Brake disc is a key component to ensure the safety of high-speed train operation. Its failure will lead to train braking failure and affect driving safety. Thermal fatigue cracks are the main failure form of high-speed train brake discs. Therefore

it is necessary to study the crack behaviors of brake disc. In order to explore the propagation law of thermal fatigue cracks

the indirect coupling simulation of the brake disc and the crack propagation simulation model based on the extended finite element method are established respectively. Firstly

the residual thermal stress of the brake disc under typical braking conditions is obtained with the finite element calculation model of the indirect coupling brake disc. Through calculation

it is found that the emergency braking with a speed of 300 km/h is the main source of residual thermal stress

and the circumferential residual tensile stress after braking is up to 767.9 MPa. Therefore

it is believed that the circumferential residual tensile stress is the cause of thermal fatigue cracks in the brake disc. Then taking the circumferential residual tensile stress as the load

the variation law of the stress intensity factors in the crack propagation was studied with the crack propagation simulation model via XFEM. It is found that the distribution of the stress intensity factors at the crack front show different distribution behaviors with the change in initial shape ratio of the crack. When the crack shape is relatively small

the stress intensity factor at the crack front is in a convex distribution

while when the crack shape is relatively large

the stress intensity factor at the crack front is in a concave distribution. The tensile load plays a major role in the crack propagation

and the crack morphology gradually tends to be flattened. The calculated results are consistent with the actual statistical data of brake disc cracks

and this study provides the certain reference for the high-speed train brake disc operation and maintenance strategies.