Adaptive spectral band integration in flash thermography: Enhanced defect detectability and quantification in composites

Poelman, Gaétan; Hedayatrasa, Saeid; Segers, Joost; Paepegem, Wim Van; Kersemans, Mathias

doi:10.1016/j.compositesb.2020.108305

Cited by 35 publications

(31 citation statements)

References 40 publications

(74 reference statements)

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“…The deeper a defect, the lower the frequency of maximum phase contrast f ∆ϕ,max (see Equation ( 3)). Since the frequency of maximum phase contrast is typically found at very low frequencies, deep defects might be attributed the same f ∆ϕ,max due to a limited frequency resolution in the experimental data [19]. Recording for a longer duration would increase the frequency resolution (defined by their inverse relationship, ∆ f = 1/t end ), but the defect detectability might become worse since the additionally evaluated part is noisy and strongly affected by lateral heat diffusion effects.…”

Section: Single-bin Evaluation: Frequency-domain Tomography (Fdt)mentioning

confidence: 99%

“…. f ∆ϕ,max [19]. Due to the high dynamic range, the obtained ASBI surface maps are represented in a logarithmic scale (after inverting the sign of the damage index values) for improved defect visibility.…”

Section: Integrated-bin Evaluation: Adaptive Spectral Band Integration (Asbi)mentioning

confidence: 99%

“…The defect detectability is significantly improved by post-processing of the recorded thermal data sequence using image processing [14][15][16] and data processing [2,3,[17][18][19][20] techniques. Some of the data processing algorithms operate directly on the time-domain data (i.e., the recorded thermal sequence), such as dynamic thermal tomography (DTT) [21,22], differential absolute contrast (DAC) [23], and thermal signal area (TSA) [24].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, performing the analysis in the frequency domain (i.e., after performing a fast Fourier transform) exhibits the advantageous property that undesirable effects of non-uniform heating and non-uniform surface emissivity are strongly reduced. Some of the analysis techniques operating in frequency domain are pulsed phase thermography (PPT) [18,25,26], modified pulse-phase thermography (PPT1/PPT2) [27], phase-domain thermal tomography (PDTT) [21], and adaptive spectral band integration (ASBI) [19]. PDTT may be considered as a phase-domain equivalent of DTT, where a pixel's phase angle instead of an indicative time provides information on the defect's depth [21].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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.

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Section: Single-bin Evaluation: Frequency-domain Tomography (Fdt)mentioning

confidence: 99%

Section: Integrated-bin Evaluation: Adaptive Spectral Band Integration (Asbi)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…NDT methods play a critical role in the evaluation and maintenance of composite materials. A wide variety of NDT techniques has been built on different principles [7,8], including x-ray computed tomography [9], terahertz testing [10,11], infrared thermography [12,13], shearography [14], eddy current testing [15,16], ultrasonic testing (UT) [17,18,19], etc.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of ultrasonic techniques for reconstructing the multilayer structure of composites

Yang

Verboven

et al. 2021

NDT & E International

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Phase inversion in (vibro‐)thermal wave imaging of materials: Extracting the AC component and filtering nonlinearity

Hedayatrasa

Poelman

Segers

et al. 2021

Structural Contr & Hlth

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In active infrared thermographic inspection of materials, heat wave is stimulated by activation of heat sources, e.g., through optical heat radiation or vibration-induced heat dissipation. Therefore, the monopolar (i.e., heating only) nature of excitation introduces an inevitable ascending trend in the measured thermal response. To obtain an improved thermal wave imaging quality, it is crucial to remove this ascending trend and to analyze the decoupled bipolar (i.e., AC) component of the thermal response. This study introduces the concept of phase inversion in thermographic inspection, as a deterministic method for (i) decoupling the AC component and (ii) filtering the prominent second-order nonlinearities from the thermal response. First, this "phase inversion thermography (PIT)" is theoretically substantiated by analysis of heat diffusion through the thickness of a solid material subjected to dissipative boundary conditions. Then, the performance of PIT in accurately decoupling the AC response from various excitation waveforms is verified by finite element simulation of optical infrared thermography on an anisotropic composite coupon. It is shown that by proper selection of the signal's initial phase and waveform duration, PIT yields the AC response with a zero-mean amplitude. At last, the experimental applicability of PIT is evaluated for two different test cases:(1) optical thermography on a backside-stiffened carbon fiber-reinforced polymer (CFRP) aircraft panel with a complex cluster of production defects and(2) low-power vibrothermography on an impacted CFRP coupon. It is shown that PIT, as a physics-based signal processing technique, robustly resolves the strongly transient onset of the excitation and systematically decouples an AC response which is equivalent to the thermal response to an ideally linear and bipolar excitation. The recorded thermal responses are post-processed through Fourier transform, and the enhanced thermal imaging quality and improved defect detectability of the decoupled AC component are demonstrated.

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Adaptive spectral band integration in flash thermography: Enhanced defect detectability and quantification in composites

Cited by 35 publications

References 40 publications

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

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

Comparative study of ultrasonic techniques for reconstructing the multilayer structure of composites

Phase inversion in (vibro‐)thermal wave imaging of materials: Extracting the AC component and filtering nonlinearity

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