| The testing and research of the mechanical properties of materials under complex loads is an important support for the performance testing of key materials in many fields such as aerospace and aviation,and is also a research that is clearly pointed out in the "National Medium and Long-term Science and Technology Development Plan Outline" for major national needs.However,the research strongly relies on advanced testing technology and instruments.At present,only a few companies have introduced high-temperature fatigue and high-temperature tensile testing instruments.However,there are no reports of in-situ testing technologies for mechanical properties of materials under high-temperature and complex static and dynamic mechanical loads,which seriously restricts In-depth research.Therefore,developing such instruments as soon as possible is of great significance for serving the country’s major needs and seizing the international commanding heights.This paper has designed and developed a composite dynamic and static mechanical load loading system,which can provide important support for key material performance testing,life prediction and reliability evaluation in many fields,and has great scientific significance and application value.This article first analyzes and studies the principle of tensile and bending composite loading and the test theory,and derives the calculation formula of the pre-tension bending elastic modulus.Through the system function analysis,the design of composite static and dynamic loading scheme and the selection of core components have been completed.The modal analysis and optimization of the key structure of the instrument are carried out using the finite element method to meet the requirements of static and dynamic loading stability.The complex static and dynamic mechanical analysis of the system was completed,and the vertical vibration and amplitude attenuation of the sample were analyzed and verified.Secondly,this article integrates the designed loading system into a complete testing machine,and explains the composition of the hydraulic oil source and the electronic control system.Analyze the cause of the fixture alignment error,and use special equipment to calibrate.Through the high temperature loading test,the load error caused by the bellows was corrected,and its work was verified within a reasonable range.Based on the digital image correlation method to detect the strain of the sample,analyze the reasons that cannot be measured under high temperature conditions and formulate an improvement plan.The feasibility of the plan is verified through experiments.Finally,this paper verifies the loading capacity of the system through experiments.Verify the loading accuracy of the system through the index verification test;obtain the stress-strain curve and the elastic modulus and yield strength change law of the sample at multiple temperatures through the high temperature tensile test;verify the bending load through the three-point bending test and the relative bending test The accuracy of the test;the composite load loading capacity of the loading system was tested through the pretension-bending test and combined with the high-temperature strain measurement system to obtain the continuous deformation image of the sample and the change rule of the continuous displacement of each position with time.To sum up,this paper designs the system from theoretical analysis,scheme design,structural optimization,and complex load analysis,to system error correction and functional improvement,to test verification,and completes a set of systems that can complete composite load loading.Further exploration of material testing technology.The development process of the material mechanical property test system in this article can provide an effective reference for subsequent equipment development. |
