Initiation of Fatigue Cracks in Ground High Carbon Steels

Abstract

The effect of grinding (including one pass grinding) on the initiation of fatigue cracks in high carbon steels (S 48 C and SK5) was studied, under different grinding conditions. The main results are summarized as follows. (1) When the grinding direction was parallel to the loading axis, the origin of the fatigue cracks was nonmetallic inclusions and abrasive grains imbedded into the steels, in every case. (2) When the grinding direction was at right angles to the loading axis, fatigue cracks were initiated in the region of grinding streaks, in every case. (3) For one pass grindings, when the grinding direction was at right angles to the loading axis, defects bred by the displacement of imbedded abrasive grains sometimes caused fatigue cracks. (4) For one pass grindings in the same direction, fatigue strength of wetly ground specimens was higher than that of dryly ground ones.