Evaluation of the Bridgman Analysis for Notched Tension Specimens

Report No. ARL-MR-1002
Authors: Brian M Powers
Date/Pages: July 2019; 27 pages
Abstract: The Johnson–Cook failure model requires knowledge of the stress state in the test specimen at the moment of failure to fit the model parameters to experimental data. This work compares two methods for determining the stress state in a plastically deformed tension specimen: an analytical solution developed in 1952 by PW Bridgman and a nonlinear finite element solution. The Bridgman solution makes simplifying assumptions about the plastically deformed zone in the specimen to formulate a closed-form solution. Solutions are presented for cylindrical tension specimens and prenotched tensions specimens that are typically used to determine Johnson–Cook failure parameters. Comparisons with finite element results show that Bridgmanâ??s assumptions are incorrect, which lead to poor predictions of the stress state in test specimens, and that the finite element results are a more accurate predictor of the stress state.
Distribution: Approved for public release
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Last Update / Reviewed: July 1, 2019