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Formulae are derived for the deflection surface of a symmetrically loaded circular plate having several points supports which are situated at equal distances apart on a single concentric circle. There is no restriction on the diameter of the support circle, which may be as large as the diameter of the plate itself. The results of this paper compare favorably with published experimental results. Numerical deflection coefficients for a uniformly loaded plate are provided, and these could be utilized for optimizing the positions and the number of concentrated supports. 相似文献
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Joseph Marin 《Journal of The Franklin Institute》1938,226(5):645-657
Various solutions have been made for determining the stresses in pipe flanges using the theory of elasticity (I). There are many cases, however, of pipe flanges which are subjected to stresses and at the same time a high temperature such that creep occurs.This paper gives an analysis of the stresses and deformations produced in a circular ring of rectangular cross section subjected to twisting couples uniformly distributed along its center line. Such a solution will also give an approximate analysis of the pipe flange. This approximation is justified in view of the complexity of the problem and the uncertainties still present in the fundamental creep-stress relation for metals. In the solution of this problem a deflection theory is also developed for straight beams subjected to bending accompanied by creep. 相似文献
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This paper is concerned with the analysis of the problem of dynamic perforation of visco-plastic plates by a cylindrical projectile, leading to a failure of the plate by a plug formation. Assuming the behavior of the plate material is nonlocal visco-plastic, the classical theory of visco-plasticity for Bingham solids is generalized to take the non-local effects into consideration. The target plate being thin, it is assumed that only the contributions of vertical shearing stress need be taken into account. The effect of the impact is represented by a uniform velocity distribution over a circular region of the plate surface. The expressions of velocity, strain rate and shear stress are obtained and some particular cases are discussed. Some numerical results concerning stress distributions are also included. 相似文献
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In this research, linear and non-linear stability behaviour of a thin circular FGM plate subjected to the uniform temperature rise and the constant angular velocity loadings is analyzed. Properties of the FGM media are distributed across the thickness based on a power law form. Each property of the metal or ceramic constituents is considered to be the function of temperature based on the Touloukian model. General equilibrium equations for such conditions are obtained based on the classical plate theory. At first, the non-linear governing equations are established in a complete asymmetrical form. After that, two different analytical methods are presented to study the bifurcation behaviour. Existence of bifurcation phenomenon is examined. Pre-buckling analysis is performed for a plate with the immovable clamped edge. Stability equations are obtained based on the adjacent equilibrium criterion. The resulted equations are solved via the two distinct methodologies, i.e. the exact solution in terms of Coulomb wave functions and the power series method. A non-linear solution is also presented to detect the equilibrium path of the heated rotating FGM plate. It is found that the angular speed may stabilize the homogeneous circular plate which buckles during uniform heating. Furthermore, snapping may occur for FGM plates under the simultaneous action of heating and uniform rotation. 相似文献
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利用级数展开法和Laplace--Fourier变换推导了文克尔地基上无限长板在半波正弦瞬态荷载作用下位移和应力的解析解。计算和分析了板的位移响应情况，并和弹性地基静荷载情况的位移进行了比较，讨论了荷载作用时间、地基参数及板参数等对位移响应的影响。对路面设计、品质评价及破坏机理分析有重要意义。 相似文献
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The grid current required to fire a thyratron has been shown to depend theoretically upon the shape of the grid current characteristic before firing as well as upon the grid circuit constants.The three-element FG-17 and the four-element FG-95 and FG-98 thyratrons have been investigated.Anomalies where excessively large grid currents were required to start the arc, occurring below certain values of temperature and plate potential, have been found and are described in some detail.Although the argon-filled FG-98 was found to be free from temperature effects over the operating range, positive shield grid potentials introduced anomalies at low plate potentials.Even though the plate and shield potentials and the temperature were kept within the recommended optimum range, it was found that for minimum grid currents at firing the negative grid impedance of these tubes necessitated a grid resistance of 100 to 1000 megohms. 相似文献
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偶应力问题的非协调元分析 总被引：2，自引：0，他引：2
从偶应力弹性体势能泛函的驻值条件出发,得到了偶应力理论中非协调元体系的能量相容原理。基于其常应力(常偶应力)分片检验条件的强形式,对平面四结点单元的非协调试探内函数进行了优化,提出了一种稳定有效的非协调元方法。有限元列式中,微转动和宏观转动相等的约束条件通过罚因子的形式引入。分析了含中心圆孔的无限平板,在单轴拉伸以及纯剪状态时,偶应力的存在对孔周应力集中的影响。算例表明,该单元计算效率高,精度好,即使在材料本征长度很小时,仍然能够得到相当理想的结果 相似文献
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Sara Baratchi Francisco J. Tovar-Lopez Khashayar Khoshmanesh Megan S. Grace William Darby Juhura Almazi Arnan Mitchell Peter McIntyre 《Biomicrofluidics》2014,8(4)
Shear stress is the major mechanical force applied on vascular endothelial cells by blood flow, and is a crucial factor in normal vascular physiology and in the development of some vascular pathologies. The exact mechanisms of cellular mechano-transduction in mammalian cells and tissues have not yet been elucidated, but it is known that mechanically sensitive receptors and ion channels play a crucial role. This paper describes the use of a novel and efficient microfluidic device to study mechanically-sensitive receptors and ion channels in vitro, which has three independent channels from which recordings can be made and has a small surface area such that fewer cells are required than for conventional flow chambers. The contoured channels of the device enabled examination of a range of shear stresses in one field of view, which is not possible with parallel plate flow chambers and other previously used devices, where one level of flow-induced shear stress is produced per fixed flow-rate. We exposed bovine aortic endothelial cells to different levels of shear stress, and measured the resulting change in intracellular calcium levels ([Ca2+]i) using the fluorescent calcium sensitive dye Fluo-4AM. Shear stress caused an elevation of [Ca2+]i that was proportional to the level of shear experienced. The response was temperature dependant such that at lower temperatures more shear stress was required to elicit a given level of calcium signal and the magnitude of influx was reduced. We demonstrated that shear stress-induced elevations in [Ca2+]i are largely due to calcium influx through the transient receptor potential vanilloid type 4 ion channel. 相似文献
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中国茄科天仙子亚族的花粉形态研究 总被引：1，自引：0，他引：1
本文作者对国产茄科天仙子亚族6个属、12种植物的花粉，用光学显微镜、扫描电镜和
透射电镜观察了它们外壁雕纹、萌发孔的类型以及外壁层次的结构。 本亚族花粉以无萌发孔
和三孔沟类型为主，其次为三沟和拟沟类型。根据花粉资料，表明花粉形态特征对于论证该亚族内属的界限和属间系统发育的关系，可以提供重要的依据。 相似文献
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In this paper is described a new method of finding the sum of the principal stresses in a two-dimensional model by means of ordinate measurements on a stretched rubber membrane as suggested by Den Hartog. The method is applied in detail on a bar with central circular hole in tension and is found to be easy in operation and of good accuracy. 相似文献
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《Journal of The Franklin Institute》2018,355(18):9351-9373
This paper deals with an application of the Sliding Mode Control (SMC) in the presence of lumped temperature disturbances in Peltier Cells (PCs). A controller is proposed so that a temperature disturbance reduction is obtained. A constructive Theorem based on a particular sliding mode surface using Lyapunov approach is demonstrated. Specifically, the proven Theorem shows a structural control law which consists of an interacting input law between the two available inputs of current and forced heat convection transfer function (ventilation input). The sliding mode surface is defined in terms of cold and hot state variables, emphasizing a new two sided control approach for PCs. In terms of applications, the localization problems are very important to minimize errors in all cases in which PCs are used. The application approach is targeted on a novel workpiece clamping device, which uses PCs to freeze water on a metallic plate under subzero temperatures. The ice structure is capable of evolving enough bonding strength to clamp workpieces form and force-fitted during machining operations without deforming the piece mechanically. This capability is especially crucial for micro parts as well as for hard to clamp pieces made of brittle or soft materials and irregular shaped complex geometries. The proposed SMC approach shows a robustness against the parametric uncertainties due to the nonlinear model of PCs. Computer simulation results as well as measurements are shown. 相似文献
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Armin Saeedi Vahdat 《Journal of The Franklin Institute》2011,348(4):622-639
This paper deals with effects of residual and axial stresses on thermoelastic damping (TED) in micro-beam resonators. Equations of coupled thermoelastic case for a capacitive micro-beam resonator have been governed using two dimensional non-Fourier heat conduction model based on continuum theory frame. A Galerkin based finite element formulation has been used to analyze TED for the first mode of vibration of the micro-beam resonator with both ends clamped and isothermal. Effect of axial stresses owing to stretching of the micro-beam on the TED ratio has been investigated. As results illustrate, this effect gets importance only when the resonator is vibrating about a large static deflection due to a bias DC voltage close to the pull-in voltage of the resonator, otherwise it can be neglected in calculations. Effect of compressive and tensile residual stresses has been also studied. The results show that compressive (tensile) residual stresses increase (decrease) the TED ratio considerably. The residual stresses effect has been also studied for various values of the micro-beam thicknesses. The results illustrate that the effect of residual stress on the TED ratio decreases by increasing the thickness of the micro-beam. The results show that, applying DC voltages near the pull-in voltage increases energy dissipation due to the TED considerably, therefore, there is a limitation for applied DC voltage for resonators, since residual stresses change the pull-in voltage of the resonator, hence, existing residual stresses can change the interval of the applied voltage limitation. 相似文献
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对一种亚毫米波频段的,缝隙型嵌套开口谐振环式频率选择表面(FSS)的极化转换特性进行了研究。通过仿真方法比较了开口环的缝隙长度、宽度、单元间距等参数的改变对谐振频率的影响,进而影响了频率选择表面的极化转换特性。通过优化,确定了频率选择表面的结构参数,得到了工作中心频率在427GHz,最大相位差为81.3度,低于3dB的轴比带宽为31.3%的频率选择表面圆极化器。 相似文献
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Chih-Bing Ling 《Journal of The Franklin Institute》1977,303(5):405-414
The convergence of the successive approximations in Howland's solution of an infinite perforated strip containing a symmetrically-located circular hole under longitudinal tension can be improved considerably by using the well known solution of an infinite perforated plate as the approximation of zero order. Further, by basing on a somewhat different physical concept, a corresponding direct solution of the problem can be formulated. Such a solution is presented in this paper. Numerical results are obtained from the solution over a wider range of values of the radius of hole, a feature hardly attainable in the previously known solutions of the problem. Further extension of the method of solution to the transverse bending problem as well as to the case of an unsymmetrically-located hole is also possible. 相似文献
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The effect of an imperfectly bonded laminar composite is examined in terms of the intensification of the torsional stresses operative near the imperfection which is assumed to be a circular shaped area. The laminar composite is modelled by four layers of different materials with the two outer layers being infinite in height and debonding occurs at the interface of the two inner layers. The analysis based on the application of Hankel transforms and the solution of a pair of dual integral equations can be easily extended to a multilayered system. Depending on the size of the layer thickness relative to the radius of the debonded area, delamination may take place either in a stable or unstable fashion. The analytical results also indicate that the influence of lamination tends to lower the stress intensity around an interface imperfection as compared to the stress state in a homogeneous solid containing the same imperfection. Numerical results are obtained for two special laminate geometries and discussed with reference to the pertinent parameters used in the current theory of fracture mechanics. 相似文献