Crack Propagation Analysis And Damage Accumulation Prediction Of Metro Gearbox Gears

Urban rail transit plays a vital role in the rapid development of society.With the continuous development of the rail transit industry,higher requirements are also placed on the operation of subway vehicles.As a key component of the subway transmission system,the gear's health directly determines whether the vehicle can operate safely.Gear bending fatigue fracture is one of the main forms of gear failure.Once the bending failure occurs,it will bring huge losses to all aspects of society.This paper mainly studies the bending fatigue crack propagation law of the gearbox gear of urban rail vehicles and the cumulative damage problem of the whole life.The main research work of the article is as follows:1.The finite element model of the gear pair is created.The method of simplifying the model and the modeling process are introduced in detail.The simulation results are analyzed.The gear meshing process is distinguished by observing the force of the tooth root during the gear meshing process.The root region establishes a local coordinate system,and through the further analysis of the force form of the root,the failure mode of the root crack initiation is determined.2.Based on the extended finite element method,a two-dimensional gear root crack propagation model is established.The expansion law of the root crack is further explored.The simulation results are compared with the test gear to verify the correctness of the model and analyze the stress change at the crack tip.The crack propagation process is divided into extended zone and instantaneous fault zone,and the failure mode in crack propagation is determined.The crack propagation law of different loading locations is explored by presetting five different loading positions.3.The finite element method is used to calculate the stress intensity factor at the leading edge of the tooth surface.The shape of the pre-crack is determined by observing the gear flank fracture.The crack is prefabricated at the position where the root bending stress is the largest,the stress intensity factor of the crack leading edge is calculated,and the variation law of the stress intensity factor at the crack front is analyzed.On this basis,the variation of the stress intensity factors of the different loading positions of the tooth surface,the short axis radius of different elliptical cracks and the pre-fabrication position of the crack are deeply explored.4.Using the continuous damage model proposed by Fang Qingyi,considering the interaction relationship between multi-level loads,the load interaction factor is introduced into the continuous damage model to correct the continuous damage model.The high-frequency fatigue test bench is used to perform the gear bending fatigue test.The test sets the two-stage root stress to load,and sets the number of cycles of the first-stage load according to the first-stage load at the percentage of 25%,50%,and 75%of the theoretical life.Based on this,a second-stage load test is performed to verify the accuracy of the model under the secondary load.