TY - JOUR A1 - Medina, A. A1 - Ol, M. V. A1 - Greenblatt, D. A1 - Müller-Vahl, H. A1 - Strangfeld, Christoph T1 - High-Amplitude Surge of a Pitching Airfoil: Complementary Wind- and Water-Tunnel Measurements N2 - RECENT interest in gust response, rotorcraft forward flight and wind energy, among other applications, has focused on streamwise oscillations of nominally two-dimensional airfoils in attached and separated flows. The airfoil may be simultaneously held at constant incidence or execute some maneuver, such as pitch. The relative freestream is spatially uniform but temporally unsteady, and this can be accomplished in a ground-test facility in two ways. The first method is to vary the output of the prime mover, such as the rotational speed of the impeller or the blower driving a wind tunnel, or (alternatively) to vary the pressure drop in the tunnel, thereby varying the flow speed in the test section, despite nominally constant primemover revolutions per minute. The second method is used to keep the tunnel’s operating speed constant, as well as to move the test article in the streamwise direction, fore and aft (for example, via an electric linear motor), such that the relative freestream speed felt by the test article varies according to some waveform. Typically, the latter approach is chosen in water tunnels, where there is too much tunnel-circuit inertia to vary the flow speed directly but where the usually low tunnel test section flow speeds enable large excursions in the relative freestream by oscillation of the test article. In fact, outright reverse flow is possible by moving the test article in the laboratory frame at a higher speed than the water-tunnel flow speed. In either case, a sinusoidal relative-speed waveform is the most intuitively realizable, and this can be combined with similar oscillations in the airfoil incidence angle or other kinematics. Although the two methods of realizing streamwise oscillations are mechanically distinct, experimental comparisons between an oscillating test article in a water tunnel and a stationary test article in a wind tunnel with a louvermechanismhave demonstrated agreement in themeasured lift and drag histories. Such experimentswere performed by Granlund et al. for a 10% freestream amplitude oscillation and fixed airfoil incidence, comparing a free-surface water tunnel and a closed-circuit wind tunnel. After buoyancy was subtracted from the wind-tunnel data (resulting from the louver pressure drop) and the model inertia subtracted from the water-tunnel data (resulting from acceleration of the test article), the remaining lift and drag histories matched well at the low freestream oscillation amplitude regime. The work of Granlund et al. was later extended to high-advance-ratio streamwise oscillations of 50% amplitude by Greenblatt et al., where the aerodynamic histories of the water-tunnel and wind-tunnel facilities were compared in combined pitch and freestreamoscillations (governed by relative pitch phase), pure pitch oscillations, and purely freestream oscillations. Agreement between the two facilities’ data for fixed-incidence streamwise oscillations was reasonably good, and in fact, better than agreement in just the static lift and drag, evidently owing to differences in blockage and model-support systems. Additionally, Greenblatt et al. determined there was no strong coupling between simultaneous freestream oscillations and pitch oscillations on resultant lift and moment coefficients. KW - Wind energy KW - Dynamic stall KW - Deep stall KW - Airfoil surging KW - Airfoil pitching PY - 2018 U6 - https://doi.org/10.2514/1.J056408 SN - 0001-1452 SN - 1533-385X VL - 56 IS - 4 SP - 1703 EP - 1709 PB - American Institute of Aeronautics and Astronautics AN - OPUS4-43994 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bernegger, Raphael A1 - Altenburg, Simon A1 - Roellig, Mathias A1 - Maierhofer, Christiane T1 - Applicability of a 1D analytical model for pulse thermography of laterally heterogeneous semitransparent materials N2 - Pulse thermography (PT) has proven to be a valuable non-destructive testing method to identify and quantify defects in fiber-reinforced polymers. To perform a quantitative defect characterization, the heat diffusion within the material as well as the material parameters must be known. The heterogeneous material structure of glass fiber-reinforced polymers (GFRP) as well as the semitransparency of the material for optical excitation sources of PT is still challenging. For homogeneous semitransparent materials, 1D analytical models describing the temperature distribution are available. Here, we present an analytical approach to model PT for laterally inhomogeneous semitransparent materials.We show the validity of the model by considering different configurations of the optical heating source, the IR camera, and the differently coated GFRP sample. The model considers the lateral inhomogeneity of the semitransparency by an additional absorption coefficient. It includes additional effects such as thermal losses at the samples surfaces, multilayer systems with thermal contact resistance, and a finite duration of the heating pulse. By using a sufficient complexity of the analytical model, similar values of the material parameters were found for all six investigated configurations by numerical fitting. KW - Absorption coefficient KW - Analytical model KW - GFRP KW - Heterogeneous KW - Pulse thermography KW - Semitransparent PY - 2018 U6 - https://doi.org/10.1007/s10765-018-2362-7 SN - 0195-928X SN - 1572-9567 VL - 39 IS - 3 SP - Article 39, ICPPP 19, 1 EP - 17 PB - Springer International Publishing AG AN - OPUS4-44003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schumacher, David A1 - Meyendorf, N. A1 - Hakim, I. A1 - Ewert, Uwe ED - Chimenti, D. E. ED - Bond, L. J. T1 - Defect recognition in CFRP components using various NDT methods within a smart manufacturing process N2 - The manufacturing process of carbon fiber reinforced polymer (CFRP) components is gaining a more and more significant role when looking at the increasing amount of CFRPs used in industries today. The monitoring of the manufacturing process and hence the reliability of the manufactured products, is one of the major challenges we need to face in the near future. Common defects which arise during manufacturing process are e.g. porosity and voids which may lead to delaminations during operation and under load. To find irregularities and classify them as possible defects in an early stage of the manufacturing process is of high importance for the safety and reliability of the finished products, as well as of significant impact from an economical point of view. In this study we compare various NDT methods which were applied to similar CFRP laminate samples in order to detect and characterize regions of defective volume. Besides ultrasound, thermography and eddy current, different X-ray methods like radiography, laminography and computed tomography are used to investigate the samples. These methods are compared with the intention to evaluate their capability to reliably detect and characterize defective volume. Beyond the detection and evaluation of defects, we also investigate possibilities to combine various NDT methods within a smart manufacturing process in which the decision which method shall be applied is inherent within the process. Is it possible to design an in-line or at-line testing process which can recognize defects reliably and reduce testing time and costs? This study aims to show up opportunities of designing a smart NDT process synchronized to the production based on the concepts of smart production (Industry 4.0). A set of defective CFRP laminate samples and different NDT methods were used to demonstrate how effective defects are recognized and how communication between interconnected NDT sensors and the manufacturing process could be organized. T2 - 44TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION CY - Provo, Utah, USA DA - 16.07.2017 KW - Carbon fiber reinforced polymers KW - Non-destructive testing KW - Smart industry (4.0) KW - Ultrasound KW - Laminography KW - Serial sectioning KW - Computed tompgraphy PY - 2018 SN - 978-0-7354-1644-4 U6 - https://doi.org/10.1063/1.5031521 SN - 0094-243X VL - 1949 SP - UNSP 020024, 1 EP - 11 PB - AIP Publishing AN - OPUS4-44773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Titschack, J. A1 - Baum, D. A1 - Matsuyama, K. A1 - Boos, K. A1 - Färber, C. A1 - Kahl, W.-A. A1 - Ehrig, Karsten A1 - Meinel, Dietmar A1 - Soriano, C. A1 - Stock, S.R. T1 - Ambient occlusion – A powerful algorithm to segment shell and skeletal intrapores in computed tomography data N2 - During the last decades, X-ray (micro-)computed tomography has gained increasing attention for the description of porous skeletal and shell structures of various organism groups. However, their quantitative analysis is often hampered by the difficulty to discriminate cavities and pores within the object from the surrounding region. Herein, we test the ambient occlusion (AO) algorithm and newly implemented optimisations for the segmentation of cavities (implemented in the software Amira). The segmentation accuracy is evaluated as a function of (i) changes in the ray length input variable, and (ii) the usage of AO (scalar) field and other AO-derived (scalar) fields. The results clearly indicate that the AO field itself outperforms all other AO-derived fields in terms of segmentation accuracy and robustness against variations in the ray length input variable. The newly implemented optimisations improved the AO field-based segmentation only slightly, while the segmentations based on the AOderived fields improved considerably. Additionally, we evaluated the potential of the AO field and AO-derived fields for the separation and classification of cavities as well as skeletal structures by comparing them with commonly used distance-map-based segmentations. For this, we tested the zooid separation within a bryozoan colony, the stereom classification of an ophiuroid tooth, the separation of bioerosion traces within a marble block and the calice (central cavity)-pore separation within a dendrophyllid coral. The obtained results clearly indicate that the ideal input field depends on the three-dimensional morphology of the object of interest. The segmentations based on the AO-derived fields often provided cavity separations and skeleton classifications that were superior to or impossible to obtain with commonly used distance-map-based segmentations. The combined usage of various AO-derived fields by supervised or unsupervised segmentation algorithms might provide a promising target for future research to further improve the results for this kind of high-end data segmentation and classification. Furthermore, the application of the developed segmentation algorithm is not restricted to X-ray (micro-)computed tomographic data but may potentially be useful for the segmentation of 3D volume data from other sources. KW - Micro-computed tomography KW - Pore segmentation KW - Skeletal classification KW - Image analysis PY - 2018 U6 - https://doi.org/10.1016/j.cageo.2018.03.007 SN - 0098-3004 SN - 1873-7803 VL - 115 SP - 75 EP - 87 PB - Elsevier Ltd. AN - OPUS4-44511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Gunella, F. A1 - Kunisch, E. A1 - Maenz, S. A1 - Horbert, V. A1 - Xin, L. A1 - Mika, J. A1 - Borowski, J. A1 - Bischoff, S. A1 - Schubert, H. A1 - Sachse, A. A1 - Illerhaus, Bernhard A1 - Günster, Jens A1 - Bossert, J. A1 - Jandt, K. D. A1 - Plöger, F. A1 - Kinne, R. W. A1 - Brinkmann, O. A1 - Bungartz, M. ED - Carragee, T1 - The GDF5 mutant BB-1 enhances the bone formation induced by an injectable, poly(l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement in a sheep defect model of lumbar osteopenia N2 - BACKGROUND CONTEXT: Targeted delivery of osteoinductive bone morphogenetic Proteins (eg, GDF5) in bioresorbable calcium phosphate cement (CPC), potentially suitable for vertebroplasty and kyphoplasty of osteoporotic vertebral fractures, may be required to counteract augmented local bone catabolism and to support complete bone regeneration. The biologically optimized GDF5 Mutant BB-1 may represent an attractive drug candidate for this purpose. PURPOSE: The aim of the current study was to test an injectable, poly (l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming CPC containing low-dose BB-1 in a sheep lumbar osteopenia model. STUDY DESIGN/ SETTING: This is a prospective experimental animal study. METHODS: Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and were filled with fiber-reinforced CPC alone (L4; CPC+fibers) or with CPC containing different dosages. KW - Bone morphogenetic protein; KW - Bone regeneration; KW - Micro-Computed-Tomography; KW - Calcium phosphate cement; KW - GDF-5 mutant; KW - Large animal model sheep; KW - Osteoporotic vertebral fracture PY - 2018 U6 - https://doi.org/10.1016/j.spinee.2017.10.002 SN - 1529-9430 SN - 1878-1632 VL - 18 IS - 2 SP - 357 EP - 369 PB - Elsevier CY - New York AN - OPUS4-44561 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gottlieb, Cassian A1 - Günther, Tobias A1 - Wilsch, Gerd T1 - Impact of grain sizes on the quantitative concrete analysis using laser-induced breakdown spectroscopy N2 - In civil engineering concrete is the most used building material for making infrastructures like bridges and parking decks worldwide. It is as a porous and multiphase material made of aggregates with a defined grain size distribution, cement and water as well as different additives and admixtures depending on the application. Different grain sizes are important to ensure the needed density and compressive strength. The resulting porous cement matrix contains a mixture of flour grains (aggregates with a grain size below 125 lm) and cement particles (particle size≈50lm). Harmful species like chlorides may penetrate together with water through the capillary pore space and may trigger different damage processes. The damage assessment of concrete structures in Germany is estimated due to the quantification of harmful elements regarding to the cement content only. In the evaluation of concrete using LIBS a two-dimensional scanning is necessary to consider the heterogeneity caused by the aggregates. Therefore, a LIBS system operating with a low energy NdCr:YAG laser, a pulse energy of 3 mJ, a wavelength of 1064 nm, a pulse width of 1.5 ns and a Repetition rate of 100 Hz has been used. Different Czerny-Turner spectrometers with CCD detectors in the UV and NIR range have been used for the detection. Large aggregates (macro-heterogeneity) can be excluded from the evaluation, whereas small aggregates in the range of the laser spot size (flour grains) cannot be spatially resolved. In this work the micro heterogeneity caused by flour grains and their impact on the quantification with LIBS will be discussed. To analyze the effect of changing grain sizes and ratios, the ablation behavior has been determined and compared. Samples with defined grain sizes were made and analyzed using LIBS. The grain size distributions were analyzed with laser diffraction (LDA). KW - LIBS KW - Concrete KW - Micro heterogeneity KW - Grain sizes PY - 2018 U6 - https://doi.org/10.1016/j.sab.2018.02.004 SN - 0584-8547 SN - 0038-6987 VL - 142 SP - 74 EP - 84 PB - Elsevier AN - OPUS4-44595 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gornushkin, Igor B. A1 - Völker, Tobias A1 - Kazakov, Alexander Ya. T1 - Extension and investigation by numerical simulations of algorithm for calibration-free laser induced breakdown spectroscopy N2 - Accuracy of calibration-free (CF) methods in laser-induced breakdown spectroscopy (LIBS) depends on experimental conditions and instrumental parameters that must match a CF LIBS model. Here, the numerical study is performed to investigate effects of various factors, such as the optical density, plasma uniformity, line overlap, noise, spectral resolution, electron density and path length on the results of CF-LIBS analyses. The effects are examined one-by-one using synthetic spectra of steel slag samples that fully comply with the mathematical model of the method. Also, the algorithm includes several new features in comparison with previously proposed CF algorithms. In particular, it removes limits on the optical thickness of spectral lines that are used for the construction of the Saha-Boltzmann plot; it retrieves the absorption path length (Plasma diameter) directly from spectral lines; it uses the more realistic Voigt line profile function instead of the Lorentzian function; and it employs the pre-calculated and tabulated thin-to-thick line ratios instead of approximating functions for selfabsorption correction. KW - Laser induced plasma KW - LIBS KW - Plasma modeling KW - Plasma diagnostics KW - Calibration free LIBS PY - 2018 U6 - https://doi.org/10.1016/j.sab.2018.06.011 SN - 0584-8547 VL - 147 SP - 149 EP - 163 PB - Elsevier B.V. AN - OPUS4-45340 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Kruschwitz, Sabine T1 - Monitoring of the absolute water content in porous materials based on embedded humidity sensors N2 - Moisture transport monitoring may indicate the onset of deterioration in porous building materials Prior to damage occurring. Most moisture measurement systems provide only qualitative values, require extensive calibration, or are destructive. Thus, non-destructive and calibration-free monitoring Systems are required. Our approach of moisture monitoring is to embed sensors that measure the relative humidity. In our experiment, screed samples are monitored during the Hydration and evaporation process. Every test sample is equipped with 10 embedded sensors which measure the relative humidity across the sample thickness. Based on Hillerborg’s approach, the relative humidity is converted into the corresponding pore saturation. In our study, the free water is computed without knowledge of the Sorption isotherm. The free water in the pore system is predicted and validated. The predicted weight decrease corresponds conclusively to gravimetrically measured weights. The embedded sensors yield the absolute liquid water content and enable an experimental, non-destructive monitoring of liquid water in porous materials. KW - Moisture measurements KW - Porous materials KW - Embedded sensors KW - Partial pore saturation KW - Sorption isotherm PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-453476 SN - 0950-0618 VL - 177 SP - 511 EP - 521 PB - Elsevier AN - OPUS4-45347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Metz, Christian A1 - Franz, Philipp A1 - Fischer, C. A1 - Wachtendorf, Volker A1 - Maierhofer, Christiane T1 - Active thermography for quality assurance of 3D-printed polymer structures N2 - Additively manufactured test specimens made of polyamide 12 (PA 12) by Laser Sintering (LS) as well as of acrylnitril-butadien-styrol (ABS) by Fused Layer Modeling (FLM), were tested with active thermography. For this, two different excitation methods (flash and impulse excitation) were used and compared, regarding the suitability for the detection of constructed and imprinted defects. To increase the quality of the thermograms, data processing methods like thermal signal reconstruction (TSR) and Fourier-Transformation were applied. Furthermore, the long-term stability of the probes towards environmental stress, like UV-radiation, heat, water contact and frost is being investigated in the presented project with artificial weathering tests. T2 - 14th Quantitative InfraRed Thermography Conference CY - Berlin, Germany DA - 25.06.2018 KW - Additive manufacturing KW - Active thermography KW - Artificial weathering PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-453919 SP - Tu.3.A.2, 1 EP - 9 AN - OPUS4-45391 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krankenhagen, Rainer A1 - Ziegler, Mathias A1 - Maierhofer, Christiane ED - Maldague, X. T1 - Systematic errors in the evaluation of uncorrected data from thermographic lock-in measurements N2 - Lock-in thermography (LT) is based on the correct evaluation of phase differences between the temperature oscillations at different surface regions of the object under test during periodic heating. Since the usual heating procedures contain a DC component, the actual heating pattern achieved is not harmonic. This causes systematic deviations when phase differences are determined by means of harmonic analysis, e.g. with FFT analysis. The resulting errors depend clearly on the ratio between DC and AC amplitude, which is demonstrated at simulated and experimentally recorded temperature transients. Further experimental LT data obtained by different oscillating energy inputs showed a variety of possible shapes of transients with different DC components. T2 - 14th QIRT Conference CY - Berlin, Germany DA - 26.06.2018 KW - NDT KW - Lock-in Thermography KW - FFT PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-453768 SP - 539 EP - 547 PB - QIRT Council AN - OPUS4-45376 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -