Crack propagation behavior in white etching layer on rail steel surface

Abstract

White etching layer (WEL) on a rail surface plays a significant role on rail surface degradation. Current metallurgical investigation found three different crack patterns in WEL (i) leading crack initiating from WEL edge and propagating along WEL boundary; (ii) crack within WEL growing vertically; (iii) trailing crack propagating either along WEL/matrix interface or kinking into rail substrate. A finite element model coupled with J-integral and stress intensity factors analysis was applied to evaluate cracking properties and predict crack extension paths. Results showed that shear mode is the dominant crack propagation mechanism. Leading crack at WEL possesses the highest potential to grow. Crack within WEL has a significant rise in cracking possibility when it extends to the lamellar interface boundary. Both of loading pressure and frictional coefficient has an accelerating effect on promoting crack propagation. Leading crack inclined with 22.6o and trailing crack inclined with 32.62o are difficult to grow.