| It is dangerous that thermal crack of the brake disc would cause accidents. If not be monitored, the brake disc will be crack to probable loss for train device and passager. Setting up a system to evaluate defect and lifespan of the brake disc for high-speed train would be easy to train safety, and it will be of very important theoretical and practical significance.In this paper the flaw assessment and life estimation of the brake disc of high-speed train as the research object. The crack of the brake disc is investigated, and the base law of fracture on a brake disc is analyzed for China Star and Xian Feng, Temperature fields and thermal stress fields of brake disc are simulated during emergency braking,, The principle on the flaw assessment and life estimation of the brake disc is studied deeply with fracture mechanics approach and test. Assessment system has been developed to evaluate defect and life span of the alloy- forging steel brake disc. This paper was focused as followed:(1) The crack of the brake disc is investigated for China Star and Xian Feng, which find the flaw disturbed law. The feature of macro-profile is analyzed, a new interpretive method is put forward for the relational law between the fatigue crack and feature of macro-profile, which provides a new method for the life estimation of the brake disc. (2) Crack propagation at the surface was discussed, including the crack propagation rate and the direction of the crack propagation with linear elasticfracture mechanism. The fracture toughness KIC and flaw growth rate with cycle da/dN are determined with SE(B) test, then the threshold stress intensity range ΔKth is computed, which offer test data for the flaw assessment and lifeestimation of the brake disc.(3 ) The principle on the flaw assessment and life estimation of the brake disc is studied deeply with fracture mechanics approach. A fatigue crack analysis...
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