PHYBAL - Short-time procedure for fatigue life calculation of metallic materials using physically based fatigue data.

In this investigation, besides mechanical stress-strain-hysteresis measurements, high-precision temperature and electrical resistance measurements were used for the microstructure-related characterisation of the fatigue behaviour, and for the fatigue life calculation of metallic materials. In a test procedure developed at the Institute of Materials Science and Engineering at the University of Kaiserslautern, short constant amplitude sequences with a stress amplitude below the endurance limit are inserted in service load spectra. The measured physical values are plotted in cyclic deformation curves for the evaluation of deformation-induced microstructural changes and the proceeding fatigue damage under service loading, equivalent as practised in conventional constant amplitude tests. The fatigue data determined in one load increase test and two constant amplitude tests serve as input values for fatigue life calculation on the basis of generalised Morrow and Basquin equations using the physically based method "PHYBAL". With only three fatigue tests, Woehler curves can be calculated in a very good accordance with conventionally determined ones. Compared to the conventional determination of Woehler curves, the application of "PHYBAL" leads to a substantial reduction of experimental time and costs.