Environmentally assisted cracking of aluminium alloys

A short review of the stress corrosion cracking (SCC) behaviour of aluminium alloys is given. Mechanisms of environmentally assisted cracking are outlined. For aluminium alloys, in which stress corrosion cracks propagate predominantly along grain boundaries, anodic dissolution and hydrogen embrittlement have been proposed. Transgranular stress corrosion cracking occurring at severe loading conditions has found particular interest concerning localised corrosion‐deformation interactions. Accelerated test methods for assessing the SCC behaviour are described, including the slow strain rate testing technique and the breaking load method. Results of recent studies on environmentally assisted cracking of aluminium alloys are summarised. Most of the work published in the last two decades has been on aluminium‐lithium based alloys and improved high strength Al‐Zn‐Mg‐Cu alloys in corrosion resistant retrogressed and re‐aged tempers.     

Wasserstoffabsorption in alkalischen Elektrolyten

Hydrogen absorption in alkaline solutions Hydrogen permeation tests were carried out in order to clarify the mechanisms of hydrogen absorption in alkaline solutions at low hydrogen coverages. The influence of different oxygen contents (no oxygen to saturation) and pH‐values (pH 9, 11 und 13) on hydrogen adsorption and absorption rates was determined as well as the hydrogen activities.     

In vitro assessment and monitoring of the implant titanium materials – physiological environment interactions

Long‐term monitoring (for 8000 exposure hours) of titanium and its implant alloys (Ti‐5Al‐4V, Ti‐6Al‐4Fe) interactions with Ringer's solutions of different pH‐values (2.5, 4.35, 6.98), simulating various conditions that can appear at the contact between implant and tissues was carried out in this paper. All data were statistics treated using Medcalc program. In vitro electrochemical behaviour of titanium and its alloys reveals their self‐passivation in Ringer's solutions. Monitoring of the open circuit potentials with time and pH have shown that the passive films on the implant materials studied were very stable for all tested periods. Interactions due to the non‐uniformity of the physiological electrolyte pH can not produce any form of local corrosion. The tested materials present low corrosion rates which attest their very good stability for 8000 exposure hours in simulated biological environment. Surface topography characterisation using atomic force microscopy (AFM) data, correlated with the electrochemical parameters, were arguments for the stability of the samples in studied bioliquids.     

Bemessung von Fensterbrüstungen aus Mauerwerk unter Ansatz der Biegezugfestigkeit

Design of masonry window parapets considering flexural tensile strength Parapet masonry is often neglected in design. However, if verification is explicitly necessary, this is often economically feasible only on the basis of flexural tensile strength. For this application, two design methods are presented with which parapet masonry can be designed as a freestanding wall considering the flexural tensile strength. In addition to a general method based on linear‐elastic stress‐strain relationship of the masonry, which is applicable to both fully and partially supported slabs, a second approach is presented, which takes into account an existing slab edge shell and thus applies especially for parapet masonry with reduced bearing length. Both methods can also be used to design freestanding walls with minor adjustments. Finally, the permissible height of a parapet made of brickwork is determined exemplarily for various applications and indicated in tabular form depending on the acting wind load.     

Characterization of corrosion behavior of aluminum welds reinforced with copper powder

This paper reports on the corrosion behavior of aluminum metal inert gas (MIG) welds reinforced with copper powder particles. Pure aluminum, AA1100 sheets, machined to a 45° v-grooved were used for this experiment. Copper powder particle reinforced samples and unreinforced samples were investigated. The corrosion behavior of the samples were investigated in 3.5 % sodium chloride (NaCl) solution, using the potentiodynamic polarization technique. The results revealed that the corrosion resistance for reinforced samples were higher than those for unreinforced samples. Hence the corrosion resistance of aluminum AA1100 welds can be improved by the addition of copper powder particle in the weld seam, and it is therefore recommended for typical industrial applications.     

Organverteilungssysteme im Transplantationswesen aus ökonomischer Sicht

Zusammenfassung.   Auch nach dem Beschlu? des Gesetzgebers zugunsten einer sogenannten Informationsl?sung bleibt das Problem angemessener Vergabekriterien für die vorhandenen Organe, da diese Frage im neuen Organspendegesetz nicht abschlie?end gekl?rt ist. In dem Beitrag werden verschiedene Allokationsverfahren bezüglich ihrer gesellschaftlichen Akzeptanz und ?konomischen Effizienz beurteilt. Dazu werden medizinische Kriterien (z.B. HLA-Kompatibilt?t) und nicht-medizinsche Kriterien (z.B. Zahlungsbereitschaft des Spenders oder Zufall) anhand verschiedener allgemein akzeptierter Zielsetzungen (z.B. gleicher Zugang zu Gesundheitsleistungen oder geringe Kosten) abgewogen. Als innovative Form eines Organgewinnungssystemes wird die Clubl?sung vorgestellt, die den Spendern erlaubt, Pr?ferenzen bei der Verwendung der Organe zu realisieren. Scoringsysteme k?nnen darüber hinaus helfen, die Transparenz der Organverteilung zu erh?hen. Aus ?konomischer Sicht sind dabei vor allem medizinische Kriterien relativ zu nicht-medizinischen Merkmalen st?rker zu gewichten.