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In civil engineering, the corrosion of steel reinforcements in structural elements of concrete bares a risk of
stability-reduction, mainly caused by the exposure to chlorides. 3D computed tomography (CT) reveals the inner
structure of concrete and allows one to investigate the corrosion with non-destructive testing methods. To carry
out such investigations, specimens with a large artificial crack and an embedded steel rebar have been
manufactured. 3D CT images of those specimens were acquired in the original state. Subsequently three cycles
of electrochemical pre-damaging together with CT imaging were applied. These time series have been evaluated
by means of image processing algorithms to segment and quantify the corrosion products. Visualization of the
results supports the understanding of how corrosion propagates into cracks and pores. Furthermore, pitting of
structural elements can be seen without dismantling. In this work, several image processing and visualization
techniques are presented that have turned out to be particularly effective for the visualization and segmentation
of corrosion products. Their combination to a workflow for corrosion analysis is the main contribution of this
work.
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.
Automated 3D Crack Detection for Analyzing Damage Processes in Concrete with Computed Tomography
(2012)
\\{\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.
This report presents a fast data assimilation method to produce an interpolating time and space temperature distribution for steel members subject to fire testing. The method assimilates collected temperature data into the numerical integration of the heat equation. This physically based method also allows the computation of lateral and axial heat flux into and inside the member.