Research On The Fatigue Life Of The On-board Equipment On The Vehicle Under Random Vibration Environment

Random vibration of vehicles will occur due to road irregularity and the runningengine. Excessive vibration may lead to on-board equipment failure because of fatiguedamage. The usage life and precision of the equipment will be affected by vibration andthe equipment maintenance is difficult. So research on fatigue life of random vibrationfor On-board equipment becomes an important research topic. A great deal of researchfocus on vibration fatigue under sine excitation, but a little is done for the randomexcitation case. The random vibration fatigue mechanism is more complex and need tobe studied deeply. The analysis theory, computation method and test are researched forthe fatigue life estimation of on-board equipment of vehicle in the thesis. Frequencyanalysis method is used for the fatigue life calculation. The main works finished in thethesis are as follows.Theory of the transportation vibration fatigue is studied. Dynamic responds ofvehicles and the model of fatigue damage cumulative rules are derived. The estimationmethods of vibration fatigue life are explained and the differences and similarities arecompared.A kind of random excitation spectrum is set forth. The vibration modes andfrequency response functions of a cantilever beam and an on-board VXI box arecompeted. The author has grasped the technique to use the fatigue analysis software afterthe random vibration lives of the examples are calculated. The dangerous positions andthe life of the box are indicated. The results are useful for the engineering designimprovement.An accelerated vibration fatigue life testing plan of a typical specimen is designedand the test is carried out. Three common detecting methods to judge the specimenfatigue are used, including direct observational method, dynamic strain measuringmethod and natural frequency checking method. Groups of the life tests are implementedwith different magnitude excitations. The results are analyzed and the uncertainties arediscussed.In summary, theory analysis, calculation and test methods for the on-boardequipment life estimation under random vibration are researched in the thesis. The resultsare useful for the engineering application.