The Use of Flexible Ultrasound Transducers for the Detection of Laser-Induced Guided Waves on Curved Surfaces at Elevated Temperatures.

Tai Chieh Wu,Masayuki Tanabe,Che Hua Yang,Makiko Kobayashi

doi:10.3390/s17061285

Abstract

In this study, a flexible ultrasonic transducer (FUT) was applied in a laser ultrasonic technique (LUT) for non-destructive characterization of metallic pipes at high temperatures of up to 176 °C. Compared with normal ultrasound transducers, a FUT is a piezoelectric film made of a PZT/PZT sol-gel composite which has advantages due to its high sensitivity, curved surface adaptability and high temperature durability. By operating a pulsed laser in B-scan mode along with the integration of FUT and LUT, a multi-mode dispersion spectrum of a stainless steel pipe at high temperature can be measured. In addition, dynamic wave propagation behaviors are experimentally visualized with two dimensional scanning. The images directly interpret the reflections from the interior defects and also can locate their positions. This hybrid technique shows great potential for non-destructive evaluation of structures with complex geometry, especially in high temperature environments.

Highlights

Structures with curved surfaces such as pipelines or pressured vessels that are required to operate at elevated temperatures are commonly seen
The defects relative position is ensured though the dynamic imaging and our understanding of guided wave propagation is ensured though the dynamic imaging and our understanding of guided wave propagation behavior
This paper demonstrates that the integration of flexible ultrasonic transducer (FUT)’s and laser-induced ultrasound applied

Summary

Introduction

Structures with curved surfaces such as pipelines or pressured vessels that are required to operate at elevated temperatures are commonly seen. Erosion, and cracks may lead to catastrophic outcomes. Nondestructive testing (NDT) techniques have been continuously developing for early detection of possible defects to ensure a structure’s integrity. Ultrasonic techniques (UTs) have been based on guided wave detection and were developed for the detection of subsurface and interior faults. UTs have some limitations such as their range of working temperatures and incomplete surface conductivity. When using ultrasonic wave detection at high temperatures, optical interferometers have overcome the temperature shortcoming, but their sensitivity is low and the preparation of a smooth specimen surface is necessary

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