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The Binder Jetting BJ process is one of the most versatile additive manufacturing technologies in use. In this process a binder is locally jetted into a powder bed for the consolidation of a 3D structure, layer by layer. Basically, all materials which can be provided as a flowable powder and, thus, spreadable to a thin layer, can be processed. Metals, ceramics and polymers are processable, but also materials from nature, such as sand, wood sawdust and insect frass. Moreover, the BJ technology is adapted to large building volumes of some cubic meters easily. Besides these striking advantages, the manufacture of ceramic parts by BJ is still challenging, as the packing density of the powder bed is generally too low and the particle size of a flowable powder too large for a successful densification of printed parts in a subsequent sintering step to an advanced ceramic product. After an introduction of binder jetting in general and highlighting some examples, strategies for obtaining dense ceramic parts by BJ will be introduced.
Ziel des FuE-Vorhabens ist die Entwicklung, Aufbau und Validierung eines gasto-mographischen Messsystems basierend auf stationärer und mobiler Sensorik zum Emissionsmonitoring in kommunalen Kläranlagen. Die Gastomographie basiert hierbei im Wesentlichen auf, aus unterschiedlichen Sichtwinkeln aufgenommenen, integralen Konzentrationsmessungen, anhand derer eine Rekonstruktion der Gasverteilung erfolgt. Das FuE-Projekt kombiniert hierfür stationäre Sensornetzwerke mit luftgestützten und bodengebundenen Robotersystemen in einem System. Letztere werden mit Reflektoren und/oder Gasdetektoren ausgestattet. Hierfür werden Open-Path-Gasmesstechnik basierend auf Tunable Diode Laser Ab-sorption Spectroscopy (TDLAS, primär CH4 in ppm·m) und In-situ-Gassensorik (CH4, ppm) auf Basis von z.B. Infrarot eingesetzt. Dies sind zwei komplementäre Methoden der Gasmessung: Die In-situ-Gassensorik ermöglicht Punktmessungen, wohingegen TDLAS-Sensoren Gaskonzentrationen integral über offene Messstre-cken von bis zu 60 m gegen Oberflächen messen. Die In-situ-Gassensorik wird für Referenzmessungen und ggf. zur Erhöhung der Rekonstruktionsqualität zum Ein-satz kommen. Die wesentlichen Neuheiten des Projekts sind:
• 2D-Gastomographie auf Basis eines mit TDLAS-basierter Open-Path-Gasmesstechnik und Reflektoren ausgestatteten heterogenen Messsystems.
• CT-basierte Rekonstruktionsalgorithmen, adaptiert an die komplexen Rahmenbedingungen.
• Validierung des Messsystems anhand realer Messungen auf Kläranlagen.
In einem laufenden Kooperationsprojekt zwischen der BAM Berlin und der MPA Stuttgart wird das probabilistische Master Curve (MC) Konzept nach ASTM E1921 hinsichtlich seiner Übertragbarkeit auf ferritisches Gusseisen mit Kugelgraphit (DCI) untersucht. Zielsetzung ist die Bereitstellung einer Vorgehensweise zur Bestim-mung und Bewertung der dynamischen Bruchzähigkeit von DCI im Übergangsbe-reich. In diesem Beitrag wird der Versuchswerkstoff der Festigkeitsklasse GJS-400 näher vorgestellt. Ferner werden erste Ergebnisse von zwei bruchmechanischen Versuchsserien an SE(B)140-Großproben bei Belastungsraten von ca. 6∙104 MPa√ms-1 bei -40 °C und 60 °C präsentiert.
Therapeutic monoclonal antibodies are the fastest-growing group of biological agents which generated a yearly turnover of USD 210 billion in 2022 and whose sales are expected to grow by 10% annually over the next 10 years. With steadily increasing market importance, analytical methods for reliable quantification of therapeutic antibodies also become more and more relevant. Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) has become the main technology for antibody quantification. This approach, however, requires enzymatic digestion of the intact protein into peptides, for which a wide range of different protocols exists that often lead to different results depending on the digestion procedure or trypsin variants used. In particular, the amount and type of detergents added for protein unfolding prior to digestion is known to create significant bias in measurement results. The overall goal of the presented project is the application of novel thermostable and surface-functionalized trypsin particles for improved antibody digestion. Specifically, a trypsin-variant described in the literature exhibiting increased activity and thermal stability above 80°C, will be examined. The application of this enzyme should allow to perform digestion at elevated temperatures where the protein is naturally unfolding thereby increasing enzyme accessibility without the need for detergents. Furthermore, we will immobilize the thermostable trypsin onto the surface to further enhance enzyme stability, prevent self-digestion, and enable separation of trypsin from target peptides before LC–MS/MS analysis. As an immobilization platform, cheap and non-porous corundum particles will be used as these show high chemical stability and low levels of interaction of matrix proteins with the functionalized surface. adsorption. In a multidisciplinary collaboration with the SALSA Photonics Lab, we will investigate the characteristics of covalent enzyme binding and unspecific peptide binding using an interface-sensitive analytical tool, vibrational sum-frequency generation (VSFG) spectroscopy. The insights gained will not only lead to new competencies in peptide and enzyme surface analysis using VSFG spectroscopy in SALSA but will also significantly contribute to optimizing antibody quantification.
Regarding feedstocks for the additive manufacturing (AM) of ceramics, two features are most critical in classical powder based AM processes: a high particle packing density (typically >50% TD) must be achieved with very fine particles (typically submicron) in order to ensure sufficient sintering activity. Three innovative approaches will be introduced to overcome this problem:
1. Layer wise slurry deposition: The use of water based ceramic slurries as feedstock for the additive manufacture of ceramics has many advantages which are not fully exploit yet. In the layerwise slurry deposition (LSD) process a slurry with no or low organic content is repetitively spread as thin layers on each other by means of a doctor blade. During the deposition, the ceramic particles settle on the previously deposited and dried material to form thin layers with a high packing density (55-60%). The LSD therefore shares aspects both of tape casting and slip casting. The LSD differentiates from the classical powder-based AM layer deposition, which typically achieves with a flowable coarse grained powder a low packing density (35-50%) only, consequently hindering the ability of sintering ceramic parts to full density. The LSD is coupled with the principles of selective laser sintering (SLS) or binder jetting, to generate novel processes which take advantage of the possibility of achieving a highly dense powder-bed.
2. Laser induced slip casting: Contrary to the LSD process, which requires drying of each individual layer, the direct interaction of ceramic slurries with intense laser radiation, for the laser induced slip casting (LIS), is a promising approach for the additive manufacture of voluminous parts.
3. Gas flow assisted powder deposition: By the application of a vacuum pump a gas flow is realized throughout the powder bed. This gas flow stabilizes the powder bed and results into an enhanced flowability and packing density of the powder during layer deposition.
The presentation will provide a detailed discussion of potentialities and issues connected to the mentioned technologies and will describe the most recent developments in their application to technical ceramics.
Within fracture mechanics safety assessment for steels in nuclear technology, the probabilistic master curve (MC) concept according to ASTM E1921 is currently used for quasi-static loading conditions as a supplement to the established deterministic ASME reference curve concept. However, for ferritic ductile cast iron (DCI), a systematic review of potential modifications to the assumptions and the procedure according to ASTM E1921 and an associated validation are still lacking. For this reason, the application of the fracture mechanics MC concept to ferritic ductile cast iron is being investigated in a joint research project between MPA Stuttgart and BAM Berlin. According to IAEA SSG-26, the safety assessment of DCI containers for transport as well as storage of radioactive materials is based on the fracture mechanics criterion of general crack initiation exclusion. Within this context, the focus of the research project is on brittle fracture. The goal is the establishment of a methodology to determine and assess dynamic fracture toughness values of DCI in the ductile-to-brittle transition regime, using samples extracted from a component.
The experimental program uses a DCI material of grade GJS-400, which is generally used for transport and storage containers of radioactive materials. Firstly, a basic mechanical-technological material characterization will be performed consisting of tensile, Charpy and Pellini tests. Following the material characterization, the loading rate relevant for brittle fracture will be determined using instrumented C(T)25-fracture tests at a temperature of -40°C. To be able to transfer the relevant loading rate to other specimen geometries or sizes, the time-dependent course of the Weibull stress is assessed via numerical analyses. With this information an extensive experimental program consisting of DC(T)9, C(T)25, C(T)50, SE(B)10, SE(B)25 and SE(B)140 specimens is performed. These experimental results will be further supported by numerical and fractographic analyses. The empirical experimental database developed for DCI materials will be used to assess the applicability of the MC concept for DCI materials under dynamic loading.
At the current time manufacturing and precracking of test specimens is ongoing. The authors provide first results concerning the mechanical-technological material characterization, the relevant loading rate for brittle fracture determined via C(T)25 tests, and some early results of other specimen types. These experimental results are also supported by preliminary numerical and statistical analyses.
Chloride binding by the hydrate phases of cementitious materials influences the rate of chloride ingress into these materials and, thus, the time at which chloride reaches the steel reinforcement in concrete structures. A particularly important role in this context is played by layered double hydroxides (LDHs), including AFm phases. Chloride binding isotherms of individual LDH/AFm phases would be required as input for computational models of chloride ingress, but such isotherms are only available for a few AFm phases, and in addition the available data are partly conflicting.
The present study, conducted in the context of RILEM TC 283-CAM ‘Chloride transport in alkali-activated materials’, significantly extends the available database by determining the chloride binding isotherms of LDH/AFm phases (monosulfate, strätlingite, hydrotalcite, and meixnerite), and of alkali-activated slags (AAS) produced with four different activators (Na2SiO3, Na2O∙1.87SiO2, Na2CO3, and Na2SO4), in NaOH/NaCl solutions at various liquid/solid ratios. Selected solids after chloride binding were analysed by X-ray diffraction, and thermodynamic modelling was applied to simulate the phase changes occurring during chloride binding by the AFm phases.
The chloride binding isotherms of LDH/AFm phases depended strongly on the liquid/solid ratio during the experiments, resolving apparent contradictions of the previously available data. The dependency on liquid/solid ratio must be attributed to kinetic restrictions, which are, however, currently poorly understood. Chloride binding by AAS pastes was generally higher than for Portland cement pastes and was only moderately influenced by the employed activator. A steep increase of the chloride binding by AAS occurred at free chloride concentrations above approx. 1.0 M, which is possibly related to chloride binding by the C-(N-)A-S-H gel in the AAS.
Gas turbine components, made of nickel-based alloys, undergo material damage due to high temperatures and mechanical stresses. These components need periodic replacement to avoid efficiency loss and failure. Repair of these parts is more cost-effective than replacement. State-of-the-art repair technologies, including different additive manufacturing (AM) and brazing processes, are considered for efficient restoration. Materials properties mismatches and/or internal defects in repaired parts may expedite crack initiation and propagation, reducing fatigue life. To understand the crack growth behavior in joining zones and predict the remaining life of repaired components, fatigue crack growth (FCG) tests were conducted on specimens of nickel-based alloys joined via brazing, pre-sintered preforms and AM. The FCG experimental technique was successfully adapted for joined specimens and results indicate that the investigated braze material provides a lower resistance to crack growth. In AM-sandwich specimens, the crack growth rates are significantly reduced at the interface of AM and cast material.
Advances in ultrafast laser manufacturing: nanostructures, thin films, and scaling perspectives
(2024)
Advanced ultrafast laser technology is a rapidly growing field that currently enables many new industrial and scientific applications. During the last decades, this has been significantly driven by the availability of high-repetition-rate laser sources and novel beam delivery concepts. At the laser side, Moore’s law equally manifests for ultrafast laser technologies, since the average output power of such lasers doubles approximately every two years. This development is mainly driven by the increase of the pulse repetition rates of energetic laser pulses, currently enforcing the development of smart beam control and novel scanning strategies for preventing heat-accumulation and plasma-shielding effects during laser-based materials processing. This keynote presentation addresses the advantages, recent developments, and perspectives of laser processing with ultrashort laser pulses. A special focus is laid on the tailored structuring of thin films as well as the manufacturing and probing of sub-diffraction surface nanostructures – an ongoing race to extreme scales. Current limitations are identified and an outlook to future scaling perspectives will be provided.
Protection against terroristic or accidental scenarios in industrial settings requires suitable designs of structures to resist blast loads. Field testing as well as finite element simulations are among the techniques available to engineers in the understanding of the structural behavior against blast loading.
As blast testing of complex scenarios can be very resource intensive, tests are generally performed for simplified scenarios. Numerical tools can be used to model these scenarios to get better insight into blast loading, structural response, and the resulting damage to the structure. During the next steps, the simplified scenario is successively modified in numerical simulations to incorporate complexities that cannot be covered in blast testing experiments. One of the conditions for this approach to work is that the original simplified numerical simulation is valid. The scopes and challenges encountered in such a validation are the focus of this presentation/article.
A relatively ‘simple’ field test of a horizontal reinforced concrete (RC) slab subjected to blast loading is taken as an example for validation of the performance of numerical tools. The blast test incorporated various measurement techniques to quantify the blast load as well as the behavior of the RC slab. Blast load was measured using flush mounted piezoelectric pressure gauges, whereas acceleration sensors and fiber-optic sensor cables were used to characterize the dynamic behavior of the slab under blast loading. Additionally, damage characteristics were ascertained also using fiber optic sensing. The application of such measurement techniques, along with different numerical software available for the analysis of the scenario in question, demonstrate the scope of our contribution.
When it comes to the challenges, it begins with proper instrumentation of the test specimen followed by the data processing. For numerical modelling, geometric conditions with appropriate boundary constraints, physical conditions such as the configuration of the rebars, as well as material parameters add to this challenge. The issues of choosing appropriate material models and comparison of results with multiple software tools will be discussed. This discussion forms the basis for a coherent approach to technical-safety assessment of blast effects on structures in its broader sense.
Erstarrungsrisse bilden sich beim Schweißen hinter dem Schmelzbad. Im verwendeten MAG-Schweißverfahren wurden stark eingespannte Schweißungen mit verschiedenen hochfesten Schweißzusätzen durchgeführt. Alle verwendeten Zusätze weisen unter gewöhnlicher Einspannung keine Tendenz zur Erstarrungsrissbildung auf. In Abhängigkeit der verwendeten Schweißparameter und des Einspanngrades konnten Erstarrungsrisse in den Nähten festgestellt werden. Die Versuche zeigen, dass beim Schweißen hochfester und stark eingespannter Kehlnähte eine Kombination von hohen Wärmeeinträgen und Schweißgeschwindigkeiten zu erhöhter Bildung von Erstarrungsrissen führen kann.
Die Angabe von Unsicherheiten bei zertifizierten Werten von Referenzmaterialien ist von entscheidender Bedeutung. Die korrekte Einbindung der Unsicherheiten zur Berechnung von Verfahrensmessunsicherheiten ist wesentlich für die Gewährleistung der Genauigkeit und Zuverlässigkeit von Messungen. In diesem Vortrag werden die verschiedenen Einflussfaktoren auf die Unsicherheit zertifizierter Werte gemäß ISO Guide 35 dargestellt. Dabei werden insbesondere die Charakterisierung, Homogenität und Stabilität als entscheidende Faktoren für die Bestimmung der Unsicherheit eines Referenzmaterials betrachtet. Abschließend wird das Konzept anhand eines konkreten Beispiels veranschaulicht, um die praktische Anwendung und die Auswirkungen auf die Berechnung von Verfahrensmessunsicherheiten zu verdeutlichen.
Weltweit stellen Waldbrände eine große Bedrohung für Umwelt, Wirtschaft und menschliches Leben dar. Der fortschreitende Klimawandel verstärkt Trockenheit und Dürre, wodurch die Größe und Intensität von Waldbränden sowie das daraus resultierende Gefahrenpotential zusätzlich erhöht werden. Um im Risikofall eine schnelle und effektive Waldbrandbekämpfung zu gewährleisten, sollen Einsatzkräfte in Zukunft von KI-basierten Ausbreitungsmodellen unterstützt werden.
Der Einsatz von maschinellem Lernen ermöglicht dabei schnelle und zielgerichtete Ausbreitungsvorhersagen in Echtzeit, die in den Prozess der Brandbekämpfung als zusätzliche Information einfließen können. Im Rahmen des durch das EU-Förderprogram Horizon 2020 finanzierte Projekt TREEADS wird ein solches Modell für Europa entwickelt.
Dazu wird mit verschiedenen Satellitendaten des Copernicus-Programms und der NASA ein auf räumlicher und zeitlicher Ebene aufgelöster Datensatz zu europäischen Waldbränden aufgebaut. Zu den erfassten Waldbränden werden wichtigen Faktoren, die Einfluss auf die Brandausbreitung haben, ergänzt. Dazu gehören das von Copernicus bereitgestellte, digitale Geländemodell Europas und verschiedene, von Sentinel-2 Messungen abgeleitete Informationen zu Vegetation und Landnutzung. Dieser 2D-Trainingsdatensatz zu realen Waldbränden wird durch die zeitlich hochaufgelösten, meteorologischen Reanalyse-Produkte – Copernicus European Regional ReAnalysis (CERRA) und ERA5-Land – vervollständigt und ist die Grundlage für ein Modell zur Ausbreitungsvorhersage von Waldbränden.
Methoden des Maschinellen Lernens können komplexe Muster in den gesammelten Daten erkennen und so zu einer verbesserten Vorhersage der Brandausbreitung beitragen. Die vielfältigen, von Copernicus bereitgestellten Daten sind dabei ein unabdingbarer Bestandteil des Modells, mit dem den Einsatzkräften ein zusätzliches Tool für den effizienten Einsatz ihrer limitierten Ressourcen zur Verfügung steht.
The presentation demonstrates an application of multi-scale optical imaging methods such as spectroscopic imaging ellipsometry and white light interference microscopy for the investigation of wide-bandgap semiconductors for power electronics. The capabilities of these methods for the development of new reference calibration samples for scanning microwave microscopes (SMM) and conductive atomic force microscopes (C AFM) are discussed.
Unlike conventional alloys, which typically consist of one main element, high-entropy alloys (HEAs) contain five or more principal elements, which broaden chemical complexity and with it a realm of synergistic mechanisms. The AlMo0.5NbTa0.5TiZr HEA initiated a subclass of Al-containing refractory (r)HEAs that has recently drawn attention [2]. The alloy has a superalloy-resembling B2/bcc nanostructure, which inspired its name refractory high entropy superalloy (RSA). With high-temperature (HT) compressive strengths beyond conventional Ni-based superalloys, this nanostructure could be used for improved HT structural applications. However, in the application-relevant HT regime the Al-Zr-rich B2 phase decomposes to form a hexagonal Al-Zr-based intermetallic (Al4-xZr5; x: 0..1) [3,4]. This work explores the fascinating yet fatal micromechanisms associated to this phase transformation, in the context of creep, annealing and oxidation experiments performed between 800 and 1200 °C.
The material was produced by arc-melting and heat treatment in argon, which lead to grain boundaries decorated with up to 7%. Interrupted constant-load creep tests were performed under vacuum (at 10-4 Pa), at 900–1100 °C with external tensile stresses of 30–120 MPa. Oxidation experiments were separately conducted for 24 hours at 800 and 1000 °C in both dry (21% O2 + 79% N2) and humid (8% O2 + 74% N2 + 18% H2O) air. After the experiments, the samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy to reveal degradation mechanisms. Crystallographic texture, orientation relationships and stabilization of an oxygen-containing iso structure (Al4-xZr5(Ox-y); y: 0..x) of the Al-Zr-rich intermetallic are found and discussed.
Die Umweltwirkungen auf ein Material werden als Überlapp der Funktionskurven von Materialempfindlichkeit und einwirkenden Umweltparametern betrachtet. Wenn entweder die Empfindlichkeit oder die Beanspruchungen Null sind, ergibt sich auch keine Umweltwirkung und bei beidseitig Werten größer Null das jeweilige Produkt der beiden. Die Akkumulation der nicht-reversiblen Effekte über die Zeit und allen Eigenschaftsänderungen entspricht der Alterung des Materials für den jeweiligen Expositionszeitraum.
Die digitale Umweltsimulation gliedert sich hier in drei Teilaspekte. Ein erster, rein materialwissenschaftlicher Teil hat die Aufgabe, alle relevanten Materialempfindlichkeiten experimentell zu quantifizieren. Ein zweiter – unter Umständen numerischer Teil – hat die Aufgabe, das Bauteil und seine Einbaulage zu digitalisieren und aus den makroskopischen Umgebungsbedingungen die relevanten mikroklimatischen Umweltparameter für alle Oberflächen- oder Volumenelemente zu bestimmen. In einem dritten Teil werden die Einwirkungen über den betrachteten Zeitraum berechnet und kumuliert. Dieses Konzept, das auf den so genannten Expositions-Reaktions-Funktionen (ERF) basiert, wird an Beispielen der Photoxidation erläutert. Dieses Vorgehen wurde schon beim ViPQuali-Projekt als Numerische Umweltsimulation umgesetzt.
Überprüft werden muss das Modell unbedingt an einer realitätsnahen Validierungsbeanspruchung. Hier werden die ermittelten ERFs mit über den kompletten Beanspruchungszeitraum geloggten Umweltparametern gekoppelt, um die berechnete mit der experimentell erfahrenen Alterungswirkung zu vergleichen. Nur so kann sichergestellt sein, dass alle für die Anwendungsumgebung relevanten Materialempfindlichkeiten einbezogen wurden.
Interactions between a polymer and a substrate interface play a vital role in understanding the improvement in thin film material properties as well as serving as a model for nanocomposites. For any non-repulsive polymer-substrate interactions, polymer segments form an irreversibly adsorbed layer and show a slowdown in the glassy dynamics and thus an increase in the thermal glass transition temperature compared to the bulk-like values. The growth kinetics of the adsorbed layer showed a deviation for both poly (bisphenol-A carbonate) (PBAC) and polysulfone (PSU), two bulky polymers containing a functional group (phenyl ring) in the backbone, compared to conventional polymers previously studied like poly-2-vinyl pyridine (P2VP). This deviation was attributed to the bulkiness of the phenyl rings. . Further investigations into the influence of the adsorbed layer on glassy dynamics were conducted. The molecular mobility and glass transition for thin films of PBAC and PSU were compared to bulk samples of each polymer. Broadband dielectric spectroscopy, atomic force microscopy, and ellipsometry were primarily used and additionally supported by sum frequency generation spectroscopy.