AN EXPERIMENTAL INVESTIGATION OF FATIGUE CRACK GROWTH RATES DURING THE COALESCENCE PHASE OF CO-LINEAR SURFACE CRACKS

摘要

This paper presents results from an experimental program which investigates the fatigue crack growth and coalescence of several collinear semi-elliptical cracks. So far the coalescence process which encompasses a significant portion of the total fatigue life is not clearly understood, therefore this investigation studies in detail the crack shape development and growth rates of coalescing cracks. Detailed measurements of crack growth rates and shape development are made during the coalescence phase. From these measurements estimates are made of the stress intensity factors in the cusp region of the coalescing cracks. Experimental results of fatigue crack growth and crack shape development, including the coalescence phase, are presented for semi-elliptical surface cracks in steel plate specimens loaded in four point bending. In these tests the fatigue crack growth and crack shape development are monitored using a novel mobile DCPD (direct current potential drop) probe arrangement.