Implementation of a Viscoplastic, Kinematic Hardening Constitutive Model for Impact Prediction

by Jeffrey R. Sachs, Wagner Associates, Sunnyvale, United States,
Charles S. White, Wagner Associates, Sunnyvale, United States,
Frederick C. Taverner, Wagner Associates, Sunnyvale, United States,

Document Type: Proceeding Paper

Part of: Engineering, Construction, and Operations in Space IV


This paper reports on a preliminary study to determine the significance of the Bauschinger effect on modeling impact and other large deformation events. Such events have significant implications for failure of structures in space environments. Hydrocodes which have been developed in the last two decades have opened the door to great opportunities to model the constitutive behavior of materials under extreme conditions of stress, strain rate and temperature. The modeling of temperature, strain rate, strain hardening and stress effects on the one dimensional states such as determined experimentally by Hopkinson bar or plate impact tests has been well established, while the relative importance of various multiaxial effects has not been as completely determined. The chief of these is the Bauschinger effect. In this work, a relatively simple viscoplastic model has been written which incorporates both isotropic-type hardening and kinematic-type hardening. The model builds upon the viscoplastic model of Brown and Anand by including a back stress variable with evanescent hardening. No yield surface is used but the model allows plastic deformation at every level of stress. This model has been implemented into the ABAQUS explicit finite element code. Material parameters to simulate aluminum and silicon iron have been determined and used to simulate various high strain rate phenomena. Model parameters both with and without the back stress variable have been used in order to elucidate the effect of including back stress in this class of problems. Simulations include one element reverse loading tests and Taylor impact tests.

Subject Headings: Stress strain relations | Failure analysis | Strain | Finite element method | Stress analysis | Strain rates | Load tests

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