Laser Lock-In Thermography for Fatigue Crack Detection

Abstract:

Article Preview

This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm3 can be detected.

Info:

Periodical:

Edited by:

W.K. Chiu and S.C. Galea

Pages:

76-83

Citation:

Y. K. An et al., "Laser Lock-In Thermography for Fatigue Crack Detection", Key Engineering Materials, Vol. 558, pp. 76-83, 2013

Online since:

June 2013

Export:

Price:

$38.00

[1] X.V. Maldague, and S. Marinetti, Pulse phase infrared thermography, J. Appl. Phys. 79 (1996) 2697-2698.

[2] K. Chatterjee, S. Tuli, S.G. Pickering and D.P. Almond, A comparison of the pulsed, lock-in and frequency modulated thermography nondestructive evaluation techniques, NDT & E Int. 44 (2011) 655-667.

DOI: https://doi.org/10.1016/j.ndteint.2011.06.008

[3] M. Choi, L. Kang, J. Park, W. Kim and K. Kim, Quantitative determination of a subsurface defect of reference specimen by lock-in infrared thermography, NDT & E Int. 41 (2008) 119-124.

DOI: https://doi.org/10.1016/j.ndteint.2007.08.006

[4] V.S. Ghali, R. Mulaveesala, and M. Takei, Frequency-modulated thermal wave imaging for non-destructive testing of carbon fiber-reinforced plastic materials, Meas. Sci. Technol. 22 (2011) art. no. 104018.

DOI: https://doi.org/10.1088/0957-0233/22/10/104018

[5] T. Li, D.P. Almond, D. Andrew and S. Rees, Crack imaging by scanning pulsed laser spot thermography, NDT & E Int. 44 (2011) 216-225.

DOI: https://doi.org/10.1016/j.ndteint.2010.08.006

[6] J. Schlichting, C. Maierhofer and M. Kreutzbruck, Crack sizing by laser excited thermography, NDT & E Int. 45 (2012) 133-140.

DOI: https://doi.org/10.1016/j.ndteint.2011.09.014

[7] A.N. Robertson, C.R. Farra and H. Sohn, Singularity detection for structural health monitoring using holder exponent, Mech. Syst. Signal Pr. 17 (2003) 1163-1184.

DOI: https://doi.org/10.1006/mssp.2002.1569

[8] H. Sohn, A.N. Robertson and C.R. Farra, Holder exponent analysis for discontinusity detection, Struct. Eng. Mech. 17 (2004) 409-428.

[9] H. Park and H. Sohn, Parameter estimation of the generalized extreme value distribution for structural health monitoring, J. Prob. Eng. Mech. 21 (2006) 366-376.

DOI: https://doi.org/10.1016/j.probengmech.2005.11.009