Development And Experimental Study Of Thermodynamic Testing Device Under Neutron Diffraction

As we all know,real life materials are often affected by high and low temperature,electric field,magnetic field and other special physical fields.However,at present,people mainly test the mechanical properties of materials under single load,but the research on the mechanical properties of materials under complex load is not deep enough.In order to meet the needs of aerospace,deep-sea exploration,biomedical and other fields,we need to further study the damage mechanism of materials under multiple loads.As a means of nondestructive testing of materials,neutron diffraction can visually observe the changes of mechanical properties of materials under complex loads,analyze the damage mechanism of their morphology and the changes of the lattice inside the materials,which is conducive to the development of various industries.Therefore,it is more and more important to test the properties of materials under multiphysical field conditions based on neutron diffraction.In this paper,the mechanical loading instruments and experimental research at home and abroad are analyzed,and the theoretical basis of thermal deformation of variable temperature loading instruments is analyzed,including thermal expansion coefficient,factors affecting thermal expansion of parts and basic equations of thermoelasticity,and the core technology of variable temperature loading instruments is analyzed.In this paper,a thermodynamic loading instrument based on neutron diffraction is independently developed by means of thermal conduction in gas atmosphere to load materials at variable temperature.The mechanical testing device can realize two ways of horizontal and vertical.The mechanical load range is larger than 6kN,the loading rate range is 0.1mm/min~2.1mm/min,the minimum resolution is 1N,the loading temperature range is-55 C-200 C,and the temperature resolution is + 1 C.In this paper,the design and analysis process of thermodynamic loading instrument under neutron diffraction is described in detail,including mechanical loading part,thermodynamic loading part,vacuum sealing part and electronic control program control part.The in-situ mechanical properties test of materials can be realized by selecting German BASLER industrial camera and Japanese Kowa camera.Through ANSYS Workbench,the statics of key components and the modal of the whole machine are analyzed by finite element method,which verifies the accuracy and rationality of the device.Finally,the parameters of temperature module are tested,including the heating and cooling rate of refrigeration and heating equipment,the temperature gradient of the intermediate specimen in the variable temperature loading test and the influence of temperature and heat transfer on the key components;the basic flow of the variable temperature mechanical property test is introduced,and the mechanical properties of brass and nickel-titanium alloy under the condition of mechanical-thermal coupling are tested.The results show that the mechanical properties of brass and nickel-titanium alloy under the condition of mechanical-thermal coupling are The tensile strength of brass increases with the increase of mechanical loading rate.With the increase of temperature,the tensile strength decreases gradually and the elongation increases continuously.At low temperature,the lower the temperature,the higher the tensile strength.The nickel-titanium memory alloy mainly exists in martensite at low temperature,and there exists cold work hardening phenomenon.With the decrease of temperature,the stress required for inflection point in elastic stage is increased.The size decreases gradually,and the elongation of the material after fracture prolongs.At high temperature,the superelasticity begins to fail with the increase of temperature.