Development And Application Of In-situ Biaxial Test System In High Temperature Environment

When the material is in service in a high-temperature environment,it will inevitably suffer various complex loads,and the complex stress state will exacerbate the failure and destruction of the material.High temperature will make this complex stress state more difficult to predict,causing greater hidden dangers to production safety.The in-plane biaxial test can effectively simulate the multiaxial plane stress state,and the high temperature environment device can test the biaxial mechanical properties at high temperatures.At present,the development of in-plane dual-axis experimental equipment is relatively slow,and there are few devices that can be used in hightemperature environments.Therefore,it has important engineering significance and research value to develop a set of in-plane dual-axis experimental machines that can provide online high-temperature environments.This paper designs and develops an in-plane biaxial mechanical test system that can be used in high-temperature environments.The problem of insufficient synchronization control precision of the dual-axis in-situ testing machine and difficulty in in-situ loading are solved.The biaxial test under high temperature environment is realized,and the maximum temperature can reach 600 ℃.The system uses an electric cylinder as the power unit,which has the advantages of stable and accurate control,large rated load,and wide speed range.Combined with the vacuum high-temperature environment chamber,it solves the problems of speckle instability and high influence of hot airflow in DIC technology at high temperature.It meets the research needs of biaxial performance of materials under high temperature environment.Taking industrial pure zirconium(Zr-702)plate as the research object,the biaxial cross sample was designed and optimized.The DIC test results were compared with the simulation results.The results obtained are in good agreement with the cross biaxial sample.The design provides a new reference.The test machine was used to perform uniaxial and biaxial tests with different ratios at 400℃.By uniaxially stretching the zirconium alloy flat specimens in the RD and TD directions,the mechanical properties and anisotropy coefficient r of the material were obtained.At high temperature,biaxial tensile test was carried out on the specimen of the cross-shaped zirconium alloy flat specimen,and the effect of multiaxial stress on the macroscopic deformation of the material was studied through different loading stress ratio tests.The high-temperature biaxial specimens were micro-characterized.The results show that Zr-702 uses slip as the main deformation mechanism at 400 ℃.The test results are consistent with the mechanical parameters of the material,which verifies the reliability and accuracy of the test system.