Investigation of bending fatigue strength limit of alloy steel gear teeth

An experimental investigation was conducted on the single-tooth pulsating bending fatigue of 38SiMnMo alloy steel at a frequency range of 140–150 Hz. Using both up–down test method and S–N curve extension method, statistical data in terms of curves and endurance limits were analysed. The testing and analytical results indicated that the ‘platform’ of fatigue curves exists and the S–N curve cannot be extended to the cyclic basic number N b in order to obtain the endurance limit. Furthermore, on the basis of the life distribution optimization, the three-parameter Weibull distribution was used for statistical data analysis. The statistical analysis showed that the bending endurance limit of 38SiMnMo alloy steel gears estimated at 99 per cent reliability and 95 per cent confidence was 284 MPa, which was located at the slightly low part of the mean line in the chart range illustrated in the standards ISO6336 and GB3480. The results demonstrated that the method described in this article was valuable.