Study On Mechanical Properties Of Microsamples

In the power generation industry,due to the limited amount of materials used in testing,the micro-sample testing technology has received great attention.Based on the characteristics of small sample size and ensuring the integrity of equipment,it has a very important engineering value for evaluating the mechanical properties of equipment materials in active service,and provides a minimal damage test method for the safe use of equipment in active service.This paper mainly studies the testing technology of mechanical properties of miniature samples,carries out the small punch bar experiment and interruption experiment,and the unidirectional tensile experiment and interruption experiment of miniature samples,and obtains a lot of valuable experimental data,and then studies the method of evaluation of mechanical properties of metal materials by the testing technology of miniature samples.The main results are as follows:(1)According to the obtained P91 steel sample,the whole process of small punch bar experiment and interruption experiment were carried out at 600 ℃ to study the microstructure evolution and fracture mechanism of P91 steel.Then the surface of the specimen was observed by scanning electron microscope and electron backscatter diffraction(EBD),and the microstructure of the specimen under different deformation morphology was obtained.It is concluded that the martensite structure is recovered with the downward movement of the punch.The voids tend to nucleate along the restored crystal interface,grow,and finally plastic flow occurs.(2)The fracture evolution mechanism of P91 steel at 600 ℃ was studied by unidirectional tensile test(MUTT)of discontinuous micro-specimens.MUTT’s engineering stress-strain curves can be divided into six distinct stages,including the elastic stage,the strain hardening stage,the uniform plastic deformation stage,the transverse and thickness direction of the neck stage,and the final fracture extension stage.In the interrupted MUTT,the entire failure evolution process from uniform deformation,necking to specimen fracture was studied using an optical microscope and a scanning electron microscope.(3)The finite element simulation of the small punch bar experiment is carried out,and the load displacement curves obtained are similar to those obtained in the experiment,which have several typical stages.The difference is that the maximum load value between the two is greatly different.However,comparing the fitting equations of simulation and experiment,it is found that the fitting coefficients are similar.