Study On Welding Residual Stresses Of Drive Axle Housing Based On Modal Experiment

Welding residual stress is materials stress which generated in heating and cooling process Although the components exist residual stress work in under the condition of smaller stress, but the residual stress of each other may result in components damage such as the occurrence of damage, fatigue and fracture, reduce the bearing capacity of the structure. Axle housing was welded by two bridge shell pieces and two end flange, in the process of production there will be residual stress, the larger residual stress also can bring adverse effect to the bridge shell, therefore understand the axle housing and residual stress is necessary.This topic on the basis of institution of modal test, combine the component residual stress of its inherent frequency and the frequency response function, through the change of natural frequency and frequency response function to derived the size of the residual stress.The concrete is divided into five steps.1. Wrote the modal identification software. Pretreatment of the measured signal should be done at first,such as eliminate trend term, filtering and smoothing and so on; Secondly, solved the power spectrum and cross-power spectrum, frequency response function, etc.; Finally, provided parameter identification method such as the admittance circle, peak picking method, PLOYMAX method. Wrote residual stress measurement software, imported frequency response function and judge the size of the residual stress by compared of the frequency response function.2. Got a piece of 400 mm* 300 mm* 4 mm steel plate by welding two pieces of 200 mm* 300 mm* 4 mm steel plate, compared with another piece of the same fabric of 400 mm* 300 mm* 4 mm contrast plate.measured the residual stress of welded plate in the method of blind hole; got the excitation response signal of two plates by using Donghua test research and development of dynamic signal acquisition system, used own modal recognition software to get the frequency response function and the former six order natural frequency value, the frequency response function was saved as a text file used to compare.3. Imported the frequency response function curves of two panels into the residual stress measurement software and compared in the it. The comparison results show that the natural frequency of welded plate with residual stress are higher than contrast plate without residual stress, and except for the first order, the bigger the order number, the higher the rate of change, the greater the frequency response function response moves to the right. This fully shows that the influence of residual stress on the component vibration characteristic, provides the basis for the drive axle housing based on the modal test of residual stress measurement.4. Using a normal axle housing as a standard, inspired by modal test and got the response signal, then calculated the frequency response function. The frequency response function was saved as text files as a standard for comparison.5. The modal experiment was carried out on the axle housing which had experienced the welding and natural aging and knock, imported the measured incentive and response signal into the modal identification software, input sampling and processing parameters, and the frequency response function is calculated. Input the frequency response function into residual stress measurement software, compared with the standard frequency response function. It is turns that frequency response function peaks of the axle housing after natural aging and knocked at right of the peak point of the standard frequency response function, its inherent frequency is higher than standard component, residual stress is greater than the standard part.