CAN SAFETY FACTORS BE REDUCED SAFELY WHEN DESIGNING AGAINST FATIGUE

Abstract— A statistical approach to the failure of engineering components is presented which takes account of the size distribution of defects within the structure, and growth of these defects caused by cyclic loading during service. Statistical design methods are illustrated by considering the failure of simple bars which are assumed to contain pre‐existing defects. It is argued that more efficient designs should result if safety factors are applied to failure rates rather than to design stresses (or some equivalent) since small reductions of the design stresses can lead to substantial decreases in the predicted failure rates. The statistical approach offers a controlled method of reducing conventional safety factors thus leading to more efficient designs. It also offers: (i) a rational method of assessing the safety of potentially hazardous engineering structures, e.g. pressure vessels, and (ii) a quantitative treatment of product reliability which can highlight methods of improving performance in service. Copyright © 1979, Wiley Blackwell. All rights reserved