Implementation of dynamic stress and failure models in VAST and Trident


  1. Jiang, L.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN);BMT Fleet Technology Limited, Kanata Ont (CAN)
In this report, a recent enhancement of the dynamic material modeling and failure analysis capability in the VAST program is described. In the present work, two widely used constitutive models for characterizing dynamic material behaviour under impulsive loading conditions, the Cowper-Symonds model and the Johnson-Cook model, are implemented in four element types in VAST including the 4- and 8-noded shell elements and the 8- and 20-noded solid elements. In addition to the instantaneousstrain- rate-based algorithm previously implemented in VAST, two new algorithms for strain rate evaluations are developed based on time-averaged total and plastic strain rate, which result in more stable numerical solutions. The capability for failure assessment is also implemented in all the four elements mentioned above. The Trident program is also updated to permit definition of the new control flags and material constants and post-process the results for failure check. Extensive numerical verifications have been performed using an example problem involving a steel plate under a sudden application of uniform pressure, and the test results indicate that the dynamic material models and failure criteria implemented are functioning correctly and are reliable.

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Report Number
DRDC-ATLANTIC-CR-2008-271 — Contractor Report
Date of publication
01 Feb 2009
Number of Pages
Electronic Document(PDF)

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