Design And Experimental Study Of In-situ Environmental Loading Device For Neutron Diffraction

With the development of science and technology,the working conditions of various materials are becoming more and more complex.The traditional material mechanics testing machine is difficult to effectively study and reveal the mechanical behavior and damage mechanism of materials under complex load environment,which restricts the improvement of material R ＆ D process and strict quality control.The great demand of material mechanical property test under complex working conditions provides new opportunities and challenges for material mechanical test technology.As a sharp tool in material science research,neutron diffraction technology has been valued and applied by more and more scholars at home and abroad,but the variable temperature mechanical loading device that can be used in neutron diffraction spectrometer is rarely reported,which greatly restricts the relevant research process.The development of a neutron diffraction mechanical loading device with the function of continuous temperature change in a wide temperature range is conducive to the in-depth study of the damage evolution mechanism of advanced materials under service conditions.It can provide important support for the R ＆ D and performance test support of key materials in important fields such as aerospace,National defense and military industry in China,and has important scientific significance and application value.Facing the above requirements,based on the construction of the temperature environment of the actual service conditions of materials,this paper creatively introduces the neutron diffraction technology into the test system,and designs and develops the test device of mechanical properties of materials in variable temperature environment.Around the above work,the main research contents of this paper are as follows.In view of the shortcomings of mechanical property testing technology and devices at home and abroad under variable temperature conditions,the system function and scheme design are completed according to the technical index requirements.By analyzing and comparing the advantages and disadvantages of various heating and cooling methods,it is proposed to realize high / low temperature loading on the specimen by induction heating and liquid gasification refrigeration,and the high and low temperature loading module is designed.The temperature field simulation analysis of the designed high and low temperature loading module is carried out by using COMSOL thermal analysis and ANSYS Workbench fluid analysis module,and then its optimization design is carried out.On the basis of comparing and analyzing the advantages and disadvantages of various mechanical loading methods,the motor lead screw method is proposed to realize mechanical loading.According to the system design scheme,the structure including the mechanical module,high / low temperature loading module and electrical control module of the loading device is designed.The system control software is compiled by Lab VIEW software to realize the electrical control of the system.The high / low temperature closed-loop control and mechanical loading closed-loop control of the system are realized by auto disturbance rejection control and impedance control methods.In this paper,calibration and functional verification tests are carried out for the hightemperature,low-temperature loading module and mechanical loading module respectively.The test device developed in this paper can realize the mechanical load loading of no less than 15 kn,the high-temperature loading range of RT ～ 1000 ℃,the high-temperature loading temperature control accuracy within 4 ℃,the lowtemperature loading range of-180 ℃ ～ 200 ℃,the low-temperature loading temperature control accuracy within 5 ℃ and the temperature gradient of the specimen not exceeding 5 ℃.This paper takes 6061T6 aluminum alloy for aerospace as the research object,and uses the developed test device to carry out a series of material mechanical properties test and analysis under the conditions of high temperature,low temperature and variable temperature.The test results show that the tensile strength of 6061T6 aluminum alloy decreases with the increase of temperature,the elongation and fracture shrinkage increase,the plasticity is better,and the tensile strength of 6061T6 aluminum alloy changes under variable temperature;The fracture shrinkage at high temperature is significantly higher than that at constant temperature,but the difference decreases gradually with the decrease of temperature.It is speculated that the fracture shrinkage below a certain temperature point will be lower than that at constant temperature;The elongation at low temperature is significantly higher than that at constant temperature.It is speculated that the elongation above a certain temperature point will be lower than that at constant temperature.The research results of this paper have certain scientific significance and application value for enriching the in-situ testing technology of material mechanical properties.At the same time,it is also a beneficial practice for expanding the function of the large scientific device of neutron spectrometer.