Development and Validation of Small Punch Testing at NIST

Abstract

Small Punch (SP) testing is a methodology that uses tiny disks (generally 8 mm in diameter and 0.5 mm thick) to estimate mechanical properties of metallic materials, such as tensile properties, fracture toughness, and ductile-to-brittle transition temperature. Empirical correlations are typically used to infer conventional mechanical properties from characteristic forces and displacements obtained from the SP test record. At NIST in Boulder, Colorado, we recently developed experimental and analytical procedures for running SP tests on various materials. We conducted SP tests on three steels with widely different tensile and fracture properties. The NIST setup was successfully qualified by comparing our results on A533B steel to the results obtained in an international round-robin, and also by comparing empirical correlations between SP data and tensile properties to similar relationships published in the literature. We also tested specimens with different surface roughness, to investigate the influence of surface finish on SP test results.