An Experimental Study on the Defect Detectability of Time- and Frequency-Domain Analyses for Flash Thermography

Abstract

A defect’s detectability in flash thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in flash thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain.

Vibro-Thermal Wave Radar: Application of Barker Coded Amplitude Modulation for Enhanced Low-Power Vibrothermographic Inspection of Composites

“…Especially for composites with high in-plane diffusivity, the latter is of high concern. Proper post-processing of the thermographic dataset is essential in order to ensure maximum detectability [ 3 , 4 , 5 , 6 ]. The test-piece may also be inspected in the transmission mode such that the defects are detected based on the thermal response transmitted to the back surface, which leads to increased detectability of deep defects [ 7 ].…”

Application of Pulsed Thermography and Post-processing Techniques for CFRP Industrial Components

“…Pulsed thermography (PT) represents a no-contact and full-field ND technique, widely used for the industrial controls of large composite surfaces due to wide detection area, fast and relatively simple detection [11,12]. In recent years, the enhancement of visual image modality, combined with fast and robust temperature processing strategy has significantly grown for a multi-functionality of Infrared thermography for specific industrial applications, characterized by difficult to inspection components or as requirement of faster inspection [13][14][15][16]. Therefore, the image-processing methods and their continuous improvement make the thermographic inspection even more suitable alternative to popular ND controls, as ultrasonic testing, for different production environments [12,16].…”

“…In recent years, the enhancement of visual image modality, combined with fast and robust temperature processing strategy has significantly grown for a multi-functionality of Infrared thermography for specific industrial applications, characterized by difficult to inspection components or as requirement of faster inspection [13][14][15][16]. Therefore, the image-processing methods and their continuous improvement make the thermographic inspection even more suitable alternative to popular ND controls, as ultrasonic testing, for different production environments [12,16]. In literature, different algorithms were proposed to enhance defect detection in terms of dimension, depth and shape [15,17,18].…”

Thermographic Analysis of Composite Metallization through Cold Spray

“…Regarding polymer composites, the application of pulsed thermography has dealt with the identification of manufacturing or induced defects, such as drilled holes [30] and delamination by impacts [31]. However, due to the recent developments of CS on composites, to the best of the authors' knowledge, there are still no thermographic studies on metallic coatings applied to composites.…”