Thermal nondestructive testing (TNDT) may be considered to be a more widely applicable method than many traditional techniques, such as X ray, ultrasonic, eddy current, liquid penetrant, etc. It can be applied to both metals and non-metals containing subsurface defects such as cracks, foreign inclusions, disbonds, delaminations, variations in thermal properties, etc. This is especially true for composite materials, and TNDT is very appropriate for screening purposes. TNDT test results may be analyzed by advanced image processing algorithms. This paper provides a concise review of composite NDT using TNDT in combination with other inspection techniques, providing an opportunity for data fusion.

Thermal (IR) and Other NDT Techniques for Improved Material Inspection

A surface crack, close to a small, well-defined heated spot, impedes lateral heat flow and produces alterations in the shape of the thermal spot image that can be monitored by thermography. Spot heating has been achieved using both cw and pulsed laser beam illumination on stainless steel and titanium samples and the technique has been found to be successful for determining the location of fatigue cracks. When using a pulsed laser beam one can also simultaneously generate wideband ultrasonic signals in the sample; this can be used to detect the presence of surface and sub-surface defects in the sample. Results are presented that have been obtained using a fixed camera and cw laser beam position with the sample being moved through the field of view of the camera. Results are also presented using a fixed camera and sample, with a raster scanned cw or pulsed lasers beam moving across the sample. A demonstration of how a non-contact ultrasonic measurement can be performed simultaneously is presented. Thermal i...

Combined laser spot imaging thermography and ultrasonic measurements for crack detection

Measurement of in-plane diffusivity in non-homogeneous slabs by applying flash thermography

We extend the flash method to retrieve simultaneously the principal in-plane and the in-depth thermal diffusivities of anisotropic solids using focused Gaussian illumination. A complete theoretical model allows calculating the temperature rise of an anisotropic and semitransparent sample. The surface temperature distribution has a Gaussian shape along the principal axes, whose radii give the principal in-plane thermal diffusivities. On the other hand, the time evolution of the spatially averaged surface temperature gives the principal in-depth thermal diffusivity. Measurements performed on opaque and semitransparent samples, covering a wide range of thermal diffusivities, validate the method. It is especially suited to characterize the principal components of the thermal diffusivity tensor of anisotropic plates from a single and fast measurement.

Simultaneous measurement of the in-plane and in-depth thermal diffusivity of solids using pulsed infrared thermography with focused illumination

EMIR: a photothermal tool for electromagnetic phenomena characterization

Characterisation of anisotropic materials by steady-state and modulated thermal ellipsometry

Jean-Claude Krapez, Gerard Gardette and Michel LemistreOffice National d'Etudes et de Recherches Aerospatiales, Sensors, Characterization & NDE Lab.,BP 72, 92322 Châtillon cedex, FranceABSTRACTThe amplitude and phase space distributions of electromagnetic fields (X- and Ku bands) are imagedand measured using microwaves interferometry revealed by photothermal films and lock-in infraredthermography. Such EM fields imaging is a powerful tool for NDE (non Destructive Evaluation) ofdielectric and radar absorbing materials.Keywords: infrared thermography, NDE, electromagnetic windows, radar materials

Microwave holography revealed by photothermal films and lock-in IR thermography: application to electromagnetic materials NDE

We have performed pulsed photothermal radiometric measurements of thermal diffusivity of silica-gel on thin- layer chromatography plates at two different IR wavelength regions ane obtained values in the region of D equals 0.2 mm2/s. We then proceeded to depth profiling of TLC plates with photoacoustic measurements with modulated excitation using IR and visible excitation.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Gerard D. Gardette

Papers

Characterisation of anisotropic materials by steady-state and modulated thermal ellipsometry

Microwave holography revealed by photothermal films and lock-in IR thermography: application to electromagnetic materials NDE

Photothermal investigations of thin-layer chromatography plates