Flying Laser Spot thermal Wave IR Imaging of Horizontal and Vertical Cracks

Wang, Y. Q.; Kuo, P. K.; Favro, L. D.; Thomas, R. L.

doi:10.1007/978-1-4684-5772-8_63

Cited by 13 publications

(7 citation statements)

References 1 publication

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“…The technique is also called as flying spot camera, and it has been proposed by Kubiak [1], theory and applications have been investigated by Gruss and Balageas [2]. Different groups [3][4][5][6] have published how the technique can be applied to detect surface breaking cracks. As a vertical crack perturbs the lateral heat flow, the crack can be made visible by evaluating the local changes of the infrared image, e.g.…”

Section: Introductionmentioning

confidence: 98%

Scanning pulse phase thermography with line heating

Oswald-Tranta

Sorger

2012

Quantitative InfraRed Thermography Journal

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Thermographic investigations with a line heating source have been carried out, to localise small subsurface defects. The object is moved along the heating source, i.e. an induction coil in our experiments. The infrared camera is recording the temperature distribution either in reflection or in transmission mode. From the recorded images, the pixel columns are extracted and a new image sequence is created. After adjusting the images according to the shift between two consecutive recorded images, the sequence represents the temporal change of the temperature after a short homogeneous heating pulse. With Fourier transformation a phase image is created, therefore the technique is called scanning pulse phase thermography. In order to find the optimal parameters, as inspection time and motion speed, finite element simulations and analytical calculations are carried out. Experimental results on ferromagnetic steel samples are presented, showing that in reflection mode a 6 mm defect in a 9 mm thick slab in a depth of 7 mm can be detected (aspect ratio = 6/7). In contrast, in transmission mode, even a 4 mm defect in 8 mm depth could be made visible (aspect ratio = 0.5).

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Section: Introductionmentioning

confidence: 98%

Scanning pulse phase thermography with line heating

Oswald-Tranta

Sorger

2012

Quantitative InfraRed Thermography Journal

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“…Since the horn is not rigidly adhered to the test-piece it is observed to chatter chaotically, typically generating broadband harmonic content in a non-repeatable manner [1]. Though there are variations on how laser-spot thermography is performed [5][6][7][8][9][10], the basis is always use of a laser to spot-heat the surface of the test-piece, and measurement of the surface temperature a distance away from the laser-spot. Given the non-repeatability and chaotic frequency content of a thermosonic inspection, the 'heating index' was developed by Morbidini and Cawley [3,4] to provide a measure of the ability of the applied vibration field to generate heat at any defects that may be present.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Crack Opening on Thermosonics and Laser-Spot Thermography

Weekes¹,

Cawley²,

Almond³

et al. 2010

AIP Conference Proceedings

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Laser-spot thermography is a novel method for detecting surface breaking cracks in metals. Another active thermographic research method is thermosonic (Sonic IR) inspection, which may potentially compete with or complement laser-spot thermography in the detection of surface breaking cracks. Thermosonic inspection generates heat predominantly by friction of crack-faces under high-power ultrasonic excitation, the resulting surface temperature rise being imaged with an infrared camera. Thermosonic inspection is therefore best suited to defects that are closed over part of their length. In contrast, laser-spot thermography detects defects by the perturbation of the radial heat flow from a spot heated with a short-pulse laser, the increased thermal impedance presented by air between the faces of the crack blocking the conduction of heat. This paper presents an experimental comparison of the performance of thermosonics and laser-spot thermography on a series of samples with different crack sizes, the opening of each crack being varied by three-point bend loading.

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“…During the 90's, Onera and Areva have developed an instrument based on the flying spot thermography [2], [3], [4] which was first developed at the Wayne State University [5]. The aim was to carry out inspections of heat exchangers in the nuclear industry.…”

Section: Results Of Flying Spot Active Thermography On Hpt Bladesmentioning

confidence: 99%

Influence of the surface roughness on images acquired by flying spot active thermography: Case of the high pressure turbine blades

Maffren

Lepoutre

Deban

et al. 2012

2012 IEEE International Instrumentation and Measurement Technology Conference Proceedings

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High pressure turbine blades undergo heavy thermomechanical constraints which drive initiation and propagation of cracks. These cracks can be difficult to detect with the current control equipment. The aim of this study is to develop an active thermography process called flying spot (scanning laser heating) in the 1-2 µm range to inspect the blades. This work is funded by the French Ministry of Defense, DGA through the PhD scholarship program and the contract 2010.60.018. (Abstract) Flying spot; SWIR thermography; surface roughness; HPT blade

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Flying Laser Spot thermal Wave IR Imaging of Horizontal and Vertical Cracks

Cited by 13 publications

References 1 publication

Scanning pulse phase thermography with line heating

Scanning pulse phase thermography with line heating

The Effect of Crack Opening on Thermosonics and Laser-Spot Thermography

Influence of the surface roughness on images acquired by flying spot active thermography: Case of the high pressure turbine blades

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