Sonic infrared (thermosonics) is a very attractive nondestructive testing technique, particularly for the quick testing of complex components. It uses a pulse of high power ultrasound in the 20 to 100 kHz range applied at one point on the test structure to generate a high frequency vibration field in the structure. These vibrations cause the surfaces of any cracks to rub together, so dissipating energy that causes a surface temperature rise local to the cracks. This transient temperature rise can be imaged by an infrared camera. The vibration produced is typically chaotic and is therefore inherently nonreproducible. Some concern has been shown about the test’s reliability and, in particular, the confidence that can be placed in a null (crack-free) test. This paper proposes the use of a heating index based on a measurement of the component vibration to give a measure of the potential of the vibration generated in a particular test to generate sufficient heat for any cracks of interest to be detected. The procedure is evaluated on a set of turbine blades with known cracks, with the vibration being measured by a simple high frequency microphone. The correlation between the heating index and temperature rise at the crack location is presented and a calibration procedure for practical testing is proposed. It is shown that the heating index provides a real-time measure of whether sufficient excitation has been applied to detect the cracks of interest if they are present in the test component. The technique promises to significantly improve the reliability of sonic infrared testing.
Chen, J.C., W.T. Riddell, K. Lick and C.-H. Wong, “Fracture Mechanics of
Crack Growth during Sonic IR Inspection,” Review of Progress in Quantitative
Nondestructive Evaluation, Vol. 26A, D.O. Thompson and D.E.
Chimenti, eds., Melville, New York, AIP, 2007, pp. 507–514.
Dillenz, A., G. Busse and D. Wu, “Ultrasound Lockin Thermography:
Feasibilities and Limitations,” Proceedings of SPIE, Vol. 3827, 1999,
pp. 10–15.
Dillenz, A., T. Zweschper and G. Busse, “Elastic Wave Burst Thermography
for NDE of Subsurface Features,” Insight, Vol. 42, 2000, pp. 815–
817.
DiMambro, J., D.M. Ashbaugh, C.L. Nelson and F.W. Spencer, “Sonic
Infrared (IR) Imaging and Fluorescent Penetrant Inspection Probability of
Detection (POD) Comparison,” Review of Progress in Quantitative Nondestructive
Evaluation, Vol. 26A, D.O. Thompson and D.E. Chimenti, eds.,
Melville, New York, AIP, 2007, pp. 463–470.
Guo, Y. and F. Rughe, “Comparison of Detection Capability for Acoustic
Thermography, Visual Inspection and Fluorescent Penetrant Inspection on
Gas Turbine Components,” Review of Progress in Quantitative Nondestructive
Evaluation, Vol. 28B, D.O. Thompson and D.E. Chimenti, eds.,
Melville, New York, AIP, 2009, pp. 1848–1854.
Han, X., Z. Zeng, W. Li, M.S. Islam, J.P. Lu, V. Loggins, E. Yitamben, L.D.
Favro, G. Newaz and R.L. Thomas, “Acoustic Chaos for Enhanced
Detectability of Cracks by Sonic Infrared Imaging,” Journal of Applied
Physics, Vol. 95, 2004a, pp. 3792–3797.
Han, X., V. Loggins, Z. Zeng, L.D. Favro and R.L. Thomas, “Mechanical
Model for the Generation of Acoustic Chaos in Sonic Infrared Imaging,”
Applied Physics Letters, Vol. 85, 2004b, pp. 1332–1334.
Han, X., M.S. Islam, G. Newaz, L.D. Favro and R.L. Thomas, “Finite-
Element Modeling of Acoustic Chaos to Sonic Infrared Imaging,” Journal
of Applied Physics, Vol. 98, 2005, Article No. 014907.
Han, X., M.S. Islam, G. Newaz, L.D. Favro and R.L. Thomas, “Finite
Element Modeling of Heating of Cracks during Sonic Infrared Imaging,”
Journal of Applied Physics, Vol. 99, 2006, Article No. 074905.
Hassan, W., C. Homma, Z. Wen, F. Vensel and B. Hogan, “Detection of
Tight Fatigue Cracks at the Root of Dampers in Fan Blades Using Sonic IR
Inspection: A Feasibility Demonstration,” Review of Progress in Quantitative
Nondestructive Evaluation, Vol. 26A, D.O. Thompson and D.E. Chimenti,
eds., Melville, New York, AIP, 2007, pp. 455–462.
Holland, S.D., C. Uhl and J. Renshaw, “Towards a Viable Strategy for Estimating
Vibrothermographic Probability of Detection,” Review of Progress in
Quantitative Nondestructive Evaluation, Vol. 27A, D.O. Thompson and D.E.
Chimenti, eds., Melville, New York, AIP, 2008, pp. 491–497.
Homma, C., M. Rothenfusser, J. Baumann and R. Shannon, “Study of the
Heat Generation Mechanism in Acoustic Thermography,” Review of
Progress in Quantitative Nondestructive Evaluation, Vol. 25A, D.O.
Thompson and D.E. Chimenti, eds., Melville, New York, AIP, 2006, pp.
566–573.
Mignogna, R.B., R.E. Green, Jr., J.C. Duke, Jr., E.G. Henneke, II and K.L.
Reifsnider, “Thermographic Investigation of High-Power Ultrasonic
Heating in Materials,” Ultrasonics, 1981, pp. 159–163.
Morbidini, M. and P. Cawley, “The Detectability of Cracks Using Sonic
IR,” Journal of Applied Physics, Vol. 105, 2009a, Article No. 093530.
Morbidini, M. and P. Cawley, “A Calibration Procedure for Sonic-IR
NDE,” Journal of Applied Physics, Vol. 106, 2009b, Article No. 023504.
Morbidini, M., P. Cawley, T. Barden, D. Almond and P. Duffour, “Prediction
of the Thermosonic Signal from Fatigue Cracks in Metals Using
Vibration Damping Measurements,” Journal of Applied Physics, Vol. 100,
2006, Article No. 104905.
Pye, C.J. and R.D. Adams, “Heat Emission from Damaged Composite-
Materials and Its Use in Non-destructive Testing,” Journal of Physics D:
Applied Physics, Vol. 14, 1981, pp. 927–941.
Rothenfusser, M. and C. Homma, “Acoustic Thermography: Vibrational
Modes of Cracks and the Mechanism of Heat Generation,” Review of
Progress in Quantitative Nondestructive Evaluation, Vol. 24A, D.O.
Thompson and D.E. Chimenti, eds., Melville, New York, AIP, 2005, pp.
624–631.
Thomas, R.L., “Thermal NDE Techniques — From Photoacoustics to
Thermosonics,” Review of Progress in Quantitative Nondestructive Evaluation,
Vol. 21A, D.O. Thompson and D.E. Chimenti, eds., Melville, New
York, AIP, 2002, pp. 3–13.
Thomas, R.L., L.D. Favro, X. Han, Z. Ouyang, H. Sui and G. Sun, “Infrared
Imaging of Ultrasonically Excited Subsurface Defects in Materials,” US
patent 6236049, 1999.
Zweschper, T., A. Dillenz, G. Riegert, D. Scherlling and G. Busse, “Ultrasound
Excited Thermography Using Frequency Modulated Elastic Waves,”
Insight, Vol. 45, 2003, pp. 178–182.