Title / Author(s) / Keywords 
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Publication | Date |
2020-07 NDT Review Nondestructive testing and evaluation (Taylor & Francis)  Additive manufacturing and non-destructive testing of topology-optimised aluminium components
S. Senck1  24, M. Happl2, M. Reiter129, M. Scheerer38, M. Kendel1, J. Glinz18, J. Kastner1124
1aResearch Group Computed Tomography bR&D Competence Center; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2FOTEC Forschungs- Und Technologietransfer GmbH, Wiener Neustadt, Austria
3Polymer Composites Group; Aerospace & Advanced Composites GmbH (AAC)6, Wiener Neustadt, Austria
Additive manufacturing, non-destructive testing, microcomputed tomography, selective laser melting, aluminium, topology optimisation
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Additive manufacturing (AM) unlocks novel industrial possibilities in relation to design optimisation for lightweight structures, e.g. in aerospace applications. However, the inherent geometric complexity of topology-optimised AM components represents a major challenge for conventional non-destructive testing (NDT) methods. Due to its flexibility and high throughput, industrial X-ray micro-computed tomography (XCT) is the most promising NDT method for AM. In this contribution, we investigate topology-optimised engine brackets that were manufactured from AlSi10 Mg using selective laser melting (SLM). We investigate the respective parts and in-process test coupons in a multiscale approach to be able to extract pore size distributions at different spatial resolutions between 105 and 1.25 µm isometric voxel size. At the lowest spatial resolutions, existing pores cannot be segmented. In contrast, decreasing voxel sizes leads to an increase in total porosity up to 1.53%. Defects like pores in load-carrying areas can profoundly influence the component´s mechanical performance; hence, extensive NDT investigations are mandatory to predict the effect of defects in aluminium AM components.
 
| NDT Review
Session: Nondestructive testing and evaluation (Taylor & Francis) | 2020-07 |
2020-02 iCT 2020 Poster Exhibition, Dinner and Lab-Tours
Wed 17:25 Room 1
Investigation of the eye formation in semi-hard cheese by using X-ray Computed Tomography
J. Auer1, M. Reiter129, S. Senck124, A. Reiter2, J. Herr12, J. Kastner1124, K. Mathmann14
1Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Berglandmilch eGen, Aschbach-Markt, Austria
X-ray Computed Tomography, eye formation, Iterative Artifact Reduction, beam hardening
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The eye formation in semi-hard cheese was investigated by using X-ray Computed Tomography (XCT). In order to set the optimal scan settings, a study of parameters was undertaken. Therefore, five different scan parameter combinations and two beam hardening correction (BHC) methods were tested. An Iterative Artifact Reduction (IAR) was compared to a correction approach that is based on a collection of predefined BHC curves. VG Studio MAX and Modular Algorithms for Volume Images (MAVI) were used to determine the overall volume of the eyes, as well as the number, size, distribution and the shape factor. As a result, the cheese sample contained 749 eyes and the overall volume of the eyes was 440.84 cm3. The sphericity of the measured eyes was 0.81 with a standard deviation of 0.178. Therefore, XCT and different imaging software tools allow an exact characterization of the inner structures of cheese.
| iCT 2020
Session: Poster Exhibition, Dinner and Lab-Tours
Wed 17:25 Room 1
| 2020-02 |
2020-02 iCT 2020 Poster Exhibition, Dinner and Lab-Tours
Wed 17:25 Room 1 Micro-computed tomography for non-destructive testing of ceramic knee implants
K. Trieb, J. Glinz8, M. Reiter29, J. Kastner124, S. Senck24
Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
ceramic total knee endoprosthesis, CT numerical simulations
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Introduction: There are many reasons for the failure of a total knee endoprosthesis. The most common are infection, loosening, instability, pain and abrasion of the polyethylene. It is therefore necessary to further develop the current models. This study examines a new completely metal-free ceramic total knee endoprosthesis. There are several reports on the clinical results and biomechanical testings. Non-destructive analysis by computed tomography (CT) is a new tool for analysis of a ceramic knee endoprosthesis. Methods: In this study, 16 samples of a ceramic total knee arthroplasty were scanned including left and right implants (sizes 3 to 6). Each sample was left in its original packaging during scanning in order to preserve its sterile state. During the scanning procedure, two samples of the same size were scanned jointly in order to minimize scanning time. The testing was exclusively non-destructive, which poses a challenge due to the high density of zirconium (6 g/cubic centimeter). We established a non-destructive test protocol especially for ceramic knee implants in which the scanning parameters were optimized and the sample orientation was determined by CT simulations. Additionally, methods for the reduction of beam hardening artifact were applied. Results: It could be shown that a correct presentation in the micro-computer tomograph is possible despite the high density of the ceramic. In the examined specimens, no internal material defects such as pores or fractures were found. A three-dimensional examination, even of objects with a high density, can be carried out flawlessly using the micro-CT. Summary: It was shown that no pores or cracks were found in the tested implants. Non-destructive testing in micro CT is a challenging method. The highly compressed material and the complex geometry of the femoral and tibial implants make measurement difficult. Sophisticated corrective tours of the scanning artifacts and a robust scanning protocol are necessary to achieve optimal results. This study provides the prerequisites for further analysis.
| iCT 2020
Session: Poster Exhibition, Dinner and Lab-Tours
Wed 17:25 Room 1 | 2020-02 |
2020-02 iCT 2020 Short talks
Wed 16:30 Room 1
X-ray Micro-Computed Tomography for monitoring the behavior of single particles under tensile strain
S. Furtner1, M. Reiter129, J. Maurer13, D. Salaberger239, J. Kastner1,1124
1Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Borealis Polyolefine GmbH6, Linz, Austria
X-ray Micro-Computed Tomography, single particles, tensile testing, in- situ stage
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X-ray computed tomography was used to evaluate single particles that were artificially deposited in a polyethylene matrix, after interrupted tensile tests. Therefore, the prepared specimens were loaded from strain 0% to strain 30% with the CT500 Deben tension/compression in-situ stage (Deben, UK). Single particles and emerged defects were detected, characterised and assessed using VG Studio MAX 3.2. Within this work, different kinds and shapes of particles and defects were investigated. The elongation was measured and stress over strain curves were calculated. The shape of the particles has an impact on the defect formation. Spherical particles tend to be pulled out of the matrix while non spherical particles tend to rupture.
| iCT 2020
Session: Short talks
Wed 16:30 Room 1
| 2020-02 |
2019-11 DIR 2019 CT & Multi-angle Radiography Multimodal Transfer Functions for Talbot-Lau Grating Interferometry Data
L. Da Cunha Melo12, B. Fröhler26, C. Heinzl238, J. Kastner2124, J. Weissenböck211
1Vienna University of Technolog (TU)57, Vienna, Austria
2Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
Other Methods, Computed Tomography, Talbot-Lau Grating Interferometry
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Talbot-Lau grating interferometry X-ray computed tomography (TLGI-XCT) generates three modalities depicting different features in the scanned specimen. The combination of two or even all three modalities is often required for an in-depth analysis of the material. We present a multimodal transfer function widget for this purpose. It enables users to edit the combined transfer functions of three modalities, resulting in a customized fused image. We implement methods to arrange the individual transfer functions in two different intuitive layouts. The weighting for each modality can be easily modified and the resulting fusion image is immediately updated. We provide a combined histogram over all modalities within a triangular visualization which we call trimodal heatmap. Through this interactive analysis technique, the user can quickly gain insights into the analysed material. We show the effectiveness of our technique with the help of real-world TLGI-XCT datasets.
| DIR 2019
Session: CT & Multi-angle Radiography | 2019-11 |
2019-11 DIR 2019 Defect Detection & Localisation At-line X-ray computed tomography of serial parts optimized by numerical simulations
M. Reiter129, C. Gusenbauer232, R. Huemer2, J. Kastner1124
1Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Nemak Linz GmbH2, Linz, Austria
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Within this work, optimisation advances of an at-line X-ray computed tomography (XCT) inspection system at Nemak Linz are presented. The ZEISS VoluMax 1500 G2 is operated together with an ABB loading robot for automated inspection of serial parts as wells as prototypes of aluminium casted cylinder heads produced for the automotive industry. Typical scanning times for these high absorbing specimens are ranging from 40 to 400 seconds.
The defect analysis software provided by the manufacturer is used to automatically identify and classify defects of serial parts and decide between okay and not okay parts. The analysis software consists of anomaly detection, defect classification and a segmentation based on deep learning that requires an initial teaching phase.
The detection seems robust, but the artificial manufacturing of parts with critical defect types and sizes at specific locations and their experimental verification is challenging and very time consuming. This work presents an exemplary verification for one selected specimen and for one particular defect type with different sizes.
Besides real also simulated data with virtual defects are evaluated using the anomaly detection software. Advantages of numerical simulation in combination with the presented anomaly detection are discussed in detail.
| DIR 2019
Session: Defect Detection & Localisation | 2019-11 |
2019-11 DIR 2019 Multi-techniques Fusion Multiscale and Multimodal Approaches for Three-dimensional Materials Characterisation of Fibre Reinforced Polymers by Means of X-ray based NDT Methods
B. Plank149, M. Schiwarth1, S. Senck124, J. Herr12, J. Kastner1124, S. Ayalur Karunakaran22
1Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Fischer Advanced Composite Components (FACC)15, Ried, Austria
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Multiscale X-ray computed tomography (XCT) usually includes scanning an entire part at lower resolution. Subsequently, a smaller sample is cut out of the respective specimen and scanned at a higher resolution. Accordingly, in this work typical XCT resolutions ranging from (135 µm)³ voxel size down to (250 nm)³ are presented.
Using different XCT-modes such as region of interest (ROI) scans or laminography (XCL) modes this multiscale approach is also possible without cutting the sample in smaller pieces. We show that cracks with a width between 122 and 56 µm can be seen at a relatively low resolution of (135 µm)³ on one example of a carbon fibre reinforced polymer (CFRP) sample. With XCL voxel sizes down to (0.75 µm)³ can be reached, showing clear structures in the range of 16 µm. Main disadvantage of XCL is that only a view layers and no full 3D-microstructure can be represent well.
Using a XCT resolution in the range of (2 µm)³ voxel size for CFRPs may lead to miss interpretation in regards of porosity because of propagation based phase contrast effects. High-resolution ROI-XCT scans at (250 nm)³ shows, that epoxy rich areas between individual C-fibres smaller than 6 µm are leading to this dark grey values, easily misinterpreted as voids.
Multimodal XCT data was generated using a Talbot-Lau Grating Interferometer (TLGI) XCT to obtain modalities such as dark-field contrast and differential phase contrast in addition to standard attenuation contrast. In one example it is shown that metal-artefacts in CFRP issued by a Cu-mesh can be significantly reduced by TLGI-XCT. This provides improved image quality and the possibility to segment voids close to metallic components.
For easier interpretation and a better understanding of material features the open source software open_iA was used with new implemented visualisation approaches for multimodal and multiscale data-visualisation.
| DIR 2019
Session: Multi-techniques Fusion | 2019-11 |
Damage characterisation of short glass fibre reinforced polyamide with different fibre content by an interrupted in-situ X-Ray computed tomography test
J. Maurer3, C. Hannesschläger6, B. Plank49, J. Kastner124
Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
Close
Short glass fibre reinforced polymers (SGFR) are increasingly used in automotive industry for the replacement of metals since they provide a significant reduction of weight. Parts with anisotropic fibre orientation were produced during the injection moulding process. Local microstructure parameters such as fibre length and orientation are decisive for the damage behaviour of the injection moulded parts.
Damage type and propagation investigation are necessary for better understanding of material behaviour under stress. X-ray computed tomography (XCT) is a suitable non-destructive method to characterise internal defects in SGFR specimens. With an interrupted in-situ XCT tensile test three dimensional damage propagation in SGFR can be observed.
In this study an interrupted in-situ computed tomography technique was used to quantify the main damage mechanism in polyamide specimens with a glass fibre content (PAGF) of 15 and 30 wt%. Double notched adapted miniature tensile specimens were cut from a plate in two orientations, 0° and 90° relatively to the melt flow. Therefore the tensile force was applied parallel and perpendicular to the expected main fibre orientation (0° respectively 90°). After every force step, a XCT scan with a voxel size of (2 µm)^3 was performed to detect the internal defects. Four different defect types were classified: matrix fractures, fibre pull-outs, fibre/matrix debondings and fibre fractures. Fibre pull-out was the dominating defect type. Defects were mainly induced in the shear region of the 0° specimens. The core region showed nearly no defects at the last load step before breakage.
Summing up the results show that visualisation and quantification of the defect volume and mechanism at certain load steps was possible with this method. Clear differences between damage induction of the 0° and 90° specimens were observed.
| DIR 2019
Session: Poster | 2019-11 |
Improved Visualization of Polymer Foams using Talbot-Lau Grating Interferometry to Reduce Metal Artifacts
J. Glinz8, S. Senck24, M. Reiter29, A. Schrempf2, D. Fürst2, J. Kastner124
Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
Close
The sufficiency of bone fixation via ceramic or metallic implants largely depends on the osseointegration at the bone-implant interface and is of major importance in trauma, orthopedic, and maxillofacial surgery. Preclinical imaging via microcomputed tomography (XCT) is the state of the art solution to study the ingrowth of mineralized tissue at the bone-implant interface and to investigate the influence of innovative materials on the regeneration of bone tissue.
However, a major challenge in XCT imaging is impaired image quality due to metallic objects such as implants and orthopedic screws as they can cause severe image artefacts characterized by bright and dark streaks due to scattering and beam hardening effects. These artefacts can severely reduce image quality, impeding the quantification of trabecular structures and therefore reducing the diagnostic value of the data. In this paper we present multi-modal image data acquired using Talbot-Lau grating interferometer (TLGI) XCT visualizing the interface between surgical screws and artificial trabecular bone. Our findings reveal that differential phase contrast (DPC) is less prone to metal artefacts improving the visualization of microstructure in bone adjacent to metal components.
For this purpose, we produced polymeric foam structures imitating the microstructure of human bone to systematically investigate the advantages of DPC imaging for multi-component applications. We created a realistic set-up of four synthetic foam cylinders produced with different filler materials representing artificial bone. Two to four titanium screws (thread diameter 1.2 mm, length 16 mm) were applied into the artificial bone parallel to each other. The specimens were investigated using a TLGI XCT system (SkyScan 1294) to extract information in relation to absorption contrast (AC), DPC, and dark-field contrast (DFC). In AC, metal streaking artefacts are severe, covering microstructure between the screws completely. DPC images in return show almost no streaking artefacts, which enhances image segmentation and volume rendering.
| DIR 2019
Session: Radiation Techniques | 2019-11 |
2019-08 DGZfP 2019 Verbundwerkstoffe / Faserkunststoffverbunde Charakterisierung der Mikrostruktur spritzgegossener faserverstärkter Thermoplaste mit Hilfe von hochauflösender Röntgen-Computertomografie
J. Maurer13, D. Salaberger239, M. Jerabek23, J. Kastner1124
1Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Reserach group computed tomography; Borealis Polyolefine GmbH6, Linz, Austria
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Faserverstärkte Kunststoffe sind aus vielen industriellen Bereichen, wie beispielsweise der Fahrzeugindustrie, Verpackungsindustrie, Bauwirtschaft oder auch der Freizeitindustrie, nicht mehr wegzudenken. Die steigenden Anforderungen an die Materialien, hinsichtlich mechanischer und physikalischer Eigenschaften, haben es notwendig gemacht sich mit der Mikrostruktur genauer zu beschäftigen. Dazu sind zerstörungsfreie Verfahren wie Röntgen-Computertomografie (CT) von großem Vorteil. Mittels CT können eigenschaftsbestimmende Faktoren, wie z.B. Faserorientierung und Faserlängenverteilung, ermittelt werden. Die Kenntnis solcher Faktoren ermöglicht es einerseits, die Herstellungsparameter zu optimieren und andererseits Modelsimulationen für die Vorhersage mechanischer Eigenschaften zu generieren.
In dieser Arbeit werden verschiedene spritzgegossene faserverstärkte Kunststoffe mittels Computertomografie untersucht und in weiterer Folge die Faserorientierung, sowie die Faserlängenverteilung, mit der hauseigenen Fasercharakterisierungssoftware analysiert. Es werden Kunststoffe aus Polypropylen verstärkt mit Glasfaser, Kohlenstofffaser, Polymerfaser oder Zellulosefaser untersucht. Unterschiede in der Dichte bzw. dem Röntgenabsorptionskoeffizienten führen zu unterschiedlich großem Kontrast zwischen Fasern und Matrix. Der Kontrast zwischen den Polymerfasern und der Kunststoffmatrix ist beispielsweise eher schwach, was wiederum Probleme bei der Bestimmung der Faserlängenverteilung bereiten kann. Weiters haben auch Fasergehalt, Faserdurchmesser und Fasergeometrie einen Einfluss auf die Datenqualität.
Die Röntgen-Computertomografie-Scans werden bei einer Voxelgröße von bis zu (1 µm)^3 durchgeführt. Die erforderlichen Messzeiten, um eine ausreichende Datenqualität für eine softwarebasierte Faseranalyse zu erreichen, liegen dabei im Bereich von drei bis zwölf Stunden. Anhand der dreidimensionalen Datensätze lassen sich Füllstoffeigenschaften, aber auch Inhomogenitäten der Matrix, bestimmen. Im Rahmen dieser Arbeit werden neben Schnittbildern und Ergebnissen der Faseranalysen, ein Vergleich der verschiedenen Faserkunststoffverbundsysteme präsentiert, sowie die Vorteile und Limitierungen von Computertomografie für die Fasercharakterisierung dieser Materialien diskutiert.
DE
| DGZfP 2019
Session: Verbundwerkstoffe / Faserkunststoffverbunde | 2019-08 |
2019-03 iCT 2019 Algorithms & Reconstruction
Wed 16:20 Auditorium An Interactive Visual Comparison Tool for 3D Volume Datasets represented by Nonlinearly Scaled 1D Line Plots through Space-filling Curves
J. Weissenböck111, B. Fröhler16, E. Gröller211, J. Sanctorum33, J. De Beenhouwer317, J. Sijbers320, S. Ayalur Karunakaran42, H. Hoeller42, J. Kastner1124, C. Heinzl138
1Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Institute of Computer Graphics and Algorithms; Vienna University of Technolog (TU)57, Vienna, Austria
3aInstitute of Computer Graphics and Algorithms bimec-VisionLab, Department of Physics; University of Antwerpen36, Antwerpen, Belgium
4Fischer Advanced Composite Components (FACC)15, Ried, Austria
Radiographic Testing (RT), Other Methods, X-ray computed tomography, visual analysis, comparative visualization, Hilbert curve, nonlinear scaling
Close
The comparison of many 3D volumes to find subtle differences is tedious, time-consuming and error-prone. Previously we presented Dynamic Volume Lines [1], a novel tool for the interactive visual analysis and comparison of ensembles of 3D volumes, which are linearized using Hilbert spacing-filling curve and represented as 1D line plots. In this paper we further demonstrate the usefulness and capabilities of our method by conducting a detailed visual analysis and evaluation of an artificial specimen from simulated 3D X-Ray Computed Tomography (XCT) and a real-world XCT titanium alloy specimen.
| iCT 2019
Session: Algorithms & Reconstruction
Wed 16:20 Auditorium | 2019-03 |
2019-03 iCT 2019 Metrology & Manufacturing
Thu 10:50 Auditorium Experimental investigation on the accuracy of XCT measurement of fiber length in fiber reinforced polymers
F. Zanini15, G. Gerardi1, J. Weissenböck211, C. Heinzl238, J. Kastner2124, S. Carmignato118
1University of Padova (UNIPD)33, Padova, Italy
2Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
X-ray computed tomography, fiber length measurement, fiber reinforced polymers, accuracy evaluation
Close
X-ray computed tomography (XCT) allows performing non-destructive measurements of fibers in fiber-reinforced polymeric materials. The accurate evaluation of fiber orientation and fiber length distribution is particularly useful as these factors have a strong influence on physical and mechanical properties of such materials. XCT data is already successfully used for fiber orientation analysis, whereas the fiber length measurement is more complex as it requires the individual fibers to be identified and segmented. Software tools able to cope with such tasks are available, but the accuracy of XCT fiber length measurement has not been thoroughly investigated so far. In this work, an experimental methodology was developed to determine the accuracy of XCT based fiber length measurements, using a reference object that was specifically designed, produced and calibrated for this purpose.
| iCT 2019
Session: Metrology & Manufacturing
Thu 10:50 Auditorium | 2019-03 |
2019-03 iCT 2019 NDT, Materials & Manufacturing
Fri 13:50 Auditorium Characterisation of fiber lay-up and defects in CFRP using Talbot-Lau grating interferometry
S. Senck124, M. Scheerer28, B. Plank149, C. Hannesschlaeger1, J. Kastner1124
1Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Aerospace & Advanced Composites GmbH (AAC)6, Wiener Neustadt, Austria
Talbot-Lau grating interferometer, phase contrast imaging, microcomputed tomography, carbon fibre-reinforced polymers, fiber lay-up, defects
Close
Using Talbot-Lau grating interferometer X-ray computed tomography (TLGI-XCT) we determine the fiber lay-up and quantify defects in loaded carbon fibre-reinforced polymer samples in three dimensions. In contrast to conventional XCT, TLGI-XCT provides three complementary image characteristics during image acquisition: a) attenuation contrast (AC), b) differential phase contrast (DPC), and c) dark-field contrast (DFC). Using a desktop TLGI-XCT system (Skyscan 1294), we visualize fibre bundles, resin rich areas, and defects (cracks and pores) in CFRP laminates that were subjected to low impact energies up to 15 Joules. The combined application of AC, DFC, and DPC volume data facilitates the intuitive visualization of fiber lay-up and the component´s microstructure, including resin-rich areas. Moreover, dark-field images yield a high contrast and a strong signal at interfaces improving the detection of microcracks in relatively large samples whereas these defects are barely detectable using standard XCT.
| iCT 2019
Session: NDT, Materials & Manufacturing
Fri 13:50 Auditorium | 2019-03 |
2019-03 iCT 2019 New Methods & Optimization
Wed 13:50 Auditorium Simulated grating-based x-ray phase contrast images of CFRP-like objects
J. Sanctorum13, J. De Beenhouwer117, J. Weissenböck211, C. Heinzl238, J. Kastner2124, J. Sijbers120
1imec-VisionLab, Department of Physics; University of Antwerpen36, Antwerpen, Belgium
2Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
Radiographic Testing (RT), Other Methods, Simulation, Phase contrast, Carbon Fibre Reinforced Polymer, GATE
Close
Because of their microstructure, carbon fibre reinforced polymers outperform conventional materials in many aspects. These
materials are, given the low x-ray absorption contrast they provide, ideally suited for phase contrast x-ray computed tomography.
For system prototyping and for benchmarking and testing acquisition and reconstruction procedures, computer simulations are a
valuable tool. In this paper, we propose the application of an alternative simulation strategy that unites Monte Carlo simulations
with numerical wave optics and involves detailed modelling of the internal carbon fibre reinforced polymer structure down to the
individual fibre scale.
| iCT 2019
Session: New Methods & Optimization
Wed 13:50 Auditorium | 2019-03 |
2019-03 iCT 2019 Poster exhibition
Thu 16:00 Agora Porosity determination in additively manufactured Ti parts using X-ray tomography
J. Glinz8, M. Reiter29, T. Gastinger2, A. Huskic2, B. Plank49, J. Kastner124, S. Senck24
Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
X-ray micro-computed tomography, Additive manufacturing, Titanium alloys, Porosity determination, Microstructure
Close
Ti6Al4V is a suitable titanium alloy for all kinds of medical implants and prostheses because of its high durability and biocompatibility. Furthermore, components of high complexity can be produced via additive manufacturing which allows for more flexibility and easy prototyping of patient specific implants. However, this flexibility implies the risk of internal defects resulting from the manufacturing process. The nondestructive investigation of critical components is therefore crucial to avoid premature failure. X-ray micro-computed tomography (XCT) is a method that can resolve internal structures three dimensionally in a non-destructive way. Nevertheless, the probability to detect defects is limited by the achievable resolution and image quality of a scan. In this contribution, we performed a systematic study to determine the pore size distribution in additively manufactured Ti6Al4V parts using XCT. We focused on the influence of scanning parameters such as voxel size, tube voltage and current on the image quality that determines the outcome of the porosity analysis. Image quality was assessed via contrast to noise ratio (CNR) and slanted-edge modulation transfer function (MTF) according to ISO 12233. Furthermore, we optimized the beam hardening correction for the scans and investigated influences of different image denoising algorithms. Results showed that tube voltage and current greatly influence the CNR of the data set while the MTF is, within limits, almost constant as long as the electron beam focus is optimized. With higher physical resolution, smaller defects can be detected, which leads to porosity values of 0.36, 1.35 and 2.54% at 10, 5 and 2.5 μm resolution respectively. Image post-processing can further influence porosity outcome because of the segmentation of noise induced particles. Different image denoising algorithms therefore can heavily reduce porosity values depending on spatial resolution.
| iCT 2019
Session: Poster exhibition
Thu 16:00 Agora | 2019-03 |
2019-03 iCT 2019 Short talks
Thu 13:50 Auditorium Tools for the Analysis of Datasets from X-Ray Computed Tomography based on Talbot-Lau Grating Interferometry
B. Fröhler16, L. Da Cunha Melo22, J. Weissenböck111, J. Kastner1124, T. Möller32, H. Hege4, E. Gröller211, J. Sanctorum53, J. De Beenhouwer517, J. Sijbers520, C. Heinzl138
1Research Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2VRVis Research Center; Vienna University of Technolog (TU)57, Vienna, Austria
3Faculty of Computer Science; University of Vienna4, Vienna, Austria
4Konrad-Zuse-Institut Berlin (ZIB)19, Berlin, Germany
5University of Antwerpen36, Antwerpen, Belgium
Radiographic Testing (RT), Other Methods, image fusion, multimodal data, transfer function design, image segmentation uncertainty
Close
This work introduces methods for analyzing the three imaging modalities delivered by Talbot-Lau grating interferometry X-ray
computed tomography (TLGI-XCT). The first problem we address is providing a quick way to show a fusion of all three modalities.
For this purpose the tri-modal transfer function widget is introduced. The widget controls a mixing function that uses the
output of the transfer functions of all three modalities, allowing the user to create one customized fused image. A second problem
prevalent in processing TLGI-XCT data is a lack of tools for analyzing the segmentation process of such multimodal data. We
address this by providing methods for computing three types of uncertainty: From probabilistic segmentation algorithms, from
the voxel neighborhoods as well as from a collection of results. We furthermore introduce a linked views interface to explore
this data. The techniques are evaluated on a TLGI-XCT scan of a carbon-fiber reinforced dataset with impact damage. We show
that the transfer function widget accelerates and facilitates the exploration of this dataset, while the uncertainty analysis methods
give insights into how to tweak and improve segmentation algorithms for more suitable results.
| iCT 2019
Session: Short talks
Thu 13:50 Auditorium | 2019-03 |
2019-02 NDT Review Journal of Nondestructive Evaluation (Springer) Porosity Determination of Carbon and Glass Fibre Reinforced Polymers Using Phase-Contrast Imaging
C. Gusenbauer32, M. Reiter29, B. Plank49, D. Salaberger39, S. Senck24, J. Kastner124
aSchool of Engineering bR&D Competence Center cSchool of Engineering and Environmental Sciences cReserach group computed tomography cResearch Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
X-ray computed tomography, Talbot-Lau grating interferometer, Differential phase contrast, Carbon and glass fibre reinforced polymers, Porosity
Close
This paper presents multi-modal image data of different fibre reinforced polymer samples acquired with a desktop Talbot-Lau grating interferometer (TLGI) X-ray computed tomography (XCT) system and compare the results with images acquired using conventional absorption-based XCT. Two different fibre reinforced polymer samples are investigated: (i) a carbon fibre reinforced polymer (CFRP) featuring a copper mesh embedded near the surface for lightning conduction and (ii) a short glass fibre reinforced polymer (GFRP) sample. The primary goal is the non-destructive detection of internal defects such as pores and the quantification of porosity. TLGI provides three imaging modalities including attenuation contrast (AC) due to absorption, differential phase contrast (DPC) due to refraction and dark-field contrast (DFC) due to scattering. In the case of the CFRP sample, DPC is less prone to metal streak artefacts improving the detection of pores that are located close to metal components. In addition, results of a metal artefact reduction (MAR) method, based on sinogram inpainting and an image fusion concept for AC, DPC and DPC, are presented. In the case of the GFRP sample, DPC between glass fibres and matrix is lower compared to AC while DPC shows an increased contrast between pores and its matrix. Porosity for the CFRP sample is determined by applying an appropriate global thresholding technique while an additional background removal is necessary for the GFRP sample.
| NDT Review
Session: Journal of Nondestructive Evaluation (Springer) | 2019-02 |
2019-02 NDT Review Journal of Nondestructive Evaluation (Springer) Case Study of Empirical Beam Hardening Correction Methods for Dimensional X-ray Computed Tomography Using a Dedicated Multi-material Reference Standard
M. Reiter129, F. De Oliveira22, M. Bartscher233, C. Gusenbauer132, J. Kastner1,1124
1aR&D Competence Center bSchool of Engineering cResearch Group Computed Tomography; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Physikalisch-Technische Bundesanstalt (PTB)45, Braunschweig, Germany
Industrial computed tomography, Dimensional metrology, Multi-material measurements, Beam hardening correction, Material influence
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This paper presents a case study of two selected beam hardening correction methods and their effects on dimensional measurements of multi-material objects. The methods under test are empirical cupping correction (ECC) and empirical dual energy calibration (EDEC). These methods were originally developed for medical applications and their potential for the reduction of artefacts is typically only analysed based on grey value images. For testing and benchmarking of the mentioned methods for dimensional metrology, a dedicated multi-material reference standard—a multi-material hole cube—is used. This reference standard was originally developed for acceptance testing of CT systems. This paper shows a second application of this standard. The reference standard has been calibrated by tactile measurements to assess centre–centre distance errors as well as patch-based bidirectional length measurement errors on beam hardening corrected data and on uncorrected data. For the application of the method also to industrial multi-material scenarios, slight modifications of the ECC method are proposed. Practical aspects of both the ECC and the EDEC approaches as well as measurement results are analysed and discussed in detail. ECC was able to significantly improve dimensional measurements and was especially able to reduce extreme errors occurring in particular in multi-material scenarios by a factor of more than 4. EDEC, the dual-energy approach, reduced grey value inhomogeneities caused by artefacts even more. Its performance for dimensional measurements was however a little worse than ECC. EDEC data resulted in a slightly larger total range of residual measurement errors, mainly due to an elevated noise level.
| NDT Review
Session: Journal of Nondestructive Evaluation (Springer) | 2019-02 |
Porosity Determination in CFRP by means of X-ray Computed Tomography Methods
B. Plank149, C. Gusenbauer132, S. Senck124, H. Hoeller22, J. Kastner1,1124
1Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
2Fischer Advanced Composite Components (FACC)15, Ried, Austria
Composite materials, Defects, Tomography
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Especially in aeronautic and space industry it is important to produce carbon fibre-reinforced polymers (CFRP) with very low porosity since there is a direct relation between porosity and mechanical properties, such as shear strength. Typical acceptable porosity values are in the range of < 2.5 vol.%.
The most common non-destructive method for measuring the porosity is ultrasonic testing (UT) assuming there is a linear correlation between ultrasonic attenuation and porosity. However, the ultrasonic attenuation coefficient depends not only on the porosity, but also on the shape and distribution of the pores, the presence of other material inhomogeneity’s and the individual material system. This can lead to significant errors in the determination of the porosity. Acid digestion and materialography are mainly used as reference method, but both methods are destructive, time-consuming and inaccurate.
This paper deals with the application of X-ray computed tomography (XCT) methods as reference for quantitative evaluation and characterization of porosity in carbon fibre-reinforced composites. The degree of accuracy strongly depends on several material and XCT parameters:
• Material parameters: woven fabric or unidirectional material, additional glass fibres or copper wires for lightning protection, higher dense epoxy used for adhesive bonding, etc.
• XCT parameters: resolution and voxel size (VS), used XCT device and modality (e.g.: cone beam XCT vs. Talbot Lau grating interferometer XCT), threshold method, etc.
In this contribution several mentioned parameters influencing the quantitative evaluation of porosity in CFRP are discussed and different types of CFRP with porosity are presented. Porosity values gained with XCT methods are compared with UT, acid digestion or materialography.
| ECNDT 2018
Session: CT-Applications | 2018-08 |
High-resolution X-ray computed tomography of inhomogeneous materials
C. Gusenbauer32, M. Reiter29, D. Salaberger39, B. Plank49, J. Kastner124
aSchool of Engineering bR&D Competence Center cReserach group computed tomography cSchool of Engineering and Environmental Sciences; Upper Austrian University of Applied Sciences (FH OÖ)172, Wels, Austria
Tomography
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In this contribution, high-resolution X-ray computed tomography (XCT) results of various inhomogeneous samples including a poplar wood sample, a carbon fibre reinforced polymer sample and an AlSiCu light metal alloy are presented. These samples have been acquired with a new lab-based nano-XCT device equipped with a nano-focus X-ray tube and two different detector systems. Depending on the material system and the measurement task, the user has to choose between these two detector types that can be exchanged by a quick mounting system. Limitations on resolution and contrast-to-noise ratio (CNR) are discussed qualitatively and quantitatively for selected measurements and evaluation tasks. Structures between 500 and 700 nm could be clearly resolved. In addition the positioning accuracy of the exchangeable flat panel detector is investigated. Detector repositioning shows high reproducibility, but systematic measurement errors are in the range of half of a voxel for repeated scans of a calibrated ball bar phantom with a system voxel size of (3 µm)³.
| ECNDT 2018
Session: CT-Applications | 2018-08 |
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