Research On Accelerated Life Testing Technology Of Mechanical Structure Under Super-gaussian Vibration Excitation

Vibration environment exists extensively in all aspects of the equipment during service,and the fatigue problems caused by it seriously threatens the reliability and safety of some important equipments and structures.If the fatigue life can be predicted accurately,scientific basis could be provided for life determination and extension in the development stage and precautions could be taken before catastrophic accident.With structures' reliability developing,the vibration fatigue life is longer and longer.Vibration accelerated testing becomes the inevitable choice to verify whether the life meets the design requirement or not.When it comes to vibration fatigue analysis of mechanical structure and accelerated life testing,the traditional method is to assume the vibration loadings to be Gaussian distributed.But many random loadings all around the actual environment present distinct super-Gaussianity,especially in some terrible working conditions and extreme environment.The super-Gaussianity has significant impact on structures' vibration fatigue life,and Gaussian assumption may endanger the equipments' service.So researching on accelerated life testing technology of mechanical structure under super-Gaussian vibration excitation has great significance and engineering value.According to the demand of life prediction and reliability evaluation of equipments under super-Gaussian vibration loadings,this dissertation has systematically studied the following problems: the dynamic stress response of structure under super-Gaussian vibration excitation,the fatigue life calculation of super-Gaussian loadings,the accelerated model for super-Gaussian vibration and the strategy of random vibration accelerated testing.The main contents and conclusions are summarized as follows:1.The formula for calculating the dynamic stress response of a cantilever beam under super-Gaussian random base acceleration excitation is proposed by using mode superimposition method.How kurtosis and bandwidth of super-Gaussian vibration excitation affect the super-Gaussianity of dynamic stress response is acquired by numerical examples.2.Diagnostic tests are conducted on notched cantilever beam by designing different test profiles to find out how the parameters of super-Gaussian vibration affect the vibration fatigue life of structure,which lay a good foundation for making scientific testing strategy.3.Dynamic strain signals at risky point of the structure are collected under different test profiles,obtaining the factors that affect the super-Gaussianity of the stress response,which validates the conclusion drawn in numerical examples.The time-domain method for estimating the fatigue life is proved effective for super-Gaussian vibration.4.Based on the physics of failure,Gaussian and super-Gaussian vibration accelerated models are derived with the help of linear system theory and stochastic process theory.After that,the method for estimating the parameters in the models is presented.The validity of the models is confirmed experimentally.5.Based on super-Gaussian accelerated models,a strategy of random vibration accelerated testing is put forward.And supporting software is designed according to the process of strategy,which is convenient for engineering application.