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

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

doi:10.3390/app10228051

Gaétan Poelman, Joost Segers + Show 3 more

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https://doi.org/10.3390/app10228051

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Journal: Applied sciences	Publication Date: Nov 13, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: Ghent University, Ablynx (Belgium)

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.

Highlights

In several industrial sectors, composite materials are replacing traditional metals and alloys due to their advantageous properties such as a high stiffness-to-weight ratio and a good corrosion resistance
We present an experimental study on the efficiency of several time- and frequency-domain analysis techniques to obtain good defect detectability on several carbon fiber reinforced polymer (CFRP) samples with different defect types, sizes, and depths
The defect detectability of both time- and frequency-domain analysis techniques for flash thermography was evaluated. Both processing techniques that evaluate a single time bin, i.e., dynamic thermal tomography (DTT) and frequency-domain tomography (FDT), and techniques that perform an integration over a range of time bins, i.e., Thermal Signal Area (TSA) and adaptive spectral band integration (ASBI), are of interest

Summary

Introduction

In several industrial sectors (e.g., aerospace sector), composite materials are replacing traditional metals and alloys due to their advantageous properties such as a high stiffness-to-weight ratio and a good corrosion resistance. The layered structure of composites makes them susceptible to internal damage features that may arise during production or during their service life. The presence of these defects may have a detrimental effect on the load-bearing capabilities of the component and must be detected. T Flash thermography (FT) is a quick, full-field and non-contact non-destructive testing (NDT) technique that detects defects by exploiting the mismatch in thermal properties between the base material and an internal defect [1,2,3,4]. At an internal boundary or defect, the thermal diffusivity mismatch between the defect and the sound material leads to a local abnormal temperature evolution.

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