A new evaluation indicator and method of rail rolling contact fatigue damage behavior based on crack morphology database

Rolling contact fatigue (RCF) damage is one of the main failure modes of rails, and small-scale twin-disc experimental simulation for evaluating rail RCF behavior is an important tool for material optimization and service-oriented material selection. However, current evaluation methods for RCF damage behavior are generally limited to single indicators and lack widely recognized and comprehensive evaluation approaches. In this study, a novel evaluation method was developed based on a damage morphology database and indicator screening. The advantages of this method are as follows: 1) The material morphology database covered the subsurface RCF damage data across various simulation rigs, roller sizes, environmental conditions, contact parameters, and rail materials, which can comprehensively reflect the material RCF damage severity; 2) A representative sample library containing 100 crack morphologies constructed based on stratified random sampling with the support of evaluation by nineteen experts in the field of wheel-rail damage, had strong objectivity and authority; 3) A novel damage evaluation indicator Sc was proposed based on the combined consideration of crack depth, crack width and crack length. And by integrating physical significance with statistical fitting (R-2 = 0.946), a novel evaluation method can directly determine the damage level of materials, specifically involving Mild (S-c <= 3), Severe (3 < S-c <= 6), and Catastrophic (S-c > 6). Moreover, application validation demonstrated that this evaluation method comprehensively evaluated rail RCF damage severity when individual indicators such as crack depth and crack length presented contradictory trends, and provided an intuitive reflection of the evolution of RCF damage severity by linking crack evaluation results with the reference crack morphologies in the sample library.