Fatigue Fracture

Abstract

Fatigue fracture is one of the primary damage mechanisms of structural components. Prior to final failure cracks or microcracks are induced. The fatigue cracking results from cyclic stresses that are below the ultimate tensile stress, or even the yield stress of the material. Surface flaws small are serving as stress risers where cracks can initiate, leading to fracture under repeated stresses. Porosity is detrimental to fatigue resistance and addition of small amounts a metal such as Ni for example, can improve the fatigue resistance by increasing the density. Fracture process can be divided into three stages crack formation, propagation and rapid fracture stage. Alumina, magnesia, zirconia, SiC and Si3N4 subjected to fatigue fracture are presented and the effects promoting or resisting their progress are considered.