Quantitative evaluation of surface crack depth with laser spot thermography

Qiu, Jinxing; Pei, Cuixiang; Liu, Haochen; Chen, Zhenmao

doi:10.1016/j.ijfatigue.2017.02.027

Cited by 34 publications

(13 citation statements)

References 9 publications

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“…(4) and to calculate the surface temperature distribution corresponding to cracks of different shape and dimensions. A numerical simulation code developed by authors is adopted in all of the forward modeling considered herein [18,[22][23] . The feasibility of the code has been validated by compared with results of both the commercial software and experiments.…”

Section: Numerical Analysis Of Llt Signalsmentioning

confidence: 99%

“…The study objects of LIT contain the laser heating method [5][6][7] , thermal image processing [8][9][10] , and the defect characterizations [11][12][13] . Until now, several studies have been conducted on characterization of surface cracks by using the LIT method [14][15][16][17][18] . The main idea of these studies is to evaluate the crack-caused asymmetries of the surface temperature distribution based on image processing.…”

Section: Introductionmentioning

confidence: 99%

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Remote measurement and shape reconstruction of surface-breaking fatigue cracks by laser-line thermography

Qiu

Pei

Yang

et al. 2021

International Journal of Fatigue

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In this paper, a method for remote measurement and shape reconstruction of fatigue cracks by using laser-line thermography (LLT) technique is developed. A new feature parameter derived from the LLT signals is proposed to evaluate the length and estimate the general inner profile of a surface-breaking fatigue crack. An inversion analysis scheme based on conjugate gradient optimization algorithm is then applied to reconstruct the detailed inner profile and dimension of the crack. The reconstruction results with both numerically simulated LLT signals and experimental signals proved the feasibility of proposed inversion scheme and remote LLT method. Based on methods of this paper, not only the size of cracks can be quantitatively evaluated, but the inner profile is also reconstructed for cracks in different shapes from the LLT signals.

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Section: Numerical Analysis Of Llt Signalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Remote measurement and shape reconstruction of surface-breaking fatigue cracks by laser-line thermography

Qiu

Pei

Yang

et al. 2021

International Journal of Fatigue

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“…If the depth of the crack is finite, the temperature distribution in the material cannot be written analytically and the solution has to be sought numerically. Several research groups have applied finite element methods (FEM) to solve the heat diffusion equation to simulate the surface temperature of a sample containing a finite crack when it is illuminated by a focused laser beam [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, in these works, only cracks wider than 40 µm were studied because in classical continuous FEM, the cracked sample is divided into two domains: the bulk and the air filling the crack [ 33 ].…”

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

Materials

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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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“…Li et al proposed a new surface crack imaging method by using laser as thermal excitation source [8]. Qiu et al adopted a laser to heat metal surface and studied the relationship between surface crack size and temperature distribution [9]. Wang et al utilized a laser to heat aerospace composite plates in order to detect internal defects [10].…”

Section: Introductionmentioning

confidence: 99%

Defect Depth Determination in Laser Infrared Thermography Based on LSTM-RNN

et al. 2020

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Carbon fiber reinforced polymer (CFRP) has been increasingly used in aviation industry since it significantly enhances the performance of aircraft. However, imperfections inside the CFRP structures pose a threat to aviation safety. Apart from the defect shape and size, flaw depth is crucial to assess the defect severity. In this work, we utilize a laser infrared thermography (LIT) system to inspect an aviation CFRP sheet and adopt a long-short term memory recurrent neural network (LSTM-RNN) to determine the defect depth. Thermographic sequences obtained by LIT are processed using thermographic signal reconstructions (TSR) method. Raw data and TSR processed data are separately used to train and test the LSTM-RNN. Results show that background noises in the original thermal signals can be effectively reduced by the TSR method, which is helpful for the models to learn the signal characteristics. Compared with two traditional methods, recurrent neural network (RNN) and convolutional neural network (CNN), we find the LSTM-RNN outperforms.

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Quantitative evaluation of surface crack depth with laser spot thermography

Cited by 34 publications

References 9 publications

Remote measurement and shape reconstruction of surface-breaking fatigue cracks by laser-line thermography

Remote measurement and shape reconstruction of surface-breaking fatigue cracks by laser-line thermography

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

Defect Depth Determination in Laser Infrared Thermography Based on LSTM-RNN

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