Post-Yield Material Characterization for Strain-Based Design

Conventional material specifications and test methods were developed to support load-based designs in which inelastic deformations are relatively small and yield strength is the primary material factor governing design. However, in strain-based designs where substantial portions of the structure soften under post-yield deformation, more detailed characterization of the post-yield material behavior is required. This paper presents a framework for describing the post-yield properties of metals (including strain-rate dependence of yield strength) a testing method for measuring post-yield strength in terms of strain and strain rate, and an analytical basis for extrapolating measured properties to static conditions for strain-based design and quality assurance (QA).