Design Analysis And Experimental Research On Tensile/Compression Module Of An In-situ Force-magnetic Coupled Testing Device

The materials science and technology is the important foundation of the national economy and science development.In practical engineering applications,the material performance is a vital guarantor to the product capabilities,wherein,the mechanical properties of the material are one of the most watched basic properties.To obtain the mechanical behavior of materials,various types of mechanical properties of mechanical testing technology came into being.However,most materials suffer variety forms of loads in their service environment.Some materials may suffer a special service environment with magnetic field and high temperature,and may behave totally different mechanical properties from normal environment.The existing testing technique is often limited to single load test forms and cannot present the actual serving conditions.Meanwhile,the traditional ex-situ observation can only collect the test parameters,but has no ability of observing the macroscopic and microscopic changes of the material in the process of failure test,restricting the development of related research.Thus,to further study the evolution mechanism of materials under complex loads and fields,it is of great theoretical significance and application value to develop an in-situ test device which can load and observe the material deformation and failure dynamically under different physical fields.Basing on the current development of related fields internal and abroad,this thesis aims to design a multi-load and multiple physical field coupled in-situ materials mechanical testing device,and focuses on the design and analysis of tensile/compression testing unit and magnetic field loading unit.The device is also integrated with the other various testing forms including twisting test,bending test,fatigue test and indentation test under electronic field and thermal field with in situ observation,meanwhile,has reasonable spatial structure and meets the coupling test requirement.On the basis,the main components of the tensile/compression testing unit is designed and checked,and finite element simulation analysis on the key transmission parts and components are carried out to verify their rationality.Furthermore,the modal analysis on the entire mechanical loading units is also carried out to predict the dynamics characteristics of the designed mechanical loading units.To ensure the accuracy of the system during testing,the causes of the error during tensile test are analyzed from the aspects of specimen clamping deformation and whole structure deformation under loading,and the corresponding error model and correction theory are proposed.The corresponding correction coefficients are deduced through calculation.Combining the two correction coefficients,the correction formula of tensile test results is deduced and verified by comparing with the commercial testing results.Basing on the foundational work above,nickel Ni6 is selected as the tensile testing material,and experimental study on its tensile/compression mechanical behavior under different loading rate and external magnetic field is carried out.The microstructures,hysteresis loops and magnetostrictive curves of Ni6 are obtained during the in-situ tensile test.The results show that with increasing of compressive stress,the residual magnetization and permeability increase,and the coercivity and saturation magnetostriction decrease.