Fatigue Life Analysis Of Structures Under Combined Static And Dynamic Loading

During the operation of aerospace vehicles,the structure will withstand a variety of complex vibration loads,including static and dynamic loads.Complex vibration loads result in a large local response of the structure and causing fatigue damage.Aiming at the typical structure under simultaneous static and dynamic loads,this paper studies its vibration fatigue life estimation method.In terms of life prediction,the basic theory of vibration fatigue is studied.Based on different models,the S-N curve is modified to obtain the fatigue limit.The vibration fatigue failure criterion and fatigue life calculation method applicable to the project are selected,and the dynamic performance of the structure under static tensile load and dynamic excitation load is studied,and suitable signs of damage and failure are given.Frequency domain and time domain life calculation methods for life estimation.To verify the accuracy of the life prediction results,the structure was subjected to random vibration fatigue tests with static load tension.The test piece is fixed on a test stand,and a static tensile load is applied to one end of the test piece.A wide-band random vibration test is performed using a form of basic force excitation by a shaker to record the fatigue failure time,and the strain-time signal of the dangerous unit and the force-time signal of the applied dynamic load are collected to provide a test basis for the calculation of the fatigue life.In this paper,the random vibration fatigue test under different static tensile conditions is used to explore the change of structure life under different static loads and the effect on the structural fatigue life.In order to ensure that the test piece can be destroyed within the effective time,the simulation analysis and life calculation are required before the test to determine the size of the static and dynamic loads.According to the existing test equipment clamping conditions and load loading forms,design test specimens and fixtures,and establish a finite element model.A modal analysis is performed on this structure to determine the natural frequency of the structure.Then perform static analysis and random response analysis to determine the static and dynamic load of the test.