The FEA-based Vibration And Fatigue Reliability Analysis Of Coach-Body Structure

With the rapid development of automobile industry, passenger car’s ownership is increasing as well. The safety of passenger car has been increasingly concerned. Body structure, as the main bearing parts of passenger car, has a significant effect for the safety of driving. Therefore, how to measure the performance of the body structure in the design is a front-burner issue in the research field of vehicles.First of all, the finite element model of passenger car body structure was established with Hypermesh. Secondly, a static characteristic analysis together with a free model analysis was conducted with the finite element solver RADIOSS. Then, a random vibration test was carried on the body structure with the help of finite element analysis software ANSYS, the input of which is B level road load spectrum under low and high speed conditions. Finally, a fatigue reliability analysis for the maximum point of body structure was conducted under random vibration on the principle of fatigue cumulative damage.Analysis shows that the maximum stress for common static analysis under four different kinds of working conditions is 240.06 MPa. Also, the maximum displacement deformation is 8.04 mm, meeting the design requirements. By having a free model analysis on passenger car, the natural frequency of passenger car can be obtained. The low-order natural frequency ranges from 8Hz to 30 Hz, effectively preventing the excitation frequency of body structure coupling with road and engine. By random vibration analyzing, using B level road load spectrum as the random vibration input, the vibration response of body structure differs from speed. At low speed, the vibration response was significant at 11.25 Hz. However, the response was significant ranges from 11.25 Hz to 22 Hz at high speed. Obviously, vehicle speed plays an important effect on the vibration response of the body structure under the condition of random load spectrum. Fatigue analysis shows that under the working condition of low speed and high speed, car body structure random vibration of the maximum fatigue coefficient were 0.1305 and 0.1305, respectively, are less than the theoretical value which is 1, satisfies the requirement of fatigue life. Therefore, the rationality of the design has been verified. The results obtained in this paper can be directly used for further optimization analysis of passenger cars.