Development And Experimental Research Of High-Temperature And High-Frequency Fatigue Test Bench For Typical Materials

The coupling of high temperature and mechanical fatigue is a typical form of complex external field action,and it is also a key factor in inducing structural failure and leading to major safety accidents.With the advancement of science and technology,the cycles of cyclic load that many parts bear during their service have far exceeded the infinite fatigue life of the traditional fatigue theory,and the fatigue life of some parts served in a high temperature environment is more difficult to predict,so the high temperature.The ultra-high cycle fatigue test is necessary to verify the fatigue performance of the material.However,the existing fatigue test equipment has low loading frequency,ultra-high cycle fatigue test cannot be realized,and does not involve the loading of temperature load,which limits the improvement and quality control of the preparation process of key materials.In response to the above problems,combined with the development history of fatigue test equipment and test methods,as well as the comprehensive analysis of high-frequency fatigue testing and high-temperature testing equipment at home and abroad,the paper developed a high-frequency fatigue test device with integrated high-temperature heating function,which can meet the needs of typical service workers.The demand for high-temperature and high-frequency fatigue performance testing of materials.The test device uses ultrasonic high-frequency vibration as the fatigue load,which can greatly improve the test efficiency and quickly complete the ultra-high cycle(10~8)fatigue test;at the same time,the high-temperature device is used to carry out the multi-temperature gradient high-frequency fatigue test,which can explore the temperature-dependent material fatigue performance Impact.The high-temperature and high-frequency fatigue test device developed in the thesis can carry out 15k Hz high-frequency fatigue test on metal material specimens in the range of room temperature to400℃(±5℃).To ensure the resonance conditions of the high-frequency fatigue test device,the natural frequency of the fatigue test piece should be consistent with the stress loading frequency.This paper first calculates the size of the specimen based on the one-dimensional vibration differential equation,and then uses Workbench to simulate and analyze the natural frequency and the stress level of the middle section of the specimen,and optimize the design of the dimensional parameters,so that the specimen meets the requirements of high-frequency fatigue testing.In the follow-up research process,the design scheme was improved according to the material characteristics.In this paper,high-frequency fatigue tests are carried out on specimens of conventional materials(6061-T6 aluminum alloy)at three temperatures.By comparing the fatigue S-N curve,the feasibility of the high-temperature high-frequency fatigue test device and test method is verified,and the influence mechanism of temperature on the fatigue performance of the material is explored according to the change of fracture morphology at different test temperatures.The high-temperature and high-frequency fatigue test of conventional materials provides a reference for subsequent tests of typical materials.In this paper,high-frequency fatigue tests at four temperatures are carried out on specimens of typical materials(TC4 titanium alloy).According to the material characteristics,the specimen design method and resonance loading method are improved,and the material thermal stability criterion is given by comparing the fatigue S-N curve.Through the observation of the macroscopic morphology and metallographic structure near the fracture,the TC4titanium Alloy is systematically analyzed fatigue failure mode.