Fatigue Life Prediction For The Semi-trailer Frame Based On Modal Frequency Response

With the development of national economy, heavy vehicle safety was highly required. But the reliability of domestic automobile dispatched, the fatigue weakness points were in multiple vehicle structure. In the stage of design mode, Modal,strength, stiffness and fatigue of auto parts were accuratly analysed and calculated, Possible failure state and fatigue life of parts can be predicted at an early stage, it can effectively shorten the product development cycle, improve the design efficiency, reduce the cost of development.In the finite element analysis, time domain signal is very complex,a large amount of data were required to deal with and brought greater difficulty.the power spectral density as the excitation model’s input signal was used, therefore efficiency of calculation can be improved. Through the modal frequency response analysis, stress or strain close to natural frequencies was obtained. Therefore, the modal frequency response is adopted to semi-trailer frame fatigue analysis in this paper.Fatigue life calculation for semi-trailer frame was achieved using analysis method based on the modal frequency response. Firstly, modal frequency response analysis for the frame was finished in Msc.Patran, Simultaneously, the vehicle multi-body dynamics model was established in ADAMS/car, the simulation analysis was conducted based on the E grade road, thus the load time history of each connection point of the frame was obtained, and the dynamic load was transfered into power spectrum density. Combined with the dynamic load analysis and the results of finite element analysis, the frame fatigue life and the most dangerous point in the life value analysis was to be get based on the Dirlik method. The calculation results show It is proved by the test that based on modal frequency response analysis of fatigue method can quickly、effectively to predict fatigue life of semi-trailer frame under random dynamic load.