Analysis On The Acoustic Response Characteristics Of The Closed Crack In Metal Plate Under The Electromagnetic Loading

During the manufacturing and using process of metal component,it is inevitable to produce micro fatigue defects on the inner or the surface.Closed crack is a common form of fatigue defects.Due to the contact characteristics of the crack interface,it always failed to detect the closed crack by using the regular ultrasonic testing.In order to achieve effective detection of closed metal crack,the electromagnetic loading method is applied to the ultrasonic detection of closed crack,which is helpful to improve the detection rate of the closed crack.Firstly,the multi-physics coupling theory of the electromagnetic field,force field and displacement field of the metal plate under electromagnetic loading is analyzed and the electromagnetic coupling equation based on the Lorentz force principle is given.The second-order nonlinear wave equation of closed crack is derived and the nonlinear acoustic modulation process is solved by the principle of wave disturbance.Secondly,the finite element simulation and experimental verification of electromagnetic ultrasonic and electromagnetic loading process are carried out.The interfacial force model of closed crack with hysteresis is built up.A multi-physics coupling model is established to simulate the modulation of the ultrasonic from the closed crack under electromagnetic loading.The acoustic response characteristics of the metal plate contained closed crack under electromagnetic loading are simulated and analyzed.Finally,the influence of the metal closed crack on the ultrasonic propagation process under the electromagnetic loading is confirmed by the experiment.The effect of the electromagnetic loading parameters on the ultrasonic modulation is studied and the detection of the metal closed crack is achieved.