BAM-Publica - Publikationsserver der Bundesanstalt für Materialforschung und -prüfung
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Thermografie-gestützte Untersuchung des Potentials des Kaltgasspritzens für die Reparatur zyklisch belasteter Bauteile
No full textDie Reparatur mittels Kaltgasspritzen ist eine vielversprechende Alternative zum teuren Austausch fehlerbehafteter Bauteile in der Luft- und Raumfahrt. Durch die Beschleunigung von Metallpartikeln auf Überschallgeschwindigkeiten und die resultierende plastische Verformung der Partikel beim Aufschlag auf das Substrat ohne Aufschmelzen ermöglicht Kaltgasspritzen den schichtweisen Materialauftrag. Die Gewährleistung der Strukturintegrität reparierter Bauteile, insbesondere an der Schnittstelle zwischen dem Substrat und dem aufgetragenen Material, bleibt jedoch eine große Herausforderung.
Um dieses Problem zu lösen, wurden verschiedene Prozesse und Behandlungen untersucht, um die Festigkeit und Tragfähigkeit der Reparatur unter zyklischer Belastung zu optimieren. Röntgen-Computertomographie (XCT) ermöglicht die Analyse der Defekte in dem aufgetragenen Material und in der Grenzfläche. Die XCT kann jedoch nur mit hohem Aufwand in-situ während der mechanischen Prüfung eingesetzt werden. Im Gegensatz dazu kann die digitale Bildkorrelation (DIC) in-situ verwendet werden, da es sich um eine berührungslose Vollfeldtechnik handelt, die jedoch in erster Linie die durch das Prüfverfahren bedingten Verschiebungen an der Oberfläche erfasst.
Um die Entwicklung der Schädigung an der Grenzfläche zu überwachen, wurde die Infrarot-Thermografie (IRT) parallel zur DIC bei der Zug- und Ermüdungsprüfung von reparierten Al6061 Proben eingesetzt. Es wurde eine gekühlte IRT-Kamera mit hoher Bildrate verwendet, die Nachverarbeitung erfolgte mittels Lock-in IRT. Mit Hilfe von IRT war es möglich, die frühe Schadensentstehung an der Grenzfläche des Substrats zu erkennen und das Risswachstum zu verfolgen. Die Bruchflächen bestätigten, dass die identifizierten Merkmale an der Grenzfläche lagen. Es werden Ergebnisse eines Vergleichs von DIC und IRT aus Ermüdungs- und Zugversuchen vorgestellt
Surface structure analysis using visual high-resolution in situ process monitoring in laser powder bed fusion
No full textParameter studies are a common step in selecting process parameters for laser powder bed fusion of metals (PBF-LB/M). Density cubes are commonly used for this purpose. Density cubes manufactured with varied process parameters can exhibit distinguishable surface structures visible to the human eye. The layer-wise process enables such surface structures to be detected during manufacturing. However, industrial visual in situ monitoring systems for PBF-LB/M currently have limited resolution and are incapable of reliably capturing small differences in the surface structures. In this work, a 65 MPixel high-resolution monochrome camera was integrated into an industrial PBF-LB/M machine together with a high-intensity LED (light-emitting diode) bar. Post-exposure images were taken to analyse differences in light reflection of fused areas. It is revealed that the grey-level co-occurrence matrix can be used to quantify the visual surface structure of nickel-based superalloy Inconel®939 density cubes per layer. The properties of the grey-level co-occurrence matrix correlate to the energy input and the resulting porosity of density cubes. Low-energy samples containing lack of fusion flaws show an increased contrast in the grey-level co-occurrence matrix compared to specimens with optimal energy input. The potential of high-resolution images for quality assurance via in situ process monitoring in PBF-LB/M is further discussed
Screening Procedures for Self-Reactive Substances, Differential Scanning Calorimetry-Onset and Heat-Flux Criteria
No full textWe present a newscreening procedure for the determination of the thermal stability of potential candidates for the class of self-reactive substances. For the classification of self-reactive substances, elaborate testing is necessary to determine the applicable type, according to the regulations. Annex 6 of the UNManual of Tests and Criteria permits that the classification procedure for self-reactive substances may be omitted, if the estimated self accelerating decomposition temperature (SADT) is greater than 75 °C for a 50 kg package using an appropriate calorimetric technique, but no technique is described. Based on stationary theories of thermal explosion, we developed a screening approach using differential scanning calorimetry (DSC) onset and heat-flux criteria, respectively, at relevant temperatures. The proposed approach is validated with experimental data
Effect of Ammonium Polyphosphate/Silicate Content on the Postfire Mechanics of Epoxy Glass-Fiber Composites Using Facile Chocolate Bar-Inspired Structures
No full textThis study investigates the postfire mechanical properties of epoxy glass-fiber
reinforced composites (EP GFRCs) using increasing concentrations of ammonium polyphosphate (APP) and inorganic silicate (InSi) to modify the char and fire residue. A facile chocolate bar-inspired structure was introduced for fire exposure and subsequent flexural testing of the GFRCs. The resin matrix used here was a diglycidyl ether of bisphenol-A (DGEBA) resin, cured with dicyandiamide (DICY), and accelerated by Urone. The microstructures of the degraded composites after three-point bending tests, were evaluated using scanning electron microscopy (SEM) and x-ray computed tomography (XCT) imaging. A previous study showed that increasing the APP and InSi content significantly enhanced flame retardancy, via improved char formation under fire conditions. However, flexural properties and fire resistance were adversely affected after fire exposure, highlighting a trade-off effect. Fiber breakage and delamination of the composites increased upon failure with increasing APP + InSi content in the composite due to unconsolidated char. The experimental values for the postfire flexural mechanics were in good agreement with the two-layer model proposed in literature. This paper presents a preliminary basis for postfire mechanical testing of epoxy composites for use in fire-safe structures, using a combination of standardized testing norms
A Self-Driving Lab for Nano- and Advanced Materials Synthesis
No full textThe recent emergence of self-driving laboratories (SDL) and material acceleration platforms (MAPs) demonstrates the ability of these systems to change the way chemistry and material syntheses will be performed in the future. Especially in conjunction with nano- and advanced materials which are generally recognized for their great potential in solving current material science challenges, such systems can make disrupting contributions. Here, we describe in detail MINERVA, an SDL specifically built and designed for the synthesis, purification, and in line characterization of nano- and advanced materials. By fully automating these three process steps for seven different materials from five representative, completely different classes of nano- and advanced materials (metal, metal oxide, silica, metal organic framework, and core–shell particles) that follow different reaction mechanisms, we demonstrate the great versatility and flexibility of the platform. We further study the reproducibility and particle size distributions of these seven representative materials in depth and show the excellent performance of the platform when synthesizing these material classes. Lastly, we discuss the design considerations as well as the hardware and software components that went into building the platform and make all of the components publicly available
Value of information‐driven innovation in Gerber saddles monitoring
No full textAbstractInnovation plays a crucial role in shaping technological, economic, and social progress in modern societies. In the realm of bridge integrity management, the development and diffusion of technologies to acquire information can significantly enhance industries' safety and functionality capabilities. Among the most widely diffused bridge types in Europe and North America, Gerber bridges are particularly susceptible to deterioration over time. Gerber saddles are typically not instrumented and are checked only through visual inspections. This paper introduces the metric of the Value of Information for Innovation to estimate the benefit associated with introducing an established technology in a new market of application. Herein, the operational value of implementing microelectromechanical inclinometers in the integrity management of Gerber saddles is quantified for the specific case of a bridge in northern Italy. Microelectromechanical systems companies may use these results to optimally select the technology price, investigate diverse market strategies, and optimize sensor arrangement
A Dual Glow Discharge Optical Emission Spectroscopic and Mass Spectrometric Study of Manufacturing and Aging in Lithium-Ion Batteries
No full textLithium-ion batteries (LIBs) are extensively employed to power small electric and stationary devices as well as electric vehicles (EVs), due to their high energy density, long cycle life, and relatively low self discharge. The rapid expansion of the EV market is expected to increase significantly the global demand for LIBs, with sales projected to reach 245 million units by 2030, according to the International Energy Agency. In order to meet this demand, it is essential to reduce manufacturing scrap rates and extend battery life. [1,2] Production efficiency can be increased by limiting production failures and detecting process deflections at early stages of manufacturing chain, for example through rigorous control of the electrode homogeneity. On the other hand, the prolongation of a battery life assumes deep knowledge of the degradation processes, such as dendrite formation and electrolytes degradation, directly correlated with a change in the elemental distribution inside the battery. [3]
As techniques capable of in-depth elemental analysis at scales from a few nm to 100 μm, Glow Discharge Optical Emission Spectroscopy (GD-OES) and Glow Discharge Mass Spectrometry (GD-MS) are suited for investigating both the homogeneity of the cathodic material in the manufacturing phase, as well as changes in its elemental distribution caused by aging. Focus has been given to lithium and fluorine distribution, whose migration inside the battery is correlated to the cycling and the electrolyte and binder degradation, respectively.
A few previous reports described depth profiling of positive and negative electrodes in LIBs using GD OES. [4 6] In this work, GD-OES spectroscopic analysis has been performed on self-made cathodes for LIBs to gain insight into the quality of the manufacturing process, targeting a standardized electrodes production. With the same cathode material, coin cells have been built and artificially aged. Post mortem analysis conducted by GD-OES with the use of an argon/neon mixture as discharge gas, helped correlating the variation of fluorine distribution with the battery state of health (SOH). GD MS analysis was employed to gain insight into battery degradation phenomena upon aging, such as transition metal dissolution from the positive electrode and lithium isotopic fractionation [3,7]. This work marks GD-techniques as versatile and efficient tools to study LIBs, unveiling significant application in both academical research and industrial manufacture
Laser-Induced Breakdown Spectroscopy for Concrete Analysis: Applications and Practical Benefits
No full textReinforced concrete structures are exposed not only to mechanical loads but also to chemical degradation, which can significantly impact their longevity and performance. Effective assessment and maintenance require a detailed understanding of the ingress of harmful species, such as chlorides or sulfates. Traditional analysis methods, like wet chemical analysis of drill dust or ground core samples, often require homogenization leading to the loss of crucial spatial information in sub-millimeter regions such as localized high concentrations of elements, e.g. in cracks.
Laser-induced breakdown spectroscopy (LIBS) offers a cutting-edge solution, providing rapid, multi-element analysis with high spatial resolution from micrometer to millimeter scales. LIBS is capable of detecting both light and heavy elements, making it a powerful tool for detailed concrete analysis. Despite its clear advantages, LIBS is not commonly used in civil engineering.
This presentation will showcase practical examples demonstrating the effectiveness and advantages of LIBS in concrete analysis, highlighting real-world applications provided by members of the “LIBS” subcommittee of the technical committee “Civil-Engineering” of the German Society for Non-Destructive Testing (DGZfP). Key examples will be discussed, including measurements from car parks or bridges, alongside an introduction to the newly released DGZfP leaflet B14 providing guidelines for the quantitative determination of chlorine content in concrete by LIBS. Furthermore, prospective applications of LIBS including material identification and classification for concrete recycling, and other emerging uses in civil engineering, will also be presented, showcasing the versatility and future potential of this technology
A new elemental analytical approach for microplastic sum parameter analysis in environmental samples – ETV/ICP-MS with CO2
No full textPlastics are indispensable in our daily lives. Due to their easy processability, durability, and lightweight properties, they are the base material of many consumer and industry products. However, with reported amounts of millions of tons per year, plastic pollution has become a globally emerging problem. In the environment, plastic waste undergoes degradation, leading to the formation of persistent, synthetic particles smaller than 5 mm, known as microplastics (MPs).
Toxicological concerns mainly arise from MP uptake by various organisms, including humans. MPs act as transport vectors for hazardous chemicals, e.g., polymer additives, bacteria, and other environmental pollutants. Existing approaches for MP analysis focus on particle size, number, and information on the polymer types. However, there is a lack of analytical tools for a fast and comprehensive assessment of the pollution situation based on the MP mass without limitations to size and polymer types. In this context, a new mass balance approach for the MPs analysis in environmental samples via electrothermal vaporization coupled with inductively coupled plasma-mass spectrometry (ETV/ICP-MS) has been developed as a complementary screening tool to existing methods.
With ETV/ICP-MS, the bulk detection of MPs via the 13C isotope as a sum parameter of common polymer types was achievable relatively unaffected by the respective size across the nano-to-micrometer scale. A new mass-based approach through an external gas calibration with carbon dioxide enabled the fast quantification of the MP content in MP-soil mixtures of different portions. By this, the analysis was achievable within a few minutes of analysis time per sample. Furthermore, the potential of polymer heteroatoms and contaminants for the sensitive detection in carbon-rich matrices was investigated
Management of Reference Data of Creep of Ni-Based Superalloys Exemplified for CMSX-6
No full textThe identification of process-structure-property relationships of materials inevitably requires the combination of research data from different measurements. Therefore, the concepts related to FAIR (findable, accessible, interoperable, reusable) data handling, increasingly reported in literature, are particularly important in the materials science and engineering domain. However, they have not yet been integrated into a single, overarching methodological framework, particularly for reference data. Here, we introduce such a framework, which covers data generation, documentation, handling, storage, sharing, data search and discovery, retrieval, and usage. Furthermore, we prototypically implement it using a real dataset with creep data of a single-crystal CMSX-6 Ni-based superalloy. The implementation is traceable and permanently accessible through open repositories. The individual elements considered in the framework ensure the functionality and usability of the data and, thus, the adherence to the FAIR principles. In conjunction with this, we present a definition for reference data of materials. Our definition underlines particularly the importance of a comprehensive documentation, e.g., on material provenance, data processing procedures, and the software and hardware used, including software-specific input parameters, as these details enable data users or independent parties to assess the quality of the datasets and to reuse and reproduce the results. Reference data that is managed according to the proposed framework can be used to advance knowledge in the materials science and engineering domain, e.g., by identifying new process-structure-property relations