Inspection Detectability Improvement for Metal Defects Detected by Pulsed Infrared Thermography

Zhengwei Yang,Gan Tian,Yin Li,Jietang Zhu,Guangjie Kou,Wei Zhang

doi:10.1007/s13320-019-0489-1

Zhengwei Yang, Gan Tian + Show 4 more

Open Access

https://doi.org/10.1007/s13320-019-0489-1

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Abstract

Aiming at the drawbacks of low contrast and high noise in the thermal images, a novel method based on the combination of the thermal image sequence reconstruction and the first-order differential processing is proposed in this work, which is comprised of the following procedures. Firstly, the specimen with four fabricated defects with different sizes is detected by using pulsed infrared thermography. Then, a piecewise fitting based method is proposed to reconstruct the thermal image sequence to compress the data and remove the temporal noise of each pixel in the thermal image. Finally, the first-order differential processing based method is proposed to enhance the contrast. An experimental investigation into the specimen containing de-bond defects between the steel and the heat insulation layer is carried out to validate the effectiveness of the proposed method via the above procedures. The obtained results show that the proposed method can remove the noise, enhance the contrast, and even compress the data reaching at 99.1%, thus improving the detectability of pulsed infrared thermography on metal defects.

Highlights

Owning to the advantages of high speed, high efficiency, non-contact, and visible inspection results, the pulsed infrared thermography nondestructive technique has been successfully applied to evaluate defects for materials, especially for metals [1,2,3]
There are some problems of non-uniform heat and surface reflection. All of these cause the thermal images with the drawbacks of low contrast and high noise, which embarrasses the evaluation of defects
Pilla et al [5] developed a differentiated absolute contrast (DAC) method to successfully perform on the semi-infinite materials, but with low calculation accuracy and Article type: Regular

Summary

Introduction

Owning to the advantages of high speed, high efficiency, non-contact, and visible inspection results, the pulsed infrared thermography nondestructive technique has been successfully applied to evaluate defects for materials, especially for metals [1,2,3]. Most of previous references available are devoted to the single frame image, and the relationships between the thermal image sequences are hardly involved On this account, a novel method based on the combination of thermal image sequence reconstruction and differential processing is proposed to enhance the contrast and remove the noise. A novel method based on the combination of thermal image sequence reconstruction and differential processing is proposed to enhance the contrast and remove the noise To this goal, this work begins with the detection on the defects in the metal using pulsed infrared thermography, followed by theoretic analysis on the root and character of the noise in the thermal image sequence. The proposed method is validated by another specimen containing de-bond defects, showing excellent performance

Experiment preparation

Experimental results and analysis

Noise analysis

Thermal image sequence reconstruction

Contrast enhancement based on the first-order differential processing

Conclusions