Abstract: The third type of rolling contact fatigue(RCF3) has been observed on wheels of two types of high-power AC locomotives with six axles(Co-Co) and eight axles(2(Bo-Bo)) operating in complicated environments, such as sharp curves and steep slopes. RCF3 occurs as continuous lateral surface cracks in the zone approximately centered at the nominal rolling circle of wheels, which seriously affects the running safety. In order to analyze the influence of axle configuration on RCF3 of locomotive wheels, two multi-body dynamic models of both six-axle and eight-axle locomotives are established using the SIMPACK multi-body software, which are combining with the damage function to predict the wheel damage under complicated operation environments. The results show that RCF3 occurs only on wheels of end unguided wheelset of the bogies and locates at the high rail when curving. Considering the left and right curves and locomotive turning around, RCF3 can occur on wheels of the 1st, 3rd, 4th and 6th axles of six-axle locomotive and all wheels of 8-axle locomotive when curving. The crack growth rate of the wheels of six-axle locomotive is about 1.2-2.5 times of that of eight-axle locomotive under the dry condition when operating on the plane curves or curves with downhill slopes, while the wear rate of wheels of eight-axle locomotive is about 1-1.5 times of that of six-axle locomotive under the wet condition when operating on the curves with uphill slopes. These lead to RCF3 more likely to occur on wheels of six-axle locomotive. The root reason is that the fixed wheelbase of six-axle locomotive is larger, resulting in the larger magnitude of negative longitudinal creep force in curves. Operating on the tangent tracks, the axle configuration of locomotives has no effect on RCF3, and RCF3 occurs on all wheels operating on downhill slopes. The decrease of curve radius or the increase of the downhill slope will lead to the increase of the growth rate of RCF3 under the dry condition, and the growth rate of RCF3 first increases and then decreases as the increase of downhill slopes under the wet condition. The reason is that the significantly increased longitudinal creepage on wheels results in the increase of the wear under the wet condition, which can wear off the initiated RCF3.

Key words: High-power AC locomotives, Axle configuration, Rolling contact fatigue, Damage function, Curve, Slope