Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
- 2017 (22) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (8)
- Vortrag (7)
- Beitrag zu einem Tagungsband (6)
- Posterpräsentation (1)
Schlagworte
- Neutron diffraction (6)
- Composites (5)
- Residual stress (5)
- Additive manufacturing (4)
- X-ray refraction (4)
- Additive Fertigung (3)
- Computed tomography (3)
- Eigenspannungen (3)
- Additive Manufacturing (2)
- Ceramics (2)
- Computed Tomography (2)
- Damage (2)
- GMR (2)
- Neutron Diffraction (2)
- Selective laser melting (2)
- Synchrotron X-ray diffraction (2)
- X-ray Refraction (2)
- Alterung (1)
- Aluminium matrix (1)
- BAM (1)
- Biomedical engineering (1)
- Blasting (1)
- Cearmics (1)
- Composite materials (1)
- Computertomographie (1)
- Crack detection (1)
- Cracks (1)
- Dentistry (1)
- Electron back-scattered diffraction (1)
- Energetic systems (1)
- Explosives (1)
- Fatigue (1)
- Gitterinterferometrische Röntgenabbildung (1)
- Grating interferometry (1)
- Heat treatment (1)
- IN718 (1)
- Image Analysis (1)
- Laser Metal Deposition (1)
- Load partition (1)
- Low carbon steel (1)
- Magnetic stray field (1)
- Medical imaging (1)
- Metal matrix composite (1)
- Metallische Werkstoffen (1)
- Microcracking (1)
- Microstructure (1)
- Microstructure and texture (1)
- Modeling (1)
- Neutronenbeugung (1)
- Neutronenstreuung (1)
- Nickel-based superalloy (1)
- Non-destructive testing (1)
- Non-linear vibration (1)
- Nonel (1)
- Phasengitter (1)
- Plastic deformation (1)
- Porosity (1)
- Prozess Monitoring (1)
- Refraction radiography (1)
- Refraction tomography (1)
- Residual Stress analysis (1)
- Röntgenrefraktion (1)
- Selective Laser Melting (1)
- Selektive Laserschmelzen (1)
- Selektives Laserschmelzen (1)
- Shock wave (1)
- Specific surface (1)
- Structural simulation (1)
- Synchrotron, BAMline (1)
- Synchrotronbeugung (1)
- TIG weld (1)
- TIG-welding (1)
- Talbot-Lau Interferometrie (1)
- Talbot-Lau interferometer (1)
- Tensile behavior (1)
- Ti-6Al-4V (1)
- Wärmebehandlung (1)
- X-ray computer tomography (1)
- X-ray imaging (1)
- X-ray phase contrast (1)
- Young's modulus (1)
- Zerstörungsfreie Prüfung (1)
- β-eucryptite (1)
Eingeladener Vortrag
- nein (7)
X-ray refraction techniques represent a very promising, yet not so wide-spread, set of X-ray techniques
based on refraction effects. They allow determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with nanometric detectability. While they are limited by the X-ray absorption of the material under investigation, we demonstrate showcases of ceramics and composite materials, where understanding of microstructural features could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography.
Im vergangenen Jahrzehnt sind gitterinterferometrische Röntgenabbildungen zunehmend in den Fokus des Interesses gerückt. Sie sind insbesondere dann Vorteil, wenn der in der Standardradiographie erreichbare Kontrast nicht genügt, schwach absorbierende Mikro- und Nanostrukturen abzubilden.
Auf Kosten mehrerer Aufnahmen gestattet die Talbot-Lau Gitterinterferometrie, die Beiträge aus Absorption, Refraktion und (refraktiver) Streuung zu trennen. Dazu werden die Störungen der Interferenzmuster von Phasengittern ausgewertet. Im Gegensatz zu einer Vielzahl anderer refraktionsbasierter Abbildungsmethoden kann diese Technik mit konventionellen Röntgenröhren (mit divergenter, polychromatischer Strahlung) angewendet werden. Damit ist die Technik geeignet, typische ZfP-Fragestellungen zu lösen.
Hier stellen wir Untersuchungen zur Effizienz von Phasengittern vor. Die Visibilität (d.h. die Höhe der Oszillation im Interferenzmuster) wird als Funktion verschiedener geometrischer Parameter verfolgt. Eine Rotation um die Achse parallel zu den Gitterstegen ändert die Form des Gitterprofils (d.h. die Verteilung der Phasenschiebungen). Die kontinuierliche Variation des Winkels und des Detektionsabstandes führt zur Identifikation von ausgezeichneten Kombinationen mit maximaler Visibilität, wobei die Abstände deutlich geringer sind als im Standardaufbau mit senkrechter Gitterbestrahlung.
Unsere Studie umfasst Simulationen für monochromatische Quelle und den Vergleich zu experimentellen Ergebnissen mit der Synchrotronstrahlung.
In der Literatur wurden die Vorteile der Talbot-Lau Interferometrie für die zerstörungsfreie Prüfung von Faserkompositen und Verbundwerkstoffen demonstriert. Hier werden als Beispiele Messungen an Aluminiumtitanat (Al2TiO5) Pulver gezeigt.
Stress-induced damage evolution in cast AlSi12CuMgNi alloy with one- and two ceramic reinforcements
(2017)
Two composites, consisting of an as-cast AlSi12CuMgNi alloy reinforced with 15%vol. Al2O3 short fibres and with 7%vol. Al2O3 short fibres + 15%vol. SiC particles were studied. Synchrotron computed tomography disclosed distribution, orientation, and volume fraction of the different phases. In-situ compression tests during neutron diffraction in direction parallel to the fibres plane revealed the load partition between phases. Internal damage (fragmentation) of the Si phase and Al2O3 fibres was directly observed in CT reconstructions. Significant debonding between Al-matrix and SiC particles was also found. Finally, based on the Maxwell scheme, a micro-mechanical model was utilized for the new composite with two ceramic reinforcements; it rationalizes the experimental data, and predicts the evolution of all internal stress components in each phase.
The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction(ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.
The performance of grating interferometers coming up now for Imaging interfaces within materials depends on the efficiency (visibility) of their main component, namely the phase grating. Therefore, experiments with monochromatic synchrotron radiation and corresponding simulations are carried out. The visibility of a Phase grating is optimized by different photon energies, varying detector to grating distances and continuous rotation of the phase grating about the grid lines. Such kind of rotation changes the projected grating shapes, and thereby the distribution profiles of phase shifts. This yields higher visibilities than derived from ideal rectangular shapes. By continuous grating rotation and variation of the propagation distance, we achieve 2D visibility maps. Such maps provide the visibility for a certain combination of grating orientation and detector position. Optimum visibilities occur at considerably smaller distances than in the standard setup.
This paper focuses on the aspect on how damage evolution processes in composite materials and structures including matrix fracture, delamination, fibre-matrix debonding, and fibre fracture can be detected by taking advantage of the material’s inherit mechanical properties. These properties can be described on the basis of non-linear mechanical phenomena measurable as an inert frequency response signal. The approach is proposed as a means for residual life structural assessment specifically in the context of VHCF.
3D imaging techniques are very fashionable nowadays, and allow enormous progress in understanding ceramic microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this feature article, we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. While the techniques are limited by the X-ray absorption of the material under investigation, we demonstrate showcases of ceramics and composite materials, where understanding of process parameter influence or simply of microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography.
Several cylindrical specimens and dental implants, presenting diagonal lattice structures with different cell sizes (600, 900 and 1200 µm) were additively manufactured by selective laser melting process. Then they were implanted for two months in a sheep. After removal, they were studied by Archimedes’ method as well as X-ray computed tomography in order to assess the penetration of bone into the lattice. We observed that the additive manufactured parts were geometrically conform to the theoretical specifications. However, several particles were left adhering to the surface of the lattice, thereby partly or entirely obstructing the cells. Nevertheless, bone penetration was clearly visible. We conclude that the 900 µm lattice cell size is more favourable to bone penetration than the 1200 µm lattice cell size, as the bone penetration is 84 % for 900 µm against 54 % for 1200 µm cell structures. The lower bone penetration value for the 1200 µm lattice cell could possibly be attributed to the short residence time in the sheep. Our results lead to the conclusion that lattice implants additively manufactured by selective laser melting enable better bone integration.
Evaluation of high spatial resolution imaging of magnetic stray fields for early damage detection
(2017)
The paper discusses the evaluation of elastic and plastic strain states in two low-carbon steels of the same steel group with high spatial resolution GMR (giant magneto resistance) sensors. The residual stress distributions of tungsten inert gas welded plates were determined by means of neutron diffraction as a reference. The normal component of local residual magnetic stray fields arise in the vicinity of the positions of maximum stress. The experiments performed on flat tensile specimen indicate that the boundaries of plastic deformations are a source of stray fields. The spatial variations of magnetic stray fields for both the weld and the tensile samples are in the order of the earths magnetic field.