Detection and Characterization of Defects in Isotropic and Anisotropic Structures Using Lockin Thermography

Lockin thermography is a well-suited method for the characterization of structures made of both metal and fiber reinforced plastic. In most cases, only phase images are analyzed, although the amplitude images might contain useful information as well. Thus, systematic studies of lockin thermography are presented, assessing amplitude and phase images for the detection and quantification of defects in isotropic (steel) and anisotropic (carbon fiber reinforced plastic) materials. Characterized defects are flat bottom holes with different diameters and various remaining wall thicknesses as well as crossed notches at different depths. The excitation frequency was varied while keeping the number of analyzed excitation periods nearly constant for each material. The data analysis was focused on the detectability of the defects both in the amplitude and phase images, including the determination of the signal-to-noise ratio and of the spatial resolution. As a result, the limits of defect detectability and spatial resolution are given for each material.

[1]  Giovanni Maria Carlomagno,et al.  Geometrical Limitations to Detection of Defects in Composites by Means of Infrared Thermography , 2004 .

[2]  Suneet Tuli,et al.  Prediction of blind frequency in lock-in thermography using electro-thermal model based numerical simulation , 2013 .

[3]  Gerd Busse,et al.  Lock-in thermography for nondestructive evaluation of materials , 1998 .

[4]  A. Bendada,et al.  Comparative Study of Active Thermography Techniques for the Nondestructive Evaluation of Honeycomb Structures , 2009 .

[5]  Wang Yang,et al.  Study on probability of detection (POD) determination using lock-in thermography for nondestructive inspection (NDI) of CFRP composite materials , 2015 .

[6]  Roberto Montanini,et al.  Quantitative determination of subsurface defects in a reference specimen made of Plexiglas by means of lock-in and pulse phase infrared thermography , 2010 .

[7]  Christian SPIESSBERGER,et al.  Active Thermography for Quantitative NDT of CFRP Components , 2010 .

[8]  L. Rosenhead.  Conduction of Heat in Solids , 1947, Nature.

[9]  W. Arnold,et al.  Size retrieval of defects in composite material with lockin thermography , 2010 .

[10]  W. Graham Richards,et al.  Art of electronics , 1983, Nature.

[11]  Christopher Duncan Wallbrink,et al.  The effect of size on the quantitative estimation of defect depth in steel structures using lock-in thermography , 2007 .

[12]  C.,et al.  Investigation of resolution in lock-in thermography : theory and experiment by , 2011 .

[13]  C A Bennett,et al.  Thermal wave interferometry: a potential application of the photoacoustic effect. , 1982, Applied optics.

[14]  Darryl P Almond,et al.  Thermal wave testing of plasma-sprayed coatings and a comparison of the effects of coating microstructure on the propagation of thermal and ultrasonic waves , 1985 .

[15]  C. Maierhofer,et al.  Characterizing damage in CFRP structures using flash thermography in reflection and transmission configurations , 2014 .

[16]  Christiane MAIERHOFER,et al.  Validation of active thermography techniques for the characterization of CFRP structures , 2016 .

[17]  Darryl P Almond,et al.  Matched excitation energy comparison of the pulse and lock-in thermography NDE techniques , 2008 .

[18]  Xavier Maldague,et al.  Round Robin comparison II of the capabilities of various thermographic techniques in the detection of defects in carbon fibre composites , 2000 .

[19]  Suneet Tuli,et al.  A comparison of the pulsed, lock-in and frequency modulated thermography nondestructive evaluation techniques , 2011 .

[20]  Antonino Squillace,et al.  Analysis of Defective Carbon-Epoxy by Means of Lock-in Thermography , 2000 .

[21]  R. J. Jenkins,et al.  Flash Method of Determining Thermal Diffusivity, Heat Capacity, and Thermal Conductivity , 1961 .

[22]  Darryl P Almond,et al.  Thermal-wave detection and characterisation of sub-surface defects , 1987 .

[23]  Ermanno G. Grinzato,et al.  Infrared thermographic detection and characterisation of impact damage in carbon fibre composites: results of the round robin test , 1998 .