| Microcrack in metal plate,such as closed-crack,may produce in the process of manufacturing processes and applications in a variety of loading.Closed-crack can be distinguished by nonlinear ultrasonic testing technique,while the nonlinear effect is very weak and may be susceptible by other factors.In order to insure the reliability of the detection of the closed crack,in this paper,the study on the characteristics of the ultrasonic nonlinearity of the metal plate with closed crack in electromagnetic loading was studied.These following points are composed in this paper.1)According to the electromagnetic ultrasonic wave detection principle,electromagnetic ultrasonic excitation simulation model was established to study the propagation characteristics of Lamb wave in aluminum plate.Based on the nonlinear principle of closed crack,the electromagnetic ultrasonic simulation model of closed crack,which considering the influences of the hysteresis effect and damping force,was built to study the influence of the closed crack interface force to ultrasonic transmission nonlinear.2)The finite element model of metal plate with a closed crack under the electromagnetic loading was established,The influence of the current,the position of loading coil on the nonlinearity of ultrasonic and the temperature distribution of the metal plate during electromagnetic loading were studied.3)Based on the principle of non-linear ultrasonic modulation of closed crack,the ultrasonic modulation model of metal plate under electromagnetic loading was established.The ultrasonic modulation phenomenon of electromagnetic cracked metal plate,and the effect of electromagnetic loading parameters and electromagnetic heat effect on the ultrasonic modulation component were analyzed through the ultrasonic modulation model.4)Ultrasonic nonlinear system was set up.The experiments of electromagnetic ultrasonic,electromagnetic loading,ultrasonic modulation were studied and the relationships between the three were analysed. |
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