A method of filmfatigue testing and the effects of rolling direction on fatigue properties in copper film

摘要

A new fatigue testing method was proposed by whtigue cracks can be initiated and propagated in a film adhered to cover an elliptical through-hole in a base plate subjected to push-pull cyclic loads. This method was based on Eshelby's elastic inhomogeneity model. According to this model, when an inclusion in an isotropic infinite body is ellipsoidal in shape, the stress and the strain within the ellipsoidal inclusion are uniform. It follows from this that a film corresponding to the inclusion has a uniform stress at all points within it. For a finite base plate, the stress and the stress intensity factor of a crack on the film were calculated by the boundary element method. Using this method of film fatigue testing, cold rolled copper films were fatigued under various stress amplitudes with a stress ratio of Rchemical bounds0, and then the effects of the rolling direction on crack initiation, propagation and fatigue life were studied.