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21.
In this paper, finite element stress analysis of functionally graded structures using a high-order spectral/hp shell finite element is presented. The shell element is based on a seven-parameter first-order shear deformation theory in which the seventh parameter, in addition to the usual six degrees of freedom, is the thickness stretch. The continuum shell element is utilized for the numerical simulations of the fully geometrically nonlinear response of functionally graded elastic shell structures. Several nontrivial shell problems are considered to report deflections and stresses, the latter being the main focus of the current paper. It is found that the stresses computed in the current study agree only in some cases with those of ANSYS and/or ABAQUS and thus requires additional study to determine the cause of the disagreement. 相似文献
22.
盐碱胁迫下杨树叶片MDA含量与各抗氧化酶的相关性 总被引:1,自引:0,他引:1
在前人的基础上,从利用偏相关分析和多元线性回归分析的方法深入分析了盐碱胁迫环境下杨树叶丙二醛(MDA)含量与超氧化物歧化酶(Superoxide dismutase,SOD)、过氧化物酶(Peroxidase,POD)、过氧化氢酶(Catalase,CAT)活性之间,以及各抗氧化酶之间的内在相关性.研究结果表明,在盐碱... 相似文献
23.
本文用三维弹性力学理论研究绕径旋转横观各向同性圆球壳的变形和应力分布,给出任意厚度圆球壳的位移和应务的封闭形式解以及数值结果。研究表明球壳上的位移和应力大小与旋转角速度的平方成正比,球面内的正应力远大于径向正应力和剪应力。 相似文献
24.
A new similarity transformation has been devised for extensive studies of accelerating non-Newtonian film flow. The partial differential equations governing the hydrodynamics of the flow of a power-law fluid down along an inclined plane surface are transformed into a set of two ordinary differential equations by means of the dimensionless velocity component approach. Although the analysis is applicable for any angle of inclination (0<π/2), the resulting one-parameter problem involves only the power-law index n. Nevertheless, physically essential quantities, like the velocity components and the skin-friction coefficient, do depend on and relevant relationships are deduced between the vertical and inclined cases. Accurate numerical similarity solutions are provided for n in the range from 0.1 to 2.0. The present method enables solutions to be obtained also for highly pseudo-plastic films, i.e. for n below 0.5. The mass flow rate entrained into the momentum boundary layer from the inviscid freestream is expressed in terms of a dimensionless mass flux parameter Φ, which depends on the dimensionless boundary layer thickness and the velocity components at the edge of the viscous boundary layer. Φ, which is thus an integral part of the similarity solution, turns out to decrease monotonically with n. This parameter is of particular relevance in the determination of the streamwise position at which the entire freestream has been entrained and viscous stresses prevail all the way to the free surface of the film. A short-cut method to facilitate rapid and yet accurate estimates of the mass flux parameter is developed to this end. 相似文献
25.
This paper deals with some comparison results for displacements and stresses in a periodically stratified elastic semi-infinite
layer determined within the framework of two approaches: (1) based on the homogenized model with microlocal parameters [Woźniak
(1987) Int J Eng Sci 25: 483–499; Woźniak (1987) Bull Ac Pol Tech Sci 35: 143–151]; (2) obtained directly from the theory
of elasticity. A body is assumed to be composed of n elastic two-component periodically repeated laminae. The perfect mechanical bonding between the layers is assumed. The normal
displacements and zero shear stresses on the boundary being a cross-section of the composite component are taken into account.
The lateral boundary surfaces are assumed to be rigid fixed. The obtained results from the two approaches are compared and
presented in the form of figures. 相似文献
26.
The asymptotic stress and strain distribution near a crack tip in rubber-like materials is determined by finite element for in-plane mixed mode loading. For large strain, the crack tip field is always in a state of uniaxial tension. The shear load affects only the orientation of the deformed near tip field in the space. A good agreement is obtained between the theoretical and numerical results. 相似文献
27.
Microdefects such as dislocations and macrocracking should be controlled during the crystal growth process to obtain high-quality bulk single crystals. Solid mechanics and material strength studies on the single crystals are of importance to solve the problems related to the generation and multiplication of dislocations and the cracking of single crystals. The present paper reviews such research activities that comprise the thermal stress analysis during crystal growth process, the dislocation density estimation during crystal growth process, and the cracking of single crystal due to thermal stress. 相似文献
28.
Hydrogen absorption into and surface oxidation of Pd–Au alloys in acidic solutions were studied by cyclic voltammetry (CV)
and chronoamperometry (CA) coupled with the electrochemical quartz crystal microbalance (EQCM). The influence of alloy bulk
and surface composition on the process of oxidation of absorbed hydrogen was examined. The stresses induced by hydrogen insertion
in Pd–Au alloys were compared with the case of pure Pd. The potential corresponding to the formation of a monolayer of surface
oxide was determined for Pd–Au alloys of different surface states. Electrochemical dissolution of Pd–Au alloys was investigated. 相似文献
29.
Normal stresses are set up by shearing a rubber block or tube. They depend strongly on the end conditions, even for relatively long specimens [A.N. Gent, J.B. Suh, S.G. Kelly III, Mechanics of rubber shear springs, Int. J. Non-Linear Mech. 42 (2007) 241-249; J.B. Suh, A.N. Gent, S.G. Kelly III, Shear of rubber tube springs, Int. J. Non-Linear Mech. 42 (2007) 1116-1126]. We have now examined a solid rubber cylinder bonded within a rigid cylindrical tube and subjected to pressure at one end. In this case, the correct end conditions for a simple shear deformation are met, at least approximately. Theoretical analysis and finite element calculations show that inwardly directed second-order stresses are set up at the wall, in contrast to the outwardly directed stresses generated by shearing a block or tube. However, for the particular geometry considered, the stresses were rather small in comparison with the applied pressure. Conditions are described under which they would be significantly larger. Stresses in a non-linearly viscous fluid under steady shear flows are expected to be similar, depending strongly on the geometry, end shapes and stress conditions. 相似文献
30.
水平均布荷载作用在地基内部时的土中应力公式 总被引:8,自引:0,他引:8
本文根据半无限体内受水平集中力作用的明德林公式,通过积分而首次完整地推导出水平矩形均布荷载作用在地基内部时的土中应力分量的解析表达式,以便工程设计人员在设计时使用。 相似文献