Wissenschaftliche Artikel der BAM
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- 2021 (70) (entfernen)
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- Additive manufacturing (8)
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- Non-destructive testing (5)
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- Laser powder bed fusion (4)
- Residual stress (4)
- Zerstörungsfreie Prüfung (4)
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- 8 Zerstörungsfreie Prüfung (70) (entfernen)
Performance of calcium phosphate cements in the augmentation of sheep vertebrae - An ex vivo study
(2021)
Oil-based calcium phosphate cement (Paste-CPC) shows not only prolonged shelf life and injection times, but also improved cohesion and reproducibility during application, while retaining the advantages of fast setting, mechanical strength, and biocompatibility. In addition, poly(L-lactideco-glycolide) (PLGA) fiber reinforcement may decrease the risk for local extrusion. Bone defects (diameter 5 mm; depth 15 mm) generated ex vivo in lumbar (L) spines of female Merino sheep (2–4 years) were augmented using: (i) water-based CPC with 10% PLGA fiber reinforcement (L3); (ii) Paste-CPC (L4); or (iii) clinically established polymethylmethacrylate (PMMA) bone cement (L5). Untouched (L1) and empty vertebrae (L2) served as controls. Cement performance was analyzed using micro-computed tomography, histology, and biomechanical testing. Extrusion was comparable for Paste-CPC(-PLGA) and PMMA, but significantly lower for CPC + PLGA. Compressive strength and Young’s modulus were similar for Paste-CPC and PMMA, but significantly higher compared to those for empty defects and/or CPC + PLGA. Expectedly, all experimental groups showed significantly or numerically lower compressive strength and Young’s modulus than those of untouched controls. Ready-to-use Paste-CPC demonstrates a performance similar to that of PMMA, but improved biomechanics compared to those of water-based CPC + PLGA, expanding the therapeutic arsenal for bone defects. O, significantly lower extrusion of CPC + PLGA fibers into adjacent lumbar spongiosa may help to reduce the risk of local extrusion in spinal surgery.
Im Europäischen EMPIR-Projekt „NanoXSpot“ (Measurement of the focal spot size of Xray tubes with spot sizes down to 100 nm) werden neue Messmethoden für Brennflecke von Röntgenröhren entwickelt. Teil des Projektes ist die Entwicklung eines zur Lochkameramethode äquivalenten Messverfahrens für kleine Brennflecke. ASTM E 1165-20, Annex A, beschreibt die Bestimmung von Brennfleckgrößen aus Kantenprofilen von Lochaufnahmen für Röntgenröhren mit Brennflecken > 50 μm. Es wurde bereits vorgeschlagen über die Analyse der richtungsabhängigen Kantenunschärfe einer Lochblende und anschließender CT-Rekonstruktion die Intensitätsverteilung des Brennflecks äquivalent zur Lochkameraaufnahme zu berechnen. Die Lochkameramethode, wie in EN 12543-2 und ASTM E 1165-20 beschrieben, ist im unteren Größenbereich für Mikrofokusröhren nicht geeignet, da Pinholes < 10 μm schwer zu fertigen sind und lange Belichtungszeiten erwartet werden. Mit Hilfe exakt gefertigter Lochblenden sowie strukturierter Targets mit
konvergierenden Strukturen wird der Bereich mit der Single-Shot-CT-Methode auf die Messung von Mikrofokusröhren, alternativ zur Vermessung von Kanten oder Strichgruppenkörpern, erweitert. Die rekonstruierten Brennfleckformen werden mit Kantenund Lochkameraaufnahmen quantitativ verglichen, um die Messgenauigkeit zu bewerten.
Außerdem werden CNR und Messzeit bestimmt, um die Wirtschaftlichkeit der Verfahren zu bewerten.
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.
In this study, the ability of an electronic nose developed to analyze and monitor odor emissions from three poultry farms located in Meknes (Morocco) and Berlin (Germany) was evaluated. Indeed, the potentiality of the electronic nose (e-nose) to differentiate the concentration fractions of hydrogen sulfide, ammonia, and ethanol was investigated. Furthermore, the impact change of relative humidity values (from 15% to 67%) on the responses of the gas sensors was reported and revealed that the effect remained less than 0.6%. Furthermore, the relevant results confirmed that the developed e-nose system was able to perfectly classify and monitor the odorous air of poultry farms.
Sehr geehrte Damen und Herren,
liebe Leserinnen und Leser,
bereits im ersten Band der N.i.Ke. Schriftenreihe des Netzwerks zur interdisziplinären Kulturerhaltung hatte ich angeführt, dass bei der Untersuchung von kulturellen Artefakten naturwissenschaftliche Untersuchungsmethoden zunehmend an Bedeutung gewinnen, sie eigentlich unverzichtbar geworden sind.
Ein besonders einprägsames Beispiel dieser fächerübergreifenden Zusammenarbeit zwischen Geisteswissenschaften, Naturwissenschaften und Restaurierungswissenschaften war die Ausstellung Johannes Vermeer. Vom Innehalten, die in diesem Jahr in der Gemäldegalerie Alter Meister in den staatlichen Kunstsammlungen Dresden gezeigt wurde. Eigens für diese Ausstellung wurde das Gemälde Brieflesendes Mädchen am offenen Fenster einer grundlegenden Restaurierung unterzogen. Diese Restaurierung diente jedoch nicht nur der Reparatur des Bildes. Um sich dem ursprünglichen Zustand des Gemäldes zwischen 1657 und 1659 anzunähern, wurden später hinzugefügte Malschichten großflächig abgenommen. Möglich wurde dies durch unterschiedliche, bildgebende materialwissenschaftliche Untersuchungen im Vorfeld, welche die wissenschaftlichen Grundlagen für die Diskussion über den weiteren Umgang mit der Lesenden schufen.
Materialanalytische Verfahren wurden und werden ständig weiterentwickelt und optimiert. Sei es, um aus einer Vielzahl von Einzelmessungen ein Gesamtbild zu erstellen, oder die Größe einer Probenentnahme so zu reduzieren, dass von einer „minimal-invasiven“ oder „quasi nicht-invasiven“ Untersuchung ausgegangen werden kann. Nun feiert die Bundesanstalt für Materialforschung und -prüfung, zusammen mit ihren Vorgängerinstitutionen, den königlichen Versuchsanstalten, in diesem Jahr ihren einhundertfünfzigsten Geburtstag. Sie blickt damit auf eine lange Tradition materialwissenschaftlicher Analysen zurück, an deren Beginn beispielsweise die metallographischen Untersuchungen von Adolf Martens stehen. Derartige Untersuchungen bilden auch heute noch einen wesentlichen Bestandteil archäometallurgischer Forschung. Die Historie bzw. die Weiterentwicklung der Methodik lässt sich hier besonders gut nachzeichnen. Jedoch blicken auch Verfahren zur Charakterisierung weiterer Werkstoffe, wie Glas, Keramik, oder organischer Materialien auf eine lange Geschichte zurück.
Die in diesem Band der N.i.Ke.-Schriftenreihe präsentierten Beiträge dokumentieren einerseits aktuelle Forschungsarbeiten, die erst in diesem Jahr in entsprechenden Fachjournalen publiziert wurden, andererseits liegen einige der Arbeiten bereits 50 Jahre zurück. Sie bekunden damit nicht nur die materialtechnologische und historische Bandbreite der Projekte, sondern offenbaren die Vielfältigkeit kulturhistorischer oder restauratorischer Fragestellungen, zu deren Beantwortung natur- und materialwissenschaftliche Forschung wesentliche Beiträge liefern können.
Ich bedanke mich bei allen Kolleginnen und Kollegen, die zur Erstellung dieser dritten Ausgabe der N.i.Ke. Schriftenreihe des Netzwerks zur interdisziplinären Kulturerhaltung beigetragen haben. Ihre Aufsätze ermöglichen den Blick in die Vielfältigkeit materialwissenschaftlicher Untersuchungen im Bereich Kunst- und Kulturgut. Ich wünsche Ihnen viel Spaß auf dieser kleinen Zeitreise.
Industrial processes release substantial quantities of waste heat, which can be harvested to generate electricity. At present, the conversion of low grade waste heat to electricity relies solely on thermoelectric materials, but such materials are expensive and have low thermodynamic efficiencies. Although thermomagnetic materials may offer a promising alternative, their performance remains to be evaluated, thereby hindering their real-world application. Here, the efficiency and cost effectiveness of thermomagnetic materials are evaluated for the usage in motors, oscillators, and generators for converting waste heat to electricity. The analysis reveals that up to temperature differences of several 10 K, the best thermomagnetic materials have the potential to compete with thermoelectric materials. Importantly, it is found that the price per watt of some thermomagnetic materials is much lower compared to that of present-day thermoelectrics, which can become competitive with conventional power plants. This materials library enables the selection of the best available thermomagnetic materials for harvesting waste heat and gives guidelines for their future development.
The determination of the anisotropy of materials’ microstructure and morphology (pore space) in diesel particulate filter (DPF) materials is an important problem to solve, since such anisotropy determines the mechanical, thermal, and filtration properties of such materials. Through the use of a dedicated (and simple) segmentation algorithm, it is shown how to exploit the information yielded by 3D X-ray computed tomography data to quantify the morphological anisotropy. It is also correlated that such anisotropy of the pore space Such anisotropy of the pore space is also correlated with the microstructure and crystallographic anisotropy of the material in several showcases: a microstructurally isotropic material, such as SiC, and some morphologically and microstructurally anisotropic cordierite materials. In the later case, the finer the grain size, the more isotropic the microstructure.
Additive manufacturing (AM) is developing rapidly due to itsflexibility in producing complex geometries and tailored material compositions. However, AM processes are characterized by intrinsic limitations concerning their resolution and surface finish, which are related to the layer-by-layer stacking process. Herein, a self-organization process is promoted as an approach to improve surface quality and achieve optimization of 3D minimal surface lightweight structures. The self-organization is activated after the powder bed 3D printing process via local melting, thereby allowing surface tension-driven viscous flow.The surface roughness Ra (arithmetic average of the roughness profile) could bedecreased by a factor of 1000 and transparent lenses and complex gyroid structures could be produced for demonstration. The concept of self-organization is further elaborated by incorporating external magnetic fields to intentionally manipulate magnetic particles, which are mixed with the polymer before printing and self-organization. This concept can be applied to develop programmable materials with specific microtextures responding to the external physical conditions.
Detection of surface breaking cracks using flying line laser thermography: A Canny-based algorithm
(2021)
In this work, we introduce a new algorithm for effectual crack detection using flying line laser thermography, based on the well-known Canny approach. The algorithm transforms the input thermographic sequence into an edge map. Experimental measurements are performed on a metallic component that contains surface breaking cracks due to industrial use. The specimen is tested using flying line thermography at different scanning speeds and laser input powers. Results obtained with the proposed algorithm are additionally compared with a previously established algorithm for flying spot thermography. The proposed Canny-based algorithm can be used in automated systems for thermographic non-destructive testing.
Mass Spectrometry (MS) and Nuclear Magnetic Resonance Spectroscopy (NMR) are valuable analytical and quality control methods for most industrial chemical processes as they provide information on the concentrations of individual compounds and by-products. These processes are traditionally carried out manually and by a specialist, which takes a substantial amount of time and prevents their utilization for real-time closed-loop process control. This paper presents recent advances from two projects that use Artificial Neural Networks (ANNs) to address the challenges of automation and performance-efficient realizations of MS and NMR. In the first part, a complete toolchain has been realized to develop simulated spectra and train ANNs to identify compounds in MS. In the second part, a limited number of experimental NMR spectra have been augmented by simulated spectra, to train an ANN with better prediction performance and speed than state-of-the-art analysis. These results suggest that, in the context of the digital transformation of the process industry, we are now on the threshold of a strongly simplified use of MS and MRS and the accompanying data evaluation by machine-supported procedures, and can utilize both methods much wider for reaction and process monitoring or quality control.
The Alpine Fault zone in New Zealand marks a major transpressional plate boundary that is late in its typical earthquake cycle. Understanding the subsurface structures is crucial to understand the tectonic processes taking place. A unique seismic survey including 2D lines, a 3D array, and borehole recordings, has been performed in the Whataroa Valley and provides new insights into the Alpine Fault zone down to ∼2 km depth at the location of the Deep Fault Drilling Project (DFDP)-2 drill site. Seismic images are obtained by focusing prestack depth migration approaches. Despite the challenging conditions for seismic imaging within a sediment filled glacial valley and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged. A set of several reflectors dipping 40°–56° to the southeast are identified in a ∼600 m wide zone that is interpreted to be the minimum extent of the damage zone. Different approaches image one distinct reflector dipping at ∼40°, which is interpreted to be the main Alpine Fault reflector located only ∼100 m beneath the maximum drilled depth of the DFDP-2B borehole. At shallower depths (z < 0.5 km), additional reflectors are identified as fault segments with generally steeper dips up to 56°. Additionally, a glacially over-deepened trough with nearly horizontally layered sediments and a major fault (z < 0.5 km) are identified 0.5–1 km south of the DFDP-2B borehole. Thus, a complex structural environment is seismically imaged and shows the complexity of the Alpine Fault at Whataroa.
Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including mesoand macropores. Within such a pore network, material moisture plays a crucial role in almost all transport processes. In the hygroscopic range, the pores are partially saturated and liquid water is only located at the pore fringe due to physisorption. Therefore, material parameters such as porosity or median pore diameter are inadequate to predict material moisture and moisture transport. To quantify the spatial distribution of material moisture, Hillerborg’s adsorption Theory is used to predict the water layer thickness for different pore geometries. This is done for all pore sizes, including those in the lower nanometre range. Based on this approach, it is shown that the material moisture is almost completely located in mesopores, although the pore network is highly dominated by macropores. Thus, mesopores are mainly responsible for the moisture storage capacity, while macropores determine the moisture transport capacity, of an amorphous material. Finally, an electrical analogical circuit is used as a model to predict the diffusion coefficient based on the pore-size distribution, including physisorption.
Laser-based additive manufacturing methods allow the production of complex metal structures within a single manufacturing step. However, the localized heat input and the layer-wise manufacturing manner give rise to large thermal gradients. Therefore, large internal stress (IS) during the process (and consequently residual stress (RS) at the end of production) is generated within the parts. This IS or RS can either lead to distortion or cracking during fabrication or in-service part failure, respectively. With this in view, the knowledge on the magnitude and spatial distribution of RS is important to develop strategies for its mitigation. Specifically, diffraction-based methods allow the spatial resolved determination of RS in a non-destructive fashion. In this review, common diffraction-based methods to determine RS in laser-based additive manufactured parts are presented. In fact, the unique microstructures and textures associated to laser-based additive manufacturing processes pose metrological challenges. Based on the literature review, it is recommended to (a) use mechanically relaxed samples measured in several orientations as appropriate strain-free lattice spacing, instead of powder, (b) consider that an appropriate grain-interaction model to calculate diffraction-elastic constants is both material- and texture-dependent and may differ from the conventionally manufactured variant. Further metrological challenges are critically reviewed and future demands in this research field are discussed.
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.
We present a preliminary investigation on distributed humidity monitoring during the drying process of concrete based on an embedded polymer optical fiber (POF). The water dissipated into the POF changes several properties of the fiber such as refractive index, scattering coefficient and attenuation factor, which eventually alters the Rayleigh backscattered light. The optical time Domain reflectometer (OTDR) technique is performed to acquire the backscattered signal at the wavelengths 650 nm and 500 nm, respectively. Experimental results show that the received signal increases at 650 nm while the fiber attenuation factor clearly increases at 500 nm, as the concrete dries out. In the hygroscopic range, the information retrieved from the signal change at 650 nm agrees well with the measurement result of the electrical humidity sensors also embedded in the concrete sample.
In this work, we present our results achieved in several research activities for development of distributed fiber optic radiation sensors using glass and polymer optical fibers. The findings show that both the measurement of the radiation-induced attenuation (RIA) along the entire sensing fiber and the accompanying change in the refractive index of the fiber core can be used for distributed radiation monitoring.
This study reports on the stress relaxation potential of stress-relieving heat treatments for laser powder bed fused 316L. The residual stress is monitored non-destructively using neutron diffraction before and after the heat treatment. Moreover, the evolution of the microstructure is analysed using scanning electron microscopy. The results show, that a strong relaxation of the residual stress is obtained when applying a heat treatment temperature at 900°C. However, the loss of the cellular substructure needs to be considered when applying this heat treatment strategy.
Extensive research is being conducted on magnesium (Mg) alloys for bone implant manufacturing, due to their biocompatibility, biodegradability and mechanical properties. Gadolinium (Gd) is among the most promising alloying elements for property control in Mg alloy implants; however, its toxicity is contro- versial. Investigating Gd behavior during implant corrosion is thus of utmost importance. In this study, we analyzed the degradation byproducts at the implant site of biodegradable Mg-5Gd and Mg-10Gd implants after 12 weeks healing time, using a combination of different imaging techniques: histology, energy-dispersive x-ray spectroscopy (EDX), x-ray microcomputed tomography (μCT) and neutron μCT. The main finding has been that, at the healing time in exam, the corrosion appears to have involved only the Mg component, which has been substituted by calcium and phosphorus, while the Gd remains localized at the implant site. This was observed in 2D by means of EDX maps and extended to 3D with a novel application of neutron tomography. X-ray fluorescence analysis of the main excretory organs also did not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy happened during degradation.
Seit 1999 existiert das MIL-HDBK 1823, die us-amerikanische Leitfaden zur Erstellung einer Probability of Detection (POD; Fehlerdetektionswahrscheinlichkeit). Obwohl das Dokument als internationaler Stand der Technik angesehen wird, ist die allgemeine Anwendung in der ZfP-Praxis von einigen Nachteilen begleitet:
1. Die beschriebenen POD‘s bilden ausschließlich die Grundlagen-POD ab, jeweils mit nur einem Fehlerparameter und einem Signalparameter. Modernere Ansätze werden hier nicht adressiert.
2. Die aktuelle Version verzichtet fast vollständig auf konkrete mathematische Formulierungen.
3. Die Richtlinie richtet sich hauptsächlich an die militärische Luftfahrt.
4. Das Dokument ist nur in englischer Sprache verfügbar.
Mit Hilfe eines BMWi-Förderprojekts wird ein weiterführendes Regelwerk auf Basis der MIL-HDBK 1823 unter deutscher Federführung erarbeitet, welches die Anwendung der POD-Berechnung auf eine breitere Basis stellt und die oben genannten Nachteile der MIL-HDBK 1823 behebt.
Das vorgestellte Projekt „normPOD“ wird eine normative, branchenübergreifend einsetzbare Beschreibung des Vorgehens bei der Berechnung einer POD zur Zuverlässigkeitsbewertung zerstörungsfreier Prüfungen entwickeln. Hierbei wird Klarheit über unterschiedliche POD-Ansätze geschaffen und anhand praktischer Beispiele aus Maschinenbau und Bauwesen ein Leitfaden für den Praxiseinsatz erarbeitet.
Das Poster gibt einen Überblick über die geplanten Arbeiten innerhalb des Projekts und lädt die Beteiligten der DGZfP-Jahrestagung zur Diskussion ein, um eine breite Basis und Akzeptanz für die entwickelten Berechnungsverfahren zu schaffen, insbesondere in Hinblick auf ZfP 4.0 und Digitalisierung.
Layer-by-layer additive manufacturing (AM) by means of laser-powder bed Fusion (L-PBF) offers many prospects regarding the design of lattice structures used, for example, in gas turbines. However, defects such as bulk porosity, Surface roughness, and re-entrant features are exacerbated in nonvertical structures, such as tilted struts. The characterization and quantification of these kinds of
defects are essential for the correct estimation of fracture and fatigue properties.
Herein, cylindrical struts fabricated by L-PBF are investigated by means of X-ray computed tomography (XCT), with the aim of casting light on the dependence of the three kinds of defects (bulk porosity, surface roughness, and re-entrant features) on the build angle. Innovative analysis methods are proposed to correlate shape and position of pores, to determine the angular-resolved Surface roughness, and to quantify the amount of re-entrant surface features, q. A meshing of the XCT surface enables the correlation of q with the classical Surface roughness Pa. This analysis leads to the conclusion that there is a linear correlation between q and Pa. However, it is conjectured that there must be a threshold of surface roughness, below which no re-entrant features can be build.