A New Method of Characterising the Misorientation in Low Angle Boundaries in Hexagonal Crystals

In this work, methods used to define the misorientation between twograins in a hexagonal crystal are presented. Transformation matricesare generally used to define the misorientation and are found to beconvenient and accurate in most cases. However, in the analysis oflow angle boundaries, it is very difficult to obtain data todetermine the transformation matrix accurately. A new method isdescribed which was developed to overcome this problem and thetechnique is demonstrated using the analysis of a boundary inTi₃Al.     

Oscillatory shearing of a class of elastic-plastic materials

Summary For a special class of elastic-plastic materials, it is shown that infinitesimal oscillatory shearing motions can be sustained without the application of body forces. Hardening, softening and perfectly plastic responses are considered.

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Zusammenfassung Für eine spezielle Klasse von elastisch-plastischen Materialien wird gezeigt, daß infinitesimale oszillatorische Scherbewegungen ohne die Anwendung von Körperkräften aufrecht erhalten werden können. Härtung, Enthärtung und ideale plastische Reaktionen werden betrachtet.

     

Pressure dependency,strength-differential effect,and plastic volume expansion in metals

Within the framework of a purely mechanical rate-type theory of finitely deforming elastic-plastic materials, a special set of constitutive equations is introduced. These equations include a dependence both on mean normal stress and on plastic strain, and involve non-normality of plastic strain-rate. They accommodate both the strength-differential effect and plastic volume expansion. Values of the material coefficients in the constitutive equations are approximately determined with the help of published experimental data for AISI 4330 steel. The plastic strain-rate is shown to have a large non-normal component, resulting in a small plastic volume expansion. The theory is in reasonable agreement with experiment for plastic strains up to about 2% in magnitude. Further experiments are suggested so that the constitutive coefficients can be completely and accurately determined.     

A large scale machine loading problem in flexible assembly

Flexible manufacturing is characterized by versatile work stations with minimum change over times and a versatile material handling system. The loading problem in flexible manufacturing is to assign tools, material, operations and jobs to work stations in order to minimize the total number of job-to-work station assignments. In this paper, we describe a special case of the general loading problem applied to flexible assembly and develop a discrete optimization model. We then discuss approaches for obtaining good heuristic solutions and present results for a large scale study.     

A constitutive restriction related to convexity of yield surfaces in plasticity

Summary An implication of the work assumption of Naghdi and Trapp is established for finitely deforming elastic-plastic materials. For a special class of materials, for which the plastic strain rate is normal to the yield surface in stress space, the result ensures convexity of the latter yield surface.

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Zusammenfassung Unter der Voraussetzung der Arbeits-Hypothese von Naghdi und Trapp wird für endlich deformierbares elastisch-plastisches Material eine Konsequenz gezogen.Danach wird eine spezielle Klasse von Materialien betrachtet, für die die plastische Dehnungsrate senkrecht auf eine Fläche gerichtet ist. Diese Fläche umschließt den elastischen Bereich der sechsdimensionalen räumlichen Spannungen. Das Ergebnis zeigt, daß diese Konsequenz eine Konvexität dieser Fläche garantiert.

     

Thermal decomposition of anomeric glycopyranosides

Thermal analysis studies coupled with chemical studies indicate that glycopyranosides undergo thermal decomposition in two overlapping stages. The initial reaction of the glycosides at temperature between 200 and 300°C is cleavage and volatilization of the glycosidic group as the corresponding alcohol, followed by intra- or inter-molecular condensation of the glycosyl portion of the molecule. At higher temperatures (310–340°C) the major reaction is fragmentation of the carbohydrate into a variety of low molecular-weight compounds. Studies with a series of anomeric methyl and phenyl glycosides indicate that, with the methyl and phenyl glycosides, the rate of the low-temperature condensation reaction was dependent on anomeric configuration of the starting glycoside.