The design of a novel line-array type of laser source for non-contact guided waves to inspect the integrity of plates

Abstract

Popular guided waves (GW) transducers employed for emitting and receiving GW when inspecting the integrity of different objects include the contact and non-contact ones. Contact transducers that must be physically mounted on the objects are piezoelectric transducers (PZT) and magnetostrictive sensors (MsS). The non-contact method can consist of laser-based transducers. However, the contact transducers could be difficult to apply to some operating situations, such as measuring objects that have high surface temperature, moving target, complex geometries and rough surfaces, and hazardous environment etc. These operating situations limit the possibility of mounting the contact transducers on the inspected objects. Therefore, it is necessary to design a non-contact type of GW transducer. This paper reports the feasibility of using laser to generate the desired GW wave mode, the novel design of optical transducers based on an integrated optical Mach-Zehnder interferometer (IOMZ), and the results of using such novel laser-based GW to inspect the defects occurred in plates. With the help of such IOMZ system to generate the required laser-based GW wave mode, the location and geometrical extents of any defect occurred in an aluminium plate can be successfully determined.