PHYBAL a Short-Time Procedure for a Reliable Fatigue Life Calculation

The reliable calculation of the fatigue life of high-strength steels and components requires the systematic investigation of the cyclic deformation behaviour and the comprehensive evaluation of proceeding fatigue damage. Besides mechanical stress-strain hysteresis measurements, temperature and electrical resistance measurements were used for the detailed characterisation of the fatigue behaviour of the steel SAE 4140 in one quenched and tempered,. one normalised, one bainitic and one martensitic condition. To guarantee optimal operation conditions the new fatigue life calculation. method PHYBAL on the basis of generalised Morrow and Basquin equations was developed. It is a short-time procedure which requires the data of only three fatigue tests for a rapid and nevertheless precise determination of S-N (Woehler) curves. Consequently, PHYBAL provides the opportunity to reduce significantly experimental time and costs compared to conventional test methods.