The effect of through-the-thickness holes on a reference-free damage diagnosis technique

摘要

Recently, a damage detection technique has been developed based on the polarization characteristics of the piezoceramic (PZT) transducers attached on the both sides of a thin and uniform metal plate. Damage is identified using instantaneously measured Lamb wave signals without using previously obtained baseline data. If the propagating waves along a thin plate encounter a discontinuity point such as a crack, mode conversion occurs and this mode conversion is extracted using the proposed technique. So for, the proposed technique is demonstrated for specimens with a uniform thickness although many structural systems have more complex structural features such as stiffeners, holes and bolts. In this study, the effect of through-the-thickness holes on the proposed technique is investigated. An array of holes creates multiple reflections and refractions of Lamb waves, and these multiple reflections and refractions may cause difficulties in analyzing responses of Lamb waves. Because the through-the-thickness holes do not produce mode conversion, it is expected that these holes do not affect the performance of the proposed technique. This study experimentally investigates whether a crack damage can be still identified even in the presence of the holes using the proposed technique.