TY - JOUR A1 - Kruschwitz, Sabine A1 - Oesch, T. A1 - Mielentz, Frank A1 - Meinel, Dietmar A1 - Spyridis, P. T1 - Non-Destructive Multi-Method Assessment of Steel Fiber Orientation in Concrete JF - Applied Sciences N2 - Integration of fiber reinforcement in high-performance cementitious materials has become widely applied in many fields of construction. One of the most investigated advantages of steel Fiber reinforced concrete (SFRC) is the deceleration of crack growth and hence its improved sustainability. Additional benefits are associated with its structural properties, as fibers can significantly increase the ductility and the tensile strength of concrete. In some applications it is even possible to entirely replace the conventional reinforcement, leading to significant logistical and environmental benefits. Fiber reinforcement can, however, have critical disadvantages and even hinder the Performance of concrete, since it can induce an anisotropic material behavior of the mixture if the fibers are not appropriately oriented. For a safe use of SFRC in the future, reliable non-destructive testing (NDT) methods need to be identified to assess the fibers’ orientation in hardened concrete. In this study, ultrasonic material testing, electrical impedance testing, and X-ray computed tomography have been investigated for this purpose using specially produced samples with biased or random Fiber orientations. We demonstrate the capabilities of each of these NDT techniques for fiber orientation measurements and draw conclusions based on these results about the most promising areas for future research and development. KW - Spectral induced polarization KW - Steel fiber reiniforced concrete KW - Fiber orientation KW - Non-destructive testing KW - Micro-computed tomography KW - Ultrasound PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543520 DO - https://doi.org/10.3390/app12020697 VL - 12 IS - 2 SP - 1 EP - 14 PB - MDPI CY - Basel Switzerland AN - OPUS4-54352 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeipert, H. A1 - Claes, L. A1 - Johannesmann, S. A1 - Lugovtsova, Yevgeniya A1 - Nicolai, Marcel A1 - Prager, Jens A1 - Henning, Bernd ED - Jumar, U. T1 - An approach to adhesive bond characterisation using guided acoustic waves in multi-layered plates JF - at - Automatisierungstechnik N2 - An approach for the non-destructive characterisation of adhesive bonds using guided ultrasonic waves is presented. Pulsed laser radiation is used to thermoacoustically excite broadband ultrasonic waves in a multi-layered sample, consisting of a metal plate adhesively joined to a polymeric layer using synthetic resin. The resulting signals are received by a purpose-built piezoelectric transducer. Varying the distance between excitation and detection yields spatio-temporal measurement data, from which the dispersive properties of the propagating waves can be inferred using a two-dimensional Fourier transform, assuming the plates to act as coupled waveguides. Coupled multi-layered waveguides show an effect referred to as mode repulsion, where the distance between certain modes in the frequency-wavenumber domain is assumed to be a measure of coupling strength. Measurements at different stages of curing of the adhesive layer are performed and evaluated. A comparison of the results shows changes in the dispersive properties, namely an increased modal bandwidth for the fully cured sample as well as an increased modal distance. KW - Adhesive bonding KW - Guided waves KW - Non-destructive testing KW - Ultrasound PY - 2021 DO - https://doi.org/10.1515/auto-2021-0089 VL - 69 IS - 11 SP - 962 EP - 969 PB - De Gruyter CY - Berlin/Boston AN - OPUS4-53762 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bruno, Giovanni T1 - Micro Non-Destructive Testing and Evaluation JF - Micro Non-Destructive Testing and Evaluation N2 - What is meant by ‘Micro Non-Destructive Testing and Evaluation’? This was the central subject of debate in this Special Issue. At present, sub-millimeter-size components or even assemblies are pervading the industrial and scientific world. Classic examples are electronic devices and watches (as well as parts thereof), but recent examples encompass additively manufactured lattice structures, stents, or other microparts. Moreover, most assemblies contain micro-components. Testing such components or their miniaturized parts would fit well within the topic of micro non-destructive testing and evaluation. In all cases, performance and integrity testing, quality control, and dimensional tolerances need to be measured at the sub-millimeter level (ideally with a spatial resolution of about a micron); most of the time, such features and components are embedded in much larger assemblies, which also need to be taken into account. The solution to this dilemma (i.e. measuring large parts with high resolution) depends on the part and on the problem under consideration. Another possible definition of micro non-destructive testing and evaluation can relate to the characterization of micro-features (e.g., the microstructure) in much larger specimens, such as damage in concrete cores or porosity in additively manufactured components. A further aspect is the use of microscopic probes to evaluate macroscopic properties. This is the case, for instance but not at all exclusively, in the use of diffraction techniques to determine macroscopic stress. The splits between testing and characterization at the micro-level (or of micro parts) from one side and handling of macroscopic assemblies on the other represent a great challenge for many fields of materials characterization. On top of that, including the use of microscopic methods to test integrity would add a further level of complexity. Imaging, mechanical testing, non-destructive testing, measurement of properties, structural health monitoring, and dimensional metrology all need to be re-defined if we want to cope with the multi-faceted topic of micro non-destructive testing and evaluation. The challenge has already been accepted by the scientific and engineering communities for a while but is still far from being universally tackled. This Special Issue yields an interesting answer to the questions posed above. It presents the progress made and the different aspects of the challenge as well as at indicates the paths for the future of NDT&E. KW - Ultrasound KW - Materials Characterization KW - Residual Stress KW - Thermography Computed KW - Tomography KW - Non-destructive Testing KW - Magnetic Methods PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556849 DO - https://doi.org/10.3390/ma15175923 VL - 15 IS - 17 SP - 1 EP - 3 PB - MDPI CY - Basel, Schweiz AN - OPUS4-55684 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vössing, Konrad A1 - Niederleithinger, Ernst ED - Faix, O. T1 - Nondestructive assessment and imaging methods for internal inspection of timber. A review. JF - Holzforschung N2 - This paper reviews state-of-the-art in nondestructive testing (NDT) and semidestructive testing (SDT) methods applicable for imaging the condition of structural timber. Both NDT and SDT imaging reveal defects, damages, and decay, while the extent of wood decay can also be quantified. Combined with an appropriate data interpretation concerning the internal defects, the mechanical properties of the material can also be assessed. The possibilities and limitations of the most relevant individual NDT and SDT methods, also in combination with each other, are outlined and compared. To facilitate comparison, many observations are reported based on the same test specimen. KW - Drilling resistance KW - Electrical resistivity KW - Radar KW - Radiography KW - Sonic stress wave KW - Ultrasound KW - Non destructive testing KW - Timber structure PY - 2018 DO - https://doi.org/10.1515/hf-2017-0122 SN - 0018-3830 SN - 1437-434X VL - 72 IS - 6 SP - 467 EP - 476 PB - De Gruyter CY - Berlin AN - OPUS4-44445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Wang, Xin A1 - Herbrand, M. A1 - Müller, M. T1 - Processing ultrasonic data by coda wave interferometry to monitor load tests of concrete beams JF - Sensors N2 - Ultrasonic transmission measurements have been used for decades to monitor concrete elements, mostly on a laboratory scale. Recently, coda wave interferometry (CWI), a technique adapted from seismology, was introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete laboratory samples and even large structural elements without having a transducer directly at the place where the change is taking place. Here, several load tests until failure on large posttensioned concrete beams have been monitored using networks of embedded transducers. To detect subtle effects at the beginning of the experiments and cope with severe changes due to cracking close to failure, the coda wave interferometry procedures had to be modified to an adapted step-wise approach. Using this methodology, we were able to monitor stress distribution and localize large cracks by a relatively simple technique. Implementation of this approach on selected real structures might help to make decisions in infrastructure asset management. KW - Ultrasound KW - Concrete KW - Monitoring KW - Coda wave interferometry KW - Embedded transducers PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-452328 DO - https://doi.org/10.3390/s19010147 SN - 1424-8220 VL - 19 IS - 1 SP - Article 147, 1 EP - 13 PB - MDPI CY - Basel AN - OPUS4-45232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tiitta, M. A1 - Tiitta, V. A1 - Gaal, Mate A1 - Heikkinen, J. A1 - Lappalainen, R. A1 - Tomppo, L. T1 - Air-coupled ultrasound detection of natural defects in wood using ferroelectret and piezoelectric sensors JF - Wood Science and Technology N2 - Air-coupled ultrasound was used for assessing natural defects in wood boards by through-transmission scanning measurements. Gas matrix piezoelectric (GMP) and ferroelectret (FE) transducers were studied. The study also included tests with additional bias voltage with the ferroelectret receivers. Signal analyses, analyses of the measurement dynamics and statistical analyses of the signal parameters were conducted. After the measurement series, the samples were cut from the measurement regions and the defects were analyzed visually from the cross sections. The ultrasound responses were compared with the results of the visual examination of the cross sections. With the additional bias voltage, the ferroelectret measurement showed increased signal-to-noise ratio, which is especially important for air-coupled measurement of high-attenuation materials like wood. When comparing the defect response of GMP and FE sensors, it was found that FE sensors had more sensitive dynamic range, resulting from better s/n ratio and short response pulse. Classification test was made to test the possibility of detecting defects in sound wood. Machine learning methods including decision trees, k-nearest neighbor and support vector machine were used. The classification accuracy varied between 72 and 77% in the tests. All the tested machine learning methods could be used efficiently for the classification. KW - Air-coupled transducers KW - Wood KW - Ultrasound KW - Ultrasonic imaging KW - Ferroelectret KW - Machine learning PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509503 DO - https://doi.org/10.1007/s00226-020-01189-y SP - 1 EP - 14 PB - Springer AN - OPUS4-50950 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schweitzer, T. A1 - Hörmann, M. A1 - Bühling, Benjamin A1 - Bobusch, B. T1 - Switching Action of a Bistable Fluidic Amplifier for Ultrasonic Testing JF - Fluids N2 - Air-coupled ultrasonic testing is widely used in the industry for the non-destructive testing of compound materials. It provides a fast and efficient way to inspect large concrete civil infrastructures for damage that might lead to catastrophic failure. Due to the large penetration depths required for concrete structures, the use of traditional piezoelectric transducer requires high power electric systems. In this study, a novel fluidic transducer based on a bistable fluidic amplifier is investigated. Previous experiments have shown that the switching action of the device produces a high-power broadband ultrasonic signal. This study will provide further insight into the switching behaviour of the fluidic switch. Therefore, parametric CFD simulations based on compressible supersonic RANS simulations were performed, varying the inlet pressure and velocity profiles for the control flow. Switching times are analyzed with different methods, and it was found that These are mostly independent of the slope of the velocity profile at the control port. Furthermore, it was found that an inversely proportional relationship exists between flow velocity in the throat and the switching time. The results agree with the theoretical background established by experimental studies that can be found in the literature. KW - Ultrasound KW - Non-destructive testing KW - Fluidic devices KW - Computational fluid dynamics KW - Concrete KW - Bistable fluidic amplifier PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525115 DO - https://doi.org/10.3390/fluids6050171 SN - 2311-5521 VL - 6 IS - 5 SP - 171 PB - MDPI CY - Basel, Switzerland AN - OPUS4-52511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Clauß, F. A1 - Epple, Niklas A1 - Ahrens, M. A. A1 - Niederleithinger, Ernst A1 - Mark, P. T1 - Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves JF - Materials N2 - The integral collection of information such as strains, cracks, or temperatures by ultrasound offers the best prerequisites to monitor structures during their lifetime. In this paper, a novel approach is proposed which uses the collected information in the coda of ultrasonic signals to infer the condition of a structure. This approach is derived from component tests on a reinforced concrete beam subjected to four-point bending in the lab at Ruhr University Bochum. In addition to ultrasonic measurements, strain of the reinforcement is measured with fiber optic sensors. Approached by the methods of moment-curvature relations, the steel strains serve as a reference for velocity changes of the coda waves. In particular, a correlation between the relative velocity change and the average steel strain in the reinforcement is derived that covers 90% of the total bearing capacity. The purely empirical model yields a linear function with a high level of accuracy (R 2 =0.99, R2=0.99, RMSE≈90μ RMSE≈90μ strain). KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Structural Health Monitoring KW - Reinforced Concrete KW - Embedded Sensors PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542316 DO - https://doi.org/10.3390/ma15030738 VL - 15 IS - 3 SP - 738 PB - MDPI AN - OPUS4-54231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Wang, Xin A1 - Mierschke, Vivien A1 - Bertschat, Anja Sophie T1 - Concepts from seismic interferometry transferred to sonic and ultrasonic concrete inspection and monitoring JF - The e-journal of nondestructive testing & ultrasonics N2 - Seismic interferometry (SI) deals either with the sensible detection of changes in the subsurface or with the reconstruction of virtual signals between two receivers by crosscorrelation of signals from diffuse sources. These concepts can be applied in NDT in civil engineering for various purposes, e. g. to detect changes in bridges. Here it is demonstrated using data from a reference structure on our test site. Practical applications can be expected in the very near future. T2 - 12th European Conference on Non-Destructive Testing (ECNDT 2018) CY - Gothenburg, Sweden DA - 11.6.2018 KW - Ultrasound KW - Concrete KW - Monitoring KW - Coda KW - Interferometry PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-468465 UR - http://www.ndt.net/?id=22760 SN - 1435-4934 VL - 23 IS - 8 SP - 1 EP - 2 PB - NDT.net CY - Kirchwald AN - OPUS4-46846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Gardner, S. A1 - Kind, Thomas A1 - Kaiser, R. A1 - Grunwald, Marcel A1 - Yang, G. A1 - Redmer, Bernhard A1 - Waske, Anja A1 - Mielentz, Frank A1 - Effner, Ute A1 - Köpp, Christian A1 - Clarkson, A. A1 - Thompson, F. A1 - Ryan, M. A1 - Mahon, D. T1 - Muon Tomography of the Interior of a Reinforced Concrete Block: First Experimental Proof of Concept JF - Journal of Nondestructive Evaluation N2 - Quality assurance and condition assessment of concrete structures is an important topic world-wide due to the aging infrastructure and increasing traffic demands. Common topics include, but are not limited to, localisation of rebar or tendon ducts, geometrical irregularities, cracks, voids, honeycombing or other flaws. Non-destructive techniques such as ultrasound or radar have found regular, successful practical application but sometimes suffer from limited resolution and accuracy, imaging artefacts or restrictions in detecting certain features. Until the 1980s X-ray transmission was used in case of special demands and showed a much better resolution than other NDT techniques. However, due to safety concerns and cost issues, this method is almost never used anymore. Muon tomography has received much attention recently. Novel detectors for cosmic muons and tomographic imaging algorithms have opened up new fields of application, such as the investigation of freight containers. Muon imaging also has the potential to fill some of the gaps currently existing in concrete NDT. As a first step towards practical use and as a proof of concept we used an existing system to image the interior of a reference reinforced 600 kg concrete block. Even with a yet not optimized setup for this kind of investigation, the muon imaging results are at least of similar quality compared to ultrasonic and radar imaging, potentially even better. The data acquisition takes more time and signals contain more noise, but the images allowed to detect the same important features that are visible in conventional high energy X-ray tomography. In our experiment, we have shown that muon imaging has potential for concrete inspection. The next steps include the development of mobile detectors and optimising acquisition and imaging parameters. KW - Concrete KW - Muon KW - Radar KW - Ultrasound KW - X-ray PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-529974 DO - https://doi.org/10.1007/s10921-021-00797-3 VL - 40 IS - 3 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-52997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rabe, U. A1 - Pudovikov, S. A1 - Herrmann, H.-G. A1 - Wiggenhauser, H. A1 - Prabhakara, Prathik A1 - Niederleithinger, Ernst T1 - Using the Corner Reflection for Depth Evaluation of Surface Breaking Cracks in Concrete by Ultrasound JF - Journal of Nondestrctive Evaluation N2 - The corner echo is a well-known effect in ultrasonic testing, which allows detection of surface breaking cracks with predominantly perpendicular orientation to the surface as, for example, corrosion cracks in metal pipes or shafts. This echo is formed by two planes, the surface of the crack and the surface which the crack breaks. It can also be classified as a half-skip method, since a reflection of the pulse occurs on the backwall before the reflection at the defect takes place. In combination with the diffraction from the crack tip, the corner echo also allows crack sizing. As shown in this paper, the corner reflection can be used in civil engineering for nondestructive inspection of concrete. Commercially available low frequency ultrasonic arrays with dry point contact sources generate SH transversal waves with sufficient divergence of the sound field in order to detect corner reflections. Ultrasonic line-scans and area-scans were acquired with a linear array on flat concrete specimens, and the data were reconstructed by the Synthetic aperture focusing technique. If the angles and the area of reconstruction are chosen accordingly, the corner echo reflection can be distinguished from other ultrasonic information. The corner echo can thus be used as a method for deciding whether a crack is a partial-depth crack or a full-depth crack and thus for obtaining a statement about crack depth. This paper presents corresponding experimental results obtained on concrete specimens with artificial test defects and cracks induced under controlled conditions. KW - Ultrasound KW - Crack depth KW - Concrete KW - Corner echo PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574631 DO - https://doi.org/10.1007/s10921-023-00956-8 SN - 0195-9298 VL - 42 IS - 2 SP - 1 EP - 19 PB - Springer Nature AN - OPUS4-57463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maack, Stefan A1 - Küttenbaum, Stefan A1 - Bühling, Benjamin A1 - Niederleithinger, Ernst T1 - Low frequency ultrasonic dataset for pulse echo object detection in an isotropic homogeneous medium as reference for heterogeneous materials in civil engineering JF - Data in Brief N2 - The dataset presented contains ultrasonic data recorded in pulse echo mode. The investigated specimen is made of the isotropic homogeneous material polyamide and has a drill hole of constant diameter running parallel to the surface, which was scanned in a point grid using an automatic scanner system. At each measuring position, a pitch-catch measurement was performed using a sampling rate of 2 MHz. The probes used are arrays consisting of a spatially separated receiving and in-phase transmitting unit. The transmitting and receiving sides each consist of 12 point-shaped single probes. These dry-point contact (DPC) probes operate according to the piezoelectric principle at nominal frequencies of 55 kHz (shear waves) and 100 kHz (longitudinal waves), respectively, and do not require a coupling medium. The measurements are performed with longitudinal (100 kHz) and transverse (55 kHz) waves with different geometric orientations of the probe on the measurement surface. The data presented in the article provide a valid source for evaluating reconstruction algorithms for imaging in the low-frequency ultrasound range. KW - Non-destructive testing KW - Ultrasound KW - Pulse-echo method KW - Reference material KW - Reconstruction algorithm KW - Validation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547326 DO - https://doi.org/10.1016/j.dib.2022.108235 VL - 42 SP - 1 EP - 11 PB - Elsevier Inc. AN - OPUS4-54732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Prabhakara, Prathik A1 - Mielentz, Frank A1 - Stolpe, Heiko A1 - Behrens, Matthias A1 - Lay, Vera A1 - Niederleithinger, Ernst T1 - Validation of novel ultrasonic phased array borehole probe by using simulation and measurement JF - Sensors N2 - Low-frequency ultrasonic testing is a well-established non-destructive testing (NDT) method in civil engineering for material characterization and the localization of cracks, reinforcing bars and delamination. A novel ultrasonic borehole probe is developed for in situ quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The aim is to examine the sealing structures made of salt concrete for any possible cracks and delamination and to localize built-in components. A prototype has been developed using 12 individual horizontal dry point contact (DPC) shear wave transducers separated by equidistant transmitter/receiver arrays. The probe is equipped with a commercially available portable ultrasonic flaw detector used in the NDT civil engineering industry. To increase the sound pressure generated, the number of transducers in the novel probe is increased to 32 transducers. In addition, the timed excitation of each transducer directs a focused beam of sound to a specific angle and distance based on the previously calculated delay time. This narrows the sensitivity of test volume and improves the signal-to-noise ratio of the received signals. In this paper, the newly designed phased array borehole probe is validated by beam computation in the CIVA software and experimental investigations on a half-cylindrical test specimen to investigate the directional characteristics. In combination with geophysical reconstruction methods, it is expected that an optimised radiation pattern of the probe will improve the signal quality and thus increase the reliability of the imaging results. This is an important consideration for the construction of safe sealing structures for the safe disposal of radioactive or toxic waste. KW - Ultrasound KW - Phased array KW - Concrete KW - Borehole PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565722 DO - https://doi.org/10.3390/s22249823 SN - 1424-8220 VL - 22 IS - 24 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-56572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Diewald, F. A1 - Epple, Niklas A1 - Kraenkel, T. A1 - Gehlen, C. A1 - Niederleithinger, Ernst T1 - Impact of External Mechanical Loads on Coda Waves in Concrete JF - Materials N2 - During their life span, concrete structures interact with many kinds of external mechanical loads. Most of these loads are considered in advance and result in reversible deformations. Nevertheless, some of the loads cause irreversible, sometimes unnoticed changes below the macroscopic scale depending on the type and dimension of the impact. As the functionality of concrete structures is often relevant to safety and society, their condition must be known and, therefore, assessed on a regular basis. Out of the spectrum of non-destructive monitoring methods, Coda Wave Interferometry using embedded ultrasonic sensors is one particularly sensitive technique to evaluate changes to heterogeneous media. However, there are various influences on Coda waves in concrete, and the interpretation of their superimposed effect is ambiguous. In this study, we quantify the relations of uniaxial compression and uniaxial tension on Coda waves propagating in normal concrete. We found that both the signal correlation of ultrasonic signals as well as their velocity variation directly reflect the stress change in concrete structures in a laboratory environment. For the linear elastic range up to 30% of the strength, we calculated a velocity variation of −0.97‰/MPa for compression and 0.33%/MPa for tension using linear regression. In addition, these parameters revealed even weak irreversible changes after removal of the load. Furthermore, we show the time-dependent effects of shrinkage and creep on Coda waves by providing the development of the signal parameters over time during half a year together with creep recovery. Our observations showed that time-dependent material changes must be taken into account for any comparison of ultrasonic signals that are far apart in time. The study’s results demonstrate how Coda Wave Interferometry is capable of monitoring stress changes and detecting even small-size microstructural changes. By indicating the stated relations and their separation from further impacts, e.g., temperature and moisture, we anticipate our study to contribute to the qualification of Coda Wave Interferometry for its application as an early-warning system for concrete structures. KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Mechanical Load KW - Microstructure KW - Concrete PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556878 DO - https://doi.org/10.3390/ma15165482 SN - 1996-1944 VL - 15 IS - 16 SP - 1 EP - 15 PB - MDPI AN - OPUS4-55687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst T1 - Ultrasonic monitoring of concrete constructions using embedded transducers JF - The e-journal of nondestructive testing & ultrasonics N2 - Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades. Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil Engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas. T2 - International Symposium on Structural Health Monitoring and Nondestructive Testing CY - Saarbrücken, Germany DA - 4.10.2018 KW - Ultrasound KW - Monitoring KW - Concrete PY - 2018 UR - http://www.ndt.net/?id=23542 SN - 1435-4934 VL - 23 IS - 12 SP - 1 EP - 6 PB - NDT.net CY - Kirchwald AN - OPUS4-46842 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vössing, Konrad A1 - Gaal, Mate A1 - Niederleithinger, Ernst T1 - Imaging wood defects using air coupled ferroelectret ultrasonic transducers in reflection mode JF - Construction and Building Materials N2 - Air-coupled ultrasound (ACU) is used to detect defects in wood panels without physically contacting the sample and with a quick scanning rate. Transducers made of cellular polypropylene (PP) with a high signal-to-noise ratio are quite suitable for ACU testing of wood. The extremely low modulus of elasticity and low density of PP transducers results in a small difference in acoustic impedance for the Transmission of ultrasonic waves between the transducer and air, allowing new areas of application to become possible. To demonstrate the suitability of the reflection technique, measurements are shown on the three samples Multiplex, LVL, and MDF and compared with transmission measurements. Due to this acoustic barrier and the use of cellular PP transducers, an exact detection of delamination and cavities is possible in wood panels up to 40 mm thick. If only one side of an object is accessible and the depth of the defect is of interest, the reflection technique is preferred at the expense of a reduced measuring accuracy and Penetration depth. KW - Wood KW - Ultrasound KW - Air coupled KW - Defects PY - 2020 DO - https://doi.org/10.1016/j.conbuildmat.2020.118032 VL - 241 SP - 118032, 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-50235 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grohmann, Maria A1 - Niederleithinger, Ernst A1 - Buske, S. A1 - Büttner, C. T1 - Application of Elastic P-SV Reverse Time Migration to Synthetic Ultrasonic Echo Data from Concrete Members JF - Journal of Nondestructive Evaluation N2 - The ultrasonic echo technique is frequently used in non-destructive testing (NDT) of concrete structures for thickness measurements, geometry determinations as well as localization of built-in components. To improve ultrasonic imaging of complex structures in concrete, we transferred a geophysical imaging technique, the reverse time migration (RTM), to NDT in civil engineering. In contrast to the conventionally used synthetic aperture focusing technique (SAFT) algorithms, RTM is a wavefield continuation method in time and uses the full wave equation. Thus, RTM can handle complicated wave propagations in any direction without dip limitation. In this paper, we focused on the application and evaluation of a two-dimensional (2D) elastic RTM algorithm considering compressional waves, vertically polarized shear waves, and Rayleigh waves. We tested the elastic RTM routine on synthetic ultrasonic echo data generated with a 2D concrete model consisting of several steps and circular air inclusions. As these complex structures can often be found in real-world NDT use cases, their imaging is especially important. By using elastic RTM, we were able to clearly reproduce vertical reflectors and lower edges of circular air voids inside our numerical concrete model. Such structures cannot be imaged with conventional SAFT algorithms. Furthermore, the used elastic RTM approach also yielded a better reconstruction of a horizontal reflector and upper boundaries of circular air inclusions. Our encouraging results demonstrate that elastic RTM has the potential to significantly improve the imaging of complex concrete structures and, thus, is a step forward for detailed, high-quality ultrasonic NDT in civil engineering. KW - Concrete KW - Ultrasound KW - Imaging KW - Reverse time migration KW - Elastic PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-580680 DO - https://doi.org/10.1007/s10921-023-00962-w SN - 0195-9298 VL - 42 IS - 3 SP - 1 EP - 18 PB - Springer Nature AN - OPUS4-58068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Xin A1 - Chakraborty, J. A1 - Niederleithinger, Ernst T1 - Noise Reduction for Improvement of Ultrasonic Monitoring Using Coda Wave Interferometry on a Real Bridge JF - Journal of Nondestructive Evaluation N2 - Reinforced concrete bridges are iconic parts of modern infrastructure. They are designed for a minimum service life of 100 years. However, environmental factors and/or inappropriate use might cause overload and accelerate the deterioration of bridges. In extreme cases, bridges could collapse when necessary maintenance lacks. Thus, the permanent monitoring for structure health assessment has been proposed, which is the aim of structural health monitoring (SHM). Studies in laboratories have shown that ultrasonic (US) coda wave interferometry (CWI) using diffuse waves has high sensitivity and reliability to detect subtle changes in concrete structures. The creation of micro-cracks might be recognized at an early stage. Moreover, large-volume structures can be monitored with a relatively small number of US transducers. However, it is still a challenge to implement the CWI method in real SHM practical applications in an outdoor environment because of the complex external factors, such as various noise sources that interfere with the recorded signals. In this paper, monitoring data from a 36-m long bridge girder in Gliwice, Poland, instrumented with embedded US transducers, thermistors, and vibrating wire strain gauges, is presented. Noise estimation and reductionmethods are discussed, and the influence of traffic, as well as temperature variation, are studied. As a result, the relative velocity variation of US waves following the temperature change with a very high precision of 10−4% is shown, and a good bridge health condition is inferred. The influence of lightweight real traffic is negligible. The study verified the feasibility of the implementation of the CWI method on real bridge structures. KW - Ultrasound KW - Coda Wave Interferometry KW - Noise KW - Concrete KW - Bridge PY - 2021 DO - https://doi.org/10.1007/s10921-020-00743-9 VL - 40 IS - 1 SP - Article number: 14 PB - Springer Nature AN - OPUS4-52052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bühling, Benjamin A1 - Maack, Stefan A1 - Schönsee, Eric A1 - Schweitzer, Thorge A1 - Strangfeld, Christoph T1 - Acoustic and flow data of fluidic and piezoelectric ultrasonic transducers JF - Data in brief N2 - This data article presents characteristic acoustic and flow data of a fluidic ultrasonic transducer as well as acoustic data of a commercial piezoelectric ultrasonic transducer used in non-destructive testing for civil engineering. The flow data has been acquired using hot-wire anemometry and a Pitot tube. The three-dimensional acoustic data of both devices has been acquired using a calibrated microphone. The distribution of characteristic acoustic properties of both transducers are extracted and given in addition to the raw data. The data presented in the article will be a valuable source for reference and validation, both for developing fluidic and alternate ultrasound generation technologies. Furthermore, they will give additional insight into the acoustic-flow interaction phenomena of high speed switching devices. This article is accompanying the paper Experimental Analysis of the Acoustic Field of an Ultrasonic Pulse Induced by a Fluidic Switch (Bühling et al., 2021) published in The Journal of the Acoustical Society of America, where the data is interpreted in detail and the rationale for characteristic sound properties of the fluidic transducer are given. KW - Ultrasound KW - Non-destructive testing KW - Air-coupled ultrasound KW - Fluidics KW - Acoustic-flow interaction KW - Piezoelectric transducer PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-531308 DO - https://doi.org/10.1016/j.dib.2021.107280 VL - 38 SP - 1 EP - 8 PB - Elsevier CY - Amsterdam AN - OPUS4-53130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Landis, E. A1 - Hassfras, Emiel A1 - Oesch, Tyler A1 - Niederleithinger, Ernst T1 - Relating ultrasonic signals to concrete microstructure using X-ray computed tomography JF - Construction and Building Materials N2 - With a goal to improve our understanding of the relationships between microstructural features and ultrasonic signal behavior, concrete specimens of varying water-to-cement ratio were imaged using X-ray computed tomography (CT), and subsequently subjected to ultrasonic testing. From the CT scans, measurements were made of cement paste density and number of interfaces. Ultrasonic signals produced using a through-transmission configuration were analyzed and fit to a diffusion model to separate absorption from scattering attenuation. The results showed that at the frequencies tested, ultrasonic dissipation rate correlated weakly with paste density, while diffusivity correlated well with number of interfaces, but only if entrained air is considered separately. Cement paste density was found to be very well predicted by diffusivity, leading to a clear power-law relationship between diffusivity and compressive strength. KW - Concrete KW - Ultrasound KW - Strength KW - CT PY - 2021 DO - https://doi.org/10.1016/j.conbuildmat.2020.121124 SN - 0950-0618 VL - 268 SP - Paper 121124, 1 EP - 12 PB - Elsevier Ltd. AN - OPUS4-52073 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bühling, Benjamin A1 - Maack, Stefan T1 - Improving onset picking in ultrasonic testing by using a spectral entropy criterion JF - The Journal of the Acoustical Society of America N2 - In ultrasonic testing, material and structural properties of a specimen can be derived from the time-of-flight (ToF). Using signal features, such as the first peak or envelope maximum, to calculate the ToF is error-prone in multipath arrangements or dispersive and attenuating materials, which is not the case for the signal onset. Borrowing from seismology, researchers used the Akaike information criterion (AIC) picker to automatically determine onset times. The most commonly used formulation, Maeda's AIC picker, is reassessed and found to be based on inappropriate assumptions for signals often used in ultrasonic testing and dependent on arbitrary parameters. Consequently, an onset picker for ultrasonic through-transmission measurements is proposed, based on a spectral entropy criterion (SEC) to model the signal using the AIC framework. This SEC picker takes into account the spectral properties of the ultrasonic signal and is virtually free of arbitrary parameters. Synthetic and experimental data are used to compare the performance of SEC and AIC pickers. It is shown that the accuracy of onset picking is improved for densely sampled data. KW - Akaike information criterion picker KW - Nondestructive testing KW - Ultrasound KW - Time of flight PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594284 UR - https://pubs.aip.org/asa/jasa/article/155/1/544/3061576/Improving-onset-picking-in-ultrasonic-testing-by DO - https://doi.org/10.1121/10.0024337 SN - 0001-4966 VL - 155 IS - 1 SP - 544 EP - 554 PB - AIP Publishing CY - Melville, NY, USA AN - OPUS4-59428 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vössing, Konrad A1 - Gaal, Mate A1 - Niederleithinger, Ernst T1 - Air‑coupled ferroelectret ultrasonic transducers for nondestructive testing of wood‑based materials JF - Wood Science and Technology N2 - Air-coupled ultrasound (ACU) is used in through transmission to detect delamination, rot, and cracks in wood without altering the structure permanently. Novel ferroelectret transducers with a high signal-to-noise ratio enable high-precision structure recognition. Transducers made of cellular polypropylene are quite suitable for ACU testing due to their extremely low Young’s modulus and low density resulting in a favorable acoustic impedance for the transmission of ultrasonic waves between the transducer and air. Thus, structures with great dimensions, with a thickness of up to 300 mm and material densities below 500 kg/m3, can be inspected. Promising results were obtained under laboratory conditions with frequencies ranging from 90 to 200 kHz. The advantage of ACU transducers is that they do not equire contact to the sample; they are accurate and cost-effective. Ultrasonic quality assurance for wood is an important avenue to increase the acceptance of wooden structures and toward sustainability in civil engineering in general. KW - Ultrasound KW - Wood KW - Defect KW - Air-coupled PY - 2018 DO - https://doi.org/10.1007/s00226-018-1052-8 VL - 52 IS - 6 SP - 1527 EP - 1538 PB - Springer AN - OPUS4-46653 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fontoura Barroso, Daniel A1 - Epple, Niklas A1 - Niederleithinger, Ernst T1 - A Portable Low-Cost Ultrasound Measurement Device for Concrete Monitoring JF - Inventions: Special Issue "Low-Cost Inventions and Patents" N2 - This paper describes a new ultrasonic measuring device called “W-Box”. It was developed based on the requirements of the DFG Forschergruppe (research unit) CoDA for a portable device for monitoring of concrete specimens, models and actual structures using embedded ultrasonic transducers as well as temperature and humidity sensors. The W-Box can send ultrasonic pulses with a variable frequency of 50–100 kHz to one selectable transducer and records signals from up to 75 multiplexed channels with a sample rate of 1 MHz and a resolution of 14 bits. In addition, it measures temperature and humidity with high accuracy, adjustable amplification, restarts automatically after a power failure and can be fully controlled remotely. The measured data are automatically stored locally on-site data quality checks and transferred to remote servers. The comparison of the W-Box with a laboratory setup using commercial devices proves that it is equally reliable and precise, at much lower cost. The W-Box also shows that their measurement capacities, with the used embedded ultrasonic transducers, can reach above 6 m in concrete. KW - Low-cost KW - Coda wave interferometry KW - Ultrasound KW - IoT KW - Non-destructive testing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546756 DO - https://doi.org/10.3390/inventions6020036 SN - 2411-5134 VL - 6 IS - 2 SP - 1 EP - 17 PB - MDPI CY - Basel, Switzerland AN - OPUS4-54675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Büttner, C. A1 - Niederleithinger, Ernst A1 - Buske, S. A1 - Friedrich, C. T1 - Ultrasonic Echo Localization Using Seismic Migration Techniques in Engineered Barriers for NuclearWaste Storage JF - Journal of Nondestructive Evaluation N2 - In the framework of non-destructive-testing advanced seismic imaging techniques have been applied to ultrasonic echo data in order to examine the integrity of an engineered test-barrier designed to be used for sealing an underground nuclear waste disposal site. Synthetic data as well as real multi-receiver ultrasonic data acquired at the test site were processed and imaged using Kirchhoff prestack depth migration reverse time migration (RTM). In general, both methods provide a good Image quality as demonstrated by various case studies, however deeper parts within the test barrier containing inclined reflectors were reconstructed more accurately by RTM. In particular, the image quality of a specific target reflector at a depth of 8 m in the test-barrier has been significantly improved compared to previous investigations using synthetic aperture Focusing technique, which justifies the considerable computing time of this method. KW - Radioactive waste disposal KW - Engineered barrier KW - Ultrasound KW - Imaging KW - Crack detection PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-537956 DO - https://doi.org/10.1007/s10921-021-00824-3 SN - 0195-9298 VL - 40 IS - 4 SP - 1 EP - 10 PB - Springer AN - OPUS4-53795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chakraborty, J. A1 - Wang, Xin A1 - Stolinski, M. T1 - Analysis of Sensitivity of Distance between Embedded Ultrasonic Sensors and Signal Processing on Damage Detectability in Concrete Structures JF - acoustics N2 - Damage detection of reinforced concrete (RC) structures is becoming a more attractive domain due to the safety issues arising in the last few decades. The damage in concrete can be caused by excessive exploitation of the structure or environmental effects. The cracks in concrete can be detected by different nondestructive testing methods. However, the available methods used for this purpose have numerous limitations. The technologies available in the market nowadays have difficulties detecting slowly progressive, locally limited damage. In addition, some of These methods cannot be applied, especially in hard-to-reach areas in the superstructures. In order to avoid these deficiencies, an embedded ultrasonic methodology can be used to detect cracks in RC structures. In this study, the methodology of crack detection supported with the advanced Signal processing algorithm was proposed and verified on RC structures of various types, and cracks occurring between embedded sensors can be detected. Moreover, different pairs of ultrasonic sensors located in the considered structures are used for the analysis of the sensitivity of distance between them. It is shown that the ultrasonic sensors placed in the range of 1.5–2 m can detect cracks, even when the other methods failed to detect changes in the structure. The obtained results confirmed that diffuse ultrasonic sensor methodology is able to monitor real structures more effectively than traditional techniques. KW - Ultrasound KW - Coda wave interferometry KW - Structural health monitoring PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543624 DO - https://doi.org/10.3390/acoustics4010007 VL - 4 IS - 1 SP - 89 EP - 110 PB - MDPI CY - Basel, Schweiz AN - OPUS4-54362 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -