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- Additive manufacturing (13)
- Laser powder bed fusion (8)
- Residual stress (7)
- Additive Manufacturing (6)
- AlSi10Mg alloy (4)
- Computed tomography (4)
- Residual Stress (4)
- X-ray refraction (4)
- AlSi10Mg (3)
- EBSD analysis (3)
- Electron backscatter diffraction (EBSD) (3)
- Fatigue crack growth (3)
- In situ heating (3)
- Laser Powder Bed Fusion (3)
- Neutron diffraction (3)
- Residual stress analysis (3)
- Creep (2)
- Diffraction (2)
- Diffraction elastic constants (2)
- Digital image correlation (DIC) (2)
- Electron backscatter diffraction (2)
- Fatigue crack propagation (2)
- Heat treatment (2)
- IN718 (2)
- In-situ heating up to 1400°C (2)
- Inconel 718 (2)
- LPBF (2)
- Microcracking (2)
- Neutron Diffraction (2)
- Refractory materials (2)
- Residual stress state (2)
- Residual stresses (2)
- Sintering (2)
- Synchrotron X-Ray Refraction (2)
- Synchrotron refraction radiography (2)
- Synchrotron µCT and refraction radiography (2)
- Texture (2)
- Thermally induced porosity (2)
- A357-T6 cast aluminum alloy (1)
- A357-T6 casting (1)
- AGIL (1)
- AISI 316L (1)
- AM IN718 (1)
- AM IN718 alloy (1)
- Al-3.85%Mg alloy (1)
- Aluminium alloys (1)
- Aluminum alloy (1)
- Analyzer-based imaging (1)
- As-built LPBF IN718 alloy (1)
- Bench braking sequence (1)
- Bragg-edge neutron 2D imaging (BENI) (1)
- Braking load history (1)
- Bulk properties ageing (1)
- Cellular structures (1)
- Ceramics (1)
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- Computed Tomography (1)
- Crack initiation period (1)
- Cracks (1)
- Crystal plasticity finite element modeling (CPFEM) (1)
- Crystallographic descriptor (1)
- Crystallographic texture control (1)
- Cyclic R-curve (1)
- DIC assisted compression (1)
- Damage characterization (1)
- Damage tolerance (1)
- Defects (1)
- Denoising filter (1)
- Diffraction methods (1)
- Diffraction peak width (1)
- Diffraction-elastic constants (1)
- Diffusion (1)
- Digital image correlation (1)
- Dislocation-climb-controlled creep (1)
- Dislocations (1)
- Distortion (1)
- Distortion upon baseplate removal (1)
- Effect of scanning strategies (1)
- Electron microscopy (1)
- Energy dispersive X Ray diffraction (1)
- Ernel average misorientation (KAM) (1)
- Evolution of bulk properties (1)
- Fatigue performance (1)
- Fractals (1)
- Fractographic observations (1)
- Friction braking (1)
- Geometric descriptor (1)
- Graphite induced hysteresis (1)
- Hystersis (1)
- IN718 PBF-LB/M (1)
- Imaging (1)
- In situ testing (1)
- In-situ (1)
- In-situ heat treatment (1)
- Inconel (1)
- Interfaces (1)
- Interphase residual stress (1)
- Keramik (1)
- Kernel average misorientation (1)
- L-PBF (1)
- L-PBF IN718 material (1)
- Laboratory XµCT (1)
- Laboratory energy-dispersive X-ray diffraction (EDXRD) (1)
- Laminated metal composite (1)
- Laminated metallic composites (1)
- Large Scale Facilities (1)
- Laser Beam Melting (1)
- Laser Powder Bed Melting (1)
- Laser beam melting (1)
- Laser powder bed fusion (LPBF) (1)
- Laser-based additive manufacturing (1)
- Lattice Structure (1)
- Load history (1)
- Macroscopic stress (1)
- Mechanical behavior (1)
- Metal additive manufacturing (MAM) (1)
- Metal matrix composite (1)
- Metallic matrix pad (1)
- Microstructural evolution (1)
- Microstructure (1)
- Microstructure and texture (1)
- Monoclinic to tetragonal transformation (1)
- Near-surface X-ray diffraction (1)
- Neutron and X-ray diffraction (1)
- Neutrons diffraction (1)
- Nickel-based superalloys (1)
- Nonlinear stress-strain curve (1)
- Online Process Monitoring (1)
- PBFLB/M AlSi10Mg alloy (1)
- Phase transformation (1)
- Plasticity (1)
- Pore size (1)
- Porosity growth (1)
- Post processing heat treatment (1)
- Powder analysis (1)
- Powder metallurgy (1)
- Power law and power-law breakdown (1)
- Power-law breakdown (1)
- Propagation modes (1)
- Pure aluminium (1)
- Qquantification and segmentation (1)
- Re-entrant surface feature (1)
- Refractory (1)
- Refractory zirconia (1)
- Residual stress in AM (1)
- Residual stress measurements (1)
- Röntgen-Refraktion (1)
- SIF evaluation (1)
- Scan strategies (1)
- Scan strategy influence (1)
- Scanning electron microscopy (1)
- Scanning electron microscopy (SEM) (1)
- Selective laser melted materials (1)
- Semi-metallic brake-pad material (1)
- Semi-metallic friction material (1)
- Semi-metallic sintered material (1)
- Si network disintegration (1)
- Stainless Steel (1)
- Statistical image analysis (1)
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- Steady-state creep (1)
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- Strain-free lattice references (1)
- Strain-free lattice spacing (1)
- Stress balance (1)
- Stress balance condition (1)
- Stress-relief heat-treatments (1)
- Surface roughness analysis (1)
- Synchrotron Energy Dispersive Diffraction (1)
- Synchrotron X-ray computed tomography (1)
- Synchrotron X-ray diffraction (1)
- Synchrotron X-ray diffraction (SXRD) (1)
- Synchrotron X-ray refraction (1)
- Synchrotron X-ray refraction radiography (1)
- Synchrotron computed tomography (1)
- Synchrotron refraction (1)
- Synchrotron tomography (1)
- Tensile testing (1)
- Thermally induced microcracking (1)
- Thermally induced porosity (TIP) (1)
- Thermography (1)
- Ti-6Al-4V (1)
- Tiatanium (1)
- Torsional fatigue (1)
- Torsional in situ fatigue testing (1)
- Toughening mechanism (1)
- Toughening mechanisms (1)
- Uniaxial compression tests (1)
- Verbundwerkstoffe (1)
- Wear resistance (1)
- X-Ray refraction (1)
- X-ray Computed Tomography (1)
- X-ray Diffraction (1)
- X-ray Refaction radiography (1)
- X-ray analysis (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray synchrotron tomography (1)
- Zirconia (1)
- pure aluminum (1)
- subgrain (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (57)
- 8.5 Röntgenbildgebung (57)
- 9 Komponentensicherheit (15)
- 9.4 Integrität von Schweißverbindungen (14)
- 5 Werkstofftechnik (5)
- 5.1 Mikrostruktur Design und Degradation (3)
- 5.2 Metallische Hochtemperaturwerkstoffe (2)
- 8.0 Abteilungsleitung und andere (2)
- 9.0 Abteilungsleitung und andere (2)
- 9.6 Additive Fertigung metallischer Komponenten (2)
Eingeladener Vortrag
- nein (10)
X-ray refraction is analogous to visible light deflection by matter; it occurs at boundaries between different media. The main difference between visible light and X-rays is that in the latter case deflection angles are very small, from a few seconds to a few minutes of arc (i.e., the refraction index n is near to 1). Trivially but importantly, deflection of X-rays is also sensitive to the orientation of the object boundaries. These features make X-ray refraction techniques extremely suitable to a) detect defects such as pores and microcracks and quantify their densities in bulk (not too heavy) materials, and b) evaluate porosity and particle properties such as orientation, size, and spatial distribution (by mapping). While X-ray refraction techniques cannot in general image single defects, their detectability is simply limited by the wavelength of the radiation.
We thereby show the application of X-ray refraction 2D mapping (topography) and tomography to different sorts of problems in materials science and technology: 1) Sintering of SiC green bodies; 2) Porosity analysis in additively manufactured alloys; 3) Fiber de-bonding in metal and polymer matrix composites.
Such techniques, especially at the Synchrotron BESSY II, Berlin, Germany, can be used in-situ, i.e. when the specimen is subjected to temperatures or external loads. Applications of in-situ X-ray refraction radiography on aluminum alloys and composites are also shown.
The use of X-ray refraction analysis yields quantitative information, which can be directly input in kinetics, mechanical and damage models.
Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses.
The triaxial distribution of the residual stress in laser powder bed fused austenitic steel 316L was determined by X-ray and neutron diffraction. The residual stress analysis results were linked to the thermal history of the specimens, which were manufactured with varying inter-layer-times and scanning velocities. A clear link between the in-process temperature of the specimens and the residual stress was found, based on in-situ monitoring data.
The experimental determination of residual stress becomes more complicated with increasing complexity of the structures investigated. Unlike the conventional and most of the additive manufacturing (AM) fabrication techniques, laser powder bed fusion (PBF-LB) allows the production of complex structures without any additional manufacturing step. However, due to the extremely localized melting and solidification, internal stress-induced deformation and cracks are often observed. In the best case, significant residual stress is retained in the final structures as a footprint of the internal stress during manufacturing.
Here we report solutions to the most prevalent challenges when dealing with the diffraction-based determination of residual stress in AM structures, in particular the choice of the correct diffraction elastic constants. We show that for Nickel-based alloys, the diffraction elastic constants of AM material significantly deviate from their conventional counterparts. Furthermore, measurement strategies to overcome the hurdles appearing when applying diffraction-based techniques to complex-shaped lattice structures are presented: a) proper sample alignment within the beam, b) the proper determination of the residual stress field in a representative part of the structure (i.e., with an engineering meaning). Beyond the principal stress magnitude, the principal direcions of residual stress are discussed for different geometries and scan strategies, as they are relevent for failure criteria.
We show that the RS in the lattice struts can be considered to be uniaxial and to follow the orientation of the strut, while the RS in the lattice knots is more hydrostatic. Additionally, we show that strain measurements in at least seven independent directions are necessary for the correct estimation of the principal stress directions. The measurement directions should be chosen according to the sample geometry and to an informed choice on the possible strain field (i.e., reflecting the scan strategy).
We finally show that if the most prominent direction is not measured, the error in the calculated stress magnitude increases in such a manner that no reliable assessment of RS state can be made.
The manufacturability of metallic alloys using laser-based additive manufacturing methods such as laser powder bed fusion has substantially improved within the last decade. However, local melting and solidification cause hierarchically structured and crystallographically textured microstructures possessing large residual stress. Such microstructures are not only the origin of mechanical anisotropy but also pose metrological challenges for the diffraction-based residual stress determination. Here we demonstrate the influence of the build orientation and the texture on the microstructure and consequently the mechanical anisotropy of as-built Inconel 718. For this purpose, we manufactured specimens with [001]/[011]-, [001]- and [011]/[111]-type textures along their loading direction. In addition to changes in the Young’s moduli, the differences in the crystallographic textures result in variations of the yield and ultimate tensile strengths. With this in mind, we studied the anisotropy on the micromechanical scale by subjecting the specimens to tensile loads along the different texture directions during in situ neutron diffraction experiments. In this context, the response of multiple lattice planes up to a tensile strain of 10% displayed differences in the load partitioning and the residual strain accumulation for the specimen with [011]/[111]-type texture. However, the relative behavior of the specimens possessing an [001]/[011]- and [001]-type texture remained qualitatively similar. The consequences on the metrology of residual stress determination methods are discussed.
The stress–strain behavior of certain ceramics, such as aluminum titanate (AT, Al2TiO5), has features that are unusual for brittle material. In particular, a substantial nonlinearity under uniaxial tension, and load–unload hysteresis caused by the increase of the incremental stiffness at the beginning of unloading. These features are observed experimentally and attributed to microcracking. In this study, we investigate the mechanical response of an AT material at room and high temperature. Microstructure and microcracking are analyzed by means of electron microscopy, and both synchrotron micro computed tomography (µCT) and refraction radiography (SXRR). Synchrotron refraction radiography is combined with in-situ heating at high-temperatures (up to 1400°C) to be able to monitor the relative closure of microcracks as a function of increasing/decreasing temperatures.
The stress–strain behavior of certain ceramics, such as aluminum titanate (AT, Al2TiO5), has features that are unusual for brittle material. In particular, a substantial nonlinearity under uniaxial tension, and load–unload hysteresis caused by the increase of the incremental stiffness at the beginning of unloading. These features are observed experimentally and attributed to microcracking. In this study, we investigate the mechanical response of an AT material at room and high temperature. Microstructure and microcracking are analyzed by means of electron microscopy, and both synchrotron micro computed tomography (µCT) and refraction radiography (SXRR). Synchrotron refraction radiography is combined with in-situ heating at high-temperatures (up to 1400°C) to be able to monitor the relative closure of microcracks as a function of increasing/decreasing temperatures.