Research On Equivalent Method Of Fatigue Test Of Drive Axle Platform Based On Actual Load Spectrum

The microbus drive axle,engine and cab together form the core three components.As the end of the powertrain,the drive axle plays the role of deceleration and torsion and changes the direction of power transmission.Fatigue durability testing is an essential and important part of the drive axle development process.Indoor bench tests can compensate for these shortcomings,but are often limited by the dynamic response capability of the loading motor and often only load a single condition,which is not a good simulation and can easily lead to over-testing or under-testing.Therefore,this paper combines the advantages of the bench test,studies the bench test and the test field test equivalent correlation method,the actual load spectrum is equivalent to the program load spectrum,and the use of CAE simulation technology to verify the load equivalence,can better provide theoretical and technical support to improve the efficiency and accuracy of the drive axle bench test.Firstly,a method was developed to collect the load spectra from the user and the test track,and a synchronous data testing system was set up to collect and process the actual load spectra from the user and the test track respectively.On this basis,the load spectrum was extracted for each gear load and the rain flow count,and the characteristics of the from-to rain flow matrix of the axle load and the from-to rain flow matrix of the tooth load at the output end of the drive axle were analysed.Secondly,the distribution of user loads at the target mileage was predicted by superimposing the axle loads and tooth loads and applying a non-parametric two-dimensional kernel density estimation method to achieve a two-way extrapolation of load magnitude and frequency.Combined with the pseudo-damage theory,a damage correlation model between the user pavement and the test site was established,and a multiple linear regression model was constructed under the constraints of each test site condition,and the NSGA-II multi-objective optimization method was applied to complete an equivalent reconstruction of the test site road test condition,which was consistent with the actual user use.Thirdly,in order to carry out fatigue strength analysis and rotational bending fatigue load spectra for the drive axle half-shafts and gears,finite element modelling of the drive axle half-shafts and master and driven gears was established with the aid of Hypermesh software and Abaqus post-processing software,boundary constraints were added,and the fatigue strength of the half-shafts and gears were analysed under ultimate torque loads.Finally,based on the finite element modelling of the drive axle half-shaft and main and driven gears,a transient dynamics model of the gear system was established and dynamics simulation analysis was carried out.Combined with the actual load spectrum of the reconstructed drive axle test field,the equivalent selection method of parameters such as torque,rotational speed and loading time required for the rotating bending fatigue test of the drive axle was studied,and the load spectrum of the fatigue test procedure was compiled.At the same time,the load spectrum for the torsional fatigue procedure was prepared by transforming the axle rain flow matrix into a Goodman average stress.The validity of the two types of procedural load equivalents before and after preparation was verified by combining the finite element models of the half shafts and the master and driven gears.