Study Of Composite Crack Propagation And Remaining Life Of Railway Vehicle Wheels

With Chinese high-speed railway,heavy-duty further promoted,rolling contact fatigue cracking has become a common wheel damage.However,due to the open service environment of wheel and rail and the complex stress state,it is difficult to study the rolling contact fatigue mechanism,and the composite crack propagation mechanism and residual life assessment criteria have not yet formed a unified understanding.To solve this problem,this paper takes the rail vehicle wheel as the research object and studies the internal composite crack propagation characteristics and the remaining life of the wheel.Firstly,investigate the current situation of research on wheel-rail contact problem at home and abroad,and introduce the development history of wheel-rail contact theory and the related knowledge of fracture mechanics theory.Secondly,a three-dimensional wheel-rail finite element model was constructed using Hypermesh,and the shape of the wheel-rail contact patch obtained by solving it was consistent with Hertzian contact theory,as the maximum stress appeared at 2-3 mm from the wheel tread,increasing and then decreasing along the radial direction of the wheel,and the axle weight would not change the location of the maximum stress.Then,by using Franc3 d to insert cracks of different locations,sizes and angles inside the wheel and calling Abaqus to solve,the obtained stress distribution near the leading edge of the crack is influenced greatly by the angle and location of the crack,while the size of the crack has less influence on it;the existing of the crack does not change the location where the maximum stress appears in the non-cracked area,but it will raise the maximum stress by 10～20%.Finally,by studying the expansion characteristics of composite cracks,it is obtained that: when the cracks are not expanded,the crack propagation is dominated by type II due to the larger value of the range of type II stress intensity factor;during the fatigue crack expansion stage,the crack direction changes significantly,the type II stress intensity factor decreases rapidly and turns into the expansion dominated by type I.Moreover,the cracks are continuously deflected in the direction parallel to the tread surface,and the crack surface shows three-dimensional characteristics.The location and size of cracks within the wheel have a significant impact on the remaining life of the wheel,and the corresponding damage tolerance limits are proposed based on this.The above research has obtained the stress distribution patterns near the leading edge of internal wheel cracks at different locations,sizes and angles,as well as the composite crack expansion characteristics,making a positive contribution to the research on rolling contact fatigue mechanisms.Summarising the influence of internal wheel cracks at different locations and sizes on the remaining wheel life,the damage tolerance of wheels containing cracks is proposed,as a reference for optimising wheel maintenance strategies.