Effect of crack tip radius and crack orientation on metal fracture. Statistical prognosis

Aluminium specimens with pre-caused cracks with different tip radii are tensile tested at two temperatures. The cracks are differently oriented to the tensile axis. The results have undergone statistical processing integrated with fundamental fracture approach. Analytical model to prognosticate the defect metal reliability and the reliability of a randomly chosen detail from a defined set in the range of applied tensile stresses is found. A method for evaluation of the cracks tip radii and cracks orientation effect on fracture is suggested. The introduced strength spaces present a principal strength history of defect metal in interval load imposing-fracture at different temperatures.     

The effect of machined topography and integrity on fatigue life

The paper reviews published data which address the effect of machining (conventional and non-conventional processes) and the resulting workpiece surface topography/integrity on fatigue performance, for a variety of workpiece materials. The effect of post-machining surface treatments, such as shot peening, are also detailed. The influence of amplitude height parameters (Ra, Rt), amplitude distribution (Rsk) and shape (Rku) parameters, as well as spatial (Std, Sal) and hybrid (Ssc) measures, are considered.There is some disagreement in the literature about the correlation between workpiece surface roughness and fatigue life. In most cases, it has been reported that lower roughness results in longer fatigue life, but that for roughness values in the range 2.5–5 μm Ra it is primarily dependent on workpiece residual stress and surface microstructure, rather than roughness. In the absence of residual stress, machined surface roughness in excess of 0.1 μm Ra has a strong influence on fatigue life. Temperatures above 400 °C reduce the effects of both residual stress and surface roughness on fatigue, due to stress relieving and the change in crack initiation from the surfaces to internal sites. The presence of inclusions an order of magnitude larger than the machined surface roughness generally overrides the effect of surface topography.     

Evaluation of superabrasive grinding points for the machining of hardened steel

Small diameter grinding points offer greater flexibility for machining free-form contours compared to traditional grinding wheels, despite fewer effective cutting edges. The paper evaluates the influence of grit size (B32, B46, B76), feed rate (125, 250 mm/min) and depth of cut (20, 40 μm) when machining D2 tool steel using electroplated CBN grinding points. Highest G-ratios (～2441) were obtained using B32 tools with corresponding workpiece surface roughness (Ra) of ～0.8 μm after ～6000 mm³ material removed, due to the greater number of effective cutting edges. Attritious wear was the primary wear mechanism although material loading was observed with B76 tools.     

Gold based catalysts on ceria and ceria-alumina for WGS reaction (WGS Gold catalysts)

Gold catalysts supported on ceria-alumina have been studied in WGS reaction. A high and stable activity was established for the catalysts supported on ceria-alumina, prepared by mechanochemical activation in comparison to the corresponding samples, where ceria-alumina support was prepared by coprecipitation. The catalysts were characterized by means of XRD, TPR, Raman and XPS spectroscopy. A correlation between WGS activity and the redox activity was found. On the basis of the results obtained a model of the reaction mechanism and of active sites was proposed.     

Application of pectic acid for removing heavy metals from vegetable oils

Summary Comparative studies on removing the metal complex from hydrogenated vegetable oils with the help of synthetic ion exchangers (Dowex 50 WX4, Wofatit KPS-200, KY-2, Amberlyst-15) and polyuronides, have shown pectic acid to be the most efficient in this respect. The removal of copper, iron, zinc and nickel from the oils ranged over 87 to 94%. The treatment has been carried out under static conditions. Pectic acid is known to be completely insoluble in vegetable oils and also completely harmless, which favours its application for this particular purpose. A practical method for removing metals on vegetable oils, applicable under production conditions, has been developed.

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Einsatz von Pectinsäure zur Entfernung von Schwermetallen aus pflanzlichen Ölen

Zusammenfassung Durch vergleichende Untersuchungen zur Entfernung des Metallkomplexes aus hydrogenierten pflanzlichen Ölen mit synthetischen Ionenaustauschern Dowex 50 WX4, Wolfatit KPS-200, KY-2, Amberlyst-15) und Polyuroniden wird festgestellt, daß die Pectinsäure die höchste Wirksamkeit aufweist. Es werden 87 bis 94% der Ionen von Kupfer, Eisen, Zink und Nickel entfernt. Die Behandlung erfolgt unter statischen Bedingungen. Wie bekannt, ist die Pectinsäure in pflanzlichen Ölen völlig unlösbar, so daß ihre Anwendung zum obengenannten Zweck stark begünstigt wird. Es wird ein leicht einsetzbares Entmetallisierungsverfahren entwikkelt, das unter Produktionsbedingungen durchführbar ist.

     

Effect of defect orientation on metal fracture-statistical prognosis

Aluminium specimens of pre-caused defects are tensile tested at different temperatures. The defects are differently oriented to the tensile axis. The results have undergone statistical processing integrated with fundamental fracture approach. Analytical model to prognosticate the metal reliability in the range of applied tensile stresses is found. A method for evaluation of the defects orientation effect on fracture is suggested. The introduced strength spaces present a principal strength history of loaded defect metal.     

Influence of demetallization of hydrogenated sunflower oil on changes in the forms of heavy metals and their pro-oxidative effects

Summary The effect of removing heavy metals from hydrogenated sunflower oil using a method based on changes in the contents of the various forms of the heavy metals copper, iron, zinc and nickel and their respective pro-oxidative effects was studied. A high degree of removal of dissociated and bounded ions was observed for hydrogenated oil, while there was no change in the contents of the co-ordination form. The pro-oxidative effect of the dissociated ions and of the bound metal ions in hydrogenated oil decreased nine-fold and seven-fold, respectively, compared with that of the non-hydrogenated oil, as a result of which the oxidation stability of hydrogenated oil increased two-fold. Comparative studies confirmed as appropriate the use of wash waters and auxiliary solutions that do not contain heavy metals for the processing of the hydrogenate after the classical technology.

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Einfluß der Entmetallisierung von hydrogeniertem Sonnenblumenöl auf die Veränderung der Schwermetallformen und deren prooxydative Wirkungen

Zusammenfassung Es wird der Einfluß des Entmetallisierens von hydrogeniertem Sonnenblumenöl mit Hilfe einer von den Autoren ausgearbeiteten Methode auf die Gehaltveränderung der verschiedenen Schwermetallformen von Cu, Fe, Zn und Ni und deren entsprechenden prooxydativen Wirkungen untersucht. Es wurde ein hoher Grad der Beseitigung der ionisch dissoziierten und ionisch verbundenen Schwermetalle festgestellt; im Gehalt der koordinativ verbundenen Formen tritt keine Veränderung ein. Die prooxydative Wirkung der ersten Form vermindert sich 9mal, und der zweiten 7mal, infolgedessen die oxydative Stabilität des hydrogenierten Öls um das Doppelte erhöht wird. Die durchgeführten Vergleichsuntersuchungen bestätigen die Zweckmäßigkeit der Anwendung vom schwermetallfreien Spülwasser und Hilfslösungen bei der Hydrogenatbearbeitung nach der klassischen Technologie.