Hysteresis, Temperature and Resistance Measurements for the Characterisation of the Fatigue Behaviour of Metals

Mechanical stress-strain hysteresis, temperature and electrical resistance measurements were performed for the detailed characterisation of the fatigue behaviour of the quenched and tempered steel SAE 4140 (42CrMo4) under constant amplitude loading and service loading. On the basis of generalised Morrow and Basquin equations the fatigue life calculation method “PHYBAL” was developed. Short constant amplitude sequences with a stress amplitude of about 80 % of the endurance limit are periodically inserted in service loading tests to measure the plastic strain amplitude, the change in temperature and the change in electrical resistance. For the fatigue assessment under service loading the average values of each constant amplitude sequence are plotted in cyclic deformation curves, similarly as practised for constant amplitude tests.