Non-Destructive Testing

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 are appropriate. The spectral NDT X-ray imaging based on photon counting provides additional material information of the samples together with 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.

Imaging quality for weld inspection

The imaging quality of the WidePIX 1×5 MPX3 imaging detector operated in the time-delayed-integration mode has been tested on BAM-5 and BAM-25 steel weld samples with IQI and DIQI attached. The spatial resolution was measured using DIQI. The narrowest wire pair resolved was the D13 (50 μm wide wires with a gap of 50 μm).

Detector contrast was evaluated using the 10FEEN IQI. All wires including the wire 16 (0.1 mm thick) were resolved behind the 8.3 mm thick steel sample wall. The signal-to-noise ratio measured (SNRm) achieved was 148 in the case of an 8.3 mm thick BAM-5 sample. SNRm of 190 was measured for the BAM-25 which is 6 mm thick steel. The SNRm was capped by the X-ray tube power. The detector has a 24-bit counter depth, therefore, allowing SNRm as high as 4000.

The resulting SNRn (normalized on the detector resolution) was 336 at 6 mm thick steel and 262 in the case of 8.3 mm thick steel.

Advanced NDT solutions

Radalytica’s robotic system prototype inspecting a glider aileron. The robot on left holds a compact X-ray tube. The X-ray imaging detector is mounted on the robotic arm on right. The final X-ray image reveals voids and impurities in the internal composite structure.

ADVACAM brings to the market a new range of X-ray imaging cameras that are optimized for composite material testing. Light materials such as carbon fibers, epoxies, etc. are easily revealed in great detail. Even challenging defects such as deep laminate wrinkles, kissing-bonds, delaminations, porosity, foreign objects and micro-cracks in the soft materials can be detected with a spatial resolution of 55 µm or better. Similar to its application in biology, the sensitivity to low energies is useful for non-destructive testing (NDT). Combining the sensitivity to low X-ray energy photons with the very high dynamic range of photon-counting detectors creates a powerful tool for NDT in the airspace industry and elsewhere.

Contrary to the classical X-ray imaging setups, the robotic system produced by Radalytica s.r.o. gives nearly absolute flexibility of viewing angles. Therefore, these robots allow X-raying from different perspectives, to better localize defects. Moreover, robots further open the possibility of using 3D imaging techniques such as computed tomography or tomosynthesis. These are methods commonly used in X-ray imaging, but with limited applicability on large complicated shapes. Robots help overcome this limit. The robotic systems could be used in quality control labs or built into production lines.

Fiber Alignment

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:

  1. Condition quality (detection, measurement, and location of voids, porosity, degree of cure).
  2. Presence, percentage, and distribution of resin filler materials, such as calcium carbonate, glass microspheres, etc.
  3. 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.

Time Delay Integration for scanning

The camera supports TDI mode for scanning large parts. Tested on:

  1. Weld of 8 cm thick steel part scanned using the TDI mode.
  2. Class B image quality achievable for large inspected parts.

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