Laser line scanning thermography for surface breaking crack detection : modeling and experimental study

Puthiyaveettil, Nithin; Thomas, K. Renil; Unnikrishnakurup, Sreedhar; Myrach, Philipp; Ziegler, Mathias; Balasubramaniam, Krishnan

doi:10.1016/j.infrared.2019.103141

Cited by 26 publications

(5 citation statements)

References 17 publications

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“…When the laser heats the material, the heat will diffuse from the heating point in different directions, and flow from the higher temperature area to the lower temperature area, and finally the temperature field will reach thermal equilibrium. When the heat source of laser heating is   , , , Q x y z t , The heat transfer equation in the 3D Cartesian coordinate system is [32]:…”

Section: Theoretical Fundamentalsmentioning

confidence: 99%

Characterization Method of Surface Crack Based on Laser Thermography

et al. 2021

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The characterization of micro cracks on metal surface plays an important role in the process of manufacturing and using, which has attracted a lot of attention. This is mainly due to the fact that the size of defects is smaller and the depth of defects is difficult to predict compared with metal materials with larger plane, which is still challenging. In order to solve this problem, this paper proposes a characterization method of surface defects based on reflective laser thermography, and designs a laser heating nondestructive testing system based on reflection. The system includes a semiconductor laser to heat the surface of metal cracks, and an infrared imager to record changes in the temperature field of the metal surface. In the process of data analysis, an Otsu adaptive threshold segmentation method is selected to quantify the defect size, which can control the quantification accuracy of defect size within 25%. A derivative analysis method is proposed to quantify the depth of defects, which can control the depth quantification accuracy of tiny defects within 7%.

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Section: Theoretical Fundamentalsmentioning

confidence: 99%

Characterization Method of Surface Crack Based on Laser Thermography

et al. 2021

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“…By scanning the laser spot along the sample surface at constant velocity (the so-called flying spot thermography), large parts can be analyzed in a fast way [ 1 , 2 ]. This method is well suited to image cracks by showing the crack length along the surface [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. A more challenging task is to evaluate the width and depth of the detected crack.…”

Section: Introductionmentioning

confidence: 99%

Sizing the Depth and Width of Narrow Cracks in Real Parts by Laser-Spot Lock-In Thermography

Colom

Rodríguez‐Aseguinolaza

Mendioroz

et al. 2021

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We present a complete characterization of the width and depth of a very narrow fatigue crack developed in an Al-alloy dog bone plate using laser-spot lock-in thermography. Unlike visible micrographs, which show many surface scratches, the thermographic image clearly identifies the presence of a single crack about 1.5 mm long. Once detected, we focus a modulated laser beam close to the crack and we record the temperature amplitude. By fitting the numerical model to the temperature profile across the crack, we obtain both the width and depth simultaneously, at the location of the laser spot. Repeating the process for different positions of the laser spot along the crack length, we obtain the distribution of the crack width and depth. We show that the crack has an almost constant depth (0.7 mm) and width (1.5 μm) along 0.7 mm and features a fast reduction in both quantities until the crack vanishes. The results prove the ability of laser-spot lock-in thermography to fully characterize quantitatively narrow cracks, even below 1 μm.

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“…As a result, an abrupt temperature discontinuity appears in the thermogram along the length of the fissure. Scanning the laser-spot along the sample surface at constant velocity while recording the temperature by an IR camera (the so-called flying spot thermography) is a fast way to image the length of surface breaking cracks [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%