Residual stress measurement and prediction in a hardened steel ring

The residual stress profile in a hardened layer of steel was measured and then compared with a finite element prediction. A thick ring made of low alloy gear steel was case hardened by carburization and quenching. The residual hoop stress variation in the 1 mm thick hardened layer was measured using the crack compliance method, in which surface strains are measured as an axial slot is incrementally extended from the outer surface inward using wire electric discharge machining (EDM). The surface residual stresses were also measured using x-ray diffraction. The results compared very well with finite element predictions using DANTE, a heat treatment simulation software package interfacing with the finite element code ABAQUS. The heat treatment cycle is simulated in an uncoupled serial analysis of carburization by diffusion, quenching by conduction and convection including phase transformation kinetics, and finally a structural analysis incorporating TRansformation-Induced Plasticity (TRIP), Accurate residual stress profiles require detailed knowledge of the heat transfer coefficients of the quench media as well as alloy-dependent descriptions for phase transformation kinetics and TRIP strains.