Stochastic Multiaxial Fatigue Load Update And Life Prediction Based On Real-time Data Monitoring

In the field of practical engineering,most of the metal structures and components are subjected to fatigue cyclic loads during operation,and fatigue has become the most important failure mode of the structure.Because the complex structure i s usually in multiaxial fatigue stress state,the research on multiaxial fatigue life prediction method has received the researchers' attention.However,due to the excessive dispersion of the prediction results,the stochastic multiaxial fatigue life calc ulated in the final calculation usually has a large deviation.With the continuous development of technology,the load data of structural components can be obtained through real-time monitoring.If real-time data monitoring can be combined with random multiaxial fatigue loading and random multiaxial fatigue life,the results of fatigue calculation analysis can be further improved.accurate.Therefore,the research on random multiaxial fatigue life prediction method based on real-time data monitoring is very important for accurate prediction of fatigue life of service structures,but the research in this area is still lacking.In this paper,the multiaxial fatigue failure criterion based on critical surface and rain flow cycle counting method are used to update the random multiaxial fatigue load under real-time data monitoring.Then,based on random multiaxial fatigue load update method,random load spectrum reconstruction method and fatigue damage accumulation theory,a random multiaxial fatigue life prediction method based on realtime data monitoring is proposed.It mainly includes the following two parts:(1)A random multiaxial fatigue load update method based on real-time data monitoring is proposed.In engineering practice,structural components are ofte n subjected to random multiaxial fatigue loads,and the update of random load spectra is based on the method of circulating rainflow counting.The equivalent uniaxial stress load spectrum is obtained by stress analysis and appropriate multiaxial fatigue failure criterion based on critical surface,and then the equivalent uniaxial stress load spectrum is processed by rain flow counting method to obtain the initial rain flow matrix;The real-time update of the monitoring data results in a real-time updated rainflow matrix.With the update of real-time data monitoring information,the predicted load spectrum will be closer to the actual value.(2)A random multiaxial fatigue life prediction method based on real-time data monitoring is proposed.The method first establishes a corresponding model based on the input information module.Then,the finite element method is used to find the dangerous point of the structure,and the stress components of the point are obtained.After the stress state at the critical point is obtained,the appropriate fatigue plane based on the critical plane is selected to simplify the multiaxial stress state to the equivalent uniaxial stress state,and then the fatigue life is calculated according to the fatigue damage accumulation theory.With the update of real-time load data collection,the predicted value of the equivalent uniaxial stress load spectrum updated in real time can be obtained,and the predicted value of multiaxial fatigue life is updated in combination with the fatigue damage accumulation theory.The method realizes random multiaxial fatigue life analysis based on real-time data monitoring,and with the continuous updating of online data,its life analysis value will more accurately approach the actual life value.