The Fatigue Life Study Of A Car Body Based On The Random Vibration

Using CAE technology in the design phase to predict vehicle performance accurately is a hot content and the future development trend. The application of Finite element method in the automotive industry and the development of computer technology provide an advanced means for the car body structure design, and we can identify problems in design and make some corresponding improvement.In this paper, the author take a car body as an example and firstly established a detailed finite element model of the body, making some appropriate simplification to meet the need of the actual analysis of the situation. The concrete simplification including vehicle door, cowling, power unit, chair, etc, using the mass element to simulate them, connected with the corresponding spot of automobile body according to their mass center.First of all, the author analyses the free modal and constrained modal of the car body. The analysis aim of free modal analysis is to test the rationality and the natural frequency distribution of the model; The way of restraint of constrained modal is the same to that of frequency response in order to obtain the frequency distribution in the situation of constrained modal.Then the author analyses the frequency response characteristics of the car body using the modal analysis method.Finally, analyses the fatigue life of the car body.First of all, generating the S-N curves of materials accordance with the mechanical properties of materials in Fatigue software and grouping the body based on the materials; then the author treatment the data of acceleration, creat PSD files, analyses the correlation between different path spectrums and create a cross-spectrum matrix and a uncross-spectrum matrix. With the results of the frequency response of the stress, the S-N curve of materials and spectral matrix, the author analyses the durability in Fatigue software to identify the poor life expectancy of the car body,on this basis conducting a sensitivity analysis, as well as a number of improvement measures. This conclusion can provide reference to improve the car body.