Development And Performance Testing Of A High-temperature Mechanical Testing Apparatus

High temperature resistance materials are widely used in aerospace application,these materials may be affected by high temperature and fast temperature fluctuations,and their mechanical properties will change after thermal shock,which could deteriorate the flight performances and crew safety.However,because of the low heating rate of the most test apparatus,it is difficult to measure the mechanical properties of materials after thermal shock.Therefore,the development of high temperature mechanical test apparatus with rapid heating rates is of great importance.Specific research contents are as follows:?1?In order to solve the three difficulties of creating a high temperature environment,clamping the specimen at high temperature and measuring the strain of the specimen at high temperature,a high-temperature mechanical testing apparatus was designed in this paper.The induction heating method was adopted to create a high temperature environment,which has a fast heating rate,the heating rate can reach 800?/min;SiC ceramic material was used to make high temperature grip,at the same time,the stress on the grip was analyzed;A pair of LVDT displacement sensors was used to measure the displacement of specimen indirectly.According to the function of each part,the apparatus is divided into loading and clamping unit?reference frame unit?heating and cooling unit?measuring unit and vacuum unit.The main indicators of the apparatus are:the temperature measurement range is from room temperature to 1200?,the displacement measurement range is from 0 to 2mm,and the tensile force measurement range is from 0 to 100Kg.?2?The software system of the high-temperature mechanical testing apparatus was designed.Tensile test of typical materials was carried out to verify the repeatability of the apparatus,a linear error correction algorithm was designed to improve the accuracy of strain measurement.The obtained tensile stress-strain curves of 6061 aluminum alloy and Q235steel show that the apparatus has good repeatability.The strain measurement correction algorithm of LVDT displacement sensor was proposed,firstly,the deformation of the connectors was corrected,secondly,the deformation of the loading section and the transition section was corrected,the results show that the deformation of the connectors is only related to the tensile force,the relation between the deformation of the connectors?_connectors and the tensile force F is?L_connectors=3.55x10^-5*F,the relationship between Young's Modulus E1 of the material measured by the apparatus after strain modification and Young's Modulus E2 of the material measured by the apparatus before strain modification is E1=2.112*E2.?3?The properties of the apparatus were verified by tensile tests of material at room temperature and mechanical properties tests at high temperature.The tensile test of 6061aluminum alloy at room temperature was carried out,the repeatability of the apparatus at different stretch speeds and the effect of tensile speeds on the mechanical properties of materials were investigated,the conclusions are as follows:The apparatus still has good repeatability at different tensile speeds,the Young's Modulus of 6061 aluminum alloy would not be affected by the change of tensile speed.The high temperature mechanical properties of graphite were carried out.Results show that the Young's Modulus of the graphite specimen will increase with the temperature increasing.After 18 cycles of preload thermal shock test,the Young's Modulus of the graphite specimen will decrease by about 25%compared with their initial value.In conclusion,all the test results show that the apparatus can provide a platform to test the mechanical properties of specimens in high temperature environment.