Model-Based Guided Wave NDE: The Evolution of Guided Wave NDE from “Magic” to “Physically Based Engineering Tool”

The utility of those waves propagating over a distance, called “guided waves,” provides abundant technical advantages in a variety of nondestructive evaluation (NDE) applications. In recent years, the field has rapidly grown as one of the most noticeable subjects in the NDE community, from not only the academic but also the practical standpoint, representing promising technological transfer. A number of commercialized inspection units and techniques are already available on the market. However, the principle of guided waves physics, which is crucial for proper usage and subsequent data analysis of the equipments has not been fully elucidated for field NDE engineers, and has mainly been set out for the purpose of simplifying the operation scheme. A simplified operation manual is necessary to bolster the market, but is quite often not sufficient to conduct the mission adequately. Do NDE engineers no longer need to understand guided wave physics? The knowledge on guided wave physics and advanced softwares are battling against the challenging task to turn the technique from magic to a reliable engineering tool. In this sense, the guided wave NDE technique now requires us to establish a firmer physical foundation, whereby its sophisticated features are understood, to enrich utility and correct the improper usage of field data; meanwhile, the instrumentation is rapidly being upgraded with more advanced functions. In this paper, the importance of a physical understanding of the characteristics of guided wave NDE is firstly addressed. Guided wave models can enhance NDE performance and alleviate the likelihood of a false call. Scattering of surface waves by a two-dimensional corrosion pit at the surface of a homogenous, isotropic, linearly elastic half-space is theoretically investigated in Sect. “A Guided Wave Measurement Model for Scattering of Surface Waves by a Corrosion Pit Based on the Use of the Elastodynamic Reciprocity”. In Sect. “Model-Based Visualization of Defects Using Tomography”, guided wave tomographic imaging of plate-like structures is presented using a probabilistic algorithm. Section “The Model-Based Guided Wave Focusing Technique to Improve Sensitivity” shows that the guided wave focusing technique can be used to focus energy in both the circumferential and axial directions in pipes. The unique nonlinear features among different guided wave modes, which can be used to choose a proper mode with better sensitivity for micro-damage detection, are reported in Sect. “Model-Based Nonlinear Guided Wave Techniques for Micro-Damage Detection”.