The Biomechanical Relevance of Stress Range and Mean Stress in the Analysis of Variable Loading on Musculoskeletal Tissues

Musculoskeletal tissues usually experience loading referred to in the fatigue failure literature as “repeated stress” or “fluctuating stress” during the performance of occupational tasks. In addition, loads experienced during occupational work often involve highly stress variability. Under these types of loading conditions, the development of cumulative damage is highly influenced by the stress range and the mean stress associated with the loading regimen. This paper describes fatigue failure analysis techniques associated with variable loading situations, including cycle counting techniques, Goodman and Gerber equations for estimation of fatigue life, and the relevance of stress range and mean stress on damage accrual.