An Fatigue Damage Model Based On Virtual Load Spectrum

Fatigue failure is the main failure mode of parts or components.Fatigue damage model is the theoretical basis of fatigue life calculation and it has become a research hotspot in the field of fatigue.At present,the calculation of fatigue life is generally done based on the fatigue life test of physical prototype.Then calculate fatigue life according to the formula of the existing damage model(Miner criterion,Manson model,etc.).However,due to objective conditions,environmental factors and many other constraints,the accuracy of fatigue life prediction needs to be improved.Therefore,carrying out fatigue life prediction model has important theoretical significance and engineering application value.The main contents of this paper are as follows:(1)Establishing a mathematical model based on virtual load spectrum construction technology.On the basis of traditional Manson model,according to the existing loading load spectrum data,a linear interpolation method is proposed.The loading working stress range of the load spectrum is virtually divided.The corresponding load working stress and working frequency are obtained accordingly.Thus an improved fatigue damage model is established.(2)Proposing the reliability criterion of the fatigue life calculation mode l.As the specimen is loaded cyclically,its cumulative damage and reliability index are all time-varying.Therefore,using the reliability index to replace the cumulative damage as a fatigue failure judgment index.Fatigue failure occurs when reliability is below critical value.(3)Research on the Monte Carlo algorithm for fatigue damage correction.For the problems of the randomness of fatigue damage value after fatigue loading,the application of Monte Carlo method is analyzed.By using the method of uniform distribution of sampling,random sampling of uniform distribution can modify the fatigue damage value.(4)The improved fatigue life calculation model is studied.Firstly,the convergence of the improved fatigue life model is proved theoretically.Secondly,the key parameters in the fatigue life model are analyzed to explore the effect of the numerical value on the prediction of fatigue life.Finally,the results of fatigue life prediction Compared with the experimental data,the accuracy of the model is verified.In this paper,an improved Manson model is built based on the virtual load spectrum construction technique.The Monte-Carlo method is introduced to correct the cyclic damage in the virtual section,and the reliability is selected as the criterion of fatigue fracture to effectively improve the improved fatigue life model.The reliability in mechanical fatigue design is benefici al to its application and promotion.