Damage characterization of SAE 1020 and 1045 steel under torsion and compression

A damage model is applied to characterize the ductile deformation of SAE 1020 and 1045 steel. Damage is evaluated for thin-walled cylindrical specimens in torsion and solid bar specimens in compression where stress triaxiality enhances crack initiation. Analyzed are the variations of the damage parameter with the average compressive axial strain at the different locations of the solid bar. Initially, stress triaxiality being largest at the center appeared to dominate damage. With increasing strain, pronounced damage tends to occur in the mid-plane at locations closer to the free surface. Change in the aspect ratio of the cylindrical bar specimens also had an effect on the stress triaxiality and hence the damage parameter. Less damage is prediated for slender bars at the same strain level although the difference is small for height to diameter ratio up to 1.86.