Non-Destructive Testing (NDT) is inspection, test, or evaluation of materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the sample. Standard radiographic X-ray imaging provides a black and white intensity or density image of the inspected sample where defects, impurities or cracks are observed if the resolution and the signal over the noise of the image is appropriate. The spectral NDT X-ray imaging based on photon counting provides additional material information of the samples together with a superior contrast and high spatial resolution.
The spectral material information is used to discriminate different materials that can be used to identify the materials of interest or to calculate their amount in the sample. A single exposure high-resolution spectral image taken with WidePIX 5×5 CdTe of a PCB unveils different components in different colors. The energy-sensitive X-ray imaging allows the identification of materials with similar overall attenuation. Colors in X-ray images now represent different materials.
A high-resolution detector (55 µm) can show fiber bunches alignment, distribution, and location. Geometrical magnification with a suitable X-ray tube allows resolutions as high as few micrometers. The following images show individual fibers of the material.
Detection of structural defects
Advanced X-ray imaging techniques allow identifications of “invisible” defects like kissing bonds as shown in the following example.
Another example is a high-resolution image of cured resin. The image is a representation of:
- Condition quality (detection, measurement, and location of voids, porosity, degree of cure).
- Presence, percentage, and distribution of resin filler materials, such as calcium carbonate, glass microspheres, etc.
- Detection of foreign objects within a molded part.
X-ray imaging of large structures
Detection of bubbles, cracks, and other defects is visual and thus NDT operators require much less training.