Vibration-based damage detection is a range of methods that utilizes the dynamic response of a structure to evaluate its condition and detect damage. It is an important approach for structural health monitoring and has drawn much attention from researchers. While multiple reviews have been published focusing on different aspects of this field, there has not been a study specifically examining the recent development across the range of methods, including natural frequency, mode shape, modal curvature, modal strain energy, and modal flexibility-based damage detection methods. This paper aims to fill this gap by reviewing the recent application of these methods in civil structures, including beams, plates, trusses, frames, and composite structural members. The merits and limitations of each method are discussed, and research opportunities are presented. This broader review also provides an opportunity for critical comparison across this range of methods. While predominantly reviewing experiment-based studies, this review also considers some numerical studies that may motivate further research.

The maximum depth for which a defect of a given size can be detected in thermographic inspections is known as the ‘probing depth’. For materials such as polymer composites, with low through-thickness thermal diffusivity, inspections are limited to thin materials or near surface inspection. With the aim of improving probing depth, the paper describes how established signal processing techniques are adapted for thermographic inspections. The procedures are implemented for both pulse thermography and pulse phase thermography inspections of laminated composite materials and sandwich structures. It is demonstrated that the adaptation significantly improves the probing depth, identifying defects that could not be identified using existing procedures. The applicability of the new approaches is discussed, paying particular attention to systematic and random errors resulting from equipment setup. Simple and efficient compensation methods to reduce the effect these errors are presented.

Corrosion of metals can occur under coatings making early visual detection almost impossible which enables corrosion to progress undetected. Nondestructive evaluation can be used to inspect parts during their life. Thermography uses the difference in thermal properties between defective and sound areas to locate defects by applying a short pulse of heat and monitoring the surface temperature of the sample with an infrared camera. However, currently, inspection is reliant on highly trained operators to analyze images for defects and in the case of corrosion, judge its growth. The aim of this research was to develop and test a novel algorithm to identify and quantify the onset of corrosion under coatings and monitor the growth. Using this algorithm, the corrosion was autonomously detected in a variety of mild steel samples exposed to three different corrosive environments. The method successfully detected, quantified, and monitored the growth of corrosion under coatings accurately and robustly using thermal images gathered by a microbolometer infrared camera. The extent of corrosion was reported with an accuracy of 3% absolute error when compared to the true extent.

A robust and reliable method for the identification of defects in adhesively bonded joints used in the membrane containment system used to store liquefied natural gas during transport on board ships is required. The adhesively bonded interface of the membrane system may contain low volume defects known as kissing defects, which are extremely difficult to detect using portable inspection techniques. A novel methodology for detecting such defects is described in the paper. To demonstrate the approach simulated kissing defects were produced in a controlled fashion in a representative secondary membrane bond using silicon grease contamination. The defects were detected using an active thermographic approach known as pulsed phase thermography (PPT) which detects subsurface defects by monitoring the effect they have on the propagation of heat through a component. Due to the low volume of kissing defects, they generally have minimal effect on the heat propagation, so the detection was made possible by application of a small load generated by application of a vacuum. The vacuum can be set-up using a reusable chamber and a standard vacuum pump and therefore is portable and can be applied on-site and in a shipyard during construction.