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131.
The thermal fracture of a bimaterial consisting of a homogeneous material and a functionally graded material (FGM) with a system of internal cracks and an interface crack is investigated. The bimaterial is subjected to a heat flux. The thermal properties of FGM are assumed to be continues functions of the thickness coordinate, while the elastic properties are constants. The method of the solution is based on the singular integral equations. For a special case where the interface crack is much larger than the internal cracks in the FGM the asymptotic analytical solution of the problem is obtained as series in a small parameter (the ratio between sizes of the internal and interface crack) and the thermal stress intensity factors (TSIFs) are derived as functions of geometry of the problem and material characteristics. A parametric analysis of the effects of the location and orientation of the cracks and of the inhomogeneity parameter of FGM’s thermal conductivity on the TSIFs is performed. The results are applicable to such kinds FGMs as ceramic/ceramic FGMs, e.g., TiC/SiC, MoSi2/Al2O3 and MoSi2/SiC, and also some ceramic/metal FGMs. 相似文献
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Multistep Redox Systems. 1,3-Dimethylidenecyclobutanes Substituted by π-Syntheses and Properties As potential redox systems 1,3-dimethylidenecyclobutanes are synthesized in which the ‘exo’-methylidene group participates in a cyclopentadienyl (type C4 )or cycloheptatrienyl (type A5 ) system. Benzo-annellated systems are also described. The formation of the C?C bond by the reaction of thioketones ( 3 and 31 ) with diazo compounds is extended to extended to 1,6,7,21 , and 24 , which so far had not been employed. In some cases, intermediate thiiranes can be isolated (e.g. 4 ) which are smoothly transformed into the target compounds of types C4 and A5 by extrusion of sulfur. The new C?C bonds may be introduced stepwise, thereby allowing the synthesis of unsymmetrically substituted 1,3-dimethylidenecyclobutanes (e.g. 20 and 35 ). Reduction of by Na does not produce bicyclobutanes but compounds 43 and 44 with one dihydrofulvene unit. 相似文献
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On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
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Physical parameters of material, such as strength and electrical conductivity, can be influenced considerably by the intermetallic compounds formed by diffusion in soldered microelectronic contacts between Cu and Sn/Pb solders. Therefore, formation and growth of these contact zones were systematically investigated on model specimens in dependence on temperature, time and chemical tin-lead concentration of the solders by means of electron probe microanalytical investigations and characterized by phase growth constants. Compared with the conventional metallographic specimen preparation method, the ion beam etching of the contact surfaces proves to be an excellently suitable means for representing the microstructure after the cooling of the samples. Moreover, the three-dimensional grain structure and technologically caused defects in the contact can be shown by ion beam slope cutting. Effects as e.g. the dendritic growth and Kirkendall pores which increasingly occur at higher temperatures are successfully proved. 相似文献