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A great amount of material properties is strongly influenced by dislocations, the carriers of plastic deformation. It is therefore paramount to have appropriate tools to quantify dislocation substructures with regard to their features, e.g., dislocation density, Burgers vectors or line direction. While the transmission electron microscope (TEM) has been the most widely-used equipment implemented to investigate dislocations, it usually is limited to the two-dimensional (2D) observation of three-dimensional (3D) structures. We reconstruct, visualize and quantify 3D dislocation substructure models from only two TEM images (stereo pairs) and assess the results. The reconstruction is based on the manual interactive tracing of filiform objects on both images of the stereo pair. The reconstruction and quantification method are demonstrated on dark field (DF) scanning (S)TEM micrographs of dislocation substructures imaged under diffraction contrast conditions. For this purpose, thick regions (>300 nm) of TEM foils are analyzed, which are extracted from a Ni-base superalloy single crystal after high temperature creep deformation. It is shown how the method allows 3D quantification from stereo pairs in a wide range of tilt conditions, achieving line length and orientation uncertainties of 3% and 7°, respectively. Parameters that affect the quality of such reconstructions are discussed.
A great amount of material properties is strongly influenced by dislocations, the carriers of plastic deformation. It is therefore paramount to have appropriate tools to quantify dislocation substructures with regard to their features, e.g., dislocation density, Burgers vectors or line direction. While the transmission electron microscope (TEM) has been the most widely-used equipment implemented to investigate dislocations, it usually is limited to the two-dimensional (2D) observation of three-dimensional (3D) structures. We reconstruct, visualize and quantify 3D dislocation substructure models from only two TEM images (stereo-pairs) and assess the results. The reconstruction is based on the manual interactive tracing of filiform objects on both images of the stereo-pair. The reconstruction and quantification method are demonstrated on dark field (DF) scanning (S)TEM micrographs of dislocation substructures imaged under diffraction contrast conditions. For this purpose, thick regions (> 300 nm) of TEM foils are analyzed, which are extracted from a Ni-base superalloy single crystal after high temperature creep deformation. It is shown how the method allows 3D quantification from stereo-pairs in a wide range of tilt conditions, achieving line length and orientation uncertainties of 3 % and 7°, respectively. Parameters that affect the quality of such reconstructions are discussed.
Concrete plays a central role as the standard building material in civil engineering. Experimental characterization of the concrete
microstructure and a description of failure mechanisms are important to understand the concrete’s mechanical properties. Computed tomography is a powerful source of information as it yields 3d images of concrete specimens. However, complete visual
inspection is often infeasible due to very large image sizes. Hence, automatic methods for crack detection and segmentation are
needed. A region-growing algorithm and a 3d U-Net showed promising results in a previous study. Cracks in normal concrete
and high-performance concrete that were initiated via tensile tests were investigated. Here, the methods are validated on a more
diverse set of concrete types and crack characteristics. Adequate adaptions of the methods are necessary to deal with the complex
crack structures. The segmentation results are assessed qualitatively and compared to those of a template matching algorithm
which is well-established in industry.
Monocrystaline Ni-base superalloys are the material of choice for first row blades in jet engine gas turbines. Using a novel visualization tool for 3D reconstruction and visualization of dislocation line segments from stereo-pairs of scanning transmission electron microscopies, the superdislocation substructures in Ni-base superalloy LEK 94 (crept to ε = 26%) are characterized. Probable scenarios are discussed, how these dislocation substructures form.
\\{\bf Zusammenfassung: }\noindent Die Steuerung von grafischen Ausgabegeräten erfordert oft mehr als ein oder zwei Optionen, wie man sie vom UNIX {\em lpr}-Kommando kennt. Hier bietet sich eine grafische Benutzungsschnittstelle zur übersichtlichen Einstellung aller möglichen Parameter und Optionen an. Wenn dieses Gerät zudem nur über eine besondere Treiber-Software zu bedienen ist und in einem heterogenen Intranet zur Verfügung gestellt werden soll, ist eine Steuerung mittels eines WWW-Servers naheliegend. Im Folgenden sollen Lösungsansätze diskutiert werden, die auf HTML/CGI- bzw. Java-Basis derartige Steuerung realisieren. {\small} It is often the case that graphical output devices need more than one or two control options like the UNIX {\em lpr}-command. A driver programme with a graphical user interface (GUI) can satisfy this requirement. If such a device shall be accessible in an heterogenous network a solution using a WWW-server can be used. Possible HTML/CGI resp. Java-based solutions are discussed in the following.