TY - GEN A1 - Langenberg, K. J. A1 - Marklein, R. A1 - Mayer, K. A1 - Krylow, T. A1 - Ampha, P. A1 - Streicher, Doreen A1 - Krause, Martin ED - Pinto, I. M. T1 - Wavefield inversion in nondestructive testing T2 - Workshop/Minisymposium on "Electromagnetics in a Complex World: Challenges and Perspectives" CY - Benevento, Italy DA - 2003-02-20 PY - 2003 SN - 3-540-20235-8 SN - 0930-8989 N1 - Serientitel: Springer proceedings in physics – Series title: Springer proceedings in physics IS - 96 SP - 1 EP - 10(?) PB - Springer CY - Berlin AN - OPUS4-2357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mayer, K. A1 - Chinta, P.K. A1 - Langenberg, K.-J. A1 - Krause, Martin T1 - Ultrasonic imaging of defects in known anisotropic and inmomogeneous structures with fast synthetic aperture methodes N2 - Imaging methods like Synthetic Aperture Focusing Technique (SAFT) are based on the principle of propagation of the measured ultrasonic wave field back to field sources. In the case of a pulse-echo measurement, this back propagation under some approximating conditions leads to an image of the scattering object with well known properties and imperfections. The back propagation through the object which is under concern needs the knowledge of material properties in respect of the wave propagation. If these properties are known, we can use imaging algorithms like SAFT with all their advantages (computational speed and robustness) not only for isotropic but also for anisotropic material; moreover, the inverse ropagation concept allows crossing boundaries between materials, even if the materials are anisotropic. Examples of this concept are given with modelled and measured data for tendon duct imaging in concrete structures, for 3D imaging of air cavities in wood specimens and for imaging of defects in anisotropic welds. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - SAFT KW - Pulse echo technique KW - Back propagation KW - Inverse scattering KW - Imaging PY - 2012 SN - 978-0-620-52872-6 SP - 1 EP - 20 AN - OPUS4-35101 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Amano, K. O. A. A1 - Hahn, S.-K. A1 - Butt, N. A1 - Vorwerk, P. A1 - Gimadieva, E. A1 - Tschirschwitz, Rico A1 - Rappsilber, Tim A1 - Krause, U. T1 - Composition and Explosibility of Gas Emissions from Lithium-Ion Batteries Undergoing Thermal Runaway N2 - Lithium-based batteries have the potential to undergo thermal runaway (TR), during which mixtures of gases are released. The purpose of this study was to assess the explosibility of the gaseous emission from LIBs of an NMC-based cathode during thermal runaway. In the current project, a series of pouch lithium-based battery cells was exposed to abuse conditions (thermal) to study the total amount of gases released and the composition of the gas mixture. First, the battery cells were placed in a closed vessel, and the pressure and temperature rise inside the vessel were measured. In a second step, the composition of gases was analysed using a Fourier transform Infrared (FTIR) spectrometer. We found that the amount of released gases was up to 102 ± 4 L, with a clear dependence on the battery capacity. This study showed that the concentration of gaseous emissions such as carbon monoxide (CO), methane (CH4), ethylene (C2H4), ethane (C2H6), and hydrogen cyanide (HCN) increased with higher cell capacity. Of the five studied flammable gases, the maximum concentrations of carbon monoxide (16.85 vol%), methane (7.6 vol%), and ethylene (7.86 vol%) were identified to be within their explosible range. Applying Le Chatelier’s law, a calculated lower explosion limit (LEL) of 7% in volume fraction was obtained for the gas mixture. The upper explosion limit (UEL) of the gas mixture was also found to be 31% in volume. A filter comprising pyrobubbles was used for the removal of the studied gas components released during the thermal abuse. The investigation revealed that the pyrobubbles filter was highly effect in the removal of HCN (up to 94% removal) and CO2 (up to 100% removal). Herein, we report the dependency of the method of thermal runaway trigger on the measured maximum temperature. KW - Lithium-ion battery KW - Thermal runaway KW - Smoke gas emission KW - Gas explosion KW - Explosion limit PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-576477 DO - https://doi.org/10.3390/batteries9060300 VL - 9 IS - 6 SP - 1 EP - 19 PB - MDPI CY - Basel, Switzerland AN - OPUS4-57647 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Krause, Martin A1 - Mayer, K. A1 - Ballier, G. A1 - Borchardt, Kerstin A1 - Chinta, P.K. A1 - Effner, Ute A1 - Milmann, Boris A1 - Müller, Sabine A1 - Nowak, Thomas Rudolf T1 - Hochgenaue Strukturerkennung von Holzbauteilen mit 3D-Ultraschall N2 - Inhalt ist die zerstörungsfreie Detailuntersuchung von Holzbauteilen mit einem dreidimensional abbildenden Ultraschall-Echoverfahren. Das neu entwickelte 3D-Verfahren berücksichtigt den anisotropen Aufbau des Holzes. Die Bildschnitte und Projektionen werden aus flächigen Ultraschallaufnahmen berechnet. Die Messungen erfolgen an Probekörpern sowie an Bauteilen aus der Praxis. In dem Forschungsvorhaben wird die für Holz neue 3D-Rekonstruktionsrechnung verwendet und mit dem Ziel weiterentwickelt, unter Berücksichtigung der anisotropen Struktur des Holzes eine dreidimensional aufgelöste Abbildung von Reflektoren im Inneren der Holzbauteile zu ermöglichen. Damit werden die bisher für Holzbauteile zur Verfügung stehenden Verfahren entscheidend ergänzt, weil nun eine hochgenaue dreidimensionale Abbildung erreichbar ist (Auflösung: 20 mm und besser). KW - Ultraschallecho-Verfahren KW - Holzbauteile KW - Abbildungsverfahren KW - Imaging PY - 2014 UR - https://www.irb.fraunhofer.de/bauforschung/baufolit/projekt/Hochgenaue-Strukturerkennung-von-Holzbauteilen-mit-3D-Ultraschall/20138035979 SN - 978-3-8167-9212-3 VL - 109 SP - 1 EP - 101 PB - Fraunhofer IRB Verl. CY - Stuttgart AN - OPUS4-32852 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chinta, P.K. A1 - Mayer, K. A1 - Krause, Martin T1 - Ultraschallmodellierung und SAFT-Rekonstruktion von Fehlstellen in Holzbauteilen T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Deutschland DA - 2010-05-10 KW - Ultraschallecho KW - Holz KW - SAFT PY - 2010 SN - 978-3-940283-26-9 IS - DGZfP-BB 122 (Poster 59) SP - 1 EP - 8 CY - Berlin AN - OPUS4-22899 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Martin A1 - Milmann, Boris A1 - Mielentz, Frank A1 - Streicher, Doreen A1 - Redmer, Bernhard A1 - Mayer, K. A1 - Langenberg, K.-J. A1 - Schickert, M. T1 - Ultrasonic Imaging Methods for Investigation of Post-tensioned Concrete Structures: A Study of Interfaces at Artificial Grouting Faults and Its Verification N2 - This paper presents the progress of successful location of grouting faults in tendon ducts with ultrasonic imaging. The examples were obtained in the research group FOR 384 funded by DFG (German Research Foundation). The co-operation of experimental research and modeling allowed imaging and identification of grouted and ungrouted areas of tendon ducts (including strands) in a large test specimen (40 m²). In addition to the criteria for indicating grouting faults in post-tensioned ducts known until now the phase evaluation of reflected ultrasonic pulses is described. Experiments and modeling of wave propagation are presented for reflections at metal plates in concrete (thickness range 0.5 mm to 40 mm) and for tendon ducts including strands. The main part of the progress was achieved by automated measurements using dry contact transducers, 3D-SAFT reconstruction including phase evaluation and modeling considering wave propagation for typical elastic parameters and exact experimental site conditions. The results for shear waves as well as for pressure waves are compared in the frequency range from 50 kHz to 120 kHz. KW - Non-destructive testing KW - Tendons KW - Prestressed concrete bridges KW - Ultrasonic echo KW - Reconstruction calculation KW - 3D-SAFT KW - Modeling (EFIT) PY - 2008 DO - https://doi.org/10.1007/s10921-008-0033-5 SN - 0195-9298 SN - 1573-4862 VL - 27 IS - 1-3 SP - 67 EP - 82 PB - Plenum Press CY - New York, NY AN - OPUS4-17922 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mayer, K. A1 - Langenberg, K.-J. A1 - Krause, Martin A1 - Milmann, Boris A1 - Mielentz, Frank T1 - Characterization of reflector types by phase-sensitive ultrasonic data processing and imaging N2 - Ultrasonic and radar imaging techniques are limited in resolution by the wavelength in the material, yet information beyond those limits is hidden in complex frequency dependent reflection coefficients. The analysis of the phase of complex reflection coefficients together with the properties of imaging algorithms can help to characterize and to classify indications of defects in concrete buildings. This paper describes a method to extract phase information from measurements and SAFT reconstructed images. The influencing factors like material properties, transducer characteristics, and imaging algorithms based on Born or Physical Optics approximations are elaborated. Simulated and experimental results are briefly discussed. KW - NDT KW - Imaging KW - Flaw characterization KW - Tendon ducts KW - Phase analysis KW - Ultrasonic echo KW - SAFT KW - FT-SAFT KW - EFIT-modeling KW - Modellierung KW - EFIT KW - Spannbeton KW - Ultraschallecho KW - Spannkanäle KW - Verpressfehler KW - Zerstörungsfreie Prüfung im Bauwesen KW - ZfP-Bau PY - 2008 DO - https://doi.org/10.1007/s10921-008-0035-3 SN - 0195-9298 SN - 1573-4862 VL - 27 IS - 1-3 SP - 35 EP - 45 PB - Plenum Press CY - New York, NY AN - OPUS4-17926 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mayer, K. A1 - Langenberg, K.-J. A1 - Krause, Martin A1 - Maierhofer, Christiane A1 - Milmann, Boris A1 - Kohl, Christoph T1 - Characterization of ultrasonic and radar reflector types in concrete by phase evaluation of the signal and the reconstructed image T2 - 9th European Conference on NDT CY - Berlin, Germany DA - 2006-09-25 KW - NDT-CE KW - Ultrasonic echo KW - Radar KW - Phase evaluation KW - Modeling of wave propagation KW - Reconstruction calculation PY - 2006 SN - 3-931381-86-2 SP - 1 EP - 8(?) PB - European Federation for Non-Destructive Testing CY - Berlin AN - OPUS4-14225 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Martin A1 - Mayer, K. A1 - Chinta, P.K. A1 - Effner, Ute T1 - Ultrasonic imaging of defects in building elements made from timber N2 - There is a great demand for non-destructive testing methods for quality assurance and to assess the safety and durability of wooden structures. Ultrasonic echo technique with shear waves in the frequency range of 50 kHz is one of those promising methods and is already frequently applied for usual and glued laminated timber. The article describes the development and first results for an imaging method for this purpose. The highly anisotropic properties of the ultrasonic velocity have to be considered. A 3D-SAFT (Synthetic Aperture Focusing Technique) imaging scheme is developed initially for synthetic data resulting from modelling the elastic wave propagation. The main part of the paper describes the experimental validation of this evaluation technique by experimental studies applying automated ultrasonic scanning techniques. 3D ultrasonic imaging results are described for test specimens made from pine and spruce wood. Another object of investigation was a pedestrian bridge made from siberian larch. KW - Ultrasonic echo KW - Imaging KW - SAFT reconstruction calculation KW - Anisotropic wave propagation KW - EFIT modelling KW - Glued-laminated timber (glulam) PY - 2013 DO - https://doi.org/10.4028/www.scientific.net/AMR.778.312 SN - 1022-6680 SN - 1662-8985 VL - 778 SP - 312 EP - 320 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-29088 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ballier, G. A1 - Mayer, K. A1 - Langenberg, K.-J. A1 - Schulze, Sebastian A1 - Krause, Martin T1 - Improvement on tendon duct examination by modelling and imaging with synthetic aperture and one-way inverse methods N2 - The knowledge of the internal structure of tendon ducts is one of the important preconditions to make predictions about the stableness and the lifetime of concrete buildings – specifically concrete bridges. Ultrasonic NDT methods can be used to have a look inside those components. To understand the complex effects resulting from elastic wave propagation, it is important to build test specimens and to analyze the measurements with the aid of modelling. At BAM (German Federal Institute for Materials Research and Testing) a new specimen is under construction to realize some of the most common geometrical structures which can be expected in the field of tendon duct testing in concrete bridges. We present various measurement concepts and a comparison between measurement and modelling with EFIT (Elastic Finite Integration Technique), as well as results of imaging methods based on conventional SAFT (Synthetic Aperture Focusing Technique) or FT-SAFT (SAFT with Fourier Techniques) together with phase evaluation. In addition we will present the results of time reversal using AFIT (Acoustic Finite Integration Technique) and a one-way wave propagation method to improve the imaging. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - SAFT KW - Ultrasonic NDT KW - Concrete KW - One way KW - AFIT KW - Time reversal PY - 2012 SN - 978-0-620-52872-6 SP - 1 EP - 8 AN - OPUS4-35102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -