Study On The Miniaturization Of Automatic Ball Indentation And Factors Influencing Measurement Accuracy

As the commonly used physical and chemical detection methods can not really obtain the mechanical properties,fracture performance and creep performance of the in-service pressure equipment structure materials,such as tensile test which must be carried out destructive test and requires sampling from service equipment which often destroys the continuity of the equipment,traditional nondestructive testing which can only detect the defects of the material and the residual thickness of the equipment,and surface metallography which can only reflect the changes of material structure,it is difficult to obtain the material properties of the after-service pressure equipment.Therefore,the study of new material performance nondestructive or micro damage detection methods will play an important role in evaluating the equipment residual life.Indentation test is an important way to achieve detection mechanical properties of materials measurement of in-service equipment especially press equipment without sampling,The business test instruments existing are from The United States and South Korea.Because of its data processing system is not open,it is hard to make a correction on domestic material properties.while indentation is an important guarantee for the completion of this process.In this paper,the scheme to realize the miniaturization of the pressure test instrument was put forward and according to the design scheme and the corresponding test data,the standard parts(such as motor,load sensor and displacement sensor)were selected and the non-standard components were designed.As test parameters have a great influence on the test results,the error could be reduced by choosing the test parameters and taking the best one,the material properties is obtained by automatic ball indentation test,so the test parameters have direct influenced on the accuracy of material properties,which means different experimental parameters and experimental environment will lead to different results.In this paper,non-service ordinary low carbon structural steel plate Q235B,low alloy steel plate always used as pressure vessel Q345R,and stainless steel plate S32168(OCr18NilOTi)were selected as research subjects.By using the finite element software ABAQUS simulation method,and combining the automatic ball indentation and traditional test,the influencing factors of the instrument miniaturization,including surface roughness,unloading number,depth ratio,unloading rate,pressure head diameter,tilt angle and other factors were studied systematically,and the effect of different test factors on the test results were analyzed.By comparison,the reasons for the influence of these experimental factors on the test results were discussed,and the optimum test parameter values were proposed.With four kinds of steel plate,low carbon steel 20,45,Q345 steel for pipes,low carbon microalloyed pipeline steel L415,L360,L290,S30408 and strain aged 16Mn,used as research objects,maximum indentation test load of the commonly used pressure vessel materials was tested by automatic ball indentation test,on the basis of which the indentation test instrument key parts were designed and reference for the miniaturization of equipment production was provided,which is of great significance to improve the ball indentation test instrument applicability.