Auswirkung von Korrosion und veränderlicher mechanischer Spannung auf das Schwingungsrißverhalten von Bauteilen

Effect of corrosion and fluctuating mechanical stress on the fatigue properties of construction units . Considerable damage is still being caused by fatigue corrosion resulting from fluctuating stresses in construction units, even though such a source of damage has been known for more than half a century. More than 10% of the total corrosion damage encountered in chemical engineering stems from this type of transcrystalline crack. The particular difficulties met with in attempts to guard against such material damage rest, on the one hand, in the multiplicity of factors influencing the loss of strength and, on the other, in the problems associated with the applicability of laboratory results to the behaviour of constructional units. In this paper the influence of corrosion medium, limiting value of stress cycle endured, thickness of construction unit, frequency, mean stress and crack-propagation characterization on stability towards vibration corrosion is dealt with and shows the design engineer how the relevant data concerning component behaviour are to be handled.     

Der Einfluß der Lipidkomplexe auf das Backverhalten von Weizen

The Effect of Lipid Complexes on the Baking Behaviour of Wheat Adding of lipids in the bread baking has been very important in the last years. The quality of bread can be improved by interactions between the lipids and other components of wheat flour. In spite of many experiments, which have been published in this field, the effect of lipids on the baking quality of flour has not been well established. This study deals with the effect of lipids, lipid-protein-complexes and lipid-starch-complexes on the baking quality of wheat flour. The results showed that high concentrations of lecithin improved the baking quality, while low concentrations decreased the loaf volume. The gliadin with its high content of polar lipids is very effective in increasing loaf volume and improving crumb characteristics. Also gliadin, which is isolated from gluten with 70% ethanol has the same effect. The gliadins with identical composition isolated from gluten, with different concentrations of ethanol, were differently effective on the loaf volume. The gliadins with high lipid content were more effective than gliadins with traces of lipids in increasing the loaf volume. The extracted lipids from gliadin were comparatively effective as gliadin in increasing the loaf volume, while the defatted protein has decreased the loaf volume. The glutenin has an adverse effect on the baking quality of flour. The lipid-starch-complexes neutralize the negative effect of the addition of gelatinized starch. This is due to the presence of some lipids not bound in these complexes.     

Über das Spreiten von Lipiden auf der Haut

On the Spreading of Lipids on the Skin The spontaneous spreading of liquid lipids on human skin is an important property for the use value of such products in cosmetic and pharmaceutical preparations. A comparative evaluation procedure based on an impression method is described, by means of which it is possible to determine the spreading rates in a reproducible manner. The standardized spreading values of a number of lipids are discussed in comparison with their chemical structure and physico-chemical data such as viscosity and surface tension. None of these data series correlates entirely with the spreading rates of all the lipids tested. However, it is possible to assess relative spreading rates within similarly structured groups of compounds.     

Der Einfluß der Emulgatoren auf das Emulsionssystem von Cremes

Influence of Emulsifiers on the Emulsion System of Creams Besides the usual emulsion systems (o/w and w/o) a further ambiphilic mixed system is described. The occurrence of an ambiphilic system was characterized by various experimental measures. A series of experiments on the utilization of active ingredients is described. The properties of a few creams derived from the basis laid by DAB, wherein the emulsifiers are substituted by creams, are discussed under special consideration of the emulsifying system. The determination of micro-penetration was carried out by which the consistency can be quantitatively expressed.     

Einfluß der Faserbehandlung auf das Feuchteverhalten von glasfaserverstärkten Epoxidharzen

The strength of glass fiber reinforced epoxy resins can be significantly reduced under exposure to moisture. Besides other factors, the interface between fiber and matrix plays an important role. It is responsible for a proper load transfer between fibers and matrix by coupling effects and significantly affects the moisture behavior of the composite. In the present study, glass fibers were treated with different sizes under defined conditions and embedded in three epoxy matrix systems. The composites were exposed to different moisture conditions. The change of the shear and impact behavior due to moisture was determined. It will be shown that the composites with coupling agent treated fibers are significantly more resistant to moisture than composites with poor fiber/matrix adhesion. Furthermore, it will be shown that also the binder plays an important role if the material is subjected to moisture.     

Einfluss der Wechselwirkung von Reaktion und Fluiddynamik auf das Verhalten von Strahlschlaufenreaktoren

Jet loop reactors are used as apparatus to facilitate chemical or biological reactions. This type of apparatus is characterized by an internal circulation flow, essentially driven by the injection of liquid. The nozzle can also be used to inject and disperse gas. The internal fluid dynamics and thus the reactor behavior is significantly determined by the introduced momentum and by the internal gas distribution. To describe the mutual influence of a gas-consuming reaction and the internal fluid dynamics, a simplified model based on a momentum balance and a material balance was used. From the exemplary calculations, a critical range for non-selective reactions and for fluid dynamic stability is given.     

Einfluß der adsorption von 3-N-alkylaminopropan-1-olen auf das zetapotential von polymeroberflächen

The principle of a measuring system for the determination of ζ-potentials of polymer sheets is described. On sheets of poly(tetrafluoroethene) and homopolystyrene characteristic differences of the ζ-potential after absorption of 3-N-alkylaminopropane-1-oles and dodecylpropylamines in aqueous solutions were detected. The influence of pH, concentration, and C-chain length of the tenside was investigated.