Gradient Fatigue Properties Of Railway HFS Wheel And LZ45CrV Axle Steels

Experimental studies on probabilistic fatigue limits and S-N curves are performed for railway HFS wheel and LZ45CrV axle steels. Following achievements are reached(1) Up-and-down tests [56] are carried out to the smooth specimens respectively from rim, web and hub of HFS wheel. A maximum likelihood method by Zhao-Yang is applied to treat the test results. And probabilistic fatigue limits are then accurately evaluated. At the same time, grouped tests are made to get S-N data to the smooth specimens from the rim, web and hub, respectively. The maximum likelihood method by Zhao-Yang-Feng-Wang is applied to treat the test results. And probabilistic fatigue S-N curves are then measured for the rim, web and hub. The probabilistic curves should be a basis of design and service analysis on the wheel fatigue capacity.(2) A comparison is performed on probabilistic fatigue limits and S-N curves for rim to web and hub to web of the HFS wheel, Gradient distributed fatigue properties are observed to the wheel material. Rim holds the highest fatigue strength capacity, web is moderate, and hub is the lowest. Difference of the strengths for rim to web tends to decrease from 26.54% to 4.86 as the increasing confidence (C) and survival probability (P). And the difference for hub to web shows a relative stable change around -15% when the C-P set changes.(3) Similarly, up-and-down tests are carried out to the smooth specimens respectively from journal and wheel seat of LZ45CrV axle. The maximum likelihood method in Int J Fatigue 2008; 30:2094-2103 is applied to treat the test results. And probabilistic fatigue limits are then accurately evaluated. Grouped tests are also made to get S-N data to the smooth specimens from the journal and wheel seat. The maximum likelihood method in Int J Fatigue 2009; 31:1550-1558 is applied to treat the test results. And probabilistic fatigue S-N curves are then measured for the journal and wheel seat. These probabilistic curves should be a basis of design and service analysis of the axle fatigue capacity.(4) A comparison is performed on probabilistic fatigue limits and S-N curves for the journal and wheel seat of the LZ45CrV axle, Gradient distributed fatigue properties are also observed in the axle material. The wheel seat holds a higher fatigue strength capacity than the journal. Difference of the strengths for the journal to wheel seat shows a little wave between-3% and -6.5%.Therefore, gradient distributed fatigue properties of the wheel and axle indicate that design and service analysis for railway wheel and axle should be carried out on a basis of knowing gradient distributed properties.