Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (69)
- Beitrag zu einem Tagungsband (25)
- Zeitschriftenartikel (13)
- Posterpräsentation (12)
- Buchkapitel (2)
Referierte Publikation
- nein (121) (entfernen)
Schlagworte
- Additive manufacturing (18)
- Neutron Diffraction (15)
- X-ray refraction (13)
- Computed tomography (12)
- Additive Manufacturing (10)
- Computertomographie (10)
- Röntgenrefraktion (10)
- Computed Tomography (9)
- Porosity (9)
- Residual stress (9)
- Additive Fertigung (8)
- Composites (8)
- Microcracking (7)
- Residual Stress (7)
- TF Material (7)
- Eigenspannungen (6)
- Zerstörungsfreie Prüfung (6)
- Neutron diffraction (5)
- Neutronenbeugung (5)
- X-ray refraction radiography (5)
- Anisotropy (4)
- Ceramics (4)
- Imaging (4)
- Kompositen (4)
- Metrologie (4)
- Non-destructive testing (4)
- Selective laser melting (4)
- Synchrotron X-ray diffraction (4)
- Synchrotron radiation (4)
- 3D Mikrostruktur (3)
- Keramiken (3)
- Load transfer (3)
- Machine Learning (3)
- Microstructure (3)
- Non-linear stress-strain (3)
- Pore orientation (3)
- Porous ceramics (3)
- Röntgen-Refraktion (3)
- Ammonium nitrate (2)
- Analytical Science (2)
- Concrete (2)
- Cordierite (2)
- Damage (2)
- Damage evolution (2)
- Defects (2)
- Fatigue (2)
- Hydrogen assisted cracking (2)
- IN718 (2)
- Keramik (2)
- Large Scale Facilities (2)
- Laser beam melting (2)
- Laser powder bed fusion (2)
- Legierungen (2)
- Leichtbau (2)
- Mechanical Properties (2)
- Metals (2)
- Modellierung (2)
- Non-destructive characterisation (2)
- Phase grating (2)
- Poren (2)
- Prill (2)
- Specific surface area (2)
- Surface roughness (2)
- Synchrotron (2)
- Talbot- Lau interferometry (2)
- Ti-6Al-4V (2)
- X-ray Computed Tomography (2)
- X-ray Refraction (2)
- X-ray computed tomography (2)
- X-ray diffraction (2)
- X-ray refraction techniques (2)
- 3D microstructure (1)
- 3D rendering (1)
- 3D-Mikrostruktur (1)
- ACEnet (1)
- Additive Fertigung (AM) (1)
- Al alloys (1)
- Alloys (1)
- Alterung (1)
- Aluminium Alloys (1)
- Aluminium alloy (1)
- Aluminium matrix (1)
- Aluminum Titanate (1)
- Aluminum alloys (1)
- Analyser based imaging (1)
- Analyser-based imaging (1)
- Artefakte (1)
- Asphalt, porosity (1)
- Auflösung (1)
- BAM (1)
- Beta-eucrytite (1)
- Beton (1)
- Bildartefakte (1)
- Bildverarbeitung (1)
- Blasting (1)
- CFK (1)
- CMAS - Calcium-Magnesium-Aluminiumsilikat (1)
- CT (1)
- Calcium phosphate (1)
- Cearmics (1)
- Ceria (1)
- Characterization (1)
- Coating (1)
- Complex microstructure (1)
- Composite (1)
- Composite materials (1)
- Computed tomography (CT) (1)
- Computer tomography (1)
- Computer-Tomographie (1)
- Computertomographie (CT) (1)
- Cordierit (1)
- Crack segmentation (1)
- Cracks (1)
- Creep (1)
- Creep models (1)
- Crystal structure (1)
- DIRECTT (1)
- DIVA Algorithm (1)
- Deep Convolutional Neural Network (DCNN) (1)
- Denoising Deblurring Sharpening (1)
- Diesel Particulate Filter Materials (1)
- Diesel particulate filter (1)
- Diesel particulate filters (1)
- Diffraction (1)
- Diffraction elastic constants (1)
- Directional interface variance analysis (DIVA) (1)
- Duplex stainless steel (1)
- Durchstrahlungsverfahren (1)
- EBSD (1)
- Elastic Constants (1)
- Energetic systems (1)
- Engineering applications (1)
- Explosives (1)
- Extrusion (1)
- FFT periodogram (1)
- Gitterinterferometrische Röntgenabbildung (1)
- Hydrogen assisted cracking (HAC) (1)
- Hydrogen embrittlement (HE) (1)
- Image Analysis (1)
- Implants (1)
- In-situ (1)
- In-situ CT (1)
- In-situ monitoring (1)
- In718 (1)
- Influence of rheology modifying admixtures on hydration of cementitious suspensions (1)
- Inhomogeneous materials (1)
- Institut Laue Langevin (1)
- Interface (1)
- Intergranular strain (1)
- Interphase residual stress (1)
- Laboratory energy-dispersive X-ray diffraction (EDXRD) (1)
- Laminographie (1)
- Laser Metal Deposition (1)
- Lattice structure (1)
- Lattice structures (1)
- Lattices (1)
- Lightweight structures (1)
- MMC (1)
- Machine learning (1)
- Manufacturing defects (1)
- Maskinteknik (1)
- Materials (1)
- Mechanical Engineering (1)
- Mechanical properties (1)
- Mechanische Eigenschaften (1)
- Medical implants (1)
- Mehrphasige Materialien (1)
- Metal Matrix Composite (MMC) (1)
- Metallische Werkstoffen (1)
- Michromechanical modeling (1)
- Micromechanical differential scheme (1)
- Micromechanical modeling (1)
- Microstructure-property relations (1)
- Microstructures (1)
- Missing wedge (1)
- Multiple-layered scaffold (1)
- Neutron and X-ray Diffraction (1)
- Neutronenstreuung (1)
- Non-destructive (1)
- Non-linear vibration (1)
- Nonel (1)
- Numerische Simulation (1)
- On-line monitoring (1)
- Orientation (1)
- PBF-LB (1)
- PBFLB/M AlSi10Mg alloy (1)
- Phase transformation (1)
- Phase-contrast X-ray imaging (1)
- Phasengitter (1)
- Plasticity (1)
- Polyamid 12 (1)
- Polycaprolactone (1)
- Pore Orientation (1)
- Pore nucleation (1)
- Porenorientierung (1)
- Porosität (1)
- Porous Ceramics (1)
- Poröse Keramik (1)
- Poröse Keramiken (1)
- Powder analysis (1)
- Preferred orientation (1)
- Prozess Monitoring (1)
- Quality control (1)
- Quantitative image analysis (1)
- Radiographie (1)
- Radon Transformation (1)
- Refraction radiography (1)
- Refraction tomography (1)
- Refraktion (1)
- Rekonstruktion (1)
- Rekonstruktionsalgorithmus (1)
- Rekonstruktionsverfahren (1)
- Residual Stress analysis (1)
- Residual Stresses (1)
- Risse (1)
- Rissen (1)
- Rissentwicklung (1)
- Rotor blade (1)
- Roughness (1)
- SEM (1)
- SLM (1)
- SXRR - Synchrotron X-ray Refraction Radiography (1)
- Scaffold (1)
- Schweißnähte (1)
- Selective Laser Melting (1)
- Selektive Laserschmelzen (1)
- Selektives Laserschmelzen (1)
- Shock wave (1)
- Si network (1)
- Sintering (1)
- Small Angle Neutron Scattering (1)
- Statistical analysis (1)
- Statistische Bewertung (1)
- Stress analysis (1)
- Stress exponent (1)
- Stress-relief heat-treatments (1)
- Structural simulation (1)
- Synchrotron X-ray computed tomography (1)
- Synchrotron X-ray diffraction (SXRD) (1)
- Synchrotron X-ray refraction (1)
- Synchrotron computed tomography (1)
- Synchrotronbeugung (1)
- Synchrotronstrahlung (1)
- Synthetic Training Data (1)
- TBC - Thermal barrier coatings (1)
- TEM (1)
- Talbot-Lau Interferometrie (1)
- Thermal (1)
- Thermography (1)
- Tomographie (1)
- Tomography (1)
- Unstrained reference (1)
- Verbundwerkstoffe (1)
- Visibility (1)
- Wall thickness (1)
- Wasserstoffunterstützte Rissbildung (1)
- Wasserstoffversprödung (1)
- Water uptake (1)
- Welding (1)
- Wind turbine (1)
- Wändedicke (1)
- Wärmebehandlung (1)
- X-Ray Computed Tomography (1)
- X-Ray Refraction (1)
- X-ray (1)
- X-ray Computed tomography (1)
- X-ray Refaction radiography (1)
- X-ray absorption and refraction CT (1)
- X-ray laminography (1)
- XCT Data Conditioning (1)
- Zirconia (1)
- grating (1)
- micromechanical modeling (1)
- refraction (1)
- topography (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (62)
- 8.5 Röntgenbildgebung (60)
- 5 Werkstofftechnik (4)
- 9 Komponentensicherheit (3)
- 9.4 Integrität von Schweißverbindungen (3)
- 2 Prozess- und Anlagensicherheit (2)
- 5.0 Abteilungsleitung und andere (2)
- 5.3 Polymere Verbundwerkstoffe (2)
- 8.0 Abteilungsleitung und andere (2)
- 9.2 Versuchsanlagen und Prüftechnik (2)
Eingeladener Vortrag
- nein (69)
Evaluating porosity in cordierite diesel particulate filter materials, part 1 X-ray refraction
(2013)
Bi-continuous porous ceramics for filtration applications possess a particularly complicated microstructure, with porosity and solid matter being intermingled. Mechanical, thermal, and filtration properties can only be precisely estimated if the morphology of both solid matter and porosity can be quantitatively determined. Using x-ray absorption and refraction, we quantitatively evaluate porosity and pore orientation in cordierite diesel particulate filter ceramics. Porosity values turn out to agree with mercury intrusion measurements, while pore orientation factors agree with published crystallographic texture data.
The residual stresses and load transfer in multiphase metal alloys and their composites (with both random planar-oriented short fibers and particles) will be shown, as studied by neutron diffraction, by X-ray computed tomography, and by a model based on the reformulation of classic Maxwell’s homogenization method.
Contrary to common understanding and state-of-the-art models, we experimentally observe that randomly oriented phases possess non-hydrostatic residual stress. Moreover, we disclose that the unreinforced matrix alloy stays under hydrostatic compression even under external uniaxial compression.
The recently developed modeling approach allows calculating the residual stress in all phases of the composites. It rationalizes the presence of deviatoric stresses accounting for the interaction of random oriented phases with fibers having preferential orientation. It also allows the explanation of the unconventional in-situ behavior of the unreinforced alloy and the prediction of the micromechanical behavior of other similar alloys.
Additiv gefertigte (AM) dreifach periodische metallische minimale Oberflächenstrukturen (TPMSS, aus dem Englischen Triply Periodic Minimum Surface Structures) erfüllen mehrere Anforderungen sowohl im biomedizinischen als auch im technischen Bereich: Abstimmbare mechanische Eigenschaften, geringe Empfindlichkeit gegenüber Herstellungsfehlern, mechanische Stabilität und hohe Energieabsorption. Allerdings stellen sie auch einige Herausforderungen in Bezug auf die Qualitätskontrolle dar, die ihre erfolgreiche Anwendung verhindern können. Tatsächlich ist die Optimierung des AM-Prozesses ohne die Berücksichtigung struktureller Merkmale wie Fertigungsgenauigkeit, interne Defekte sowie Oberflächentopographie und -rauheit unmöglich. In dieser Studie wurde die quantitative zerstörungsfreie Analyse von Ti-6Al-4V-Legierung TPMSS mit Hilfe der Röntgen-Computertomographie (XCT) durchgeführt. Es werden mehrere neue Bildanalyse-Workflows vorgestellt, um die Auswirkungen der Aufbaurichtung auf die Wanddickenverteilung, die Wanddegradation und die Verringerung der Oberflächenrauheit aufgrund des chemischen Ätzens von TPMSS zu bewerten. Es wird gezeigt, dass die Herstellungsgenauigkeit für die Strukturelemente, die parallel und orthogonal zu den hergestellten Schichten gedruckt werden, unterschiedlich ist. Verschiedene Strategien für das chemische Ätzen zeigten unterschiedliche Pulverabtragsfähigkeiten und damit ein Gradient der Wanddicke. Dies wirkte sich auf die mechanische Leistung unter Druck durch die Verringerung der Streckspannung aus. Eine positive Auswirkung des chemischen Ätzens ist die Verringerung der Oberflächenrauhigkeit, die möglicherweise die Ermüdungseigenschaften der Bauteile verbessern kann. Schließlich wurde XCT eingesetzt, um die Menge des zurückgehaltenen Pulvers mit der Porengröße des TPMSS zu korrelieren, wodurch der Herstellungsprozess weiter verbessert werden kann.
Additively manufactured (AM) metallic sheet-based Triply Periodic Minimal Surface Structures (TPMSS) meet several requirements in both bio-medical and engineering fields: Tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some challenges related to quality control. In fact, the optimization of both the AM process and the properties of TPMSS is impossible without considering structural characteristics as manufacturing accuracy, internal defects, and as well as surface topography and roughness. In this study, the quantitative non-destructive analysis of TPMSS manufactured from Ti-6Al-4V alloy by electron beam melting was performed by means of laboratory X-ray computed tomography (XCT).
Additively manufactured (AM) triply periodic metallic minimum surface structures (TPMSS, from the English Triply Periodic Minimum Surface Structures) fulfill several requirements in both biomedical and engineering fields: tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some quality control challenges that may prevent their successful application. In fact, optimization of the AM process is impossible without considering structural features such as manufacturing accuracy, internal defects, and surface topography and roughness. In this study, quantitative nondestructive analysis of Ti-6Al-4V alloy TPMSS was performed using X-ray computed tomography (XCT). Several new image analysis workflows are presented to evaluate the effects of buildup direction on wall thickness distribution, wall degradation, and surface roughness reduction due to chemical etching of TPMSS. It is shown that the fabrication accuracy is different for the structural elements printed parallel and orthogonal to the fabricated layers. Different strategies for chemical etching showed different powder removal capabilities and thus a gradient in wall thickness. This affected the mechanical performance under compression by reducing the yield stress. A positive effect of chemical etching is the reduction of surface roughness, which can potentially improve the fatigue properties of the components. Finally, XCT was used to correlate the amount of powder retained with the pore size of the TPMSS, which can further improve the manufacturing process.
A paradigm shift in the description of creep in metals can only occur through multi-scale imaging
(2022)
The description of creep in metals has reached a high level of complexity; fine details are revealed by all sorts of characterization techniques and different theoretical models. However, to date virtually no fully microstructure-driven quantitative description of the phenomenon is available. This has brought to interesting inconsistencies; the classic description of (secondary) creep rests on the so-called power law, which however: a- has a pre-factor spanning over 10 orders of magnitude; b- has different reported exponents for the same material; c- has no explanation for the values of such exponents.
Recently, a novel description (the so-called Solid State Transformation Creep (SSTC) Model) has been proposed to tackle the problem under a different light. The model has two remarkable features: 1- it describes creep as the accumulation of elementary strains due to dislocation motion; 2- it predicates that creep is proceeding by the evolution of a fractal arrangement of dislocations. Such description, however, needs a great deal of corroborating evidence, and indeed, is still incomplete.
To date, we have been able to observe and somehow quantify the fractal arrangement of microstructures through Transmission Electron Microscopy (TEM), observe the accumulation of dislocations at grain boundaries by EBSD-KAM (Electron Back-Scattered Diffraction-Kernel Angular Misorientation) analysis, quantify the kinetic character (solid state transformation) of experimental creep curves, and estimate the sub-grain size of the fractal microstructure through X-ray refraction techniques. All pieces of the mosaic seem to yield a consistent picture: we seem being on the right path to reconstruct the whole elephant by probing single parts of it. What is still missing is the bond between the various scales of investigation.
In this work, synchrotron X-ray refraction radiography (SXRR) was combined with in-situ heat treatment to monitor microstructure and porosity evolution as a function of temperature. The investigated material was a laser powder bed fusion (LPBF) manufactured AlSi10Mg, where the initial eutectic Si network is known to break down into larger particles with increasing temperature. Such alloy is also prone to thermally induced porosity (TIP). We show that SXRR allows detecting the changes in the Si-phase morphology upon heating, while this is currently possible only using scanning electron microscopy. SXRR also allows observing the growth of pores, usually studied via X-ray computed tomography, but on much smaller fields-of-view. Our results show the great potential of in-situ SXRR as a tool to gain in-depth knowledge of the susceptibility of any material to thermally induced damage and/or microstructure evolution over statistically relevant volumes.
The availability of high-performance Al alloys in AM is limited due to difficulties in printability, requiring both the development of synergetic material and AM process to mitigate problems such as solidification cracking during laser powder bed fusion (LPBF). The goal of this work was to investigate the failure mechanism in a LPBF 7017 Aluminium alloy + 3 wt% Zr + 0.5 wt% TiC. The processing leads to different categories of Zr-rich inclusions, precipitates and defects.
The micromechanical behavior of an annealed Ti-6Al-4V material produced by Laser Powder Bed Fusion was characterized by means of in-situ synchrotron X-ray diffraction during a tensile test. The lattice strain evolution was obtained parallel and transversal to the loading direction. The elastic constants were determined and compared with the conventionally manufactured alloy. In the plastic regime, a lower plastic anisotropy exhibited by the lattice planes was observed along the load axis (parallel to the building direction) than in the transverse direction.
Also, the load transfer from α to β phase was observed, increasing global ductility of the material. The material seems to accumulate a significant amount of intergranular strain in the transverse direction.
Additively manufactured (and in particular laser powder bed fused) materials represent a manyfold challenge for the materials scientist and engineer because of their distinctive microstructure. If laser powder bed fusion is used to produce components, the complexity level increases because meso-structures (e.g., overhanging features, surface and internal defects) gain importance. Furthermore, if the main advantage of additive manufacturing, i.e., the freedom of design, is to be fully exploited, and geometrically complex structures, such as lattices, are manufactured, then such structures become meta-materials. This means that the geometry and the materials properties become equally important.
This matryoshka-like (more literary than the dry “multi-scale”) complexity makes the characterization of the residual stress fields by means of diffraction methods so difficult with the current means, that new paradigms are necessary to tackle the challenge.
Indeed, classic open problems acquire an extra layer of difficulty, such that new solutions need to be found and the sometimes-dormant debate needs to be re-opened. Examples include the determination of: a- the unstrained reference: this reference can become location-dependent and needs to be carefully determined; b- the so-called diffraction elastic constants, which becomes immensely challenging since even the single-crystal elastic constants are not known for additively manufactured materials.
On top of this, other problems arise. The determination of the principal axes of stress becomes non-trivial because the hatching strategy sometimes dominates over the sample geometry. Even further, in complex structures, such as lattices, the textbook statement that the strain measurement in six independent directions uniquely identifies the strain tensor becomes simply invalid. The peculiar surface features of additively manufactured materials transform trivial tasks into formidable challenges: the precise alignment of a specimen in a beam or the determination of surface stresses with laboratory X-rays need to be thoroughly re-discussed and lay far from being routine tasks.
In this paper, we will show a few examples of the cases mentioned above. We will demonstrate that sometimes the classic approach works very well, but other times surprising conclusions can be drawn from in-depth studies of the residual stress in additively manufactured materials. In short, we predicate that classic methods cannot be used on additively manufactured materials and structures without a critical evaluation of their validity and application range.
Alternative to conventional transmission-based radiography and computed tomography, X-ray refraction techniques are being increasingly used to detect damage in light materials. In fact, their range of application has been recently extended even to metals. The big advantage of X-ray refraction techniques is that they are able to detect nanometric defects, whose size would lie below the resolution of even state-of-the-art synchrotron-based X-ray computed tomography (SXCT). The superiority of synchrotron X-ray refraction radiography and tomography (SXRR and SXRCT) has been shown in the case of light materials, in particular composites. X-ray refraction techniques also yield a quantitifaction of the amount of damage (the so-called relative internal specific surface) and can well be compared with damage models. At the same time, it is impossible for SXRR and SXRCT to image single defects. We show that the combination of refraction- and transmission-based imaging techniques yields an impressive amount of additional information about the type and amount of defects in microstructured materials such as additively manufactured metals or metal matrix composites. We also show that the use of data fusion techniques allows the classification of defects in statistically significant representative volume elements.
Alternative to conventional transmission-based radiography and computed tomography, X-ray refraction techniques are being increasingly used to detect damage in light materials. In fact, their range of application has been recently extended even to metals. The big advantage of X-ray refraction techniques is that they are able to detect nanometric defects, whose size would lie below the resolution of even state-of-the-art synchrotron-based X-ray computed tomography (SXCT). The superiority of synchrotron X-ray refraction radiography and tomography (SXRR and SXRCT) has been shown in the case of light materials, in particular composites. X-ray refraction techniques also yield a quantitifaction of the amount of damage (the so-called relative internal specific surface) and can well be compared with damage models. At the same time, it is impossible for SXRR and SXRCT to image single defects. We show that the combination of refraction- and transmission-based imaging techniques yields an impressive amount of additional information about the type and amount of defects in microstructured materials such as additively manufactured metals or metal matrix composites. We also show that the use of data fusion techniques allows the classification of defects in statistically significant representative volume elements.
Wir präsentieren Labor- und Synchrotron-Röntgenrefraktionstechniken, wie sie an der BAM implementiert sind.
Wir zeigen, dass die Labor-Röntgenrefraktionstopographie (XRRT) und die Synchrotron-Röntgenrefraktionsradiographie (SRRR) außergewöhnliche Werkzeuge zur Untersuchung von Schädigungen und inneren Defekten (Poren, Mikrorisse) in leichten Materialien wie Keramiken und Kompositen sind. Tatsächlich nutzen diese Techniken den an Grenzflächen auftretenden Röntgenbrechungseffekt aus, um den Kontrast zwischen dem (schwach absorbierenden) Objekt und dem Hintergrund zu erhöhen. Dies ermöglicht die Erkennung sehr kleiner Objekte (sogar bis zu 1 nm Rissöffnung) und die Quantifizierung ihrer spezifischen Oberfläche, die mit ihrem Einfluss auf die Materialeigenschaften korreliert. Wir zeigen die folgenden Anwendungen: a) Quantifizierung der Faserentbindung in laminaten Epoxid-Kohlenstoff-Verbundwerkstoffen; b) Mapping der Porengröße in gesinterten Keramiken; c) Eindringstiefe von Aschen in Keramikschutzschichten; d) Quantifizierung der Porenorientierung in Diesel Partikelfiltern; e) 3D-Darstellung von Makrorissen und Faserentbindung in Verbundwerkstoffen auf Ti-Basis für Anwendungen in der Luft- und Raumfahrt (unter Verwendung von Röntgenrefraktionstomographie).
Die Degradation von Wärmedämmschichten(thermal barrier coatings - TBCs) in Gasturbinen durch glasartige Calcium-Magnesium-Aluminiumsilikat (CMAS)Ablagerungen aus verschiedenen Quellen istseit vielen Jahren ein anhaltendes Problem. In dieser Studie wurde mit Hilfe derSynchrotron-Röntgen-Refraktions-Radiographie (SXRR), und vergleichend mit der Elektronenmikroskopie, das Eindringen von CMAS in die poröse Struktur von atmosphärisch plasmagespritzten (APS)TBCs sowie die Bildung und das Wachstum von Rissen unter thermisch zyklischer Belastung untersucht. Die Ergebnisse deuten darauf hin, dass die Infiltration sowie deren Kinetik im Brenner-Teststand wesentlich vom Benetzungsverhalten des CMAS beeinflusst werden. Trotz desoffensichtlichen Angriffs von CMAS auf die Korngrenzen hat die Wechselwirkung von Yttriumdioxid-stabilisiertem Zirkoniumdioxid (YSZ) mit intrudiertem CMAS keinen unmittelbaren Einfluss auf die Struktur und Dichte der innen Oberflächen(Risse, Poren). In einem späteren Stadium wird die Bildung von Rissen senkrecht zur äußeren Oberfläche in einer breiteren Zone der TBC-Schicht beobachtet.
In this talk the basics of X-ray computed tomography (XCT) are presented, together with a description of complementary techniques such as Laminography and Stereoradiography.
A overview of the common reconstruction approach and of the artifacts that can occur during reconstruction or acquisition of XCT images is also given.
Finally, application examples in the field of construction materials are given, whereby several experimental techniques (Region of Interest Approach) and data analysis methods (e.g. Digital volume correlation) are explained. Such techniques and algorithms are used to extract quantitative information from ex- and in-situ experiments.
In this seminar I present the microstructure and micromechanical properties of diesel particulate filter materials, and then particularize them to porous microcracked aluminum titanate.
I show that neutron diffraction is particularly suited for bulk studies, especially under applied load or at high temperatures. The combination of macroscopic and microscopic tests with modeling and simulation yields great added value to understand the mechanics of microcracking.
In Additive Manufacturing everybody is talking about Free Form, Unconventional Design, Re-thinking Components, “Think out of the box”.
However, there are a few outstanding question: a) What are the material properties ? They certainly differ from literature values for conventional materials; b) How about the microstructure? It is different from conventional materials. Does it stay so with ageing? How does it form? c) Do we properly take residual stress into account? We often blame them for our ignorance about failure scenarios. d) Do we apply tailored heat treatments? Very often, we follow conventional schedules…
This talk describes the summary of the efforts carried out within the BAM Project AGIL.
At BAM, we aimed to thoroughly investigate the microstructure and how it evolves as a function of load and temperature (service), to determine the material properties after different process and service conditions, to properly determine residual stress and the way it impacts mechanical properties and component performance, to properly quantify the impact of (unavoidable?) defects, and to determine heat treatments tailored to the process-specific material (stress relieve, microstructure homogenization etc.).
The Project AGIL was and is intimately coupled with the project ProMoAM, dealing with online monitoring of AM processes.
Um das Material- und Schädigungsverhalten von additiv gefertigtem Polyamid 12 (PA12) unter quasistatischer Belastung zu charakterisieren, wurden mechanische Tests und Röntgenverfahren zur Bestimmung der Mikrostruktur eingesetzt. Die Proben wurden nach dem Prinzip des Selektiven Lasersinterns (SLS) hergestellt. Unter quasistatischer Belastung mit Haltezeiten ergab sich ein viskoplastisches Materialverhalten. Im Zugversuch wurde eine maximale Zugfestigkeit von 40.6 MPa und eine Bruchdehnung von 7.4% beobachtet. Mittels Röntgenrefraktion wurde eine Erhöhung von inneren Oberflächen beobachtet, die senkrecht zur Zugrichtung orientiert sind. Die Analyse der Gesamtporosität aus Computertomographie-Messungen ergab keine Änderung infolge der Zugbelastung. Jedoch wurde eine bimodale Porengrößenverteilung und eine steigende Sphärizität festgestellt. Das Materialverhalten wurde mit dem Chaboche-Modell simuliert und ergab eine sehr gute Übereinstimmung mit den experimentellen Ergebnissen. Allerdings gestattet dieses Modell nicht, das Schädigungsverhalten abzubilden. Daher wurde zur Simulation des Schädigungsverhaltens das Modell gemäß dem Ansatz von Gurson, Tvergaard und Needleman unter Berücksichtigung der mikrostrukturellen Parameter erweitert. Der Schwerpunkt des Beitrags liegt auf den Röntgenverfahren zur experimentellen Bestimmung der Mikrostruktur.
Wir präsentieren Labor- und Synchrotron-Röntgenrefraktionstechniken, wie sie an der BAM implementiert sind.
Wir zeigen, dass die Labor-Röntgenrefraktionstopographie (XRRT) und die Synchrotron-Röntgenrefraktionsradiographie (SRRR) außergewöhnliche Werkzeuge zur Untersuchung von Schädigungen und inneren Defekten (Poren, Mikrorisse) in leichten Materialien sind. Tatsächlich nutzen diese Techniken den an Grenzflächen auftretenden Röntgenbrechungseffekt aus, um den Kontrast zwischen dem (schwach absorbierenden) Objekt und dem Hintergrund zu erhöhen. Dies ermöglicht die Erkennung sehr kleiner Objekte (z. B. bis zu 1 nm Rissöffnung) und die Quantifizierung ihrer spezifischen Oberfläche, die mit ihrem Einfluss auf die Materialeigenschaften korreliert. Wir zeigen die folgenden Anwendungen: a) Quantifizierung der Faserentbindung in laminaten Epoxid-Kohlenstoff-Verbundwerkstoffen; b) Mapping der Porengröße in gesinterten Keramiken; c) Klassifizierung von Defekttypen in additiv gefertigter Ti6Al4V-Legierung; d) Früherkennung des Versagens in Aluminium-Keramik-Verbundwerkstoffen (unter Verwendung von In-situ-Experimenten); e) 3D-Darstellung von Makrorissen und Faserentbindung in Verbundwerkstoffen auf Ti-Basis für Anwendungen in der Luft- und Raumfahrt (unter Verwendung von Röntgenbeugungstomographie).