Effect of stop-hole-induced material removal on the fatigue properties of cracked DT4C steel

Abstract

There is a lack of a quantitative study on the appropriate value of material removal Lr from the crack-tip front induced by drilling a stop-hole. The effect of Lr variation on the fatigue life and post-initiation fatigue crack growth rate (da/dN) of a cracked specimen was studied for two different stop-hole geometries (circle and ellipse). Three different values of Lr = 0.3, 0.6 and 0.9 mm were selected for the parametric study by changing the location of the stop-hole center in relation to the initial fatigue crack-tip. The results show that Lr = 0.6 mm results in the longest fatigue life and lowest post-initiation da/dN for all the specimens repaired by either circular or elliptical stop-holes. In addition, the fatigue-life extension and post-initiation da/dN reduction resulted from the elliptical stop-hole are significantly more than those of the circular stop-hole for the same Lr.