Research On Acoustic Emission Evaluation And Dic Characterization Method Of Steel Damage For Pressure Equipment

In recent years,with the rapid development of the economy and the increasing progress of science and technology in China,the demand for pressure equipment in petroleum,chemical and other industries is increasing.Its safety and reliability in service are related to the safety of operators,the development of enterprises and the social stability.Usually,the pressure equipment in service will be in a harsh environment such as high temperature,high pressure or strong corrosion,coupled with the influence of its own material and alternating load during service,the stress of the steel for pressure equipment is continuously concentrated after loading,resulting in stress fatigue and the deterioration of steel performance,which seriously threatens the safe use of pressure equipment.Therefore,it is very important to identify and characterize the damage characteristics of steel for pressure equipment.As an advanced and increasingly mature non-destructive testing technology,Acoustic Emission Technology has been widely used in the integrity evaluation of materials and components because it can effectively identify material damage and achieve on-line monitoring.However,at present,the relatively mature and most widely used AE signal analysis method is mainly to make a qualitative judgment of material damage,it is difficult to realize the quantitative analysis of material damage process.Based on this,two kinds of typical pressure equipment steel P92 and 4130 X are selected as the research object in this paper.First of all,the uniaxial tensile and cyclic loading tests are carried out on the two kinds of material specimens,and the Acoustic Emission Technology and Digital Image Correlation(DIC)Technology are used to monitor the damage and measure the non-contact strain.Secondly,based on the standard deviation in statistics,a new parameter,Strain Standard Deviation(SSD),which is used to characterize the surface plastic evolution of materials under damage,is constructed,and the damage mechanism of materials is analyzed by Scanning Electron Microscope,and the SSD evolution curve is verified.Subsequently,the information entropy parameters are calculated by using the complete time domain waveform of AE signals,and the quantitative analysis of the damage process of the specimens is realized through information entropy.Finally,a method of combining AE Shannon entropy with SSD is proposed to quantify the internal damage and surface strain of steel for pressure equipment and to characterize the damage evolution law.