Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- 6 Materialchemie (10)
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- 5 Werkstofftechnik (3)
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- 3 Gefahrgutumschließungen; Energiespeicher (2)
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To better understanding the failure of adhesive joints tensile tests were carried out on miniature test specimens from Norway spruce in the synchrotron. Urea-formaldehyde resin was used as adhesive. e. For comparison purposes, tensile tests were carried out on solid wood and on bonded miniature tensile shear samples with acoustic emission. The acoustic emission signals of all the experiments occurred with classified pattern recognition. This resulted in two classes of signals for each two frequency peaks. One class consisted of the low-frequency and the other of the higher-frequency peak of higher intensity, but this was essentially independent from the structure (solid wood or plywood) and size scale of the test specimens. The influence of the adhesive layers was determined on wood test specimens on laboratory scale and on miniature test specimens with an adhesive layer and selected fiber orientations. This gave evidence that the sound emission signals from the failure of the adhesive layer presumably of the class with low frequency signals peak in the range of services can be assigned.
Abstract Hydrogenated nitrile butadiene rubber (HNBR) elastomer was thermo-oxidatively aged at different temperatures up to 150 °C. Fourier transform infrared spectroscopy (FTIR), compression stress relaxation (CSR) and international rubber hardness degree (IRHD) microhardness were used to characterise the chemo-mechanical changes of HNBR O-rings during thermo-oxidative ageing. FTIR shows the development of carbonyl, methyl and ester groups but the nitrile content was not affected by ageing. The effect of sample geometry during CSR was investigated. CSR data were converted through integrated kinetic laws. The conversion has proven its sensibility to detect heterogeneous ageing. This was confirmed by the IRHD measure-ments across the section of O-rings. The influence of compression during ageing was assessed through IRHD measurements across the section of compressed and uncom-pressed aged O-rings. The DLO effect was more pronounced in compressed O-rings. By applying the model of Wise et al., theoretical IRHD and oxidation profiles were determined on the basis of IRHD experimental data of compressed O-rings. Good agreements between the experimental and the theoretical IRHD profiles in the core region were obtained. However, near the edge, the theoretical IRHD values were overestimated.
Auger electron spectroscopy
(2020)
An introduction in the application of Auger Electron Spectroscopy to surface chemical analysis of nanoparticles is given. Auger Electron Spectroscopy is a mature method in the field of surface chemical analysis. The chapter addresses the physical basis of the method, the principal design of recent instruments together with modes of operation and options for the presentation of spectra, as well as different approaches for qualitative (including identification of chemical species) and quantitative surface analysis of elements. An application paragraph on surface chemical analysis of nanoparticles by AES or SAM introduces the different measurement approaches and sample preparation strategies applied by analysts. The analysis of nanoparticle ensembles, the so-called selected point analysis where a narrow primary electron beam is centered on an individual nanoparticle, and chemical mapping of individual nanoparticles (or a line scan across) are addressed. Existing literature is reviewed and informative case studies presented. Limitations and pitfalls in the application of AES in surface chemical analysis of nanoparticles are also addressed.
Automotive engine lubricants
(2019)
In 2003, ASTM Manual 37, Fuels and Lubricants Handbook: Technology, Properties, Performance and Testing, featured a chapter discussing automotive lubricants, including engine oils, automatic transmission fluids, manual transmission fluids, gear lubricants, and greases. This chapter, by Schwartz, Tung, and McMillan, surveyed all of these classes of lubricants, up to its publication in 2003.
More recently, the period between 2003 and 2010 has been addressed as part of a book copublished by ASTM and SAE International (coeditors Simon Tung and George Totten), where Fox surveyed the development of engine oil specifications that emerged during those years.
This chapter surveys the evolution of engine oil design and testing since 2002 and concludes with insights into future directions offered by recent tribological research. Our objective is to provide a reader new to the field with an understanding of the following:
- Engine oil composition and formulation
- North American engine oil specification development, and an outline of emergent European specifications
- How emergent specifications and legislative requirements are linked to the introduction of new engine hardware
- How tribological innovation can contribute to future enhancements in engine efficiency
In parallel, we will provide several tables comparing groups of contemporaneous specifications.
Characterization of nanomaterials by transmission electron microscopy - Measurement procedures
(2020)
In this chapter, approaches are proposed for the descriptive and quantitative characterization of nano-objects with nanometer resolution. Measurements are based on the analysis of the characteristics of 2D projections of individual particles visualized on transmission electron micrographs.
Incorporation of spectroscopic methods (EDS and EELS) for elemental analysis of nano-objects is recommended to identify subpopulations of nano-objects in mixtures based on their chemical composition. The focus lies on the determination of physicochemical properties which are essential in a legislatory and regulatory context to define the material as a nanomaterial (NM), and to assess its safety and toxicological potential, using widely accessible equipment.
In this chapter sample preparation, image acquisition, and nanoparticle size and shape characterization methods using the scanning electron microscope (SEM) in reflective and transmitted working modes are described. These help in obtaining reliable, highly repeatable results. The best solutions vary case-by-case and depend on the raw (powdered or suspension) nanoparticle material, the required measurement uncertainty and on the performance of the SEM.
ln den letzten Jahren wurden diverse Prüfverfahren und Methoden entwickelt, um die Leistungsfähigkeit von Beton bzw. Bindemittel hinsichtlich des Widerstands gegenüber betonaggressiven Einwirkungen beurteilen zu können. Ein wesentliches Ziel von Prüfverfahren zur Beurteilung der Dauerhaftigkeit von Baustoffen ist, die im Laufe der Nutzungsdauer zu erwartenden Einwirkungen auf den Baustoff realitätsnah abzubilden. Dazu sind die Prüfparameter auf die im jeweiligen Anwendungsbereich vorherrschenden Umgebungs- und Randbedingungen anzupassen. Daneben sind auch die Bewertungskriterien individuell unter Berücksichtigung der im Einzelfall geforderten Nutzungsdauer eines Bauwerks festzulegen. Eine systematische Zuordnung von adäquaten Prüfverfahren bzw. Prüfparametem und Bewertungskriterien für die verschiedenen Anwendungsbereiche im Betonbau, in denen betonaggressive Einwirkungen auftreten, ist mit Ausnahme von Einzelfällen bislang nicht vorhanden. Daneben stellt sich in der Praxis immer wieder das Problem, das Angriffspotenzial der Umgebung eines Bauwerks (prüftechnisch) zu erfassen und zu bewerten.
Der Hauptausschuss Baustofftechnik des DBV hat daher den Arbeitskreis „Chemischer Angriff auf Beton“ beauftragt, dieses Merkblatt zu erarbeiten, das auf Basis von einschlägigen Erfahrungen der Baupraxis und wissenschaftlichen Erkenntnissen Grundsätze und bewährte Methoden zur Beurteilung der Einwirkungs- und Widerstandsseite beim chemischen Angriff auf Beton aufzeigt und diesbezüglich Hinweise für verschiedene Anwendungsbereiche im Betonbau liefert.
Chemischer Angriff auf Betonbauwerke - Bewertung des Angriffsgrads und geeignete Schutzprinzipien
(2014)
In verschiedenen Bereichen des Betonbaus ist Beton einem chemischen Angriff von außen ausgesetzt, der die Dauerhaftigkeit des betreffenden Bauteils bzw. des gesamten Bauwerks beeinträchtigen kann. Für einen chemischen Angriff in natürlichen Böden und Grundwässern bestehen normative Vorgaben in DIN 4030-1 [R10] bzw. DIN 1045-2 [R19], um den Angriffsgrad anhand der Art und Konzentration der angreifenden Stoffe in Expositionsklassen XA1 (schwach angreifend) bis XA3 (stark angreifend) einzustufen. Hinsichtlich weiterer maßgeblicher Einflussfaktoren wird an dieser Stelle nicht näher differenziert, ob und inwieweit die Regelungen für Böden und Grundwässer auch auf andere Bereiche mit chemischem Angriff auf Beton zu übertragen sind, ist stets im Einzelfall zu überprüfen. Ebenfalls sind die zu treffenden Maßnahmen über die Vorgaben der DIN EN 206-1/DIN 1045-2 [R19] hinaus anwendungsspezifisch festzulegen. Der Hauptausschuss Baustofftechnik (HABT) des DBV hat daher den Arbeitskreis "Chemischer Angriff auf Beton" beauftragt, dieses Merkblatt zu erarbeiten, das Hilfestellung bei der Bewertung einer projektspezifischen chemischen Angriffssituation auf Beton sowie bei der Planung und Ausführung von Schutzprinzipien leisten soll.
Conclusions and perspectives
(2020)
This chapter briefly summarizes the methods selected within this book for the characterization of nanoparticles with regard to commonly accessible properties: nanoparticle size and size distribution, shape, surface area, surface charge, aggregation state, structure, chemical composition, surface chemistry, and nanoparticle number concentration. Current progress of measurement and analysis, as far as possible according to standard operation procedures, has been the focus of this work. A number of new and less commonly used methods have not been covered, and we outline some of these in this chapter. Future challenges such as automated measurement and analysis, read-across approaches for the prediction of properties, knowledge of measurement uncertainties, the need for certified reference materials, and the necessity to complement measurements methods to obtain more reliable results are covered, and the unmet measurement requirements for real-world nanoparticles are described.