TY - JOUR A1 - Coniglio, Nicolas A1 - Cross, Carl Edward T1 - Characterization of solidification path for Aluminium 6060 weld metal with variable 4043 filler dilution JF - Welding in the world N2 - Aluminium alloy 6060 is typical of a family of Al-Mg-Si extrusion alloys, which are considered weldable only when using an appropriate filler alloy such as 4043 (Al-5Si) or 5356 (Al-5Mg). This study concerns the thermal analysis and solidification path determination of aluminium alloy 6060 diluted with variable amounts of 4043. Casting of controlled mixtures of alloys 6060 and 4043 was used to simulate different weld dilutions in order to facilitate thermal analysis. Thermal analysis and metallography were applied in order to reveal solidification reactions and phases, and allow calculation of solid fraction versus temperature curves. Although the liquidus temperature was little affected, different phases formed with increased 4043 dilution, with a trend toward lower temperature reactions and a larger fraction interdendritic constituent. KW - Aluminium alloys KW - Light metals KW - Solidification cracking KW - Cracking KW - Defects KW - Hot cracking KW - Analysis techniques KW - Cooling KW - Cooling rate KW - Temperature KW - Practical investigations KW - Microstructure KW - Dilution KW - Reference lists PY - 2006 UR - http://www.iiw-iis.org/ SN - 0043-2288 SN - 1878-6669 VL - 50 IS - 11/12 SP - 14 EP - 23 PB - Springer CY - Oxford AN - OPUS4-14219 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cotic, Patricia A1 - Jaglicic, Z. A1 - Niederleithinger, Ernst A1 - Stoppel, Markus A1 - Bosiljkov, V. T1 - Image fusion for improved detection of near-surface defects in NDT-CE using unsupervised clustering methods JF - Journal of nondestructive evaluation N2 - The capabilities of non-destructive testing (NDT) methods for defect detection in civil engineering are characterized by their different penetration depth, resolution and sensitivity to material properties. Therefore, in many cases multi-sensor NDT has to be performed, producing large data sets that require an efficient data evaluation framework. In this work an image fusion methodology is proposed based on unsupervised clustering methods. Their performance is evaluated on ground penetrating radar and infrared thermography data from laboratory concrete specimens with different simulated near-surface defects. It is shown that clustering could effectively partition the data for further feature level-based data fusion by improving the detectability of defects simulating delamination, voids and localized water. A comparison with supervised symbol level fusion shows that clustering-based fusion outperforms this, especially in situations with very limited knowledge about the material properties and depths of the defects. Additionally, clustering is successfully applied in a case study where a multi-sensor NDT data set was automatically collected by a self-navigating mobile robot system. KW - Non-destructive testing KW - Concrete KW - Defect detection KW - Data fusion KW - Cluster analysis KW - Image fusion KW - Thermography KW - Radar KW - Ultrasonics KW - Defects PY - 2014 DO - https://doi.org/10.1007/s10921-014-0232-1 SN - 0195-9298 SN - 1573-4862 VL - 33 IS - 3 SP - 384 EP - 397 PB - Plenum Press CY - New York, NY AN - OPUS4-33831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cross, Carl Edward A1 - Böllinghaus, Thomas T1 - The Effect of Restraint on weld Solidification Cracking in Aluminium JF - Welding in the world KW - Aluminium alloys KW - Light metals KW - Solidification cracking KW - Cracking KW - Defects KW - Hot cracking KW - Crack initiation KW - Strain KW - Restraint PY - 2006 SN - 0043-2288 SN - 1878-6669 VL - 50 IS - 11/12 SP - 51 EP - 54 PB - Springer CY - Oxford AN - OPUS4-14220 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ermilova, Elena A1 - Weise, Matthias A1 - Hertwig, Andreas T1 - Application of imaging ellipsometry and white light interference microscopy for detection of defects in epitaxially grown 4H-SiC layers JF - Journal of the European Optical Society-Rapid Publications N2 - Critical defects, also known as device killers, in wide bandgap semiconductors significantly affect the performance of power electronic devices. We used the methods imaging ellipsometry (IE) and white light interference microscopy (WLIM) in a hybrid optical metrology study for fast and non-destructive detection, classification, and characterisation of defects in 4H–SiC homoepitaxial layers on 4H–SiC substrates. Ellipsometry measurement results are confirmed by WLIM. They can be successfully applied for wafer characterisation already during production of SiC epilayers and for subsequent industrial quality control. T2 - EOS Annual Meeting (EOSAM 2022) CY - Porto DA - 12.09.2022 KW - Imaging ellipsometry KW - White light interference microscopy KW - 4H–SiC KW - Defects PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574209 DO - https://doi.org/10.1051/jeos/2023018 SN - 1990-2573 VL - 19 IS - 1 SP - 1 EP - 8 PB - EDP Sciences AN - OPUS4-57420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaul, Holger A1 - Brauser, Stephan A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Methods to obtain weld discontinuities in spot-welded joints made of advanced high-strength steels JF - Welding in the world N2 - Resistance spot welding is the major joining technique in mass car production. This applies in particular to high-strength steel and advanced high-strength steel (AHSS) joining of thin sheet steel components for lightweight body shell structures. Joining of AHSS in mass production might lead to weld discontinuities under certain circumstances. Those discontinuities in form of cracks might be an initial start of cracking in the spot-welded joints regarding fatigue loads. It is of great interest to figure out, if, in comparison to specimens without weld discontinuities, the crack initiating point changes and if the fatigue resistance might be reduced by the discontinuities. In this contribution, an overview of potential discontinuities is given. Their possible causes are discussed and means for their detection are highlighted. Among the possible causes of weld discontinuities, two major groups are distinguished: the welding parameters as primary influences in the welding process, and the production-specific influences as secondary ones. With emphasis on major cracks penetrating the weld nugget, these influences are analysed. Finally, a combination of extreme welding parameters with production-specific influences is chosen in order to establish a method which enables the preparation of fatigue test specimens with reproducible major cracks in different locations of the spot-welded joints. This method is than applied in order to prepare spot weld specimens for fatigue tests. KW - Cracking KW - Defects KW - Fatigue loading KW - High strength steels KW - Resistance spot welding PY - 2011 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 11/12 SP - 99 EP - 106 PB - Springer CY - Oxford AN - OPUS4-25026 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Simone A1 - Schulze, Rolf-Dieter A1 - Brademann-Jock, Kerstin A1 - Swaraj, Sufal A1 - Friedrich, Jörg Florian T1 - Characterisation of plasma polymers by thermoluminescence JF - Surface and coatings technology N2 - Thin plasma polymer films were deposited using the pulsed plasma mode. These plasma polymers should possess a more regular structure than those produced by the conventional continuous-wave (cw) mode, because of lower monomer fragmentation caused by the plasma pulses and the chemical chain propagation during the plasmaless (free!) periods. The thermoluminescence method was applied to functional groups carrying plasma polymer layers which are used in medical technology. Examples are formation of biocompatible, biosensoric and bioactive coatings or in metal polymer composites such as adhesion-promoting interlayers. In addition to the use of the conventional X-ray Photoelectron Spectroscopy for thin film characterization, the new method of thermoluminescence was applied to characterize undesired defects and structural specifics produced in the polymer films by pp or cw plasma mode. The main areas of focus were oxygen-containing groups produced by post-plasma oxygen introduction via auto-oxidation, oxidation of implemented unsaturations and trapped radical sites known as typical irregular structures in plasma polymers. KW - Plasma polymers KW - Thermoluminescence KW - Structure KW - Defects KW - Pulsed plasma KW - Continuous-wave plasma PY - 2006 DO - https://doi.org/10.1016/j.surfcoat.2005.12.003 SN - 0257-8972 VL - 201 IS - 3-4 SP - 543 EP - 552 PB - Elsevier Science CY - Lausanne AN - OPUS4-12818 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, M. A1 - Diercks, P. A1 - Manzoni, Anna Maria A1 - Čížek, J. A1 - Ramamurty, U. A1 - Banhart, J. T1 - Positron annihilation investigation of thermal cycling induced martensitic transformation in NiTi shape memory alloy JF - Acta Materialia N2 - Thermal cycling of a Ni-excess NiTi alloy was conducted between 50 °C and liquid nitrogen temperature to induce martensitic transformations and to reverse them after. The starting point was an annealed and slowly cooled state, the end point a sample thermally cycled 1500 times. Positron annihilation lifetime spectra and Coincidence Doppler Broadening profiles were obtained in various states and at various tem- peratures. It was found that the initial state was low in defects with positron lifetimes close to that of bulk NiTi. Cycling lead to a continuous build-up of a defect structure up to 20 0 −50 0 cycles after which saturation was reached. Two types of defects created during cycling were identified, namely pure dislo- cations and vacancies attached to dislocations. KW - Shape memory alloy KW - Thermal Cycling KW - Defects KW - Positron annihilation spectroscopy KW - Austenite-to-martensite phase transformation PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-533641 DO - https://doi.org/10.1016/j.actamat.2021.117298 VL - 220 SP - 117298 PB - Elsevier Ltd. AN - OPUS4-53364 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nellesen, J. A1 - Laquai, René A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hentschel, M. P. A1 - Anar, N. B. A1 - Soppa, E. A1 - Tillmann, W. A1 - Bruno, Giovanni T1 - In situ analysis of damage evolution in an Al/Al2O3 MMC under tensile load by synchrotron X-ray refraction imaging JF - Journal of Materials Science N2 - The in situ analysis of the damage evolution in a metal Matrix composite (MMC) using synchrotron X-ray refraction radiography (SXRR) is presented. The investigated material is an Al alloy (6061)/10 vol% Al2O3 MMC after T6 heat treatment. In an interrupted tensile test the gauge section of dog bone-shaped specimens is imaged in different states of tensile loading. On the basis of the SXRR images, the relative change of the specific surface (proportional to the amount of damage) in the course of tensile loading was analyzed. It could be shown that the damage can be detected by SXRR already at a stage of tensile loading, in which no Observation of damage is possible with radiographic absorption-based imaging methods. Moreover, the quantitative analysis of the SXRR images reveals that the amount of damage increases homogeneously by an average of 25% with respect to the Initial state. To corroborate the experimental findings, the damage distribution was imaged in 3D after the final tensile loading by synchrotron X-ray refraction computed tomography (SXRCT) and absorption-based synchrotron X-ray computed tomography (SXCT). It could be evidenced that defects and damages cause pronounced indications in the SXRCT images. KW - Composite materials KW - Defects KW - Micro analysis PY - 2018 DO - https://doi.org/10.1007/s10853-017-1957-x SN - 0022-2461 SN - 1573-4803 VL - 53 IS - 8 SP - 6021 EP - 6032 PB - Springer US AN - OPUS4-44241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rabe, Torsten A1 - Mücke, Udo A1 - Rudert, Rainer A1 - Uematsu, K. T1 - Characterization of defects in dry-pressed green bodies JF - Key engineering materials T2 - 7th Euro Ceramics - Conference and Exhibition of the European Ceramic Society (ECerS) CY - Brugge, Belgium DA - 2001-09-09 KW - Green body characterization KW - Dry pressing KW - Defects KW - Microstructure KW - Computer tomography PY - 2002 UR - http://www.scientific.net/1013-9826/authors/27601 SN - 1013-9826 VL - 206-213 SP - 649 EP - 652 PB - Trans Tech Publ. CY - Aedermannsdorf AN - OPUS4-1024 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Regina A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc T1 - Numerical method of active thermography for the reconstruction of back wall geometry JF - NDT & E international N2 - The paper presents a numerical method to detect and characterise defects and inhomogeneities by means of active thermography. The objective was to determine the wall thickness of structure elements with an inaccessible back wall, e.g., elements of pipes or containers. As test specimens we used PVC samples with the thickness of about 2 cm that had spatial variations in the back wall geometry. Flash lamps provided the heating. To measure the thickness of the wall, we employed the Levenberg–Marquardt method, which we applied here to experimental thermographic data for non-destructive testing. We started the inversion procedure by making a rough first estimation of the back wall geometry following the echo defect shape method, and then we calculated the thickness of the back wall. We found reasonable reconstruction results which differed from the real value significantly below 1 mm at the defect centre, whereas the error wais increased at the edge of the defect, depending on its shape and depth. KW - Pulse thermography KW - Wall thickness KW - Inverse problems KW - Reconstruction KW - Defects KW - Rekonstruktion KW - Inverse Probleme KW - Defekte PY - 2013 DO - https://doi.org/10.1016/j.ndteint.2012.10.010 SN - 0963-8695 VL - 54 SP - 189 EP - 197 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-28895 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -