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111.
A study has been made of ‘combined’ joints consisting of mechanical fastening and adhesive bonding between rigid adherends. The mechanical characteristics of such ‘hybrid’ butt and lap shear joints have been derived by theoretical analysis. Results from experimental tests in combined joints giver reasonable agreement with the theoretical equations relating joint load to deformation. 相似文献
112.
113.
Yutaka Kagawa Yasuo Kogo Hiroshi Hatta 《Journal of the American Ceramic Society》1989,72(6):1092-1094
Thermal expansion behaviors of a Si3 N4 -whisker-reinforced sodaborosilicate glass matrix composite are studied. An abrupt increase of the coefficient of thermal expansion is observed and is attributed to formation of crystobalite in the sodaborosilicate glass matrix. This thermal expansion behavior is discussed with special reference to the phase transformation of the crystobalite. 相似文献
114.
Atsuhiko Yamanaka Tooru Kitagawa Masayuki Tsutsumi Toshihiro Kashima Hiroyuki Fujishiro Kimiko Ema Yoshinobu Izumi Shigehiro Nishijima 《应用聚合物科学杂志》2004,93(6):2918-2925
High strength polyethylene fiber (Toyobo, Dyneema® fiber: hereinafter abbreviated to DF) has a negative thermal expansion coefficient. Relation between fiber structure and thermal strain of DF used as reinforcement of DF reinforced plastic (DFRP) for cryogenic use was investigated. The crystallinities and orientation angles of several kinds of polyethylene fibers having different modulus from 15 to 134Gpa (herein after abbreviated to DFs) were measured by NMR and X‐ray. We obtained the parameters of the mechanical series‐parallel model composed of crystal and amorphous by crystallinity and modulus. Thermal expansion coefficients of DFs were estimated by mechanical series‐parallel model. All DFs having different modulus showed negative thermal expansion coefficients in the temperature range from 180 to 300K, and absolute values of those markedly increased by increasing tensile modulus of DF. The estimated thermal expansion coefficients showed negative values, and thermal strains showed a similar curve to observed ones mostly. Average thermal expansion coefficients in the temperature range from 180 to 300K estimated by mechanical model agreed with the observed ones. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2918–2925, 2004 相似文献
115.
以TiO2 ZrO2 P2O5为复合成核剂,采用传统熔融冷却法获得了高ZnO含量的Li2O-A l2O3-SiO2系统的基础玻璃。通过差热分析确定了该玻璃的热处理条件、晶化性能,利用梯温炉实验、X射线衍射分析和扫描电镜对晶化试样的物相和微观结构进行了研究,讨论了热处理制度对玻璃的析晶及热膨胀系数的影响。研究结果表明:含10%(质量分数)ZnO的LAS系统样品玻璃最佳核化温度为(710±2)℃,玻璃的晶化活化能E为(275±2)kJ/mol,晶化指数n为3.11±0.2,样品玻璃在较低温度下失透,并且随着晶化温度升高,样品的热膨胀系数加大。 相似文献
116.
《Expert systems with applications》2014,41(16):7161-7170
The features extracted from the cardiac sound signals are commonly used for detection and identification of heart valve disorders. In this paper, we present a new method for classification of cardiac sound signals using constrained tunable-Q wavelet transform (TQWT). The proposed method begins with a constrained TQWT based segmentation of cardiac sound signals into heart beat cycles. The features obtained from heart beat cycles of separately reconstructed heart sounds and murmur can better represent the various types of cardiac sound signals than that from containing both. Therefore, heart sounds and murmur have been separated using constrained TQWT. Then the proposed novel raw feature set has been created by the parameters that have been optimized while constraining the output of TQWT together with that of extracted by using time-domain representation and Fourier–Bessel (FB) expansion of separated heart sounds and murmur. However, the adaptively selected features have been used to obtain the final feature set for subsequent classification of cardiac sound signals using least squares support vector machine (LS-SVM) with various kernel functions. The performance of the proposed method has been validated with publicly available datasets and the results have been compared with the existing short-time Fourier transform (STFT) based method. The proposed method shows higher percentage classification accuracy of 94.01 as compared to 93.53 of STFT based method. In comparison with STFT based method, it is noteworthy that the proposed method uses well defined and lower dimensionality of feature vector that can reduce the computational complexity. 相似文献
117.
118.
Walter Brockmann 《The Journal of Adhesion》1989,29(1):53-61
Adequate adhesion between metals and polymers is primarily the result of chemical bonds in the boundary layer. This region, however, is subject to degradation by moisture. Three modes of deterioration are observed. The first is a largely reversible weakening effect in the polymer layer near the metal oxide surface. The structure of this layer differs from that of the bulk and is influenced by the chemical and physical properties of the surface. The second is a slow transformation of the oxide by hydration and a diffusion of oxide constituents into the polymer. This process is irreversible and is influenced by the state of the surface and chemical properties of the polymer. The third is a fast deterioration of the oxide by primary corrosion usually initiating at an unprotected edge but occasionally arising within the body of a joint. 相似文献
119.
120.
The objective of this study was to determine how the fracture of adhesive joints depends on elastic beam parameters describing the adherends and the applied loads. The basic specimen geometry was the cracked lap shear joint constructed of aluminium alloy with various adherend and bondline thicknesses. Loads were applied in different combinations of bending, tension and shear to generate a failure envelope for each adhesive and specimen geometry. It was found that crack propagation for precracked specimens occured at a critical strain energy release rate but was also a function of the GI/GII ratio and the bondline thickness. The experiments also showed that the loads required to propagate a crack in a precracked specimen were always lower than the loads required to break the fillet. Hence, by treating uncracked joints as being cracked, where the fictitious crack tip is assumed to coincide with the location of the fillet, a conservative estimate of the failure load is obtained. 相似文献