A Test for Evaluating the Effects of Stress-States on Damage Evolution with Specific Application to the Hot Rolling of Free-Cutting Steels

A new conical splay test is developed to assess the mechanisms of damage evolution in a range of stress states representative of hot rolling. The test consists of a bulk forming operation between open dies, during which plastic deformation occurs across a gradient of stress states from near-uniaxial tension to highly compressive. The transition between tensile and compressive stress state allows the microstructure to be accurately linked to the corresponding stress state. FE simulation of the new test is used to analyze the stress-state history during deformation. A low-carbon free-cutting steel, which is prone to edge cracking during hot rolling, is studied and the modes of damage evolution are discussed.