the proposed model. Good accuracies are achieved.