Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches

Abstract

The characteristics of removable magnetostrictive thin patches are investigated for the generation of guided waves in plates. The directivity patterns of SH, S0 and A0 modes have been measured in a thin metallic plate for different combinations of static and dynamic magnetic field directions. This used different coil geometries such as racetrack and spiral coils to generate the dynamic magnetic field, as well as separate biasing static magnetic fields from permanent magnets. This arrangement generated signals via both Lorentz and magnetostrictive forces, and the resultant emitted guided waves were studied for different dynamic and static magnetic field directions and magnitudes. It is demonstrated that different guided wave modes can be produced by controlling these parameters.

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.…”

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

“…The magnetostrictive patch used in the experiments was fabricated from a VACOFLUX 48 iron–cobalt alloy supplied by ® VACUUMSCHMELZE GmbH & Co., Hanau, Germany, with the dimensions and properties given in Table 1 . These patches exhibit isotropic behavior when different static and dynamic fields are applied [ 29 ], as demonstrated by placing the patch under a coil and permanent and then rotate the system by 90° while monitoring the vibration behavior. It was shown that rotation had minimal effect on the vibration of the specimen.…”

“…The magnetostriction phenomenon is widely used for different applications, such as the active element in ultrasonic transducers used to generate elastic waves for nondestructive testing and inspection [ 28 , 29 , 30 , 31 ], microelectromechanical systems or MEMS [ 29 ], positioning sensors [ 32 ], level-gauging sensors [ 33 ] and accurate actuation mechanisms [ 34 ].…”

“…This experimental paper helps to explain and demonstrate the response of a thin patch due to magnetostriction from different orientations and relative amplitudes and excitation frequencies of dynamic and static magnetic fields. The experimental sample used here is a patch bonded to a large glass plate to generate ultrasonic guided waves in the plate [ 29 ], but the general findings of the forces generated at the patch can be applied to other types of guided waves where a patch may be applied to a pipe or a bar, for example.…”