TY - THES A1 - Fritsch, Tobias T1 - A Multiscale Analysis of Additively Manufactured Lattice Structures N2 - Additive Manufacturing (AM) in terms of laser powder-bed fusion (L-PBF) offers new prospects regarding the design of parts and enables therefore the production of lattice structures. These lattice structures shall be implemented in various industrial applications (e.g. gas turbines) for reasons of material savings or cooling channels. However, internal defects, residual stress, and structural deviations from the nominal geometry are unavoidable. In this work, the structural integrity of lattice structures manufactured by means of L-PBF was non-destructively investigated on a multiscale approach. A workflow for quantitative 3D powder analysis in terms of particle size, particle shape, particle porosity, inter-particle distance and packing density was established. Synchrotron computed tomography (CT) was used to correlate the packing density with the particle size and particle shape. It was also observed that at least about 50% of the powder porosity was released during production of the struts. Struts are the component of lattice structures and were investigated by means of laboratory CT. The focus was on the influence of the build angle on part porosity and surface quality. The surface topography analysis was advanced by the quantitative characterisation of re-entrant surface features. This characterisation was compared with conventional surface parameters showing their complementary information, but also the need for AM specific surface parameters. The mechanical behaviour of the lattice structure was investigated with in-situ CT under compression and successive digital volume correlation (DVC). The Deformation was found to be knot-dominated, and therefore the lattice folds unit cell layer wise. The residual stress was determined experimentally for the first time in such lattice structures. Neutron diffraction was used for the non-destructive 3D stress investigation. The principal stress directions and values were determined in dependence of the number of measured directions. While a significant uni-axial stress state was found in the strut, a more hydrostatic stress state was found in the knot. In both cases, strut and knot, seven directions were at least needed to find reliable principal stress directions. KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Surface roughness analysis KW - Computed tomography PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-470418 SP - 1 EP - 97 PB - Universitätsbibliothek Potsdam CY - Potsdam AN - OPUS4-53476 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kowarik, Stefan A1 - Pithan, L. T1 - kowarik-labs/AI-reflectivity: v0.1 N2 - AI-reflectivity is a code based on artificial neural networks trained with simulated reflectivity data that quickly predicts film parameters from experimental X-ray reflectivity curves. This project has a common root with (ML-reflectivity)[https://github.com/schreiber-lab/ML-reflectivity] and evolved in parallel. Both are linked to the following publication: Fast Fitting of Reflectivity Data of Growing Thin Films Using Neural Networks A. Greco, V. Starostin, C. Karapanagiotis, A. Hinderhofer, A. Gerlach, L. Pithan, S. Liehr, F. Schreiber, S. Kowarik (2019). J. Appl. Cryst. For an online live demonstration using a pre-trained network have a look at github. KW - Artificial neural networks KW - X-ray reflectivity PY - 2019 U6 - https://doi.org/10.5281/zenodo.3477583 PB - Zenodo CY - Geneva AN - OPUS4-51888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gottlieb, Cassian A1 - Günther, Tobias A1 - Wilsch, Gerd A1 - Bohling, Christian T1 - Chemometrics for the analysis of cement-based materials N2 - The analysis of the chemical composition of cement-based materials like concrete is a crucial task in civil engineering. Concrete is a multi-phase material made of cement, water, aggregates, additives and admixtures. During the damage assessment of concrete structures, the external ingress of harmful species like chlorine, alkalis or sulfates needs to be determined. In order to provide a fast and precise analysis of concrete the application of LIBS offers unique possibilities as the technique can detect all elements at air atmosphere. To determine the condition of concrete, the information about the chemical composition, the ingress of harmful species as well as the evaluation of characteristic values like the used cement type or the type of aggregates are needed. This work presents the two-dimensional evaluation of concrete samples using LIBS and multivariate data analysis of atomic and molecular emission. For the evaluation of the main components different classification methods will be applied to identify the heterogeneity of the samples. With respect to their specific phase, different species will be quantified using multivariate regression (PLS) and important figures of merit will be presented. All results will be verified using Standard procedure of wet chemistry (XRF, potentiometric titration and ICP-OES). T2 - 10th Euro-Mediterranean Symposium CY - Brno, Czech Republic DA - 08.09.2019 KW - Heterogeneous material KW - Chemometics KW - Cement KW - Concrete PY - 2019 AN - OPUS4-51838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd A1 - Günther, Tobias A1 - Völker, Tobias T1 - Mobile LIBS system for evaluation of concrete structures on site N2 - Features and application of a mobile LIBS system for evaluation of concrete structures on-site. T2 - EMSLIBS 2019 CY - Brno, Czech Republic DA - 08.09.2019 KW - On-site KW - LIBS KW - Concrete KW - Mapping KW - Evaluation PY - 2019 AN - OPUS4-51711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd A1 - Günther, Tobias A1 - Völker, Tobias T1 - LIBS for the analysis of concrete N2 - Special features and examples of using LIBS on concrete. T2 - Workshop on tandem LIBS/LA-ICP-MS CY - Berlin, Germany DA - 18.11.2019 KW - Mobile system KW - LIBS KW - Concrete KW - Damage KW - Chloride KW - Sulphate KW - Mapping PY - 2019 AN - OPUS4-51710 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd A1 - Günther, Tobias A1 - Millar, Steven A1 - Völker, Tobias T1 - Mobile LIBS-System for condition assesment of concrete structures on-site N2 - Application of a mobile LIBS system for on-site investigation of chemical composition of concrete. T2 - SMAR 2019 CY - Potsdam, Germany DA - 27.08.2019 KW - Mobile system KW - LIBS KW - Concrete KW - Damage KW - Chloride KW - Sulphate KW - Mapping PY - 2019 AN - OPUS4-51706 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd A1 - Günther, Tobias A1 - Völker, Tobias T1 - Fast quantitave chemical analysis of concrete using LIBS N2 - Overview of application of LIBS for the fast and automated quantitative chemical analysis of concrete. T2 - NDT-E Workshop CY - Berlin, Germany DA - 12.06.2019 KW - Sulphate KW - LIBS KW - Concrete KW - Damage KW - Chloride KW - Mapping PY - 2019 AN - OPUS4-51704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd A1 - Gottlieb, Cassian A1 - Günther, Tobias A1 - Millar, Steven A1 - Völker, Tobias T1 - Laser-Induced Breakdown Spectroscopy (LIBS) Automated 2D chemical analysis of chloride content in concrete structures N2 - The application of a LIBS system is presented. A diode-pumped low energy laser (3 mJ, 1.5 ns, 100 Hz) and a compact NIR spectrometer are used. A scanner allows the two-dimensional element mapping. For the quantitative analysis calibration of the system is carried out with reference samples in a concentration range of chlorine of 0.05 wt.% to 2.5 wt.%. To determine the 2D distribution of harmful elements (Cl, C), concrete cores were drilled, split and analyzed directly. By comparing the chloride ingress and the carbonation, the interaction of both processes can be visualized in one measurement that takes less than 10 minutes with a drill core of 50 mm x 100 mm. Results obtained were compared and verified with standard measurements. T2 - Concrete Solutions 2019 CY - Cluj Napoca, Romania DA - 30.09.2019 KW - Chloride KW - Beton KW - LIBS KW - Schädigung PY - 2019 AN - OPUS4-51703 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, G. A1 - Staude, Andreas A1 - Dunlop, J.A. T1 - Trilobite compound eyes with crystalline cones and rhabdoms show mandibulate affinities N2 - Most knowledge about the structure, function, and evolution of early compound eyes is based on investigations in trilobites. However, these studies dealt mainly with the cuticular lenses and little was known about internal anatomy. Only recently some data on crystalline cones and retinula cells were reported for a Cambrian trilobite species. Here, we describe internal eye structures of two other trilobite genera. The Ordovician Asaphus sp. reveals preserved crystalline cones situated underneath the cuticular lenses. The same is true for the Devonian species Archegonus (Waribole) warsteinensis, which in addition shows the fine structure of the rhabdom in the retinula cells. These results suggest that an apposition eye with a crystalline cone is ancestral for Trilobita. The overall similarity of trilobite eyes to those of myriapods, crustaceans, and hexapods corroborates views of a phylogenetic position of trilobites in the stem lineage of Mandibulata. KW - Trilobite compound eyes KW - Computed Tomography PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-510784 SN - 2041-1723 VL - 10 SP - 2503 PB - Nature AN - OPUS4-51078 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Oesch, Tyler A1 - Stenzel, Ludwig A1 - Weise, Frank T1 - Non-destructive Evaluation of the Contribution of Polymer-Fibre Orientation and Distribution Characteristics to Concrete Performance during Fire N2 - Although concrete itself is not a combustible material, concrete mixtures with high density, such has high-performance concretes (HPCs), are susceptible to significant damage during fires due to explosive spalling. Past research has shown that the inclusion ofpolymer fibres in high density concrete can significantly mitigate this fire damage. The exact mechanisms causing this increased spalling resistance are not yet fully understood, but it is thought that the fibres facilitate moisture transport during fire exposure, which in turn contributes to relief of internal stresses in the spalling-susceptible region. In this study, X-ray Computed Tomography (CT) was applied to observe the interaction between polymer fibres and cracking during thermal exposure. For this purpose, two concrete samples containing different polymer fibre types were subjected to incremental application of a defined thermal exposure. CT images were acquired before and after each thermal exposure and powerful image processing tools were used to segment the various material components. This enabled a detailed analysis of crack formation and propagation as well as the visualization and quantification of polymer fibre characteristics within the concrete. The results demonstrated that the orientation of both fibres and cracks in polymerfibre reinforced concrete tend to be anisotropic. The results also indicated that crack geometry characteristics may be correlated with fibre orientation, with cracks tending to run parallel to fibre beds. Clear quantitative relationships were also observed between heating and increasing cracking levels, expressed in terms of both crack surface area and crack volume. KW - Concrete KW - Fire resistance KW - Polymer fibre PY - 2019 SN - 978-3-030-00867-3 U6 - https://doi.org/10.1007/978-3-030-00868-0_4 VL - 95 SP - 51 EP - 73 PB - Springer Nature Switzerland AG CY - Zürich AN - OPUS4-51077 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -