Vibration Fatigue Research Based On Meso Mechanics

Under the dynamic load,the local structure of the aircraft will appear a larger response,the resulting fatigue failure is one of the main forms of structural damage.Therefore,it is of great significance to analyze the vibration fatigue life of the typical aircraft structure under random dynamic load.Based on the in-depth study of the effects of multi-axial stress equivalence and meso mechanics,this paper predicts the vibration fatigue life of a typical aircraft structure more accurately.In terms of multi-axial stress equivalent,this paper realizes the transformation from multi-axial stress to uniaxial stress in the frequency domain according to two equivalent criteria of Von Mises and Lemaitre,and then the life is predicted with the existing mature single axis vibration fatigue analysis theory.It solves the multi axial fatigue problem of the structure under random loading.In meso mechanics,a damage model based on meso mechanics is proposed in this paper according to the characteristics of the high locality of metal fatigue damage.Based on the response mapping relationship between macro elements and meso RVE,the model transforms the macro fatigue problem into the damage problem of meso RVE,and considers that the vibration fatigue life is equal to the failure life of meso RVE.Compared with the traditional time and frequency domain analysis method,the model further divides the vibration fatigue life into two stages: the initiation life and the extended life of the micro crack,and the fatigue life and the damage evolution process of each stage under random excitation are analyzed and calculated.The application of the above method can theoretically improve the prediction accuracy of the vibration fatigue life.In order to verify the correctness and applicability of the relevant theory,this paper takes a typical aviation reinforced structure as an example,and the results show that using the Lemaitre multi-axis equivalent criterion to determine the structural dangerous position results is more accurate and the meso damage model life expectancy estimation error is smaller,the combination of the two can get a better life expectancy prediction results.