INFLUENCE OF TEST PARAMETERS ON THE MEASUREMENT OF THE ESSENTIAL WORKOF FRACTURE OF ZINC SHEETS

The Essential Work of Fracture (EWF) concept is used to characterize t he fracture of thin plates of a zinc alloy. The consistency and applic ability of the EWF approach are discussed. The successive stages of th e fracture process were studied: the evolution of the shape of the cra ck tip was observed with a scanning electron microscope, the shape of the plastic zone and the evolution of necking in the ligament ahead of the crack tip were measured using a laser profilometer and the onset of cracking in the ligament was detected by means of a TV camera coupl ed with acoustic emission recording. The influence of both test parame ters and material parameters on the Essential Work of Fracture (omega( e)) and on the CTOD (delta(c)) are elucidated. The effects of specimen geometry, deformation rate, texture and grain size are especially inv estigated. The main advantages and drawbacks of the EWF method are hig hlighted.