The effect of rolling direction reversal on fatigue crack morphology and propagation

Abstract The effect of repeated rolling direction reversal on crack morphology, propagation and RCF life of rail steel is investigated in this paper. It has been established that reversal is of beneficial effect on RCF life. This effect is a function of the reversal regime. An optimum reversal is achieved when the number of rolling cycles per reversal is between 25% and 37% of the uni-directional RCF life cycles of the material. Under such a reversal regime, the RCF life is almost doubled. Rolling direction reversal appears to affect RCF cracking propagation as well as morphology. A new mechanism, the ‘variable crack face friction mechanism’, is proposed to explain this effect.