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弹性力学空间问题的复变函数解贾普荣(西北工业大学,西安710072)1基本方程对于弹性力学一般的空间问题,位移和应力分量可用伽辽金的3个双调和函数表出 ̄[1]。设f_1(x,y,z),f_2(x,y,z),f_3(x,y,z)为双调和函数,即位移分量... 相似文献
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本文根据桩在轴向谐振力作用下,探讨了非均质层下基桩的动力稳定性问题,分析了各种地基土横向抗力系数K以及桩的几何特征,激振频率,桩土阻尼对桩动力稳定性的影响,结果表明,随地基土层的不同,基桩的动力不稳定区域将发生不同的变化,随桩径,桩长的增大,基桩的动力不稳定区域将逐渐减小,表明地基土的横向抗力对桩的动力稳定性起加强作用,桩土阻尼对基桩的动力稳定性影响较大,得出了一些有价值的结论,可为工程设计提供参考依据。 相似文献
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在心理学中,刺激量感觉量之间的关系,没有考虑到感觉适应的影响,适应现象是各种感觉都普遍具有现象,建立一种考虑适应作用的心理物理学定律,是很有必要的,利用心理物理学定律,分析材料的力学性能,被称为“软机械”方法曾被应用于评价食品的质量,在本中,我们讨论如何应用这部“软机械”,测定材料的“硬”指标-软科学性能。 相似文献
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单源低能离子束辅助沉积类金刚石薄膜摩擦性能的研究 总被引:4,自引:7,他引:4
目前,制备类金刚石薄膜的方法很多,然而其中的多数在沉积过程中都需要基本具有比较高的温度,这不不可避免地会对耐温性较差的材料造成损伤,或使机械零部件发生变形和尺寸变化,因此,利用单源低能离子束辅助沉积法制备了非晶碳薄膜,并且利用喇曼光谱和俄歇电子能谱研究了薄膜的结构,发现了其为无定形的类金刚石薄膜,薄膜中的碳原子成键主要sp^2杂化键,研究表明,随着离子能量和束流的增大,薄膜的显微硬度,摩擦系数和寿 相似文献
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铝合金材料剪切断裂实验分析 总被引:4,自引:1,他引:4
金属材料受载作用发生断裂,断裂面形式有拉断,剪断和拉剪混合型,由于剪断过程中塑性变形较为复杂,问题的研究难度大,观点争论多,本文对LY12-M铝合金材料复合型平面应变载荷状态下的几种断裂试验结果作了分析,认为在II型,近II型时发生的剪切型断裂,启裂点在裂尖附近应力三维度取最大值处,剪断的开裂方向则与启裂点上最大剪应力方向有关,同时对LC9R超强铝合金作常规破坏试验,该材料在拉伸,扭转与压缩试验时均呈剪切断裂,断裂面沿最大剪应力方位,破坏剪应力随试件应力三维度的降低而增大,综合分析试验结果得到了一些有用的结论。 相似文献
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大型相关失效工程网络系统可靠度的近似算法 总被引:6,自引:0,他引:6
为避开失效模式(或系统可靠路径)的NP难题(non—polynomial increase hard problem),提出递推分解算法,降低大型工程网络系统可靠度分析中的计算复杂性,同时,将改进的多维正态变量积分公式,引入递推分解算法之中,计算多失效模式(或系统可靠路径)的联合概率,并最终计算工程网络系统的失效概率和可靠度,对于特别复杂的工程网络系统,采用上下界的方法,给出具有很高精度的可靠度近似值。实例分析表明,本文提出的方法,具有较高的精度和计算效率。 相似文献
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随着现代科学技术的进步,机器设备正日益向高速,重载和高精度的方向发展。因此,如何改善材料的摩擦损性能和机器零件的润滑状态,以延长机器设备的使用寿命,已经受到摩擦学工作者的广泛关注,在基础润滑油中加入各种添加剂是改善其润滑性能的重要方法,而对材料表面进行改行处理则是改善其摩擦磨损性能的有效方法,若将这两种方法配合使用,可能获得更好的实用效果,然而有关的研究工作还很不深入和系统,基于这情况,对润滑油极 相似文献
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V. L. Sennitskii 《Journal of Applied Mechanics and Technical Physics》2006,47(1):68-70
The ideal fluid flow due to fluid penetration through the boundary of an infinitely long solid cylinder in contact with a
solid wall is determined. A formula is derived according to which the force exerted by a finite-length part of the cylinder
on the wall is directed into the wall and can thus have an arbitrarily large absolute value.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 82–84, January–February, 2006. 相似文献
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A. N. Prokunin 《Fluid Dynamics》2003,38(3):443-457
The results of an experimental investigation of spherical particles with different surface roughnesses rolling under their own weight down an inclined pipe wall in a Newtonian fluid at low Reynolds numbers, both with (friction should be taken into account) and without contact with the wall, are presented. It is shown that a fixed particle moves differently in different fluids with similar viscosities and densities. This fact, as well as the possibility of particle motion without contact with the wall, cannot be explained within the framework of the usual hydrodynamic theories. An example is the dependence of the particle motion on the static pressure. 相似文献
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Torsion problems for a cylinder with a rectangular hole and a rectangular cylinder with a crack 总被引:1,自引:0,他引:1
Using the method of singular integral equation and the crack-cutting technique, the rigorous solutions are obtained for a
cylinder with a rectangular hole and a rectangular cylinder with a crack, which exactly satisfy the boundary conditions and
the conditions at the corner points. After that the torsional rigidities and the stress intensity factors at the crack tip
are determined. Next, for the doubly connected circular cylinder with a rectangular hole the expressions for the singular
stresses around the concave corner points are derived and the generalized stress intensity factors are then defined. Since
the crack-cutting technique is used in this paper, the solution of the matching rectangular cylinder is also obtained and
its numerical results coincide with those in references. Thus the method proposed here is verified.
The project supported by National Natural Science Foundation of China 相似文献
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S. N. Bagir-zade G. P. Guseinov 《Journal of Applied Mechanics and Technical Physics》1973,14(6):832-838
A study is made of the motion of a liquid toward a well with a hemispherical end-face with unsteady-state spherical-radial filtration in a fractured-porous stratum consisting of hemispherical regions with different values of the permeability of the system of cracks, superposed one on another. A Laplace transform is used to find exact solutions to the problem of the lowering of the stratum pressure as a function of time and distance as well as of the output of a well working with a constant end-face pressure. The article discusses partial cases corresponding to the exploitation of closed and bounded open fractured-porous strata by a central well with a hemispherical end-face. On the basis of numerical calculations, the effect of the parameters of fractured-porous strata on the change in the indices of the process of their exploitation is established. It is established that, with the exploitation of fractured-porous strata, the process of the lowering of the end-face pressure of the well and its output become stabilized with sufficiently large values of the time.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 115–123, November–December, 1973. 相似文献
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The problem of the asymmetric flow around a cylinder of a nonviscous jet is considered and, in particular, of flow with one free boundary. The problem of the choice of circulation is posed, based on a generalization of the Zhukovskii-Chaplygin postulate. Several possibilities are considered and the principle of the minimum of the maximum velocity on a contour is proposed, which qualitatively and quantitatively truly reflects certain aspects of the interaction of the cylinder with the flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 50–58, September–October, 1977. 相似文献
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An exact analytic solution is found to the following plane hydrodynamic problem. An unbounded flow of an ideal incompressible fluid flows around a plate BB' placed at right angles to the velocity vector of the flow at infinity. The pressure on the free boundary P is equal to the pressure in the flow. From an opening in the center of the plate, a jet with flow rate Q from a cavity with pressure P0 encounters the flow head-on. As a result of the solution, it is found that for fixed width of the opening the values of Q allowed by the scheme are limited. In the limiting case Q = 0 Chaplygin's flow is obtained with stagnation region at the front [1], and in the limiting case Q = Qmax a jet out of a cavity with pressure P0 into a cavity with pressure P. As Q varies in this interval, the total drag, regarded as the drag of the plate and the chamber from which the jet emerges, takes a minimal value at a certain point. If the width of the opening tends to the length of the slab, the problem of the collision of two jets is obtained; if the width of the opening tends to zero (Q o), the problem of jet flow past a slab with a source is obtained. It is shown that the replacement of the jet by the source gives a good approximation in both the sense of the force characteristics and in the sense of the behavior of the free streamlines.Translated from Izvestiya Akademii Nauk SSSR, Hekhanika Shidkosti i Gaza, No. 5, pp. 47–54, September–October, 1979.We thank L. I. Sedov for his interest in the work and G. Yu. Stepanov for proposing the method of solution and for a helpful discussion. 相似文献
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L. A. Tkacheva 《Fluid Dynamics》2013,48(3):352-365
The problem of the impact of a body with a plane bottom (of the type of a box) on a thin liquid layer at a small angle is solved in the two-dimensional formulation. The nonlinear shallow water equations are used, together with the method of matched asymptotic expansions. It is found that at certain values of the input parameters of the problem the liquid pressure diminishes near the lower end of the body and becomes smaller than the atmospheric pressure, which results in liquid separation from the box bottom. The numerical results show that all input parameters of the problem have a considerable effect on the nature of body motion. The liquid separation effect on body motion is analyzed. 相似文献