TY - JOUR A1 - Küttenbaum, Stefan A1 - Maack, Stefan A1 - Braml, T. A1 - Taffe, A. A1 - Haslbeck, M. T1 - Bewertung von Bestandsbauwerken mit gemessenen Daten. Teil 1: Konzept, Messungen und Leistungsfähigkeit der ZfP‐Verfahren JF - Beton- und Stahlbetonbau N2 - Gegenüber dem Neubauentwurf können bei der Bewertung von bestehender Bausubstanz Sicherheitsreserven genutzt werden, da Unsicherheiten, die beim Bau auftreten können, besser bekannt oder nicht mehr vorhanden sind. Können solche Unsicherheiten genauer bewertet werden, z. B. durch die Feststellung der genauen Lage der Spannglieder bei einer Spannbetonbrücke, so können Sicherheitsbeiwerte reduziert werden, ohne dass es dabei zu Auswirkungen auf das normativ festgelegte Zuverlässigkeitsniveau kommt. Mittlerweile sind Prüfmethoden an Bauwerken wirtschaftlich einsetzbar und auch so leistungsfähig, dass die für die Tragfähigkeit und Gebrauchstauglichkeit wesentlichen Parameter identifiziert werden können. Ein wesentlicher Punkt ist hierbei die Integration derartiger Messergebnisse in Rechenmodelle, die für die Nachrechnung des Bauwerks verwendet werden. Dies können sowohl semiprobabilistische Rechenmodelle als auch vollprobabilistische Modelle sein. Bei semiprobabilistischen Methoden können aus den Messergebnissen Teilsicherheitsbeiwerte berechnet und abgeleitet werden, die dann in den bekannten Nachweisformaten gemäß den Eurocodes und der Nachrechnungsrichtlinie berücksichtigt werden. Bei vollprobabilistischen Nachweisen können die Messdaten in Form von Verteilungsdichtefunktionen mit gemessenen Variationskoeffizienten direkt in das Rechenmodell eingehen. In einer dreiteiligen Aufsatzreihe werden die Messverfahren und die Nutzung der Ergebnisse bei der Nachrechnung vorgestellt. Der vorliegende Teil 1 zeigt die Möglichkeiten des Einsatzes von zerstörungsfreien Prüfverfahren und bewertet deren Leistungsfähigkeit. Messen heißt wissen. Dieses Wissen spiegelt die Realität wider und soll den Tragwerksplaner bei der Entscheidungsfindung über die Sicherheit und Zuverlässigkeit von Bestandsbauwerken unterstützen. KW - Nachrechnung KW - Zerstörungsfreie Prüfung KW - Messunsicherheit KW - Brücken KW - Beton PY - 2019 DO - https://doi.org/10.1002/best.201900002 SN - 1437-1006 VL - 114 IS - 6 SP - 370 EP - 382 PB - Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG CY - Berlin AN - OPUS4-48156 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kowarik, Stefan A1 - Bogula, A1 - Boitano, A1 - Carla, A1 - Pithan, A1 - Schafer, A1 - Wilming, A1 - Zykov, A1 - Pithan, T1 - A novel 3D printed radial collimator for x-ray diffraction JF - Review of Scientific Instruments N2 - We demonstrate the use of a 3D printed radial collimator in X-ray powder diffraction and surface sensitive grazing incidence X-ray diffraction. We find a significant improvement in the overall Signal to background ratio of up to 100 and a suppression of more than a factor 3⋅10⁵ for undesirable Bragg reflections generated by the X-ray “transparent” windows of the sample environment. The background reduction and the removal of the high intensity signals from the windows, which limit the detector’s dynamic range, enable significantly higher sensitivity in experiments within sample environments such as vacuum chambers and gas- or liquid-cells. Details of the additively manufactured steel collimator geometry, alignment strategies using X-ray fluorescence, and data analysis are also briefly discussed. The flexibility and affordability of 3D prints enable designs optimized for specific detectors and sample environments, without compromising the degrees of freedom of the diffractometer. KW - 3D printing PY - 2019 DO - https://doi.org/10.1063/1.5063520 SN - 0034-6748 VL - 90 IS - 3 SP - 035102, 1 EP - 8 PB - AIP AN - OPUS4-48171 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zheng, H. A1 - Ertel, Jens-Peter A1 - Kourmpetis, M. A1 - Kanfoud, J. A1 - Niederleithinger, Ernst A1 - Gan, T.-H. T1 - Integrity testing of cast in situ concrete piles based on an impulse response function method using sine‑sweep excitation by a shaker JF - Journal of Nondestructive Evaluation N2 - In this study, an Impulse Response Function analysis of pile response to sine-sweep excitation by a low cost, portable Shaker was used to identify defects in piles. In straightforward impact-echo methods, echoes from the pile toe and defects are visible in the time domain measurements. However, these echoes are not present in the time domain records of piles subjected to sine-sweep excitations, due to interactions between the input and output signals. For this reason, the impulse response function in the time domain has been calculated and is able to identify the echoes from pile impedance changes. The proposed methodology has been evaluated both numerically and experimentally. A one-dimensional pile-soil interaction system was developed, and a finite difference method used to calculate the pile response to sine-sweep excitation. The numerical simulations indicate that impulse response measurements with a synthesized logarithmic, sine-sweep excitation could be an effective tool for detecting defects in piles. The methodology was further tested with field trials on 6 cast in situ concrete test piles including 1 intact pile and 5 defective piles subjected to sine-sweep excitations by a shaker. In 5 of the 6 cases the echoes from the pile toe could be identified in the deconvoluted waveforms—the impulse Response functions. Damage detection is more difficult and dependent on the selection of the optimal regularization parameter. Further research and optimization of the deconvolution process is needed to evaluate the effectiveness compared to standard pile integrity testing methods. KW - Pile testing KW - Shaker KW - Deconvolution PY - 2019 DO - https://doi.org/10.1007/s10921-019-0595-4 SN - 0195-9298 SN - 1573-4862 VL - 38 IS - 2 SP - 55, 1 EP - 18 PB - Springer CY - Cham, Switzerland AN - OPUS4-48185 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Caetano, D. M. A1 - Rabuske, T. A1 - Fernandes, J. A1 - Pelkner, Matthias A1 - Fermon, C. A1 - Cardoso, S. A1 - Ribes, B. A1 - Franco, F. A1 - Paul, J. A1 - Piedade, M. A1 - Freitas, P. P. T1 - High-Resolution Nondestructive Test Probes Based on Magnetoresistive JF - IEEE Transaction on Industrial Electronics N2 - This paper discloses two high-sensitivity probes for Eddy Current Nondestructive Test (NDT) of buried and surface defects. These probes incorporate eight and 32 magnetoresistive sensors, respectively, which are optimized for high sensitivity and spatial resolution. The signal processing and interfacing are carried out by a full-custom application-specific integrated circuit (ASIC). The ASIC signal chain performs with a thermal input-referred noise of 30 nV/√Hz at 1 kHz, with 66 mW of power consumption, in a die with 3.7 × 3.4 mm 2 . NDT results are presented, showing that there is an increase in spatial resolution of surface defects when contrasted to prior art, enabling the probes to resolve defects with diameters of 0.44 mm, pitches of 0.6 mm, and minimum edge distance as low as 0.16 mm. The results also show that the probe for buried defects is a good all-round tool for detection of defects under cladding and multiple-plate flat junctions. KW - ASIC KW - Magnetoresistive sensor KW - Nondestructive testing KW - Eddy current testing KW - High resolution PY - 2019 DO - https://doi.org/10.1109/TIE.2018.2879306 VL - 66 IS - 9 SP - 7326 EP - 7337 PB - IEEE AN - OPUS4-48239 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Burgholzer, P. A1 - Berer, T. A1 - Ziegler, Mathias A1 - Thiel, Erik A1 - Ahmadi, Samim A1 - Gruber, J. A1 - Mayr, G. A1 - Hendorfer, G. T1 - Blind structured illumination as excitation for super-resolution photothermal radiometry JF - Quantitative InfraRed Thermography Journal N2 - Photothermal radiometry with an infrared camera allows the contactless temperature measurement of multiple surface pixels simultaneously. A short light pulse heats the sample. The heat propagates through the sample by diffusion and the corresponding temperature evolution is measured at the sample’s surface by an infrared camera. The main drawback in radiometric imaging is the loss of the spatial resolution with increasing depth due to heat diffusion, which results in blurred images for deeper lying structures. We circumvent this information loss due to the diffusion process by using blind structured illumination, combined with a non-linear joint sparsity reconstruction algorithm. The structured illumination is realized by parallel laser lines from a vertical-cavity surface-emitting laser (VCSEL) array controlled by a random binary pattern generator. By using 150 different patterns of structured illumination and our iterative joint sparsity algorithm, it was possible to resolve 1 mm thick lines at a distance down to 0.5 mm, which results in a resolution enhancement of approximately a factor of four compared to the resolution of 5.9 mm for homogenous illuminated thermographic reconstruction. KW - Super-resolution imaging KW - Thermography KW - Blind structured illumination KW - VCSEL array PY - 2019 DO - https://doi.org/10.1080/17686733.2019.1655247 SN - 1768-6733 VL - 17 IS - 4 SP - 268 EP - 278 PB - Taylor & Francis Group CY - Milton, UK AN - OPUS4-49122 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaal, Mate A1 - Caldeira, Rui A1 - Bartusch, Jürgen A1 - Schadow, Florian A1 - Vössing, Konrad A1 - Kupnik, M. T1 - Air-coupled ultrasonic ferroelectret receiver with additional bias voltage JF - IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control N2 - High sensitivity is an important requirement for air-coupled ultrasonic sensors applied to materials testing. With a lower acoustic impedance than any piezoelectric material, charged cellular polypropylene (PP) offers better matching to air with a similar piezoelectric coefficient. The piezoelectric properties of charged cellular PP originate from their polarization, creating permanent internal voltage. The sensitivity of the sensor can be increased by applying additional dc bias voltage, as it has been done already for transmitters. This work presents the first ultrasonic sensor based on charged cellular PP including a high-voltage module providing dc bias voltage up to 2 kV. This bias voltage led to an increase in the signal-to-noise ratio of up to 15 ± 1 dB. The measurement of the received signal depending on the applied bias voltage is proposed as a new method of determining the internal voltage of ferroelectrets. The sensor combined with a cellular PP transmitter was applied to nondestructive testing of a rotor blade segment and glued-laminated timber, enabling imaging of the internal structure of these specimens with a thickness around 4 cm. KW - Acoustic sensors KW - Ferroelectret KW - Nondestructive testing KW - Ultrasonic imaging KW - Ultrasonic transducers PY - 2019 DO - https://doi.org/10.1109/TUFFC.2019.2925666 SN - 0885-3010 SN - 1525-8955 VL - 66 IS - 10 SP - 1600 EP - 1605 PB - IEEE AN - OPUS4-49131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Falahat, A.M. A1 - Kupsch, Andreas A1 - Hentschel, M.P. A1 - Lange, A. A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Manke, I. T1 - Correction approach of detector backlighting in radiography JF - Review of Scientific Instruments N2 - In various kinds of radiography, deficient transmission imaging may occur due to backlighting inside the detector itself arising from light or radiation scattering. The related intensity mismatches barely disturb the high resolution contrast, but its long range nature results in reduced attenuation levels which are often disregarded. Based on X-ray observations and an empirical formalism, a procedure is developed for a first order correction of detector backlighting. A backlighting factor is modeled as a function of the relative detector coverage by the sample projection. Different cases of sample transmission are regarded at different backlight factors and detector coverage. The additional intensity of backlighting may strongly affect the values of materials’ attenuation up to a few 10%. The presented scenario provides a comfortable procedure for corrections of X-ray or neutron transmission imaging data. KW - X-ray imaging KW - Neutron imaging KW - Radiology KW - Backlighting KW - Digital detector array PY - 2019 DO - https://doi.org/10.1063/1.5097170 SN - 0034-6748 VL - 90 IS - 12 SP - 125108 PB - American Institute of Physics CY - Melville, NY, USA AN - OPUS4-50217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Johann, Sergej A1 - Bartholmai, Matthias T1 - Smart RFID Sensors Embedded in Building Structures for Early Damage Detection and Long-Term Monitoring JF - Sensors N2 - In civil engineering, many structures are made of reinforced concrete. Most Degradation processes relevant to this material, e.g., corrosion, are related to an increased level of material moisture. Therefore, moisture monitoring in reinforced concrete is regarded as a crucial method for structural health monitoring. In this study, passive radio frequency identification (RFID)-based sensors are embedded into the concrete. They are well suited for long-term operation over decades and are well protected against harsh environmental conditions. The energy supply and the data transfer of the humidity sensors are provided by RFID. The sensor casing materials are optimised to withstand the high alkaline environment in concrete, having pH values of more than 12. Membrane materials are also investigated to identify materials capable of enabling water vapour transport from the porous cement matrix to the embedded humidity sensor. By measuring the corresponding relative humidity with embedded passive RFID-based sensors, the cement hydration is monitored for 170 days. Moreover, long-term moisture monitoring is performed for more than 1000 days. The Experiments show that embedded passive RFID-based sensors are highly suitable for long-term structural health monitoring in civil engineering. KW - RFID based sensors KW - Embedded sensors KW - Corresponding relative humidity KW - Porous building materials KW - Reinforced concrete KW - Corrosion KW - Civil engineering PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500831 DO - https://doi.org/10.3390/s19245514 VL - 19 IS - 24 SP - 1 EP - 18 PB - MDPI CY - Basel, Swiss AN - OPUS4-50083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dietz, T. A1 - Gottlieb, Cassian A1 - Kohns, P. A1 - Ankerhold, G. T1 - Comparison of atomic and molecular emission in LIBS for the quantification of harmful species in cement-based materials JF - Spectrochimica Acta Part B N2 - Due to the penetration of harmful chlorides into concrete, e.g. from de-icing salt, damage processes such as chloride-related pitting corrosion can occur if critical values are exceeded. In this study, multiphase materials such as chloride-contaminated concrete are examined in detail. A direct comparison is made by analyzing the spectroscopic information of simultaneously measured atomic and molecular emissions with laser-induced breakdown spectroscopy (LIBS). In addition, the influence on the calibration is examined on the basis of the combined spectral information of both reaction paths of the penetrated chlorides. The calibration models of univariate and multivariate methods were validated using reference samples with wet chemical analysis. The results are applied to a concrete sample of a parking deck, which was also analyzed by potentiometric wet chemistry. In order to account for the heterogeneity of concrete, spatially (200 μm) and spectroscopically (0.1 nm) resolved LIBS measurements were performed using a fully automated laboratory system. Simultaneous measurements with three spectrometers allow the analysis of the emission processes of several elements such as Cl, Ca, O, Si and Mg as well as the newly formed molecules CaO and CaCl. The evaluation of the molecular emission in combination with atomic lines extends the analytical performance, since different concrete phases such as aggregates and cement matrix can be better represented. The measurements were carried out in ambient air and with helium purge gas. The limit of detection (LOD) achieved for a combined evaluation of atomic and molecular emission was determined to be 0.028 wt%. KW - Laser-induced breakdown spectroscopy (LIBS) KW - Cement-based materials KW - Atomic and molecular mapping KW - Chemometrics PY - 2019 DO - https://doi.org/10.1016/j.sab.2019.105707 SN - 0584-8547 VL - 161 SP - 105707 PB - Elsevier B.V. AN - OPUS4-50438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bulling, Jannis A1 - Gravenkamp, H. A1 - Birk, C. T1 - A high-order finite element technique with automatic treatment of stress singularities by semi-analytical enrichment JF - Computer Methods in Applied Mechanics and Engineering N2 - This paper presents an approach to the automatic enrichment of finite elements in the vicinity of a stress singularity. The enrichment consists of semi-analytical singular modes constructed using the Scaled Boundary Finite Element Method (SBFEM). In contrast to analytical methods, the SBFEM provides modes for inhomogeneous and anisotropic materials without additional effort. The finite element basis can be of arbitrary order and remains unaltered by the enrichment. The approach requires enrichment in only one layer of elements around a node. Due to the compatibility of SBFEM with FEM, there is no Need for transitional elements, and there are no parasitic terms. The approach is tested for several benchmark problems. The stress intensity factors are computed based on techniques inspired by the SBFEM. The proposed procedure is compared to a Standard finite element implementation and shows a significant improvement in the error of the displacement field for problems involving singular stresses. KW - Enriched finite element method KW - Scaled boundary finite element method KW - Stress intensity factors KW - Singular stress PY - 2019 DO - https://doi.org/10.1016/j.cma.2019.06.025 VL - 355 SP - 135 EP - 156 PB - Elsevier B.V. AN - OPUS4-48979 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -