The Effect of Changes in Magnetic Field and Frequency on the Vibration of a Thin Magnetostrictive Patch as a Tool for Generating Guided Ultrasonic Waves

Abstract

A set of experiments was designed and conducted to investigate the vibrational ultrasonic response of a thin magnetostrictive patch bonded to a glass plate, with changes in static and dynamic magnetic fields applied to the patch. Such arrangements are often used as a means of generating guided waves in pipes or plates, by attaching a patch to a sample’s surface. The effect of varying the applied static and dynamic magnetic field’s amplitudes and directions and the frequency of the dynamic magnetic field was studied. It was demonstrated that the vibration of the magnetostrictive patch could be controlled and enhanced by optimizing the magnetic fields. It was also shown that for low-amplitude dynamic magnetic fields, Lorentz forces generated within the patch and the resonant frequency of the patch could also contribute to the enhancement of the vibration of the patch for low-amplitude fields. For high-amplitude dynamic magnetic fields, the magnetostriction effect can be the main transduction mechanism, which can be optimized for non-destructive testing and inspection purposes.

Defect Detection and Imaging in Composite Structures Using Magnetostrictive Patch Transducers

“…Previous work by the authors has established some of the operating conditions that result from these configurations [ 23 , 24 ], including the radiation patterns of the A0, S0 and SH0 guided wave modes. In Configuration 1, no significant Lorentz forces were expected, leaving only magnetostrictive forces as the driving mechanism.…”

“…These initial tests indicated that variations in B s and B d could lead to the generation and enhancement of specific guided wave modes while suppressing others. Further work conducted by the authors [ 24 ] investigated the effect of variation of further parameters, such as the excitation frequency and the combined variation of B s and B d . It was demonstrated that the magnetostrictive patch provided a wide active transduction range, but that sensitivity was optimum at an excitation frequency of 120 kHz.…”