On the special angle of surface cracks propagation in the railway rail heads

•Crack-like defects were studied on running surfaces of railway rails theoretically.•The most dangerous orientation of the crack for its Mode II growth was revealed.•Inclination angle (20–40°) and growth direction of the crack agree with engineering data well.•The conditions for finding the characteristic angle have been put down.•The characteristic angle is the basis for formation of pitting, squat, checks. Investigation of crack-like surface defects on running surfaces of railway rails was carried out using the Keer-Bryant model scheme. For this purpose by singular integral equation method, the contact problem for an elastic half-plane with an edge crack was solved, taking into account the general conditions of crack faces interaction (slip, stick, opening). Dependence of the range of stress intensity factors KII in contact cycle on crack orientation angle for different service parameters, namely friction between the wheel and the rail, length of the crack and friction between its faces was investigated in detail. As a result, it has been shown that surface cracks on running surfaces of rails grow in the direction of the rolling stock traffic at shallow characteristic angle by transverse shear mechanism. This angle is a basis for formation of typical surface contact fatigue damages, such as pitting, squat, checks. The conditions for finding it have been put down. Characteristic angle values found theoretically agree with engineering data well.