Shear strain based multiaxial fatigue parameters applied to variable amplitude loading

The Kandil-Brown-Miller parameter and Fatemi-Socie parameter are comparatively studied in the perspective of application to multiaxial fatigue under variable amplitude loads. The former is given in terms of shear strain and normal strain, whereas the latter uses normal stress instead of normal strain. The planes of maximum shear strain range and maximum damage are examined as the critical plane. Fatigue lives are evaluated by rainflow cycle counting on the shear strain history and applying the Miner-Palmgren damage rule. Predicted lives are compared with experimental lives obtained on S45C steel. It is found that both parameters can correlate test data within an acceptable accuracy irrespective of which plane is used for the critical plane. (C) 1999 Elsevier Science Ltd. All rights reserved.