Acoustic Emission Characteristics Of Q235A Steel During Tensile Process And Acoustic Source Localization

Q235A steel has been widely used because of its good physical and chemical properties.However,in the practical application of the steel,it is easy to be damaged caused by the tensile failure of the material and the crack development of the material..Therefore,it is necessary to monitor and evaluate the dynamic damage of steel effectively.Acoustic emission testing is recognized for its applicability to the damage of linear structures.At the same time,acoustic emission testing can make a reasonable evaluation of the overall defects of the component,Therefore,it is widely used in nondestructive monitoring.The core of this paper is that using acoustic emission tests the tensile failure process of common steel Q235 A in building structure and adopting the wavelet packet-cross correlation analysis method analyzes the acoustic emission source.Through the analysis of damage monitoring signal and sound source localization on the tensile,it provides a reliable basis for the development process of steel's damage and the change of steel material structure.Besides,it also provides a technical reference for grasping crack growth and the components' damage of steel under different loading rate.The main works of this paper are listed as follows:1.According to the field test conditions,the time parameters of acoustic emission testing are studied by field loading test.The threshold value of acoustic emission is determined by field measurement method.Based on those works,the time parameters of acoustic emission detection also are determined by breaking the lead test.2.In order to monitor the damage of the tensile process of steel and the development of internal crack,the AE characteristics of Q235 A steel under different loading rates were analyzed by acoustic emission testing equipment.It is found that the acoustic signal parameters in the process of the material stretching can be exactly consistent with the mechanical effect,and this result provides a practical value for monitoring the tensile failure process of steel.Then,through the damage model of steel tensile failure established by selecting the appropriate AE parameters and the acoustic signal parameters of the load condition,it is found that damage model is of representative.3.Based on the analysis of the limitation of time difference and location accuracy,the method of wavelet packet combined with cross-correlation is used to locate the AE source accurately.The calculated by wavelet packet combined with cross-correlation method of time and time by the acoustic emission signals of the sensor received are compared,verified the technology of wavelet packet method combined with cross-correlation analysis can provide a accurate Location for acoustic emission source.