Effect of High Temperature on Thermal Fatigue Crack Initiation Life of Automotive Gray Cast Iron Brake Disc

Abstract

：The brake disc of a vehicle often works at high temperature, and its damage caused by thermal fatigue easily takes place. So the performance of the vehicle brake disc is directly related to the safety of driving, and it is very necessary to study the thermal fatigue crack initiation life of the brake disc at high temperature. The monotonic tensile and compressive tests of gray cast iron HT200 sample for vehicle brake discs are carried out at 500 ℃, and the stress-strain curves are analyzed to obtain mechanical properties at 500 ℃; then based on these parameters, the finite element software ABAQUS is used to establish the thermal-structure coupled finite element model of the vehicle brake disc with the initial temperature of 400 ℃, and the temperature fields and stress fields on the brake disc for emergency braking condition are analyzed. Finally, the effect of the plastic property of HT200 on the thermal fatigue crack initiation life of the brake disc on the 500 ℃ is studied by using strain fatigue method according to the Miner linear cumulative damage theory. The results show that the thermal stress during braking is far greater than the mechanical stress, which is the main cause of fatigue cracks; the plastic property of gray cast iron HT200 of brake disc has a great influence on the thermal fatigue crack initiation life of the brake disc. The effect of plastic property on the life of the brake disc should be introduced in the study of the crack initiation life of the brake disc. The thermal fatigue crack initiation life of brake disc is calculated by using the circumferential strain of brake disc during braking at high temperature and considering the plastic properties of material at high temperature, which lays a foundation for the evaluation of thermal fatigue life of brake disc.

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