Ultrasonic transducers and monitoring methods for high resolution structural health monitoring

Abstract

An overview is presented covering novel methods for structural health monitoring (SHM) including the scientific background of different, lately developed methods, dominantly based on the transport properties of guided ultrasonic waves. Among the issues presented and discussed are mode and velocity selective contact and non contact transducers including testing methods for array transducers allowing, respectively, adapted optimized operation. Principles of operation, including holographic and tomographic imaging and high resolution integral temporal monitoring, are presented. Special attention is given to wideband excitation in combination with spectroscopic and dispersive imaging based on respective data acquisition and evaluation. Furthermore, compensation methods for temperature variations by acoustic thermometry are presented. The advantages and possible shortcomings of locally selective and integral SHM are discussed and examples are presented for aircrafts, civil structures, and their sections.