Research Of Security On The Plate Hole Cracks In A Wagon Wheel

The type840D wheel used to be the largest amount of wagon wheels in service, with its number almost up to3.2million. The fatigue crack around the plate hole of840D wheel was the main form of wagon wheel malfunctions, which resulted in a couple of operation accidents, seriously threats the railway transportation safety.Based on the analysis to abundant investigation and statistic data of the crack around plate hole of840D wheel, plus the simulation to stress and crack intensity factor of wheel-rail load and heat load during braking, this thesis studies the crack initiation condition, crack propagation law, residual life, crackallowance size and serving safety. The primary work and remarks of this thesis are as follows:1. Experimental research on crack initiation and propagation lawThe analysis of macroscopic and microscopic fracture pattern and metallographic character were processed to determine the crack initiation mechanism and propagation model; then crack initiation life of spoke plate were studied.2. Simulation research on crack initiation and propagation lawThe stress and strain of plate hole and crack stress intensity factor have been analyzed by finite element method according to the wheel-rail mechanical load and heat load during braking. The stress superimposing method was put forward for solving the stress superimposition under mechanical and thermal loads. The model was set up to study influence of rim wear and plate hole offset on crack initiation life and residual life, then the crack forming life, expanding life and residual life are calculated under braking condition and other typical conditions on the Datong-Qinhuangdao Railway. Based on this, the load cause of crack forming and expanding was analyzed, the influence mechanism of rim wear, position of plate hole and other geometrical factors on crack forming and expanding were discussed.3. Simulation of complex crack stress intensity factor and study on breaking rulesThe3D FE model of crack around plate hole was set up applying the1/4node displacement method and the sub-model technique. Based on study on complex crack intensity factor, the stress intensity factor variation rules under different crack dimensions were simulated, then breaking rules of complex crack around plate hole were established, critical dimensions of crack expanding was predicted.4. Statistical analysis on the sample data According to the sample data both in tracking observation of the operating wheels on the Datong-Qinhuangdao Railway and the management information system of railway wagon (HMIS), which was equal to20316, obtained from7wagon plants. This thesis draw relationships among crack ratio with employ time, rim thickness and hole offset. The probability model that can be used to predict the crack initiation lifespan and expansion velocity was built with the adoption of a2-parameter Weibull distribution, then the crack initiation lifespan and expansion velocity under different reliability were analyzed and the safety states of operating840D wheels could thus be inferred.5. The engineering application of the plate hole crack studyBased on real braking conditions on the Datong-Qinhuangdao Railway, braking conditions in straight line and curve line were complementary, the influence on wheel strength was simulated by inputting tread braking heat This thesis made a correction to the UIC510-5wheel strength assessment using mean stress method. The structure optimization of wagon wheel spokes and the feasibility analysis to the rim crack expanding study are also put out.