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51.
G. Lange 《Materialwissenschaft und Werkstofftechnik》2003,34(1):80-85
Failures by notch induced fatigue fractures Notches produce local stress concentrations and promote the formation of fatigue cracks. Characteristic types of notches as a result of design, manufacturing and operation are presented and remedial measures are discussed. Examples demonstrate the effect of different kinds of notches on various components. 相似文献
52.
Recently, efficient scheduling algorithms based on Lagrangian relaxation have been proposed for scheduling parallel machine
systems and job shops. In this article, we develop real-world extensions to these scheduling methods. In the first part of
the paper, we consider the problem of scheduling single operation jobs on parallel identical machines and extend the methodology
to handle multiple classes of jobs, taking into account setup times and setup costs. The proposed methodology uses Lagrangian
relaxation and simulated annealing in a hybrid framework. In the second part of the paper, we consider a Lagrangian relaxation
based method for scheduling job shops and extend it to obtain a scheduling methodology for a real-world flexible manufacturing
system with centralized material handling.
This research was supported in part by the Office of Naval Research and the Department of Science and Technology grant N00014-93-1017. 相似文献
53.
This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue). 相似文献
54.
55.
垂直平行密集束状孔落矿有底柱崩落法是一种新的采矿方法。通过爆破模型试验,测试爆破应力,观察分析爆破效果,探求最佳布孔形式,选择最优爆破孔网参数。试验结果表明:用平行束状孔取代扇形落矿,改善了爆破效果,简化了采场结构,减少了采切工程量。 相似文献
56.
In this work we investigated the mechanism of the electrochemical intercalation reactions in rf sputtered nickel oxide thin films electrodes by two techniques: mechanical stress change measurements by means of an optical technique and mass changes using an electrochemical quartz microbalance (EQCM). The experiments were performed in alkaline electrolytes containing cations of the first column of the periodic table. Reversible mass and volume changes were observed. In order to explain these experimental results, an exchange reaction is proposed, in which the oxidation process is accompanied by the deinteractional of a relative large number of “light” cations, simultaneously with the intercalation of a smaller number of heaviest cations. 相似文献
57.
Taijiro Nonaka Rodney J. Clifton Taichiro Okazaki 《International Journal of Impact Engineering》1996,18(7-8):889-898
An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake. 相似文献
58.
Y. Kraftmakher 《International Journal of Thermophysics》1994,15(5):983-991
Relaxation phenomena due to equilibration of point defects in metals are reviewed. The relaxation effect in specific heat observed in tungsten and platinum confirms that in both cases the nonlinear increase in the high-temperature specific heat has to be attributed to point-defect formation. Relaxation phenomena observed by measurements of electrical resistivity and positron annihilation are also considered. The comparison of the data seems to be favorable for the conclusion that all the phenomena are of one origin. 相似文献
59.
60.
用毛细管流变仪研究了乙基纤维素(EC)及其高密度聚乙烯(HDPE)复合物,纤维素芳族酯(CAE)及其聚碳酸酯(PC)复合物的剪切流变特性和机理。结果表明,EC对HDPE/EC复合物的粘度影响不大,而少量(5%)CAE的加入使PC/CAE复合物粘度大大下降,且复合物流变曲线呈现新的特征。 相似文献