Reliability Analysis Of Fuel Pump Bracket

A study on a fuel pump bracket is carried out in this paper. The origin fuel pump failed in both working environment and random vibration test. A series of dynamic characteristics analysis and dynamic response analysis are carried out on the fuel pump bracket by using the FEA (Finite element analysis) and modal analysis method. Based on the analysis results, the paper gives a structure modify scheme, and the new fuel pump bracket has succeeded in the random vibration test.The CAE finite element model of the fuel pump bracket is set up and the boundary conditions are confirmed. Due to the fuel pump bracket is a complex assembly, this paper builds a FEA model which can reflect the real structure and dynamic character with the application of suitable short form which can deal with the real connection between every part and simulate the rubber washers of the structure correctly.Based on the free condition and fixed condition modal test result, the finite element model is modified. The improved model can meet the test result very well and the natural frequency and the corresponding vibration mode are determined at the same time. In order to make sure the cracked reason, this paper take a spectrum analysis on the bracket and using S-N life curve to make a fatigue life calculation by the analysis results. The main cracked reason is the stress concentration of the welded position where produce large stress when receive a random load.According to these analysis results, the paper gives a structure modify scheme which can reduce the stress concentration effectively. In order to validate the dynamic characteristic of the improved fuel pump bracket, the new FEA model is set up and the modal analysis and the spectrum analysis are carried out. Comparing with the results of origin fuel pump bracket and improved fuel pump bracket, the natural frequency has only litter change but the dynamic stress of the improved fuel pump bracket is obviously lower than the stress of the origin fuel pump bracket when they are in the same condition of power spectrum. It has been proved that the improved fuel pump bracket can meet the request by both the FE calculation and the random vibration test.Further more, the paper also makes the harmonic response analysis on the origin and the improved fuel pump bracket in order to make sure the dynamic stiffness and the structure response when receive the harmonic load with different frequency.