Design Analysis And Experimental Research Of A Piezoelectric In-Situ Fatigue Testing Device Working At Middle/Low Frequencies

At present, the material products are widely used, and the research on the fatigue property of materials is more and more important. Accordingly, people put higher forward demand for methods of testing the materials fatigue properties. Most of the microstructure and fracture of the specimens are analyzed by the existing ex-situ fatigue testing methods to explain the fatigue fracture mechanism. The material mechanical properties in-situ testing methods which establish the dynamic relationship between the microscopic and the macroscopic fracture failure are studied a little. In view of the current domestic and international material fatigue testing devices, there are some problems such as large volume, poor functional expansion ability, poor compatibility, expensive price and so on. In this paper, based on the in-situ test technique, a miniature piezoelectric in-situ fatigue testing device working at medium / low frequencies is developed.The piezoelectric in-situ fatigue testing device with strong functional expansion capability,electromagnetic and thermal stability, which is inergrated with microscopic testing equipment can complete testing in the mode of in-situ tensile-tensile fatigue load and evaluate material failure mechanism in fatigue test. The main contents of this paper are listed as follows:(1) Through the analysis on the domestic and foreign research on fatigue testing device,the author developed a piezoelectric in-situ fatigue testing device, completed designing key parts of it, and under the premise of satisfying the testing function, selected sensors and piezoelectric stack Optimally, eventually completed manufacturing and assembling the device.(2) Used finite element analysis software ANSYS WORKBENCH respectively to complete finite element simulation analysises of the flexible hinge, the whole machine and the speciments to corroborate the static and dynamic using safety and rationality of the flexure hinge and the whole device, and to predict the fatigue life of the Materials under different types of fatigue loads.(3) Completed integrating and debugging the mechanical and electric control parts of device and testing the force sensor and displacement sensor linearity and calibrating these sensors; corrected the parameter error of force sensor and displacement sensor caused by deformation of device frame; tested the static and dynamic output performances of the device.(4) Based at the device, carried out in-situ tensile-tensile fatigue test of AZ41 M wrought magnesium alloy which is corroded by chemical solution so as to study the microstructure evolution of materials in fatigue process;carried out in situ fatigue test of 1060 aluminum with different types of gaps to analyse the notch sensitivity of material under fatigue condition; carried out in situ fatigue test at room temperature of 1:2 copper-steel(H62 brass and 304 stainless steel) composite with prefabricated indentation flaw on its surface and integrated heating unit to carry out thermal-fatigue test of this material to explore the influence of temperature on materials fatigue properties.