TY - CONF A1 - Niederleithinger, Ernst A1 - Effner, Ute A1 - Behrens, Matthias A1 - Smith, Sean A1 - Büttner, C. A1 - Friedrich, C. A1 - Mauke, R. T1 - Application of ultrasonic techniques for quality assurance of salt concrete engineered barriers: Shape, cracks and delamination N2 - The closure of underground nuclear waste disposal facilities requires reliable gas- and watertight engineered barriers. In Germany, barriers made from salt concrete have been evaluated in full scale. While the barriers seem to fulfill the requirements regarding permeability, some unexpected cracks have been detected at the surface and at depth. In cooperation between the Federal Company for Radioactive Waste Disposal (BGE) and the Federal Institute for Materials Research and Testing (BAM), several experiments have been carried out to evaluate the applicability for ultrasonic measurements in crack detection and general quality assurance. Both commercial instruments and specially developed devices have been tested on site. Using commercial ultrasonic echo devices designed for concrete inspection it was possible to detect cracks and object in salt concrete up to a depth of 2 m. The check for delamination in shotcrete is another field of application. A unique device available at BAM, the wide aperture, deep penetration instrument LAUS, was able to locate cracks and objects up to a depth of 8 m so far, which is thought to be a record for ultrasonic echo measurements in concrete. Adapted imaging procedures, partly adopted from geophysics, helped to reveal 3D structure at depth. In addition, we have developed ultrasonic probes to be deployed in boreholes, currently at up to 20 m depth. They can collect information on cracks and other features in a radius of about 1.5 m around the borehole in the current version and might be used in echo or transmission mode. Evaluation experiments have been performed at an experimental barrier at the ERAM site in Morsleben, Germany. The results showed several empty and injected cracks as well as built in instrumentation. The results have been verified using borehole endoscopy as well as core examination and will be used to set up a reliable quality assurance system for engineered barriers. All instruments are based on ultrasonic shear wave transducers with a frequency range between 25 kHz and 100 kHz. Current research focuses on the improvement of the hardware (e. g. optimization of array characteristics) and imaging techniques as Reverse Time Migration, both aiming at the improvement of depth of penetration, resolution and probability of detection. T2 - Modern 2020, 2nd International Conference about Monitoring in Geological Disposal of Radioactive Wast CY - Paris, France DA - 09.04.2019 KW - REverse Time Migration (RTM) KW - Engineered Barrier System (EBS) KW - Non-Destructive Testing KW - Ultrasonic Echo KW - Large Aperture Ultrasonic System (LAUS) KW - Synthetic Aperture Focusing Technique (SAFT) PY - 2019 AN - OPUS4-48974 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Kotschate, Daniel A1 - Bente, Klaas T1 - Advances in air-coupled ultrasonic transducers for non-destructive testing N2 - Conventional ultrasonic testing involves the application of a fluid couplant for impedance matching. Increasing use of lightweight structures, composite materials and adhesive joints mostly in aerospace and automotive industry created an increasing interest in air-coupled ultrasonic testing methods, to protect sensitive surfaces and simplify maintenance. Commercially available air-coupled transducers consist of a piezocomposite material and matching layers to reduce the impedance mismatch between the transducer and air. This contribution is an overview of innovative approaches using new piezoelectric materials and other physical principles to transmit and receive an ultrasonic pulse in air. Capacitive and piezoelectric micromachined ultrasonic transducers (CMUTs and PMUTs) produce high pressure levels, but they exhibit a very narrow bandwidth. Optical laser-based methods for transmitting and receiving ultrasound promise a higher bandwidth, but do not achieve the same sensitivity as conventional air-coupled transducers. Ferroelectrets are charged cellular polymers exhibiting piezoelectric properties, having a very small acoustic impedance well matched to air. Ferroelectret transducers achieve about the same bandwidth as the most broadband conventional air-coupled transducers, having a higher sensitivity. Thermoacoustic transducers use heat to initiate an acoustic wave, acting as transmitters in ultrasonic range. Thermoacoustic transducers enable excitation of extremely broadband pulses while producing high pressure levels, which opens new possibilities for advanced signal processing. The newest member of the family of air-coupled ultrasonic transmitters is the plasma-based transducer, using both the thermoacoustic effect and the movements of the ions (so called ionic wind) to create acoustic waves. T2 - International Congress on Ultrasonics CY - Bruges, Belgium DA - 03.09.2019 KW - Air-coupled transducers KW - Non-destructive testing KW - Ferroelectret KW - Thermoacoustics KW - Plasma acoustics PY - 2019 AN - OPUS4-48963 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pohl, Rainer A1 - Casperson, Ralf A1 - Ehlers, Henrik A1 - Pelkner, Matthias T1 - Eindraht und GMR versus Spulen - Gegenüberstellung verschiedener Wirbelstromsensoren N2 - An der BAM gibt es seit vielen Jahren Erfahrungen in der Entwicklung und im Bau speziell angepasster Wirbelstromsonden. Mit der Zielstellung, eine möglichst hohe Ortsauflösung zu erreichen, wurde vor einigen Jahren die sogenannte Eindrahtsonde (Patentanmeldung Nr. WO2015177341A1) entwickelt. Diese besteht aus der Kombination eines einzelnen dünnen Drahtes als Sender und GMR-Sensoren (giant magneto-resistance, Riesenmagnetwiderstand) als Empfänger. Beim Aufbau solcher Wirbelstromsonden hat sich der Einsatz sogenannter Starr-Flex-Leiterplatten bewährt. Der Aufbau und die Funktionsweise der Sensoren werden erläutert. Anhand spezieller Muster kleiner Vergleichsfehler werden Ortsauflösung, Richtungsabhängigkeit, Tiefenwirkung und Randeffekt hochauflösender Wirbelstromsonden aus Spulensystemen mit der Eindrahtsonde gegenübergestellt. T2 - Wirbelstromprüfung, Aktuelle Anwendungen und Entwicklungen, 1. Fachseminar der DGZfP CY - Celle, Germany DA - 10.09.2019 KW - GMR-Sensoren KW - Wirbelstromprüfung KW - Wirbelstromsenoren PY - 2019 AN - OPUS4-48949 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Ertel, Jens-Peter T1 - PileInspect N2 - The EC funded project PileInspect (2013-2016) has tried to improve the traditional low strain pile integrity test by using a shaker instead of a hamm and sophisticated higher order spectra analysis methods to provide automated, reliable interpretation. However, the results, even if promising, have not seen full validation yet. A second module, providing depth information by regularized deconvolution, was developed and tested successfully, but doesn't deliver additional information compared tomteh traditioanl test. T2 - DFI Seminar Pile Integrity Testing CY - Bruxelles, Belgium DA - 12.09.2019 KW - Pile integrity testing KW - Shaker KW - Higher order spectra KW - Deconvolution PY - 2019 AN - OPUS4-48948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buljak, V. A1 - Bruno, Giovanni T1 - Modeling of elastic modulus evolution in porous ceramics due to thermally induced cracking N2 - Within polycrystalline porous ceramics used in automotive applications as diesel particulate filters, it is evidenced that during cooling from firing temperature micro cracks are gradually formed. The cracks are formed as a consequence of strong thermal anisotropy of grains. Typically these micro cracks are granting better thermal shock resistance, with respect to dense materials, but reduce stiffness. The reduction can be quantified by measuring the drop in elastic properties of bulk material which, depending on the level of porosity, can decrease even by 50% with respect to its value at high temperature. It is further observed that upon subsequent heating these cracks are closing and partially or totally healing at very high temperatures. Such peculiar behavior results in partial or complete recovery of the elastic properties of bulk material upon completing one thermal cycle. Despite its evident practical application, still there is no constitutive description of this phenomenon, capable of predicting the evolution of Young's modulus as a function of temperature history. For reliable numerical simulation of this phenomenon, it is required to model fracture. To model inter-crystalline fracture, an effective strategy is to use cohesive elements, since crack patterns are a priori known. Major limitation of this approach is that the cohesive elements already implemented within commercial codes cannot take into account crack healing upon subsequent heating. In this study new cohesive element is developed and numerically implemented within ABAQUS commercial finite element code, capable to model crack opening, closing and healing. Further on, a computer code is generated to build numerical model of porous ceramic specimens that takes into account experimentally measured crystallographic orientation and porosity, and models the microstructure by using Voronoi polygons. The developed numerical tools serve as a framework for more realistic simulations, required to study the hysteresis in elastic properties within porous ceramics provoked by thermal cyclic. In a subsequent phase, an inverse analysis procedure is developed, in which macroscopic properties are used to calibrate parameters entering into micro crack model. The approach is centered on a minimization of a discrepancy function designed to quantify the difference between experimentally measured quantities and their computed counterpart. The model is calibrated on the basis of experimental data regarding the drop of bulk Young's modulus with decrease of temperature. Developed procedure is tested with porous cordierite sample, and obtained results are quit promising despite the current limitation of using only two-dimensional model. T2 - European Ceramic Society Conference 2019 CY - Turin, Italy DA - 16.06.2019 KW - Microcracking KW - Cordierite KW - Inverse Problems KW - Finite elements KW - Cohesive Elements KW - Young's modulus PY - 2019 AN - OPUS4-48926 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lugovtsova, Yevgeniya A1 - Johannesmann, S. A1 - Henning, B. A1 - Prager, Jens T1 - Analysis of Lamb wave mode repulsion and its implications to the characterisation of adhesive bonding strength N2 - Lamb waves are widely used for non-destructive evaluation of material parameters as well as for detection of defects. Another application of Lamb waves is quality control of adhesive joints. Researchers are currently investigating shear horizontal and zero-group velocity modes for characterisation of the adhesive bonding strength. In a new approach, Lamb wave mode repulsion is used to obtain the coupling strength between different layers to characterise the adhesive bonding strength. The modes of the individual layers become coupled in the multilayered systems forming particular regions, the so-called mode repulsion regions. This study investigates these modes and their interaction in two-layered plate-like structures with varying coupling strength both numerically, with the Scaled Boundary FEM, and experimentally. T2 - International Congress on Ultrasonics CY - Bruges, Belgium DA - 03.09.2019 KW - Lamb waves KW - Multi-layered system KW - Adhesive joint KW - Mechanical strength KW - Scaled Boundary FEM PY - 2019 AN - OPUS4-48910 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Serrano Munoz, Itziar A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Nadammal, Naresh A1 - Bruno, Giovanni T1 - Influence of scanning strategies on the development of residual stresses in a LPBF IN718 alloy N2 - This presentation is a brief summary on the activites that 8.5 division has been carrying out on the measurements of residual stresses of a Laser Power Bed Fusion IN718 alloy. T2 - Euromat 2019 CY - Stockholm, Sweden DA - 02.09.2019 KW - Laser Powder Bed Melting KW - AM IN718 alloy KW - Residual stresses KW - Neutron diffraction KW - Synchrotron Energy Dispersive Diffraction PY - 2019 AN - OPUS4-48895 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wasmer, Paul A1 - Bulling, Jannis A1 - Gravenkamp, Hauke A1 - Prager, Jens T1 - Acoustic-structure interaction in the scaled boundary finite element method for primsatic geometries N2 - Due to the short wavelength compared to the dimensions of the structure, the simulation of ultrasonic waves is still a challenging task. A numerical method well suited for this purpose is the semi-analytical Scaled Boundary Finite Element Method (SBFEM). When applying this method, only the boundary of a computational domain is discretized using finite elements, while the interior is described by an analytical ansatz. Hence, the number of degrees of freedom is reduced significantly compared to the classical Finite Element Method (FEM). In recent years, a particular formulation of the SBFEM for the simulation of ultrasonic guided waves was developed. The method constitutes an efficient algorithm for prismatic structures of arbitrary length, such as plates, pipes, or beams. Wave propagation phenomena in such structures can be modeled for isotropic and anisotropic inhomogeneous waveguides. Even though the method is an efficient tool for the simulation of guided waves in solid media, a reliable model for the simulation of acoustic wave propagation in fluids as well as acoustic-structure interaction in terms of SBFEM is still missing. In principle, the fluid can be described by a displacement-based formulation and thus be implemented in existing SBFEM algorithms for solid bodies. However, due to the discretization with classical finite elements, spurious modes occur, which cannot be separated from the physical modes straightforwardly. The spurious modes can be suppressed using a penalty parameter. Although very accurate results were achieved for some problems, this procedure has been proven unreliable for certain cases. For this reason, we propose a different approach in this contribution. We employ a pressure model to simulate the acoustic behavior of fluids. The implementation of the pressure model results in a higher effort due to the necessity of incorporating coupling terms, but it presents a stable alternative without spurious modes. The accuracy of the method is demonstrated in comparison with analytical solutions and results obtained using the FEM. T2 - GACM 2019 CY - Kassel, Germany DA - 28.08.2019 KW - Scaled Boundary Finite Element Method KW - Guided Waves KW - Acoustic-structure interaction PY - 2019 AN - OPUS4-48846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Casperson, Ralf T1 - DICONDE für ET N2 - Evaluierung der Eignung von DICONDE zur Speicherung von Wirbelstromprüfdaten im Kontext der Industrie/ZfP 4.0. T2 - 3. Sitzung des DGZfP FA ZfP 4.0 UA Schnittstellen CY - Bochum, Germany DA - 28.08.2019 KW - Wirbelstromprüfung KW - DICONDE KW - ZfP 4.0 KW - Industrie 4.0 PY - 2019 AN - OPUS4-48839 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baensch, Franziska A1 - Brunner, A. J. T1 - Towards predictor development for assessing structural integrity of components made from wood materials using Acoustic Emission monitoring and signal analysis N2 - Against the background of sustainable resource management and efficiency, wood-based materials are currently experiencing a revival and, among others, plywood, Laminated Veneer Lumber and glued laminated timber are becoming increasingly more important in the building sector. Even though these materials are so-called engineered products, the element wood is naturally grown with intrinsic variability in mechanical properties and requires professional handling on-site. Otherwise, load-bearing structures made of wood materials may entail certain risks. Critical situations can, in principle, be avoided by implementing a structural health monitoring system into components or structures made from wood material. The aim is to indicate accumulation of mechanical damage and to eliminate or at least significantly reduce the risk of unexpected failure. Toward this purpose, the failure behavior of several layered wood materials under quasi-static tension was investigated in laboratory-scale experiments by means of acoustic emission (AE) measurement. Based on spectral analysis and pattern recognition, two classes of AE signals are identified for each investigated lay-up that are characterized by either low or high frequency contents in the respective power spectra. AE activity and intensity of both signal classes are analyzed, striving for predictors appropriate for AE monitoring concepts. T2 - 5th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures CY - Potsdam, Germany DA - 27.08.2019 KW - Wood materials KW - Acoustic Emission KW - Structural integrity PY - 2019 AN - OPUS4-48802 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -