Abstract
Non-destructive testing (NDT) is a broad group of testing and analysis techniques used in science and industry to evaluate the properties of a material, structure, or system for characteristic defects and discontinuities without causing damage. Recently, infrared thermography is one of the most promising technologies as it can inspect a large area quickly using a non-contact and non-destructive method. Moreover, thermography testing has proved to be a valuable approach for non-destructive testing and evaluation of structural stability of materials. Pulsed thermography is one of the active thermography technologies that utilizes external energy heating. However, due to the non-uniform heating, lateral heat diffusion, environmental noise, and limited parameters of the thermal imaging system, there are some difficulties in detecting and characterizing defects. In order to improve this limitation, various signal processing techniques have been developed through many previous studies. This review presents the latest advances and exhaustive summary of representative signal processing techniques used in pulsed thermography according to physical principles and thermal excitation sources. First, the basic concept of infrared thermography non-destructive testing is introduced. Next, the principle of conventional pulsed thermography and signal processing technologies for non-destructive testing are reviewed. Then, we review advances and recent advances in each signal processing. Finally, the latest research trends are reviewed.
Highlights
Non-destructive testing (NDT) is helpful for manufacturing defect-free products, but it is used for maintenance and condition inspection of industrial structures and facilities [1]
The passive approach is generally used in the research on materials that are at different temperature compared with the ambient, while in the case of active approach, an external excitation source, such as optical flash lamps, halogen heat lamps, mechanical ultrasonic vibration, or hot and cold air gun is employed with the intention of inducing thermal contrast
With the Pulsed Phase Thermography (PPT) described in the previous section, Principal Component Thermography (PCT) is most applicable for pulsed thermography (PT) data processing
Summary
Non-destructive testing (NDT) is helpful for manufacturing defect-free products, but it is used for maintenance and condition inspection of industrial structures and facilities [1]. IRT technology is being applied in research and development in various industries [6,7], including non-destructive testing, detailed structural condition monitoring, predictive maintenance, manufacturing quality assurance, energy cost reduction, metal and composite material evaluation, gas leak detection, and more. There is a growing trend to integrate thermography technology into other conventional NDT technologies to compensate for each other’s limitations It will result in better inspection capability and the possibility that more information can be acquired in a single test than a particular technique. Pulsed thermography is one of the active infrared techniques, which uses an optical device as an external heat source. A profound work review is required, including the principle, developments, strengths and limitations, signal processing, and research trends for thermography NDT with optical excitation sources.
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