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

Qiu, Jinxing; Pei, Cuixiang; Yang, Yang; Wang, Rongbang; Liu, Haochen; Chen, Zhenmao

doi:10.1016/j.ijfatigue.2020.105950

Cited by 10 publications

(5 citation statements)

References 22 publications

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“…For this purpose, a rectangular crack model and an elliptical crack model are proposed to representing the crack profile with 3 independent parameters. The elliptical model of detailed crack shape described by the crack length L, center position C and depth D, is more suitable for the practical fatigue crack [12,14] .…”

Section: Quantitative Evaluation Of Crack Profiles With Signals Of Litmentioning

confidence: 99%

“…An inspection system is also developed based on the homogenous LIT technique for the in-situ inspection of the multi-layered first wall panels in the vacuum vessel (VV) of a Tokamak device [7][8][9] . Moreover, we have developed a laser array spots thermography (LAST) technique for the efficient inspection and evaluation of the surface cracks [10][11][12][13][14][15][16] . The LAST method transforms a laser beam to a matrix of laser spots highly localized nearby the crack and adopts an infrared camera to catch the perturbation of the temperature field due to the crack.…”

Section: Introductionmentioning

confidence: 99%

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Studies on the infrared thermography technique for quantitative nondestructive evaluation of surface crack and delamination of multilayer structures

Yang

Liu

et al. 2023

International Conference on Optical and Photonic Engineering (icOPEN 2022)

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In this paper, some researches on the laser infrared thermography (LIT) and the eddy current infrared thermography (ECIT) for quantitative nondestructive testing and evaluation of surface cracks and delamination of multilayer structures are introduced. At first, a laser array spots thermography (LAST) method for inspection of surface cracks in metallic structures is presented. LAST related measurement and image processing methods for inspection and quantitative evaluation of crack profiles are introduced in detail. Second, LIT technique and numerical analysis methods for detection and sizing of interface delamination of multilayer structures are introduced aiming at application to the in-vessel structures of Tokamak fusion reactors, such as the first wall panels of blanket modules. At last, some studies on the quantitative nondestructive evaluation of delamination of thermal barrier coating system of gas turbine blades with ECIT are given. The numerical methods for forward analysis of heat generation and transfer process of infrared thermography, and for inverse analysis of defect size with infrared thermography signals are emphasized in this paper, in addition with experimental validations of both the numerical methods and the new inspection techniques.

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Section: Quantitative Evaluation Of Crack Profiles With Signals Of Litmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Studies on the infrared thermography technique for quantitative nondestructive evaluation of surface crack and delamination of multilayer structures

Yang

Liu

et al. 2023

International Conference on Optical and Photonic Engineering (icOPEN 2022)

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“…In the detection of surface cracks, thermography methods show great potential due to their advantages of being non-contact and full-field [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Nondestructive Surface Crack Detection of Laser-Repaired Components by Laser Scanning Thermography

et al. 2022

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As a revolutionary new technique, laser-engineered net shaping (LENS) is a layer additive manufacturing process that enables accurate, rapid and automatic repair of industrial component damage. In the laser repair (LR) process or in service, surface cracks can appear, which have a detrimental effect on the repair quality and the mechanical performance; therefore, the surface crack detection of repaired components has attracted much attention. Laser spot thermography is an important nondestructive testing method with the advantages of non-contact, full-field and high precision, which shows great potential in the crack detection of repaired components. The selection of thermographic process parameters and the optimization of thermal image processing algorithms are key to the success of the nondestructive detection. In this paper, the influence of material properties and thermographic process parameters on the surface temperature gradient is studied based on the simulation of laser spot thermal excitation, and the selection windows of thermographic process parameters for iron-based and nickel-based alloys are obtained, which is applied to the surface crack detection of repaired components. To improve the computational efficiency of thermal images, the Prewitt edge detection algorithm is used in the thermal image processing, which realized fast extraction of cracks with a high signal-to-noise ratio (SNR), and the detection sensitivity of crack width can reach 10 μm. To further study the influence of surface roughness on the thermographic detection, repair layers with and without polishing process are characterized, which show that the Prewitt edge detection algorithm is well applicable to crack detection on surfaces with different roughness level.

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

Cited by 10 publications

References 22 publications

Studies on the infrared thermography technique for quantitative nondestructive evaluation of surface crack and delamination of multilayer structures

Studies on the infrared thermography technique for quantitative nondestructive evaluation of surface crack and delamination of multilayer structures

Nondestructive Surface Crack Detection of Laser-Repaired Components by Laser Scanning Thermography

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

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