Flaw Characteristics in Dynamic Fatigue: The Influence of Residual Contact Stresses

Abstract

The effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation‐induced flaws is studied. Indentation fracture mechanics is used to analyze the growth of well‐defined “median/radial” cracks in combined residual (elastic/plastic) contact and applied (uniform) tensile fields, and thence to determine strength characteristics. In this way a general formulation is obtained for the fatigue strength at constant stress rate. Experimental confirmation of the essential predictions of the theory is obtained from strength tests on Vickers‐indented soda‐lime glass disks in water environment. It is thereby implied that residual stresses can have a significant deleterious influence on the fatigue behavior of any brittle solid whose controlling flaws have a contact history. Such effects need to be considered in the design of structural ceramics, most notably where fracture‐mechanics calibrations of crack‐velocity parameters are used for lifetime predictions.