Prediction of crack induced failure phenomena in rolling operations

Abstract

Modern ductile bulk fracture criteria are calibrated and evaluated in cold cross rolling processes using a boron-alloyed tempered steel as workpiece material. Notches were rolled into more than 400 workpieces in order to investigate the occurrence of core cracks (Mannesmann-effect). The used tools have been designed and produced to deform the workpiece under different stresstriaxialities (0.2 to 0.6) and Lode-Parameters (-0.9 to 0). Both the roller width and the number of workpiece rotations per Diameter reduction have been found to be important parameters influencing ductility decisively. The simulative results show a significant influence of both stress-triaxiality and Lode-Parameter on ductility.