Constitutive response of welded HSLA 100 steel

Abstract

The dynamic mechanical behavior of a welded joint of high-strength, low alloy (HSLA) 100 steel was investigated by both quasi-static (103 s −1) and high strain rate (103 s −1) tension loadings at ambient and low temperatures. The constitutive responses for the microstructurally different weld and base steels, along with the interface, which included the heat-affected zone (HAZ), were analyzed and compared. This response is successfully modeled by the mechanical threshold stress (MTS) constitutive equation for different regions of the welded joint, which shows qualitatively different behavior. The necking and failure occurred uniformly within the weld metal but not in the HAZ. The main mechanism for the failure of the welded joints is void growth. Microstructural characterization revealed that the nucleation of voids occurred mainly at the interface between the base and the weld metal, and initiated at inclusions. Measurements of damage distributions across HAZ were made to evaluate the contribution of porosity variation to the constitutive response. In both the quasi-static and dynamic tests, the deformation localization in the form of necking first appeared in the weld metal. Fractographic observation demonstrates that void evolution is a dominant factor in the macroscopic mechanical response. The Gurson–Tvergaard model was included in the modeling effort to incorporate the effect of void opening on the mechanical response as well as tensile instability. The MTS constitutive model was successfully implemented to the tensile regime of loading.