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 - Kroggel, O. A1 - Krause, Martin A1 - Schickert, M. A1 - Langenberg, K.-J. T1 - Moderne Verfahren der Bauwerksdiagnose, Entwicklung und Anwendung - Die DFG-Forschergruppe FOR384 stellt ihre Ergebnisse vor - Ultraschall T2 - Fachtagung 2005 des Deutschen Ausschusses für Stahlbeton in Zusammenarbeit mit der Bundesanstalt für Materialforschung und -prüfung "Zerstörungsfreie Prüfverfahren und Bauwerksdiagnose im Betonbau" CY - Berlin, Deutschland DA - 2005-03-10 KW - Ultraschallecho-Verfahren KW - Beton KW - Fundamente KW - Erhärtungsverhalten KW - Tomographie PY - 2005 SP - A5 EP - A10 PB - BAM CY - Berlin AN - OPUS4-11718 LA - deu 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 - 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 - 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 - CONF A1 - Langenberg, K.J. T1 - Wavefield Inversion in Nondestructive Testing T2 - Workshop "Electromagnetics in a Complex World", University of Sannio CY - Benevento, Italy DA - 2003-02-20 PY - 2003 AN - OPUS4-3832 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -