Study On Ultrasonic Response Characteristics Of Metal Plastic Deformation

In bad environment,metal materials can appear performance degradation in the early period under long-term overloaded service,and its service life will be reduced.Currently,the traditional linear ultrasonic testing technique can only detect macroscopic defects in surface and inside of materials,but it can do nothing for the early material performance degradation.The nonlinear ultrasonic testing technology is a good solution to this problem.Because of its excellent characteristics of non-contact,high detection efficiency and avoiding the nonlinear disturbance introduced by the coupling agent and the problems of complex surface pretreatment process in the piezoelectric ultrasonic detection.the nonlinear electromagnetic ultrasonic testing technology has attracted wide attention.At present,the study of the nonlinear electromagnetic ultrasonic testing is relatively rare,and there are many critical problems unresolved.In this paper,the 6061 aluminum alloy specimens with plastic deformation are defected by nonlinear electromagnetic ultrasonic testing technology.The main research work is as follows:(1)Combining the basic principle of electromagnetic ultrasonic with the principle of nonlinear ultrasonic,The bulk wave propagation with nonlinear electromagnetic ultrasonic testing technology is analyzed in theory aspect,and the change law of nonlinear response for plastic deformation of the dislocation model and elastoplastic model are analyzed.(2)Through the study of the performance test and parameter selection of nonlinear ultrasonic testing equipment,the nonlinear ultrasonic testing system is built.By changing the measuring position and driving voltage,different specimens is tested,and the nonlinear coefficient and second harmonic influenced by plastic deformation are analyzed.(3)Based on the analysis of nonlinear piezoelectric ultrasonic testing and nonlinear electromagnetic ultrasonic testing,the electromagnetic ultrasonic propagation characteristics of second harmonic in the plastic defect is studied,the feasibility of nonlinear electromagnetic ultrasonic technology on of plastic defect detection is further verified.Nonlinear electromagnetic ultrasonic testing technique has a broad application prospect;therefore,the study of the electromagnetic ultrasonic nonlinear response characteristics on the defects of the early material plastic deformation has important theoretical significance and engineering practical value.