Fitting of S-N Fatigue Curves of 20CrMoH Steel for Bearing
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Abstract
In order to get the safe service stress of 20CrMoH steel for reasonable and efficient design,rotary bending fatigue test was performed with standard bar fatigue specimens according to the service condition of axis parts in machinery industry.Parabola curve model was used to fit the S-N curve of mean value and the P-S-N curve of 0.1% failure probability and 95% confidence level for middle life and long life services.Comparison of two fitting methods,linear mathematical model and Parabola curve model,was made by means of applied statistics of fatigue.Preliminary study shows that whether in the case of 50% failure probability or in the case of 0.1% failure probability and 95% confidence level,the S-N curves fitted by Parabola curve model all exhibited higher correlation coefficient and more conservative fatigue life estimation in the middle and low stress areas,and were closer to the original data in high stress area than results fitted by linear mathematical model.
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