Development Of A High-temperature Mechanical Test Apparatus Using Induction Heating

High-temperature structural materials are used in important parts such as brake discs and throat linings of aerospace vehicles,which play an important role in promoting the development of aerospace.And the key part of the performance testing and characterization of high temperature structural materials lies in the development and research of high temperature mechanical test apparatus.However most of the existing material performance test apparatus in the country use a high-temperature electric furnace to create a high-temperature environment.This heating method has a slow heating rate(?80 ?/min)and low heating efficiency(50% to 55%).Therefore,this paper uses the induction heating method to develop a high-temperature mechanical test apparatus,which has the advantages of high heating speed and high efficiency,and can simulate the performance test of high temperature structural materials under hightemperature vacuum working conditions.Focusing on the development of the high-temperature mechanical test apparatus,the main research contents of this paper are as follows:(1)A high-temperature mechanical test apparatus using jnduction heating is designed to rapidly increase the temperature of the sample,which has the characteristics of rapid heating rate of the sample(800 ?/min),large applicable temperature range(room temperature to 1500 ?),and high heating efficiency(80%).It can accurately simulate the extreme working environment conditions of high temperature thermal shock of aerospace vehicles.According to the test task,the modular design concept is adopted to design the high-temperature mechanical test apparatus.The main structure of the apparatus consists of mechanical module,heating and cooling module,measuring module and vacuum module.Based on the functions realized by each module,the structure refinement and hardware device selection are completed.The designed test device can apply force load range from 0 to 1000 N,measurement temperature range from room temperature to 2000 °C,and measurement displacement range from 0 to 2 mm.The finite element is used to analyze the model structure to determine and optimize the installation location of the main measurement components.(2)The hardware and software integration of the high-temperature mechanical test apparatus is completed,and the critical hardware calibration and vacuum system are detected.In the core hardware detection,the weight of the calibration force sensor is detected by the weight,and the parameters of displacement sensor is detected by the micro-motion measurement gantry,so as to ensure that the accuracy and accuracy reach the test requirements,and the conversion coefficient of the sensor data transmitted to the acquisition card is determined.They are 0.09637 and 0.00039246 respectively.The vacuum system was debugged,and the problems occurred during the debugging process were adjusted and improved.Finally,the test results of the vacuum module showed that the vacuum of the test device could reach-0.1 MPa,meeting the test environment requirements of the vacuum module 0.5 Pa.(3)The high-temperature mechanical test apparatus is used for the graphite performance test to verify the performance of the test apparatus.The test results show that the three graphite samples can be heated to 1200 ? and remain stable.The maximum temperature of the sample drops at 11 th cycles under the circulating current of 220 ~ 900 A.In the case where the preload is 310 N circulating current is 220~900A,the maximum temperature of the sample decreases at 4th cycle,indicating that the preload accelerates the failure of the sample.At 25 ?,500 ?,750 ?,1000 ?,1200 ?,1500 ?,the elastic modulus of the samples were 7.31 GPa,8.76 GPa,9.83 GPa,10.77 GPa,11.2 GPa,11.71 GPa.It shows that the elastic modulus of graphite samples increases with the increase of temperature.The test results verify that the hightemperature mechanical test apparatus meets the expected design specifications.