Based On Stereo Vision Component Biaxial Fatigue Test And The Coupling Vibration Analysis

Fatigue caused by structural damage in the actual project accounted for about 70%,of which vibration damage caused by structural damage is most prominent.The study of vibration fatigue mainly focuses on the theoretical aspects and the uniaxial vibration fatigue test,and the research content is relatively incomplete,especially for the multi-axis vibration fatigue test.The experimental study of single-axis and biaxial vibration fatigue is carried out by using the method of three-dimensional visual method,which includes the pre-pull specimen and the not pre-pull specimen.A series of digital speckle images of the cracked peripheral region of the prefabricated cracked beam specimen under a series of sinusoidal alternating loads are collected by a high-speed digital image correlation system.The change of the natural frequency of the specimen and the displacement field and strain field of the tip region of the prefabricated crack are calculated by using the Digital image correlation(DIC)technique.The change law of displacement,strain and cycle period is analyzed through the analysis of the displacement,the main strain and the strain in the out of plane direction at the tip of the pre-fabricated crack under different cyclic cycles.At the same time,based on the Abaqus and fe-safe platforms,the dynamic model of the specimen was established,and the crack propagation of the specimen was simulated by simulating uniaxial and biaxial vibration.The results were compared with those of the three-dimensional digital image correlation method.The thickness,width,prefabrication crack depth,width,distance from the fixed end,and the change of the axial excitation displacement are simulated under the condition of uniaxial and biaxial vibration fatigue due to the accuracy of the simulated fatigue life.The fatigue life of the specimen and the influence of the crack propagation are analyzed.It is concluded that the prefabricated crack depth,the length from the fixed end and the axial excitation displacement have a greater effect on the fatigue life and crack propagation.The main work of the thesis includes:1?The system consists of fatigue loading system and data acquisition system.The fatigue loading system is mainly composed of bearing,exciter,NI control equipment,amplifier,sensor and so on.The data acquisition system is composed of NI acquisition equipment,sensor,high speed camera,CCD controller,image acquisition and analysis software and so on.2?The first-order natural frequency vibration fatigue test was carried out on the non-pre-tensioned cracked beam specimen.The changes of the natural frequency of the specimen and the method of stereoscopic vision are used to analyze the displacement and strain field of the specimen during the uniaxial vibration fatigue.3?The first-order natural frequency vibration fatigue test of the pre-tensioned cracked beam specimen was carried out.The change of the natural frequency of the specimen and the displacement and strain field of the specimen during the uniaxial vibration fatigue are analyzed by the method of stereoscopic vision at different loading accelerations.4?The vibration fatigue tests of the cracked beam specimens were carried out at the same time in the transverse and vertical directions.The change of the natural frequency of the specimen and the displacement and strain field of the specimen during the biaxial vibration fatigue are analyzed by the method of stereoscopic vision when the prefabricated crack is different from the excitation length and different loading acceleration.5?The fatigue model of the specimen was simulated by using the fe-safe software as the calculation platform.The fatigue life of the specimen was simulated by uniaxial and biaxial vibration fatigue.In this study,the influence of thickness,width,prefabricated crack length,width and position on single-axis,biaxial vibration fatigue life and crack propagation length was considered.The effect of the change of axial excitation force on the life of the biaxial vibration fatigue specimen and the length of crack propagation during biaxial vibration fatigue was considered.