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 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 - CONF A1 - Arndt, R.W. A1 - Grosse, C.U, A1 - Maehner, D. A1 - Niederleithinger, Ernst A1 - Taffe, A. A1 - Algernon, D. A1 - Berger, J. A1 - Kessler, S. A1 - Krueger, M. A1 - Kruschwitz, Sabine A1 - Ufermann-Wallmeier, D. A1 - Walther, A. T1 - Non-destructive testing in civil engineering: A memorandum for teaching at German-speaking universities N2 - This contribution summarizes actual developments and draft fundamental teaching topics in the field of nondestructive testing in civil engineering (NDT-CE). It is based on the first memorandum on teaching and research in the field of NDT-CE at German speaking universities and provides an overview of the academic education and highlights possible focuses, especially in teaching but also takes into account noteworthy developments and topics in research in the field of NDT-CE. Suggestions are given for the development and advancement of the teaching curricula in regards to a comprehensive and sound professional education of students in civil engineering and adjacent disciplines. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Curriculum KW - NDT-CE KW - University KW - Competencies PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563269 UR - https://www.ndt.net/article/ndtce2022/paper/61547_manuscript.pdf SP - 1 EP - 10 PB - NDT.net AN - OPUS4-56326 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rabe, U. A1 - Pudovikov, S. A1 - Herrmann, H.-G. A1 - Wiggenhauser, H. A1 - Prabhakara, Prathik A1 - Niederleithinger, Ernst T1 - Evaluation of retroreflective corner echo for detection of surface breaking cracks in concrete by ultrasound N2 - The retroreflective corner echo is used, for example, in ultrasonic non-destructive testing of metals to find fatigue cracks in tubes or shafts. If the much weaker crack tip signal is additionally detected, the crack length can also be determined. A corner reflection occurs in cases of surface breaking cracks with predominantly perpendicular orientation to the surface. The intensity of the corner reflection depends on the angle of incidence and on the ultrasonic wave mode used. For the reliable detection of vertical surface breaking cracks in metals, transversal waves are commonly used, which propagate at an angle of 37° to 53° to the inspection surface. As shown in this contribution, the wide spread low frequency ultrasonic arrays with dry point contact sources available for ultrasonic testing of concrete also allow to receive corner echoes. These devices generate transversal waves in concrete structures with a large divergence of the sound field. A series of experiments was carried out with such dry point contact arrays on concrete specimens with artificial test defects and controlled induced cracks of different depths. The ultrasonic time-of-flight signals were recorded, exported and reconstructed utilising the SAFT (Synthetic Aperture Focusing Technique) algorithm. The SAFT reconstruction parameters were adjusted to visualize the corner echo indication. As will be shown, with this targeted processing, the reproducible detection of surface breaking cracks in concrete is possible. The retroreflective corner echo can thus be exploited in civil engineering for non-destructive inspection of concrete. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Concrete KW - Crack depth KW - Ultrasound KW - SAFT PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563365 UR - https://www.ndt.net/article/ndtce2022/paper/27256_manuscript.pdf IS - 27256 SP - 1 EP - 4 PB - NDT.net AN - OPUS4-56336 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 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 - 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 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 - CONF A1 - Niederleithinger, Ernst A1 - Guangliang, Y. A1 - Mahon, D. A1 - Gardner, S. T1 - Muon tomography applied to assessment of concrete structures: First experiments and simulations. N2 - Non-destructive techniques for reinforced or prestressed concrete inspection 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 new fields of application. As a first step towards practical application in civil engineering 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. In a second step, we have performed simulations to assess the potential for a set of important testing problems such as grouting defects in tendon ducts. The next steps include the development of mobile detectors and optimizing acquisition and imaging parameters. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Muon tomography KW - Concrete KW - Inspection KW - Simulation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563224 UR - https://www.ndt.net/article/ndtce2022/paper/60943_manuscript.pdf SP - 1 EP - 8 PB - NDT.net AN - OPUS4-56322 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Abraham, O. A1 - Niederleithinger, Ernst A1 - Schmidt, F. A1 - Sörensen, J.D. A1 - Thöns, S. A1 - Chapeleau, X. A1 - Ferria, H. T1 - Infrastar Training School on Fatigue and Reliability Analysis of Structures - Training for Assessment of Risk N2 - The Infrastar training school provides lectures and hands-on training to Master and PhD students, early-stage researchers and (young) professionals on all aspects of asset management of civil infrastructures with respect to fatigue of materials. It is organized yearly since 2019 and up to 20 profiles are selected to attend the 3.5-day training. A team of 7 teachers provides insight in multi-disciplinary and intersectoral basic concepts in three core fields, ranging from the design to the dismantling of the structures (bridges and wind turbines): 1. Monitoring and auscultation, 2. Structural and action models, 3. Reliability, risk and decision analyses. Each year, a recognized expert is invited to deliver a keynote lecture to raise interest in a specific aspect of one of the fields covered. The presentation is recorded and published on the training school website. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Doctoral School KW - Multidisciplinary KW - Fatigue KW - Reliability PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563253 UR - https://www.ndt.net/article/ndtce2022/paper/61021_manuscript.pdf SP - 1 EP - 3 PB - NDT.net AN - OPUS4-56325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolditz, O. A1 - Jacques, D. A1 - Claret, F. A1 - Bertrand, J. A1 - Churakov, S. V. A1 - Debayle, C. A1 - Diaconu, D. A1 - Fuzik, K. A1 - Garcia, D. A1 - Graebling, N. A1 - Grambow, B. A1 - Holt, E. A1 - Idiart, A. A1 - Leira, P. A1 - Montoya, V. A1 - Niederleithinger, Ernst A1 - Olin, M. A1 - Pfingsten, W. A1 - Prasianakis, N. I. A1 - Rink, K. A1 - Sampier, J. A1 - Szöke, I. A1 - Szöke, R. A1 - Theodon, L. A1 - Wendling, J. T1 - Digitalisation for nuclear waste management: predisposal and disposal N2 - Data science (digitalisation and artificial intelligence) became more than an important facilitator for many domains in fundamental and applied sciences as well as industry and is disrupting the way of research already to a large extent. Originally, data sciences were viewed to be well-suited, especially, for data-intensive applications such as image processing, pattern recognition, etc. In the recent past, particularly, data-driven and physics-inspired machine learning methods have been developed to an extent that they accelerate numerical simulations and became directly usable for applications related to the nuclear waste management cycle. In addition to process-based approaches for creating surrogate models, other disciplines such as virtual reality methods and high-performance computing are leveraging the potential of data sciences more and more. The present challenge is utilising the best models, input data and monitoring information to integrate multi-chemical-physical, coupled processes, multi-scale and probabilistic simulations in Digital Twins (DTw) able to mirror or predict the performance of its corresponding physical twins. Therefore, the main target of the Topical Collection is exploring how the development of DTw can benefit the development of safe, efficient solutions for the pre-disposal and disposal of radioactive waste. A particular challenge for DTw in radioactive waste management is the combination of concepts from geological modelling and underground construction which will be addressed by linking structural and multi-physics/chemistry process models to building or tunnel information models. As for technical systems, engineered structures a variety of DTw approaches already exist, the development of DTw concepts for geological systems poses a particular challenge when taking the complexities (structures and processes) and uncertainties at extremely varying time and spatial scales of subsurface environments into account. KW - Data science KW - Digitalization KW - Nuclear waste KW - Disposal KW - Predisposal PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-569387 DO - https://doi.org/10.1007/s12665-022-10675-4 SN - 1866-6280 VL - 82 IS - 1 SP - 1 EP - 11 PB - Springer AN - OPUS4-56938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grohmann, Maria A1 - Niederleithinger, Ernst A1 - Buske, S. T1 - Geometry Determination of a Foundation Slab Using the Ultrasonic Echo Technique and Geophysical Migration Methods N2 - The ultrasonic echo technique is a frequently used method in non destructive testing for geometry Determination of concrete building elements. Important tasks are thickness measurements as well as the localization and characterization of built-in components and inhomogeneities. Currently mainly the synthetic aperture focusing family of techniques (SAFT) is used for imaging. These algorithms have difficulties in imaging steeply dipping interfaces and complicated structures such as steps and lower boundaries of voids. As an alternative two geophysical migration methods, pre-stack Kirchhoff depth migration and pre-stack Reversetimemigration (RTM)were tested in this paper at a reinforced concrete foundation slab. The slab consists of various reinforcement contents, different thicknesses and two pile heads. In a first step, both methods were evaluated with synthetic 2D data. In the second step, ultrasonic measurement data recorded with shear wave transducers on a line profile on the foundation slab were processed. The use of an automatic scanner simplified the measurements. A comparison of the geophysical migration results with those of SAFT shows, in particular for RTM, a significant improvement in the Imaging of the geometry of the foundation slab. Vertical borders were reconstructed and the location and structure of the lower boundary of the foundation slab were reproduced better. Limitations still exist in imaging the piles below the slab. KW - Kirchhoff migration KW - Ultrasonic echo technique KW - Synthetic aperture focusing technique (SAFT) KW - Reverse-time migration PY - 2016 DO - https://doi.org/10.1007/s10921-016-0334-z SN - 0195-9298 (Print) 1573-4862 (Online) VL - 2016/Band 1 IS - 35:1 SP - 1 EP - 13 PB - Springer CY - New York AN - OPUS4-35838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Stähler, S. A1 - Niederleithinger, Ernst A1 - Pirskawetz, Stephan A1 - Nowak, Thomas Rudolf A1 - Weise, Frank ED - Sens-Schönfelder, Christoph ED - Ritter, Joachim ED - Wegler, Ulrich ED - Große, Christian T1 - Detection of subtle changes in materials by Coda Wave interferometry T2 - Noise and diffuse wavefields workshop CY - Neustadt an der Weinstraße, Germany DA - 2009-07-05 KW - Coda wave interferometry Beton KW - Schädigung KW - Ultraschall-Transmission PY - 2009 SN - 978-3-00-027952-2 SN - 0947-1944 VL - II SP - 59 EP - 61 AN - OPUS4-20574 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Katzenbach, R. A1 - Klingmüller, O. A1 - Hillmann, S. A1 - Willmes, Michael T1 - REFUND: Untersuchung von Bestandsgründungen für eine Entscheidung zur Wiedernutzung T1 - REFUND: Investigation of existing foundations and decision making before re-use N2 - Vor einer geplanten Weiter- oder Wiedernutzung von Bestandsgründungen stellt sich die Frage nach deren Lage, Geometrie und Zustand im Untergrund. Hierfür gibt es verschiedene Prüfverfahren. Die Abläufe bei Planung und Prüfung sind jedoch bisher nicht standardisiert und die Möglichkeiten bzw. Grenzen der Prüfverfahren den Planern wenig bekannt. Im Forschungsprojekt REFUND (2014–2016) wurden unter Berücksichtigung der aktuellen Normen und des Stands der Technik Ablaufdiagramme für die Planung der Wiedernutzung sowie die Untersuchung des Bestands entwickelt. Dies geschah getrennt für Einzel- und Streifenfundamente, Platten und Pfähle. An zwei Praxisbeispielen wurden die Abläufe getestet und optimiert. Die Ergebnisse wurden in einem Handbuch zusammengefasst. Es soll Planer und andere Verantwortliche bei der wirtschaftlich und technisch optimierten Durchführung von Wiedernutzungsprojekten unterstützen. N2 - Before re-using existing foundations they have to be investigated for position, geometry and condition in the subsurface. The procedures and protocols haven't been standardized yet. Capabilities and limitations of appropriate testing methods are not known to all stakeholders. In the frame of the research project REFUND (2014-2016) we have developed decision trees for the planning and the investigation process, separately for single and strip foundations, slabs and piles. The protocols were tested in line with two actual projects. The results have been compiled in a handbook, which will support planners and other participants in a technical and economical optimized way to perform re-use of foundations. KW - Fundament KW - Wiedernutzung KW - Entscheidung KW - Zerstörungsfrei PY - 2017 DO - https://doi.org/10.1002/bate.201700038 SN - 1437-0999 VL - 94 IS - 10 SP - 676 EP - 681 PB - Ernst & Sohn CY - Berlin AN - OPUS4-42615 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Linder, S. A1 - Paasche, H. A1 - Tronicke, J. A1 - Niederleithinger, Ernst A1 - Vienken, T. T1 - Zonal cooperative inversion of crosshole P-wave, S-wave, and georadar traveltime data sets N2 - In this study, we use and extend a recently developed zonal cooperative inversion approach and apply it to the inversion of three independent geophysical field data sets. We invert crosshole P-wave, S-wave, and georadar data sets acquired in sand and gravel dominated unconsolidated sediments to detect and characterize different sedimentary units relevant for an engineering or hydrological site characterization. The zonal cooperative inversion of the three traveltime data sets results in a single subsurface model, which is a geophysical three-parameter model (P-wave, S-wave, and georadar velocity) outlining the major subsurface zonation while explaining all input data sets. Comparing our zonal model to direct push (DP) logging data (tip resistance, sleeve friction, and dielectric permittivity) shows good agreement; i.e., the zones in our geophysical model largely correspond to major DP parameter changes. Furthermore, we demonstrate how the sparse DP data can be inter- and extrapolated to the entire tomographic plane which allows for further geotechnical and hydrological interpretations. This study illustrates that the zonal cooperative inversion approach is highly flexible and an excellent tool to characterize a variety of environments in terms of multiple physical parameters. KW - Seismic KW - Georadar KW - Direct push techniques KW - Crosshole tomography KW - Cooperative inversion KW - Site characterization PY - 2010 DO - https://doi.org/10.1016/j.jappgeo.2010.10.003 SN - 0926-9851 VL - 72 IS - 4 SP - 254 EP - 262 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-23266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Galindo Guerreros, Julio Cesar A1 - Niederleithinger, Ernst A1 - Mackens, S. A1 - Fechner, Th. T1 - Crosshole and downhole seismics: a new quality assurance tool for jet grout columns N2 - Sealing and strengthening of the subsoil by grout injection is a major issue in the field of geotechnical engineering. One commonly applied method is jet grouting, which allows creating columns of grouted soil by eroding and mixing the in-situ soil with a thin cement suspension. A general difficulty linked with this method is in predicting the resulting column diameter and its material strength. In this paper, we illustrate the application of a newly developed non-destructive quality assurance tool used to determine the diameter of jet grout columns. This approach incorporates standard crosshole and downhole seismic measurements. To demonstrate its effectiveness, we tested the new approach within two-dimensional finite-difference numerical simulations. Additional field tests showed that this tool is also applicable in real site conditions. For this purpose, three jet grout columns were produced with different process parameters in a depth between 3 and 10 m. The evaluated diameters were within 1 and 1.5 m, slightly deviating from the previously predicted range by the jet grouting contractor. Moreover, we were able to detect the base of the columns at a 10-m depth with no significant difficulties. On the other hand, unsaturated, less compacted sands between the groundwater level and surface considerably affected the seismic data, hence complicating the detection of the top of the columns. KW - Jet grouting KW - Quality assurance PY - 2016 DO - https://doi.org/10.3997/1873-0604.2016042 SN - 1569-4445 IS - 14 SP - 493 EP - 501 PB - EAGE CY - Houton, NL AN - OPUS4-38977 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mackens, S. A1 - Fechner, T. A1 - Rios, N.I.C. A1 - Tweeton, D. A1 - Galindo Guerreros, Julio Cesar A1 - Niederleithinger, Ernst T1 - A new approach to determine the diameter of a jet grouted column using seismic methods N2 - Jet grouting is a geotechnical method of ground improvement to increase shear strength and stiffness of soils. The method is typically used to construct in-situ geometries of grouted soil such as panels or columns. The diameter of grouted columns and its material strength depend on various process parameters and the subsurface soil properties. It is only vaguely possible to predict the final column diameter. Therefore, it is a general practice to excavate a test column and perform a visual examination. However, an excavation to control the in situ diameter is often impossible, especially under complex site conditions, such as a high ground water table. Therefore, as part of a research project, borehole seismic measurements (crosshole, downhole and tomography) were tested as a quality control to verify the extent of the column and to monitor the influence of the jet grout injection on the soil over time. The field surveys were conducted before and after the jet grouting process at different time intervals. The acquired seismic data show clear traveltime differences which allow the determination of the specific column depth and diameter. The tomogram measured in the natural soil and the tomograms of the measurements after the injection process were used to visualize the time dependent effects of the jet grout injection on the soil. T2 - SAGEEP 2015 - 28th Symposium on the application of geophysics to engineering and environmental problems CY - Austin, TX, USA DA - 22.03.2015 KW - Jet grouting KW - Grouted column KW - Column diameter KW - Seismic tomography KW - Quality assurance KW - Diameter PY - 2015 DO - https://doi.org/10.4133/SAGEEP.28-021 SP - 142 EP - 146 AN - OPUS4-33678 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Niederleithinger, Ernst A1 - Wang, Xin A1 - Epple, Niklas A1 - Schumacher, T. A1 - Ahmend, S. A1 - Klikowicz, P. ED - Yokota, H. ED - Frangopol, D. W. T1 - Ultrasonic coda wave monitoring of concrete structures: First experiences with large-scale experiments and real structures N2 - Ultrasonic monitoring, making use of the sensitivity of the coda of repeated transmission meas-urements to changes in stress, temperature, moisture, as well as localized or distributed damage, has gotten at-tention in structural health monitoring (SHM) research recently. Analysis methods such as coda wave inter-ferometry (CWI), including its nonlinear extension, have been shown to be able to measure ultrasonic wave velocity changes with a 1∙10-5 resolution, while indicators such as cross-correlation or cross-coherence have been used to distinguish between reversible and irreversible changes. Several small- and large-scale laboratory experiments have demonstrated that stress changes in structures can be captured or damage detected in a very early stage. The use of this technique for pre-warning before failure are currently under investigation, as well as detailed research on the physical causes and the connection between ultrasonic wave properties and materi-al/structural behavior. Recently, several of large-scale laboratory and real structures have been instrumented with embedded ultrasonic transducers to gather experience and evidence on how to use this technology in re-al-world applications. Preliminary results from installations on a new bridge, an existing bridge, a tunnel, a la-boratory earthquake test as well as a historic stadium in Germany, Poland, and the United States, respectively, are presented. Environmental influences (mainly temperature) and validation by load tests are discussed. KW - Coda wave interferometry KW - Structural health monitoring KW - Ultrasound KW - Concrete KW - Bridges PY - 2021 SN - 978-0-367-23278-8 DO - https://doi.org/10.1201/9780429279119-345 SP - 2525 EP - 2531 PB - Taylor & Francis CY - London, UK AN - OPUS4-54168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Azari, H. A1 - Shams, S. A1 - Köpp, Christian A1 - Timofeev, Juri A1 - Niederleithinger, Ernst T1 - Development of reference specimens for nondestructive evaluation of concrete bridge decks N2 - Decades of non-destructive evaluation (NDE) for the quality assurance of concrete bridges revealed the necessity of developing procedures for building reference specimens for different defects. External objects have been widely used in specimen construction to represent defects. However, embedded materials can alter the actual defect characteristics, interrupting the NDE responses. This study proposes new approaches to fabricating reference specimens for reinforced concrete that feature substantial defects, including cracks, delamination, honeycombing and rebar corrosion, without external objects. As a result, realistic responses can be acquired to identify promising NDE methods for characterising actual deteriorations. The procedures were produced with the intent of being reproducible in any laboratory. Destructive and non-destructive testing methods were performed to verify the effectiveness of the processes in creating defects. This study provides research laboratories with techniques for fabricating reference specimens for characterising defects and assessing the performance of NDE technologies. KW - Concrete structures KW - Reference KW - Specimen KW - Non-destructive testing KW - Laboratory tests PY - 2023 DO - https://doi.org/10.1680/jfoen.21.00030 SN - 2043-9911 SP - 1 EP - 12 PB - ICE Publishing AN - OPUS4-56957 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brömme, T. A1 - Schmitz, C. A1 - Oprych, D. A1 - Wenda, A. A1 - Strehmel, V. A1 - Grabolle, Markus A1 - Resch-Genger, Ute A1 - Ernst, S. A1 - Reiner, K. A1 - Keil, D. A1 - Lüs, P. A1 - Baumann, H. A1 - Strehmel, B. T1 - Digital imaging of lithographic materials by radical photopolymerization and photonic baking with NIR diode lasers N2 - Photo-initiated cross-linking of multifunctional acrylic esters in polymeric binders was investigated based on digital imaging using the Computer-to-Plate (CtP) technology applying laser exposure in the near-infrared (NIR). Generation of initiating radicals occurs by electron transfer from the excited state of the NIR-sensitizer to the radical generator, an onium salt. Iodonium salts derived from several borates and those with the bis(trifluoromethylsulfonyl)imide anion resulted in lithographic materials with high sensitivity. Photo-induced electron transfer plays a major function to generate initiating radicals by a sensitized mechanism but thermal events also influence sensitivity of the coating. Internal conversion was the major deactivation pathway while a certain fraction of NIR-dye fluorescence was also available. A line shape focused laser system with emission in the NIR was successfully used to bake the materials. KW - Iodonium KW - Near-infrared laser KW - Photonic baking KW - Photophysics KW - Photopolymer PY - 2016 DO - https://doi.org/10.1002/ceat.201500453 SN - 0930-7516 SN - 1521-4125 VL - 39 IS - 1 SP - 13 EP - 25 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-35303 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ernst, A. A1 - Klein, S. A1 - Hall, T. A1 - Ávila Calderón, Luis A1 - Bähre, D. T1 - Electrochemical dressing of hard tools for abrasive precision machining N2 - In this study an approach for dressing metallic bonded honing stones with hard cutting grains on the basis of electrolysis is investigated. By a combination of concepts from electrochemical machining (ECM) and electropolishing a test rig was designed and put into operation. In general, it can be stated that the Approach investigated in this paper has proved to be a suitable dressing method for honing stones. However, the dressing result is highly dependent on bond components, cutting grain size and concentration which lead to local differences in the material removal and irregular topographies. This could be overcome, for example, by setting the dressing parameters more precisely based on the best results presented in this paper. T2 - International Symposium on ElectroChemical Machining Technology CY - Saarbrücken, Germany DA - 14.11.2019 KW - Irregular topography KW - Honing KW - Electrochemical dressing KW - Honing Stone KW - Laser Scanning Microscopy KW - Electropolishing PY - 2019 SN - 978-3-00-064086-5 SP - 96 EP - 108 PB - Fertigungstechnik Saarbrücken CY - Saarbrücken AN - OPUS4-49490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Galindo Guerreros, Julio Cesar A1 - Niederleithinger, Ernst A1 - Mackens, S. A1 - Fechner, T. T1 - Quality assurance of jet grout columns with borehole seismic measurements N2 - Sealing and strengthening of the subsoil by injection is a major issue in the field of geotechnical engineering. One commonly applied method is jet grouting, which allows creating columns of grouted soil by eroding and mixing the in-situ soil with a thin cement suspension. A general difficulty linked with this method is to predict the resulting column diameter and its material strength. In this paper we illustrate the application of a newly developed non-destructive quality assurance testing tool used to determine the diameter of jet grout columns. This approach incorporates standard crosshole and downhole seismic measurements. To demonstrate its effectiveness, we tested the new approach within two-dimensional finite-difference numerical simulations. Additional field tests showed that this tool is also applicable in real site conditions. For this purpose, three jet grout columns were produced with different process parameters in a depth between 3.0 and 10 m. The evaluated diameters were within 1.0 and 1.5 m, slightly deviating from the previously predicted range by the jet grouting contractor. Moreover, we were able to detect the base of the columns at 10 m depth with no significant difficulties. On the other hand, unsaturated, partly unconsolidated sands between ground water level and surface considerably affected the seismic data, hence complicating the detection of the top of the columns. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Jet grout KW - Seismics KW - Crosshole KW - Downhole PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-346753 UR - https://www.ndt.net/?id=18277 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-34675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grohmann, Maria A1 - Niederleithinger, Ernst A1 - Buske, S. T1 - Bestimmung der Geometrie einer Fundamentplatte mit dem Ultraschall-Echo-Verfahren unter Anwendung geophysikalischer Migrationsmethoden N2 - Das Ultraschall-Echo-Verfahren ist ein klassisches Verfahren in der zerstörungsfreien Prüfung zur Bestimmung der Geometrie von Bauteilen. Die Prüfaufgaben beinhalten unter anderem die korrekte Dickenbestimmung der Baukörper sowie die Lokalisierung von Einbauteilen und Fehlstellen. Stand der Technik bei den Abbildungsverfahren ist die SAFT–Rekonstruktion (Synthetic Aperture Focusing Technique). Diese Verfahrensfamilie hat Schwierigkeiten bei der Darstellung von steilen Grenzflächen und komplizierten Strukturen, wie beispielsweise Stufen oder Unterkanten von Hohlräumen und Hüllrohren. Als Alternative werden seit einiger Zeit geophysikalische Migrationsmethoden evaluiert. Am Beispiel eines Stahlbetonfundamentes mit verschiedenen Bewehrungsgehalten, unterschiedlichen Dicken sowie zwei Pfahlköpfen wurden die Kirchhoff-Migration und die Reverse-Time Migration (RTM) getestet. Die strahlenbasierte Kirchhoff-Migration arbeitet ähnlich wie die SAFT-Rekonstruktion. Die RTM basiert auf der vollständigen Wellengleichung. In einem ersten Schritt wurden die Methoden an einem synthetischen, auf der akustischen Wellengleichung basierenden zweidimensionalem Modell getestet. Im zweiten Schritt wurden reale Messdaten, die mit Scherwellenprüfköpfen an der Fundamentplatte aufgenommen wurden, bearbeitet. Der Einsatz eines Scannersystems vereinfachte die Messungen. Die Experimente, die in diesem Manuskript vorgestellt werden, sind von bedeutendem Interesse für die Evaluierung geophysikalischer Migrationsmethoden an analogen Modellen. Ein Vergleich der Migrationsergebnisse mit den bisherigen SAFT-Ergebnissen zeigt insbesondere für die RTM eine deutliche Verbesserung in der Abbildung der Bauteilgeometrie. Vertikale Kanten konnten dargestellt sowie die Lage und Struktur der Rückwände exakter reproduziert werden. Grenzen bestehen noch bei der Darstellung der Pfahlköpfe, da die von dem zylinderförmigen Pfahl kommenden Signale verrauscht sind. Ursachen dafür sind u.a. die Bewehrung, Randeffekte sowie Mehrfachreflexionen an dem Pfahlschaft. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-320249 SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Poster 10, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-32024 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Berger, J. A1 - Zahedi-Azad, S. A1 - Voss, H. A1 - Ernst, O.C. A1 - Hammerschmidt, R. A1 - Boeck, T. A1 - Martin, J. A1 - Bonse, J. A1 - Krüger, J. A1 - Schmid, M. T1 - CuInSe2-based micro-concentrator solar cells fabricated from In islands grown by laser-assisted MO-CVD N2 - Micro-concentrator solar cells offer a promising route for reducing material usage in photovoltaics. For Cu(In,Ga)Se2, multiple micro-concentrator manufacturing methods have already been evaluated. All of them involve either high preparation complexity or post-processing to recycle unused precursor or absorber materials. In this work, a new method using laser-assisted metal-organic chemical vapor deposition (LA-MOCVD) was applied to directly grow arrays of indium micro-islands. These arrays are examined and further processed to CuInSe2 micro-solar cell arrays. The geometry and morphology of the islands were investigated and compared before and after absorber formation. The investigation shows that the absorber growth is limited to the vertical direction normal to the substrate surface and that the starting morphology is preserved. Furthermore, the absorber island arrays are processed into micro-modules and operational solar cells are achieved as a proof of principle. These not yet optimized arrays reach a conversion efficiency of 0.65% under 1 sun illumination. Under 17 suns of light concentration, the efficiency gain is between 60 and 250%. This work demonstrates the method's viability for the fabrication of micro-solar cell arrays, with clear potential for achieving higher conversion efficiencies through future optimization. KW - Micro-concentrator solar cells KW - Laser-assisted chemical vapor deposition KW - CISe KW - Bottom-up fabrication KW - Resource efficiency PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-656711 DO - https://doi.org/10.1016/j.solmat.2026.114284 SN - 0927-0248 VL - 301 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-65671 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stähler, S.C. A1 - Sens-Schönfelder, C. A1 - Niederleithinger, Ernst T1 - Monitoring stress changes in a concrete bridge with coda wave interferometry N2 - Coda wave interferometry is a recent analysis method now widely used in seismology. It uses the increased sensitivity of multiply scattered elastic waves with long travel-times for monitoring weak changes in a medium. While its application for structural monitoring has been shown to work under laboratory conditions, the usability on a real structure with known material changes had yet to be proven. This article presents experiments on a concrete bridge during construction. The results show that small velocity perturbations induced by a changing stress state in the structure can be determined even under adverse conditions. Theoretical estimations based on the stress calculations by the structural engineers are in good agreement with the measured velocity variations. KW - Bridges (structures) KW - Concrete KW - Interferometry KW - Structural acoustics PY - 2011 DO - https://doi.org/10.1121/1.3553226 SN - 0001-4966 SN - 1520-8524 VL - 129 IS - 4 SP - 1945 EP - 1952 PB - AIP CY - Melville, NY, USA AN - OPUS4-28588 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -