Development And Experimental Study On In-situ Tensile Testing Instrument For Variable Temperature And Variable Monitoring Angle

As We all know,the mechanical parameters of materials are thevaluable indexes to evaluate the properties of materials.Destructive testing and nondestructive testing are the two methods of obtaining mechanical properties of materials.Destructive testing is usually used to obtain macroscopic properties,such as elastic modulus,yield strength and tensile strength etc.And nondestructive testing,is mainly used to obtain the material microstructure changes,including the defect location,defect type and grain changes when materials are damaging.In many technology of non-destructive testing,the neutron diffraction stress analysis technique,as the only technical means of non-destructive testing of three-dimensional stress inside the polycrystalline material,utilizes the displacement of the diffraction peak to get strain.How to build the relationship between mechanical testing of materials and the internal structure of the material is also an important subject in the field of materials.Therefore,this paper designs the in-situ tensile testing instrument which based on the variable temperature and variable angle under neutron diffraction,and uses the instrument to carry out the research of material testing.This paper summarizes the development of materials testing equipment under the neutron diffraction instrument domestic and overseas,and give a brief introduction including the domestic and foreign devices and their performance indicators which were developing based on the neutron diffraction.On this basis,designed and developed the material testing equipment which are conformed to the technical indicators of the neutron diffraction which belonged to a Chinese research institute.The main contents of this paper include as follows:Based on the requirements of the research institute,the variable temperature and variable angle in-situ diffraction test instrument used by neutron diffraction is designed.According to the calculation and 3D modeling to confirm the plan of the device.And using analysis software to finish the static analysis of the key components and the heat transfer of the fixture.Debugging the mechanical structure and control system;And testing the repeatability of the instrument,giving the practical testing on the response of the halogen lamp heating and the influences of the high temperature on the transmission parts.The instrument uses the grating to indirectly measure the deformation of the specimen.We proposed the calibration algorithm based on the deformation of the specimen.At the same time,due to the special shape of the specimen,The correction modulus of the transition part is modified and calibrated.The accuracy of the algorithm is verified by comparing the obtained mechanical properties of the material with the parameters obtained from the standard commercial instrument.In this paper,45 steel and 6061 aluminum materials were used to study the tensile test at room temperature,in order to verify the accuracy and reproducibility of the test equipment.Carrying out a series of 45 steel on the high temperature tensile test by the device,coming conclusions as follows: the higher the rate of tensile testing,the higher of tensile strength and the yield limit;tensile rate does not have an impact on the elastic modulus;Temperature will affect the 45 steel tensile strength and strain,the higher the temperature,the lower the tensile strength and strain;in the 45 steel elastic stage after heating,compared to the traditional high temperature test,will make its tensile strength,yield limit stronger,but decrease the elastic modulus;in the 45 steel plastic stage after heating will increase the tensile strength,plastic slippage;temperature will affect thestrain of 45 steel,the higher the temperature,the higher the strain rate.