Modern X-ray methods can be used to address issues that are very difficult or impossible to solve using conventional NDT methods. Wherever materials with high radiation adsorption have to be radiated, X-ray methods are used at Fraunhofer IKTS. In addition to material-scientific investigations for industry, this also includes non-destructive examinations of archaeological finds, musical instruments or woody plants.
In order to detect defects, to make certain structures visible inside or to obtain further information from the test objects, the scientists use X-ray methods that work with very high radiation energies. This allows volume tests and other investigations, e.g. on surface tensions, to be carried out on samples of a wide range of materials and geometries.
X-ray line detectors are gradually replacing the X-ray films still commonly used in radiography and are indispensable above all for X-ray computed tomography. They are mostly used when continuous goods are to be examined or when the size of the object only permits strip illumination in order to avoid unwanted scattered radiation.
In the conventional detector principle, the incident X-ray photons are first converted into visible light and, in a second step, into electrical signals by means of photodiodes. The L100 X-ray detector line developed by Fraunhofer IKTS eliminates the intermediate step and works directly converting. This significantly increases resolution and speed. In addition, thanks to single photon detection, the X-ray photons can be evaluated with regard to their energy. This enables "dual energy" applications in which materials are distinguished by their composition.
The prototypes currently being tested have a line length of 102.4 mm and achieve a resolution of 100 μm. The setup of two absorber materials enables the detection of X-ray quanta from the energy ranges 30-200 keV and 2-40 keV. This allows the X-ray line to be used for both imaging and diffraction. Due to the minimum counting time of 20 μs, objects can be examined at a speed of up to 50 m/s, depending on the inspection concept.
The developed line detector is built from customer-specific individual circuits (ASIC), so that cost-effective manufacturing and a variety of configurations – in particular also practically any size – are possible. Together with the CT control and analysis software XVision developed at Fraunhofer IKTS, customized X-ray micro-CT systems can be realized and equipped with intuitive user guidance.
Industrial micro-computed tomography (μCT) is an established analytical technique for technical and scientific applications and is increasingly used in the examination of artistic and cultural goods. It is an ideal technique for visualizing air pockets, cracks, and other material inhomogeneities within an arbitrarily shaped object. Micro-computed tomography enables non-destructive three-dimensional inspection of objects with high spatial resolution.
Fraunhofer IKTS has a micro-CT system that can be adapted to the inspection task according to customer requirements. This allows the examination of very small components such as electronic parts as well as large objects such as art objects or fossils.
High resolution computed laminography (HRCL) is a newly developed X-ray tomography method developed by Fraunhofer IKTS, whereby the specimen can be examined with high resolution (up to 2 µm³) and with only one rotation. Extensive sample preparation is no longer necessary. The method makes it possible to examine small areas of large-area and planar circuit carriers in particular with high resolution and non-destructively. Thanks to a modified measurement setup and an optimized reconstruction algorithm compared to micro-CT, the high-resolution examination of printed circuit boards of any size is now no longer a problem. For example, control boards for automotive or power electronics as well as embedded systems can be analyzed non-destructively and without preparation effort.
X-ray diffraction is a method used by Fraunhofer IKTS to determine the composition of mixtures of substances. In this process, X-rays are diffracted at ordered structures such as crystals or quasicrystals and the diffraction intensity distribution is measured.
In addition, Fraunhofer IKTS uses X-ray diffraction for the determination of residual stresses by the Sinus2y method. Here, the sample is tilted in a reflex by a certain range y (Psi). To determine the distribution of residual stresses over the specimen, measurements are taken at various points, but at least in the extreme areas (edges, corners and center). Since texture influences the results of many methods, even the Sinus2y method only provides reliable values if the layer under investigation is untextured. Therefore, the pole figures for at least two different reflections are recorded at different points of the object under investigation. The residual stress can then be derived from the peak positions determined.