Evaluation Of Fatigue Performance And Remaining Life Of Wheel Webs Of Emus

With the gradual improvement of my country’s four horizontal and four vertical railway network construction,in 2020,the total service mileage of national railways increased by about 5% year-on-year.The total service mileage of high-speed railways and intercity railways increased by about 11.43% year-on-year,continuing to lead the world.High-speed train wheels are key components for vehicle operation,steering,and load bearing as well as transmission.Its safety and reliability directly determine the quality of vehicle operation.At present,under the action of alternating loads,fatigue damage happens in the tread and nontread areas of the wheel,such as tread peeling,web corrosion cracks and wheel hub cracks,which seriously threaten driving safety.Therefore,it is of great significance to predict the remaining life of cracked wheels under service conditions and to conduct reasonable maintenance to ensure driving safety.In this study,the imported wheel ER8 C steel rolling material is selected as the research object.The main research contents are as follows:First,the uniaxial tensile properties,low-cycle and high-cycle fatigue properties,and crack growth rate characteristics tests were carried out on the ER8 C rolled steel material for wheel webs,and the fatigue-related material parameters were obtained.Taking into account the differences in geometry,loading methods and surface roughness of full-size wheels and small specimens,the service performance of full-size wheels is predicted,which makes the remaining life prediction of wheels more accurate and closer to engineering reality.Secondly,the three-dimensional geometric modeling of the wheel set and track is established,and the model is divided into hexahedral solid elements.Boundary conditions and loads are applied to the model,and the critically safe part of the wheel web area is determined to be located at the transition between the hub and the web,which is 186 mm from the wheel center.Then,the five-level load spectrum was used to inversely derive the stress spectrum of the critical safety part of the wheel web and the modified Miner criterion was introduced to evaluate the fatigue life of the key part of the wheel web.The calculation results show that the wheels can reach the design service life index.Finally,based on the 5-level load spectrum,combined with the actual fracture morphology of the wheel,semi-elliptical cracks of different depths are implanted in the critical safety part of the wheel web.The remaining life of the cracks is evaluated by using the damage tolerance method,combining Paris,i LAPS and NASGRO models and the crack propagation test data.The calculation results show that cracks located at the critical safety part of the wheel web will not propagate,when the length is less than 0.6 mm.The calculation of the three models illustrates that the cracks will expand from 2 mm to 8 mm for approximately 868,000 kilometers,2.032 million kilometers,and 3.832 million kilometers,respectively.That meet the design life needs.The traditional and EI-Haddad modified Kitagawa-Takahashi(K-T)diagrams are established for wheels,and the critical defect sizes are 1.5 mm and 1.1 mm,respectively.The research results can provide theoretical guidance for wheel design,overhaul and maintenance.