Experimental Research On Tensional Mechanical Properties Of Metal Materials Under High Temperature And Pre-torsion

Materials are the basis for human survival and development, especially the metal material, widely are used in electronic information, aerospace, defense weapons, automobile manufacturing and other fields. Materials work in extremely complex environment, and are often subjected to the joint action of high temperature and complex mechanical load, resulting in the evolution of performance and failure. At present due to lack of material support capability, various accidents emerge in endlessly caused by material failure. Therefore, it is of great scientific significance to carry out research on testing technology of the mechanical properties of materials under complex environment. For this problem, the main research work of this paper is as follows:(1) Aiming at the self-developed multi-load and multi-physical field in-situ micro mechanical material performance tester, the paper combining with the present situation in related fields, carried out the perfect work of the structure and function of instrument part, including: designed a novel clamp which is suitable for tension and torsion loading; combined with theoretical analysis finding that frame flexibility has great influence on the displacement measurement results, we proposed a correction algorithm of displacement measurement error, and then modified the instrument according to the results of tensile test; aiming at functional requirements of multi-field testing, designed the temperature loading and water cooling system, and ensured sensor and the core mechanical components to work in safe environment.(2) On the basis of the work, this paper selects 45 steel and 6061 aluminum alloy as a typical material samples. Tensile test of repetitive experiment was carried out by using correction calibration test instrument. The test results show that repeatability of instrument is good after the improvement and calibration.(3) The constitutive relation model of typical materials is introduced in this paper. The analysis shows that the Johnson-Cook constitutive model is easy to be solved, which is suitable for the thermal mechanical coupling analysis of metallic materials. Through the fitting of 45 steel at room temperature quasi static tensile stress strain curve, the Johnson cook strength model and the related parameters are obtained, respectively on 45 steel with different torsion angles and different temperature under the action of tension was simulated and analyzed by using the model parameters.(4) In order to further study the high temperature pre-torsion mechanical behavior and damage mechanism of metal materials, tension tests under high temperature and pre-tension angles on 45 steel were carried out. Testing results on one hand, validated the high temperature test instruments and combined tension torsion testing function, on the other hand, combined with the results of tensile test at room temperature to high temperature and the pre-torsion effects on the mechanical properties of materials, and compared with the simulation results, two conclusions were obtained: after the pre-torsion 0-45 degrees tensile stress-strain curve is not great, more than 45 degrees, 45 steel tensile strength and yield strength increase obviously; softening is more obvious when more than 450 ℃, the yield strength and tensile strength of 45 steel decreased sharply, indicating that 45 steel should not be above this temperature range to take service.