Effect of Indentation Strain Rate on Plastic Properties in SS400 Steel Weld Zone

Abstract

Indentation testing including spherical and three-sided (Berkovich) indenter tips were conducted to evaluate the strain rate effect on the plastic properties in the weld zone of a popular structural steel, SS400, in this study. Two types of indentation test were under taken at a number of strain rate values from 0.03 to 0.2 s⁻¹ in the weld metal (WM), heat-affected zone (HAZ), and base metal (BM) regions of the weld zone. The plastic properties including strain hardening exponent (n), yield strength (σ_y), and α value that represents the yielding part of structural steel, in WM, HAZ, and BM were then extracted from the combination of spherical and Berkovich load-depth curves by utilizing a proposed method. As the result, the indentation strain rate effects on plastic properties in all regions of the weld zone were evaluated. The results revealed that plastic properties in the weld zone’s components are influenced by the strain rate, where σ_y and n decrease with the decreasing strain rate, whereas α value decreases when the strain rate increases.