Fracture analysis approach of DP600 steel when subjected to different stress/strain states during deformation

Abstract

One of the major manufacturing processes to produce components from flat sheets is forming. The automotive industry is one of the highest markets for stamped parts and is, thus, a major driving force for the development of new materials and technologies. In recent decades, there is increasing competition and growing demand for light weight, high-performance, and crashworthiness structures in the automotive vehicle forced steel industry, automakers, and the scientific community to focus more on efficient manufacturing. In recent decades, the increasing competition and growing demand for steel structures in automobiles was observed, especially for advanced high-strength steel (AHSS) parts. Thus, a better understanding of the formability of these materials is necessary to reduce costs and optimize the process. In order to better understand the mechanical behavior of AHSS, many authors have been researching the fracture aspects related to the stamping conditions. The main aim of this study was to analyze the type of fracture in DP600 steel when subjected to different stress/strain states (uniaxial and biaxial stress and plane strain) imposed by deep drawing and stretching. The experimentations led to a detailed understanding of the influence of stress/strain state in the mechanism of fracture, particularly, under plane strain—which showed quasi-cleavage regions surrounded by dimples. In addition, the microstructural analysis confirmed that the DP600 steel can show ductile fractures with some aspects of brittle behavior, depending of which stress/strain state was used for deformation. As a result, the DP600 forming limit curve related to micromechanisms of fracture generated by uniaxial and biaxial tensile stress and plane strain was presented.