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有环壳过渡段的锥—柱组合壳的应力和稳定性 总被引:1,自引:0,他引:1
用解析方法计算了受静水外压载荷作用的有环壳过渡段的锥—柱组合壳中的应力值,并用瑞利法计算了其失稳临界载荷。计算结果说明,利用环壳过渡值锥—柱壳形成光滑连接,可使连接部位的局部应力值显著降低,并使失稳临界载荷有所提高 相似文献
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以剪压破坏时配有斜筋的混凝土梁为研究对象,考虑临界斜裂缝处各钢筋拉应力和剪应力的影响,基于极限平衡理论和复合应力状态下混凝土的强度准则,建立了极限抗剪承载力的计算公式。对配有斜筋混凝土梁进行的试验研究发现,理论值与试验值的误差不超过5%。研究表明:箍筋与纵筋、斜筋与纵筋的相对配筋率以及剪跨比对临界斜裂缝顶端混凝土受压区的高度影响较为显著,进而影响抗剪承载力;临界斜裂缝顶端混凝土在复合应力状态下发生破坏,竖向压应力的作用不应忽略;斜筋和箍筋的剪应力对极限抗剪承载力影响较小,计算中可不予考虑。 相似文献
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本文在文献[1]、[2]的基础上,利用将内力及位移展开成k=(h/λ)~(1/2)及斜锥偏度参数m的双重渐近幂级数的方法,得出了斜锥壳的渐近解,同时以直角斜锥壳承受正压力情况为例,给出了它的应力计算分析表达式。 为了验证所给公式的精确程度,计算了斜锥壳薄膜应力的数值解,并作了两个斜锥壳试件的电测试验。结果表明,本文所得的渐近解的误差基本上在(h/λ)~(1/2)及m~2的量级范围內。 对于斜锥壳这类形状复杂的构件,直接求解薄壳基本方程是很困难的,数值解只能求出在给定尺寸时的解答,不能得出适用于一般尺寸的解析解,对具有小参数特点的构件,渐近解的优点在于能得到具有一定精度的应力分析表达式,便于工程设计应用。 相似文献
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本文对轴对称加肋旋转壳及其组合壳体(锥-锥,锥-柱,球-柱壳等)在轴对称静载荷作用下的线弹性强度和稳定性计算,采用性能良好的轴对称拟协调单元推导了有限元的计算列式,并将计算结果与静水压力下的锥-柱-锥结合壳,加肋锥-柱结合壳的其它计算结果和实验结果进行比较。 相似文献
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建立了一种纵横加肋圆柱壳有限元分析的正确的力学模型,通过大量数值计算,论证了纵骨尺寸,纵骨间距对壳体应力状态的影响,提出了一种等效各向同性壳的近似解析公式,为开展纵横加肋圆柱壳的结构设计打下了良好的基础。 相似文献
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在文献[1]中作者得到了具有刚性加强端的斜锥壳的渐近解法.本文在此基础上进一步讨论横向稀肋加固的斜锥壳的渐近解法.所谓“稀肋”是指相邻两肋的简单边界效应相互影响在工程精度范围内可忽略不计的肋条,例如肋间距l≥3(rh)~(1/2)时(2h——薄壳厚度,r——两肋处壳体的最大平均半径).对于本文所讨论的常用的肋条横截面尺寸,分析结果表明,作为应力状态的第一次渐近解[误差为(h/λ)~(1/2)量级,λ——壳体中心面的特征曲率半径],肋对壳体薄膜应力状态没有影响.而在求解简单边界效应时,可将肋与壳的连接处看成弹性固支边界来处理,即认为此处的壳体转角γ_1为零,而周向应变ε_2等于肋的应变值。在分析过程中,讨论了肋截面形心偏心及形心主轴偏斜等因素对壳体应力状态的影响,证明了在第一次近似时它们可忽略不计. 为了验证所得结果的精确程度,在文献[1]的试件上,进一步作了具有稀肋加强的斜锥壳的电测试验.试验结果证实,本文所得的渐近解的误差基本上在(h/λ)~(1/2)及斜锥偏度m~2的量级范围内. 为了节省篇幅,本文不再给出斜锥壳各基本应力状态的内力及位移表达式,以及它们的待定函数的确定方法,需要时可参阅文献[1]. 相似文献
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1.前言弹性锥壳的一般弯曲、稳定和振动问题,在实际工程中经常遇到,但对其研究基本上限于轴对称问题且都是以挠度函数和应力函数为基本未知量.我们认为,对于锥壳的特征值问题、弹性地基锥壳以及锥壳组合结构,则宜采用锥壳的位移解法.本文作者之一曾对锥壳一般弯曲问题的位移解法进行了系统的研究,以广义超几何函数给出了一般解.在应用文献[1]结果的基础上,本文通过引入一个广义载荷q_n(s,θ,t),得到了以位移函数U(s,θ,t)表示的弹性锥壳一般弯曲、稳定和振动(包括弹性地基影响)问题的统一型式的控制方程.文献[2]用级数给出了锥壳横向自由振动问题的解,但应指出,由于文献[2]中 相似文献
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采用格林函数法,导出了U型波纹管圆环壳部分和截头扁锥壳部分的非线性的积分方程,其中的四个未知参数由圆环壳和截头扁锥壳的连接条件确定,联合应用梯度法和积分方程迭代法建立了U型波纹管大挠度分析的迭代算法,开发了相应的程序系统,数值结果表明,本文方法具有较高的精度,压缩角对峰值应力和刚度影响十分显著,应用作为波纹管设计的重要参数。 相似文献
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刚性元方法和块状岩体稳定性分析 总被引:6,自引:1,他引:6
本文提出的刚性元方法是一种数值分析方法,它将变形体离散为一些刚性块体(剐性元)和块体之间的可变形薄层(节理元)的组合体,在各种载荷条件下求出块体的运动以及薄层的变形和应力分布。本文联合岩石系统的失稳准则来使用刚性元方法,成功地研究了块状岩体的稳定性问题。计算实例表明,本文提出的方法可以正确地反映块状岩体的失稳机制,是一种合理和可行的岩体稳定性分析手段。 相似文献
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针对白鹤滩水电站左岸坝基河谷底部边坡岩体爆破开挖,采用现场岩体位移监测、锚索轴力监测及数值模拟的手段,研究了爆破开挖扰动下锚固节理岩质边坡的位移突变特征及其能量机理。研究结果表明:对于深切河谷底部高地应力边坡岩体爆破开挖,爆炸荷载挤压及地应力作用下,岩体所积聚的应变能快速释放,导致了节理岩质边坡的位移突变,突变位移包括节理张开位移和岩体回弹位移两部分;地应力水平越高、岩体弹性模量越低,总的突变位移量越大;预应力锚索主要通过抑制节理张开位移来控制边坡岩体的位移突变,锚索预应力等级越高,其吸能和释能速率越高,对节理岩体位移突变的控制效果越好,当锚索的预应力等级高到一定程度后,节理岩体的突变位移不再随锚索预应力等级的升高而显著减小。 相似文献
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《International Journal of Solids and Structures》2007,44(13):4256-4271
This paper presents the experimental and theoretical investigation of property of stress wave propagation in jointed rocks by means of SHPB technique and fractal geometry method. Our aim focuses on the influence of the rough joint surface configuration on stress wave propagation. The comparison of behavior of reflection and transmission waves, deformation and energy dissipation of a rough joint surface characterized by its fractal feature with that of a smooth plane joint has been carried out. It has shown that the rough joint surface distinctly affects the stress wave propagation and energy dissipation in the jointed rocks. The rougher the joint surface was, the more permanent deformation occurred and the more attenuation stress wave took place as well. A nonlinear relationship between the normalized energy dissipation ratio WJ/WI of the jointed rock and the joint roughness in terms of the fractal dimension has been formulated. It seems that the ratio WJ/WI, presenting how much energy has been dissipated in the joint, nonlinearly increased with the increment of the fractal dimension D of the jointed surface. The ratio WJ/WI of a roughly jointed rock, however, tends to be the same as that of a smoothly jointed rock if the fractal dimension is less than a critical value Dc = 2.20. The energy dissipation ratio at the critical point Dc seem to be a constant, not dependent of rock type but fractal joint configuration. 相似文献
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The effects of the curvature radius of a cylindrical shell on stress intensity factors are investigated in circumferential (inner and outer) semielliptical surface cracks in a cylindrical shell. What is new in this paper is to have given: (1) The stress intensity factors for surface cracks in a cylindircal shell are determined by photoelastic technique. (2) By a special method photoelastic slices are handled for obtaining a clear caustic curve, and the stress intensity factors for surface cracks in a cylindrical shell are determined by the caustic method. (3) An approximate equation of curvature correction factor Fc is proposed. (4) Effects of the curvature radius R of a cylindrical shell on the stress intensity factors of surface cracks are obtained. The results of this paper are in fair agreement with already existing analytical results. The approximate equation of curvature correction factor Fc can be widely used for engineering purposes. 相似文献
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A method for solving boundary-value problems of plasticity with allowance for the stress mode is developed. To describe the
elastoplastic deformation of an isotropic material, use is made of constitutive equations that include two nonlinear functions
dependent on the stress mode and determined experimentally. The elastoplastic state of a thin cylindrical shell under axisymmetric
loading is calculated as a numerical example. The numerical results demonstrate good convergence of the method. The effect
of the stress mode on the strain distribution in a cylindrical shell is assessed 相似文献
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S. N. Kukudzhanov 《Mechanics of Solids》2008,43(5):815-826
We study the natural vibrations and the dynamic stability of nearly cylindrical orthotropic shells of revolution subjected to meridional forces uniformly distributed over the shell ends. We consider shells of medium length for which the shape of the midsurface generatrix is described by a parabolic function. Using the theory of shallow shells, we obtain the resolving equation for the vibrations of the corresponding prestressed shell. In the isotropic case, this equation differs from the well-known equation [1] by an additional term, which can be of the same order as the other terms taken into account. We consider shells of both positive and negative Gaussian curvature. We assumed that the shell ends are freely supported. The formulas and universal curves describing the dependence of the minimum frequency, the wave generation shape, and the dynamic instability domain boundaries on the orthotropy parameters, the preliminary stress, the Gaussian curvature, and the amplitude of the shell deviation from the cylinder are given in dimensionless form. We find that in the case of prestresses the orthotropy parameters and the shell deviation from the cylinder (of the order of thickness) can significantly change the least frequencies, the wave generation shape, and the dynamic instability domain boundaries of the corresponding prestressed orthotropic cylindrical shell.In this case, we note that for convex shells under preliminary compression the influence of the elastic parameter in the axial direction is stronger than the influence of the elastic parameter in the circular direction, while the situation is opposite in the case of concave shells. In the case of preliminary extension, the leading role of any orthotropy parameter can vary depending on the value of the preliminary stress and the Gaussian curvature. 相似文献
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Hongtao Zhang Jianming Zhu Yinghua Liu Bingye Xu Xiaochun Wang 《Acta Mechanica Solida Sinica》2012,25(2):177-185
This paper aims to determine the strength properties of jointed rock masses by means of the homogenization method.To reflect the microstructure of jointed rock masses,a representative element volume (R... 相似文献
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The paper studies the interaction of a spherical shock wave with an elastic circular cylindrical shell immersed in an infinite acoustic medium. The shell is assumed infinitely long. The wave source is quite close to the shell, causing deformation of just a small portion of the shell, which makes it possible to represent the solution by a double Fourier series. The method allows the exact determination of the hydrodynamic forces acting on the shell and analysis of its stress state. Some characteristic features of the stress state are described for different distances to the wave source. Formulas are proposed for establishing the safety conditions of the shell.Translated from Prikladnaya Mekhanika, Vol. 40, No. 9, pp. 94–104, September 2004. 相似文献
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平面壳单元是由平面应力单元和平板弯曲单元叠加组合而成,具有简单的理论表达,但是它在计算曲面壳体结构时误差较大。为了进一步提高平面壳单元的计算精度,本文提出了一种计算平面壳单元刚度矩阵的新方法。通过该方法在高斯积分点建立多个单元局部坐标系,并保证每个局部坐标系都位于单元在高斯点处的切平面上,从而可以有效适应曲面壳体形状,达到进一步提高平面壳单元计算精度的目的。为了在这种新坐标系下计算单元刚度矩阵,给出了求解形函数对局部坐标的导数、局部到自然坐标系积分转换的雅可比、以及局部到整体坐标系的转换矩阵的新型计算方法。通过将这些新坐标系以及新计算方法运用到平面壳单元DKQ24中,可以有效提高平面壳单元尤其是在计算曲面壳体时的精度。计算结果表明,本文方法和平面壳单元相结合,不仅具有平面壳单元简单的理论表达式,还能得到满意的精度。另外,本文方法还可以应用到其他类型的平面壳单元,为提高其他类型平面壳单元的计算精度提供了一种新的途径和思路,具有广阔的应用前景。 相似文献