Degradation von Werkstoffen
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- Acoustic emission (1)
- Ageing (1)
- Alterung (1)
- Aspergillus flavus (1)
- Bondline (1)
- Carbon fibre-reinforced-plastics (1)
- Crop protection formulations (1)
- Damage evolution (1)
- Deterioration (1)
- Dichtheit (1)
Organisationseinheit der BAM
- 3 Gefahrgutumschließungen; Energiespeicher (2)
- 3.4 Sicherheit von Lagerbehältern (2)
- 5 Werkstofftechnik (2)
- 5.3 Polymere Verbundwerkstoffe (2)
- 7 Bauwerkssicherheit (2)
- 4 Material und Umwelt (1)
- 4.1 Biologische Materialschädigung und Referenzorganismen (1)
- 7.0 Abteilungsleitung und andere (1)
- 7.1 Baustoffe (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
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.
Die zunehmende Anwendung hochfesten Betons in ermüdungsbelasteten Bauwerken, herausfordernde Belastungsszenarien im Bereich von On- und Offshore Windenergieanlagen bezüglich sehr hoher Lastwechselzahlen sowie das gleichzeitige Streben nach energie- und ressourcenschonendem Bauen stellen die Bemessung von Beton gegen Ermüdung vor neue Aufgaben. Eine Vielzahl von Studien beschreibt bereits die Auswirkung von Einflussfaktoren wie Mischungszusammensetzung, Feuchte, Probekörpergröße oder Belastungsart auf die Ermüdungsfestigkeit und den Ermüdungsprozess. Aufgrund der unterschiedlichen Geometrien und Mischungen der in den verschiedenen Studien verwendeten Proben sind die Auswirkungen der Einflussfaktoren jedoch kaum miteinander vergleichbar. In dem vom Bundesministerium für Wirtschaft und Klimaschutz (BMWK) geförderten Verbundprojekt WinConFat wurden deshalb verschiedene Einflussfaktoren gezielt an Proben mit einheitlichen Mischungen untersucht. Das durch die Bundesanstalt für Materialforschung und -prüfung (BAM) bearbeitete Teilprojekt fokussierte sich auf den „Einfluss der Probengeometrie und -größe auf die Ermüdung von Beton“. Neben der Erhebung von Daten zur Ermüdungsfestigkeit wurde der Ermüdungsprozess mit zerstörungsfreien Prüf- und Messmethoden untersucht. Diese Prüfmethoden wurden auch hinsichtlich ihrer Anwendbarkeit zur Erfassung der ermüdungsbedingten Schädigungsentwicklung an Betonbauwerken im Rahmen von Monitoringkonzepten bewertet. Untersucht wurden die Ermüdungsfestigkeiten und der Ermüdungsprozess an Zylindern mit drei unterschiedlichen Betonmischungen sowie unterschiedlicher Größe und Schlankheit. Die Ergebnisse dieser Untersuchungen werden im Folgenden vorgestellt und diskutiert.
Our earlier study based on historical and scientific analysis showed that Iranians used a considerable range of materials in the sizing process. Unlike many nations who used limited sizing materials to improve the mechanical strength and to smoothen the paper surface, Iranians have used various materials for sizing process from Taimurid (15th century) to Safawid (16th century) and Qajar (19th century) periods. Further to our earlier study on the Sizing Materials used in Persian manuscripts and miniature paintings, scientific analysis was carried out to investigate their behaviour against the mould fungus Aspergillus flavus. In the first stage fourteen different sizing materials that was identified from Persian historical recipes were reconstructed. In the second stage fungicidal property of each sizing samples against Aspergillus flavus fungus were identified that will be presented in this paper.
Packaging containers for dangerous goods that include aggressive liquids require that any packaging material that is based on high-density polyethylene has a high degree of stability and durability. This work is focused on testing the environmental stress cracking of the high-density polyethylenes used for such containers in contact with crop protection formulations, in particular, two model liquids established in Germany as standardized test media representatives for crop protection formulations containing the various admixtures typical for such products. One of the liquids is water-based and contains mostly surface-active ingredients, while the other is solvent-based and includes some emulsifiers. Originally established for pin impression tests, these model liquids and their individual components were here used for the first time as environmental media in the Full Notch Creep Test, which addresses the resistance against environmental stress cracking. The Full Notch Creep Test was carried out on five high-density polyethylene types with both model liquids, and also on one selected material with its components. The evaluation was focused on the fracture surface structures, which were visualized by a scanning electron microscope and by optical in situ imaging of the notch opening. While the water-based model liquid and its surface-active individual components induced environmental stress cracking with the characteristic pattern for a craze-crack mechanism and so-called brittle fracture on the surface, the solvent-based model liquid and its soluble ingredients exhibited rather ductile failure behavior, caused by the plasticizing effect on the polymer that reduced the yield stress of the high-density polyethylene.
For both cases, fracture surface analysis, together with side views of the crack opening, showed a clear relation between surface pattern, notch deformation (e.g., by blunting), or crack opening due to crack growth with time to failure and the solubility of the liquids in high-density polyethylene.
Langzeitversuche über 10 Jahre an Federkern-Metalldichtungen mit Aluminium- bzw. Silberummantelungen
(2023)
Federunterstützte Metalldichtungen mit Aluminium(Al)- oder Silber(Ag)-Ummantelung werden u.a. in Behältern für Wärme entwickelnde radioaktive Abfälle eingesetzt, da diese Dichtungen eine sehr gute Dichtheit gewährleisten sowie Langlebigkeit und Beständigkeit gegenüber erhöhten Temperaturen und radioaktiver Strahlung aufweisen. Auch wenn die Sicherheit solcher Behälter und der verwendeten Dichtungen vielfach belegt wurde, sind sie Gegenstand andauernder Forschung, etwa im Hinblick auf eine absehbar benötigte verlängerte Zwischenlagerdauer. Aus diesem Grund werden an der Bundesanstalt für Materialforschung und -prüfung (BAM) im Fachbereich 3.4 „Sicherheit von Lagerbehältern“ seit über 20 Jahren Versuche an solchen Metalldichtungen durchgeführt. Dabei sollen zusätzliche Erkenntnisse hinsichtlich der Sicherheitsreserven der Dichtungen in unterstellten Störfallszenarien (axiale Bewegung des Deckelsystems bzw. Aufweitung der Nutgeometrie) und insbesondere detailliertere Erkenntnisse zum Langzeitverhalten gewonnen werden.
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.
The described investigation of carbon-fibre-reinforced plastics (CFRP) documents that damage evolution can be observed by means of X-ray refractography. Comparative investigations with synchrotron technique on CFRP and grey-scale analysis on glass fibre-reinforced-plastics (GFRP) confirm these results. Moreover it was found that the fracture mechanical properties of the matrix system influence damage nucleation and propagation in the laminate during static and fatigue loads. Single-step fatigue tests were carried out on Laminates with RIM135 and LY556 matrix systems made from non-crimped fabric (NCF) or twill weave in different fibre orientations. The damage to the LY556 laminates was characterized by laminate cracks growing rapidly over the whole specimen width, whereas the damage on the RIM135 laminates was characterized by an earlier onset of micro-cracking followed by laminate cracks. The specimens were fatigued up to 108 (very high cycle fatigue (VHCF) regime) load cycles. S-N-curves of damage initiation were drawn and boundaries were identified for endurance within the VHCF regime. A phenomenology based model focusing on matrix stress was applied to reproduce the first inter-fibre failure (IFF) under static and fatigue loads.