THE EFFECT OF STATIC TENSILE STRAIN ON FATIGUE FAILURE - AN EXPERIMENTAL-STUDY USING LASER SPECKLES

This paper describes a study on the surface roughness change due to fa tigue and the effect of static tensile strain on fatigue failure. Fati gue damage manifests in the form of surface roughness change. The roug hened surface topography is responsible for crack nucleation. An impro ved laser speckle technique which can detect surface roughness change is employed to investigate the damage and failure of Al 5052-H32 produ ced by cyclic strains superimposed on static tensile strains. Within t he range we investigated, the effect of static strain on fatigue life is noticeable but limited. By introducing a parameter called ''apparen t strain'', we have proposed a damage model to incorporate the effect of static strain into the cyclic strain-life relation. (C) 1998 Elsevi er Science Ltd.