A Lower-Bound Temperature and Strain-Rate Dependent Strength Model for AISI 304 SS

Abstract

The use of a material in a design where failure carries environmental or health and safety risk requires computational design using a conservative strength model. The materials design engineer must determine and be able to justify a lower-bound stress-strain curve. This paper uses the AISI 304 / 304L system to demonstrate how such a model might be derived. It addresses the question of variability in materials properties. Also discussed is the contribution of strain-rate dependence that is relevant to applications involving impact or explosive loading conditions. Designers and those reviewing and approving designs are more comfortable with the use of temperature dependent than strain-rate dependent material properties. Ignoring strain-rate dependence can lead to overly conservative designs, even when the objective is a conservative design. The Mechanical Threshold Stress model is used to demonstrate, in the 304 / 304L system, a lower-bound temperature and strain-rate dependent constitutive model. This model implements a state-variable approach and easily accounts for temperature and strain-rate dependent material properties as well as strain hardening. A wealth of literature data is used to benchmark and validate the model. Comparison of model predictions with applicable ASME and ASTM code standards is described.