The Research Of Aluminum Alloy Car Body Model Updating Base On Sensitivity Analysis

It's a significant task to improve vehicle dynamic performances and predict the mode parameters of the high speed trains by accurate finite element model. However, the error in the aluminum alloy car body modeling cannot be avoided. In order to keep accuracy of the finite element model and provide a reliable mathematic basis for the later structure design and optimization, the model updating of aluminum alloy car body was systematically studied based on the sensitivity analysis in this paper. The main contents are shown as follows.Firstly,the sensitivity analysis method of structure mode frequency and mode correlation coefficient were studied. The influence of structure mode shapes changes on modes eigen-value sensitivity was discussed. The sensitivity analysis method of mode frequency and mode correlation coefficient were derived based on the influence of mode shape changes. As varied design parameters of the car body finite element model, the design parameters change ratios were used to replace the physical design parameters and unify the mode parameter sensitivity to design parameters. Base on the unified sensitivity analysis method, the sensitivities of four modes to thirteen design parameters of aluminum alloy car body were calculated including the first order diamond, the first order vertical bending ,the first order torsion and the first order literal bending.Secondly, the high speed train mode test method and its procedures were researched. In the frequency range of 0-50Hz, the mode parameters were identified and the simulation modes were calculated with finite element method. Considering the mode frequencies errors and the correlation coefficients of mode shapes, the matching and judging principles of modes accuracy were founded. The accuracy of finite element model is evaluated combining the judging guide with the mode errors.Thirdly, the parameter sensitivity result is used to choose sensible mode updating parameters. Taking the mode frequency error and mode shape correlation constant as the updating objective, the multi objective function of car body model updating is modeled. The shortage of the least square method is avoided with the Tikhonov theory and detail of solve steps.Then, the multi objective function of car body model updating was solved under the constraints of Tikhonov regulation method. The updated model of car body was validated with mode accuracy matching and judging principles. In order to ensure the parameters actual range and physical sense, the updated parameters was concluded and compared.Finally, the influences of three main factors on the car body model updating were studied, which included the weight coefficient ratio of updating objectives, the initial model error of car body and the incomplete characteristic of updating modes. The influence trends on car body model updating were considered in three fields, including updating efficiency,the accuracy of updated modes and design parameters.