Study on temperature time related high cycle fatigue damage life model of M50 bearing steel
The fatigue limits and S-N curves at 25,200,and 315 ℃ were measured by using the QBWP-10000 cantilever rotary bending fatigue testing machine.The slow,stable,and fast crack propagation rate curves at different temperatures were tested using a universal testing machine.Based on the fact that fatigue cracks in M50 bearing steel mainly originate from carbides in the steel,a local damage life model related to temperature and time was established by combining the temperature dependent variation of parameters such as elastic modulus and Poisson's ratio with the hardening effect caused by cyclic stress at the carbide interface.Research has found that the stress intensity factor of fatigue defects such as carbides in M50 bearing steel is the amount of fatigue damage;the increase in temperature shortened the crack initiation time and accelerated the crack propagation rate,thereby reducing the fatigue ultimate strength of M50 bearing steel;the main factors affecting the initiation life are the number of cycles,temperature,fatigue defects,and local hardening of carbide interfaces caused by applied cyclic stress.
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