U型波纹管大挠度变形的积分方程描述及其迭代算法

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。     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅰ)-GOVERNING EQUATION AND GENERAL SOLUTION

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｔｈｅｏｒｙｏｆｆｌｅｘｉｂｌｅｓｈｅｌｌｓ,ｅｓｔａｂｌｉｓｈｅｄｂｙＥ .Ｌ .Ａｘｅｌｒａｄ[1,2 ]( 1 976,1 987) ,ｉｓａｓｉｍｐｌｉｆｉｅｄｔｈｅｏｒｙｆｏｒｔｈｉｎｓｈｅｌｌｓ,ｉｎｗｈｉｃｈｓｈｅｌｌｓｏｆｒｅｖｏｌｕｔｉｏｎａｒｅｆｏｒｍｕｌａｔｅｄｉｎｍｅｒｉｄｉｏｎａｌｄｉｒｅｃｔｉｏｎｂｙｂｅｎｄｉｎｇｔｈｅｏｒｙｏｆｔｈｅｓｈｅｌｌｓａｎｄｂｙｔｈｅｍｅｍｂｒａｎｅｔｈｅｏｒｙｉｎｔｈｅｃｉｒｃｕｍｆｅｒｅｎｔｉａｌｄｉｒｅｃｔｉｏｎ .ＴｈｅＡｘｅｌｒ…     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅰ)-GOVERNING EQUATION AND GENERAL SOLUTION

The overall bending of circular ring shells subjected to bending moments and lateral forces is discussed. The derivation of the equations was based upon the theory of flexible shells generalized by E.L. Axelrad and the assumption of the moderately slender ratio less than 1/3 (i.e., ratio between curvature radius of the meridian and distance from the meridional curvature center to the axis of revolution). The present general solution is an analytical one convergent in the whole domain of the shell and with the necessary integral constants for the boundary value problems. It can be used to calculate the stresses and displacements of the related bellows. The whole work is arranged into four parts: (Ⅰ) Governing equation and general solution; (Ⅱ) Calculation for Omega-shaped bellows; (Ⅲ) Calculation for C-shaped bellows; (Ⅳ) Calculation for U-shaped bellows. This paper is the first part.     

储罐用波纹管的几何非线性分析

根据现场实际,对储罐连接波纹管进行了几何非线性有限元分析。将波纹管视为旋转薄壳,基于Sanders小应变,中等转动薄壳理论,通过引入“伪载荷”而建立起一个形式简单,易于实施的迭代格式,并进行了数值求解。文末以50000m^3储罐－波纹管－管道系统为例,研究了波纹管危险点的等效应力随长度的变化规律,并由此给出一种波纹管安全运行长度的设计方法。     

FINITE ELEMENT DISPLACEMENT PERTURBATION METHOD FOR GEOMETRIC NONLINEAR BEHAVIORS OF SHELLS OF REVOLUTION OVERALL BENDING IN A MERIDIONAL PLANE AND APPLICATION TO BELLOWS (Ⅰ)

ＩｎｔｒｏｄｕｃｔｉｏｎＢｅｌｌｏｗｓ,ａｓｈｅｌｌｏｆｗｒｉｎｋｌｅｄｍｅｒｉｄｉａｎｏｆｒｅｖｏｌｕｔｉｏｎ ,ｈａｓｂｅｉｎｇｉｎｃｒｅａｓｉｎｇｌｙｕｓｅｄｉｎｍｏｄｅｒｎｅｑｕｉｐｍｅｎｔａｓａｎｅｌａｓｔｉｃ＿ｓｅｎｓｉｔｉｖｅｅｌｅｍｅｎｔａｎｄａｆｌｅｘｉｂｌｅｊｏｉｎｔ.Ｔｈｅｆｏｒｍｅｒｉｓｕｓｕａｌｌｙｓｕｂｊｅｃｔｅｄｔｏｌａｒｇｅｄｉｓｐｌａｃｅｍｅｎｔｓａｔｉｔｓｅｎｄｓ,ａｎｄｔｈｅｌａｔｔｅｒｍａｙｐａｒｔｌｙｅｎｔｅｒｉｎｔｏｐｌａｓｔｉｃｓｔａｔｅ .Ｈｅｎｃｅ ,ｂ…     

FINITE ELEMENT DISPLACEMENT PERTURBATION METHOD FOR GEOMETRIC NONLINEAR BEHAVIORS OF SHELLS OF REVOLUTION OVERALL BENDING IN A MERIDIONAL PLANE AND APPLICATION TO BELLOWS (Ⅰ)

In order to analyze bellows effectively and practically, the finite-element-displacement-perturbation method (FEDPM) is proposed for the geometric nonlinear behaviors of shells of revolution subjected to pure bending moments or lateral forces in one of their meridional planes. The formulations are mainly based upon the idea of perturba-tion that the nodal displacement vector and the nodal force vector of each finite element are expanded by taking root-mean-square value of circumferential strains of the shells as a perturbation parameter. The load steps and the iteration times are not as arbitrary and unpredictable as in usual nonlinear analysis. Instead, there are certain relations between the load steps and the displacement increments, and no need of iteration for each load step. Besides, in the formulations, the shell is idealized into a series of conical frusta for the convenience of practice, Sander’s nonlinear geometric equations of moderate small rotation are used, and the shell made of more than one material ply is also considered.     

FINITE ELEMENT DISPLACEMENT PERTURBATION METHOD FOR GEOMETRIC NONLINEAR BEHAVIORS OF SHELLS OF REVOLUTION OVERALL BEDING IN A MERIDIONAL PLANE AND APPLICATION TO BELLOW (Ⅱ)

The finite-element-displacement-perturbation method (FEDPM)for the geometric nonlinear behaviors of shells of revolution subjected to pure bending moments or lateral forces in one of their meridional planes (Ⅰ) was employed to calculate the stress distributions and the stiffness of the bellows. Firstly, by applying the first-order perturbation solution (the linear solution)of the FEDPM to the bellows, the obtained results were compared with those of the general solution and the initial parameter integration solution proposed by the present authors earlier, as well as of the experiments and the FEA by others.It is shown that the FEDPM is with good precision and reliability, and as it was pointed out in (Ⅰ) the abrupt changes of the meridian curvature of bellows would not affect the use of the usual straight element. Then the nonlinear behaviors of the bellows were discussed. As expected, the nonlinear effects mainly come from the bellows ring plate,and the wider the ring plate is, the stronger the nonlinear effects are. Contrarily, the vanishing of the ring plate, like the C-shaped bellows, the nonlinear effects almost vanish. In addition, when the pure bending moments act on the bellows, each convolution has the same stress distributions calculated by the linear solution and other linear theories, but by the present nonlinear solution they vary with respect to the convolutions of the bellows. Yet for most bellows, the linear solutions are valid in practice.     

FINITE ELEMENT DISPLACEMENT PERTURBATION METHOD FOR GEOMETRIC NONLINEAR BEHAVIORS OF SHELLS OF REVOLUTION OVERALL BEDING IN A MERIDIONAL PLANE AND APPLICATION TO BELLOW (Ⅱ)

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｅｑｕａｔｉｏｎｓａｎｄｔｈｅｓｏｌｕｔｉｏｎｐｒｏｃｅｄｕｒｅｓｏｆｔｈｅｆｉｎｉｔｅ＿ｅｌｅｍｅｎｔ＿ｄｉｓｐｌａｃｅｍｅｎｔ＿ｐｅｒｔｕｒｂａｔｉｏｎｍｅｔｈｏｄ (ＦＥＤＰＭ)ｆｏｒｔｈｅｇｅｏｍｅｔｒｉｃｎｏｎｌｉｎｅａｒｂｅｈａｖｉｏｒｓｏｆｓｈｅｌｌｓｏｆｒｅｖｏｌｕｔｉｏｎｓｕｂｊｅｃｔｅｄｔｏｐｕｒｅｂｅｎｄｉｎｇｍｏｍｅｎｔｓｏｒｌａｔｅｒａｌｆｏｒｃｅｓｉｎｏｎｅｏｆｔｈｅｉｒｍｅｒｉｄｉｏｎａｌｐｌａｎｅｓｗｅｒｅｐｒｅｓｅｎｔｅｄｉｎ (Ⅰ ) .…     

THE NONLINEAR CHARACTERISTICS OF U-SHAPED BELLOWS——CALCULATIONS BY THE METHOD OF PERTURBATION

In this paper,the linear exact solution and nonlinear solutionfor U-shaped bellows have been obtained by using the general so-lution of circular ring shell and the method of perturbation.     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅳ)-CALCULATION FOR U-SHAPED BELLOWS

This is one of the applications of Part (I), in which the angular stiffness, and the corresponding stress distributions of U-shaped bellows were discussed. The bellows was divided into protruding sections, concave sections and ring plates for the calculation that the general solution (I) with its reduced form to ring plates were used respectively, but the continuity of the surface stresses and the meridian rotations at each joint of the sections were entirely satisfied. The resent results were compared with those of the slender ring shell solution proposed earlier by the authors, the standards of the Expansion Joint Manufacturers Association (EJMA), the experiment and the finite element method. It is shown that the governing equation and the general solution (I) are very effective. Contributed by HUANG Qian Biography: ZHU Wei-ping (1962-)     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅲ)-CALCULATION FOR C-SHAPED BELLOWS

ＩｎｔｒｏｄｕｃｔｉｏｎＣ＿ｓｈａｐｅｄｂｅｌｌｏｗｓｏｒｒｅｆｅｒｒｅｄｔｏａｓｓｅｍｉ＿ｃｉｒｃｌｅｂｅｌｌｏｗｓａｒｅｗｉｔｈｃｏｍｐｌｅｘｃｏｎｆｉｇｕｒａｔｉｏｎ(Ｆｉｇ .1) .Ａｔｔｈｅｃｏｎｃａｖｅａｎｄｃｏｎｖｅｘｊｏｉｎｔｓｏｆｔｈｅｓｈｅｌｌ,ｆｏｒｅｘａｍｐｌｅａｔｐｏｉｎｔＣ ,ｔｈｅｌａｔｉｔｕｄｅａｎｇｌｅψｉｎｃｒｅａｓｅｓｂｙ 180°ａｂｒｕｐｔｌｙ .Ｓｏｉｔｉｓｔｈｅｋｅｙｔｏｃａｌｃｕｌａｔｉｏｎｆｏｒｂｅｌｌｏｗｓｔｈａｔｍａｋｉｎｇｕｐｓｏｌｕｔｉｏｎｓｅｘａｃｔ…     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅲ)-CALCULATION FOR C-SHAPED BELLOWS

This is one of the applications of Part (I), in which the angular stiffness, the lateral stiffness and the corresponding stress distributions of C-shaped bellows were calculated. The bellows was divided into protruding sections and concave sections for the use of the general solution (I), but the continuity of the stress resultants and the deformations at each joint of the sections were entirely satisfied. The present results were compared with those of the other theories and experiments, and are also tested by the numerically integral method. It is shown that the governing equation and the general solution (I) are very effective. Contributed by HUANG Qian Biography: ZHU Wei-ping (1962-)     

非线性MEMS微梁的重心有理插值迭代配点法分析

文章利用重心有理插值迭代配点法分析计算非线性MEMS微梁问题。通过处理MEMS微梁的几何通过假设初始函数,将微梁非线性控制方程转换为线性化微分方程,建立逼近非线性微分方程的线性化迭代格式。采用重心有理插值配点法求解线性化微分方程,提出了数值分析MEMS微梁非线性弯曲问题的重心插值迭代配点法。给出了非线性微分方程的直接线性化和Newton线性化计算公式,详细讨论了非线性积分项的计算方法和公式。利用重心有理插值微分矩阵,建立了矩阵-向量化的重心插值迭代配点法的计算公式。数值算例结果表明,重心插值迭代配点法求解微梁非线性弯曲问题,具有计算公式简单、程序实施方便和计算精度高的特点。     

Nonlinear free vibration of spinning cylindrical shells with arbitrary boundary conditions

The aim of the present study is to investigate the nonlinear free vibration of spinning cylindrical shells under spinning and arbitrary boundary conditions. Artificial springs are used to simulate arbitrary boundary conditions. Sanders' shell theory is employed, and von Kármán nonlinear terms are considered in the theoretical modeling. By using Chebyshev polynomials as admissible functions, motion equations are derived with the Ritz method. Then, a direct iteration method is used to obtain the nonlinear vibration frequencies. The effects of the circumferential wave number, the boundary spring stiffness, and the spinning speed on the nonlinear vibration characteristics of the shells are highlighted. It is found that there exist sensitive intervals for the boundary spring stiffness, which makes the variation of the nonlinear frequency ratio more evident. The decline of the frequency ratio caused by the spinning speed is more significant for the higher vibration amplitude and the smaller boundary spring stiffness.     

多自由度非线性动力学方程的能量校准算法

针对非线性动力学方程,通过Taylor展开和Duhamel积分,得到一个具有待定参数的逐步积分求解公式;通过数学变换,将原动力学方程转换为一个能确定待定参数的能量校准方程;最后将该参数回代入逐步积分公式,得到数值解.数值算例的结果说明了该方法的有效性,可以消除算法阻尼和抑制数值解发散,同时,在大步长的条件下也得到了非常准确而且稳定的结果,可以对系统长期性态进行仿真.     

ON PROBLEMS OF U-SHAPED BELLOWS WITH NONLINEAR DEFORMATION OF LARGE AXISYMMETRICAL DEFLECTION(Ⅱ)——COUNTING VARIATION OF THICKNESS DISTRIBUTION

On the basis of paper[1],assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry,perturbation solutions of the corresponding problems of large axisymmetrical deflection are given.The effects of thickness distribution variation,which result from technology factors,on stiffness of bellows are discussed.     

A new numerical technique for the analysis of parametrically excited nonlinear systems

A new computational scheme using Chebyshev polynomials is proposed for the numerical solution of parametrically excited nonlinear systems. The state vector and the periodic coefficients are expanded in Chebyshev polynomials and an integral equation suitable for a Picard-type iteration is formulated. A Chebyshev collocation is applied to the integral with the nonlinearities reducing the problem to the solution of a set of linear algebraic equations in each iteration. The method is equally applicable for nonlinear systems which are represented in state-space form or by a set of second-order differential equations. The proposed technique is found to duplicate the periodic, multi-periodic and chaotic solutions of a parametrically excited system obtained previously using the conventional numerical integration schemes with comparable CPU times. The technique does not require the inversion of the mass matrix in the case of multi degree-of-freedom systems. The present method is also shown to offer significant computational conveniences over the conventional numerical integration routines when used in a scheme for the direct determination of periodic solutions. Of course, the technique is also applicable to non-parametrically excited nonlinear systems as well.     

ON PROBLEMS OF U-SHAPED BELLOWS WITH NONLINEAR DEFORMATION OF LARGE AXISYMMETRICAL DEFLECTION (Ⅱ)——COUNTING VARIATION OF THICKNESS DISTRIBUTION

On the basis of paper [1], assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry, perturbation solutions of the corresponding problems of large axisymmetrical deflection are given. The effects of thickness distribution variation, which result from technology factors, on stiffness of bellows are discussed.     

非线性转子-轴承系统的周期解及近似解析表达式

通过对普通打靶方法进行改造提出一种确定非线性系统周期轨道及周期的新型打靶算法。首先通过改变系统的时间尺度，将非线性系统周期轨道的周期显式地出现在非线性系统的系统方程中，然后对传统打靶法进行改造，将周期也作为一个参数一起参与打靶法的迭代过程，迭代过程包含对周期轨道和周期的求解，迭代过程中的增量通过优化方法选择，从而能迅速确定出系统的周期轨道及其周期。应用所求的结果结合谐波平衡方法求得了非线性系统的周期轨道的近似解析表达式，理论上通过增加谐波的阶数任何精度的周期解都可以得到。最后将该方法应用于非线性转子轴承系统，求出了在某些参数下转子的周期解及其近似解析表达式，通过与四阶Runge-Kutta数值积分结果比较，验证了方法的有效性，计算结果对于转子系统运动的定量控制有重要理论指导意义。     

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅳ)-CALCULATION FOR U-SHAPED BELLOWS

ＩｎｔｒｏｄｕｃｔｉｏｎＵ＿ｓｈａｐｅｄｂｅｌｌｏｗｓａｒｅｕｓｕａｌｌｙｓｅｅｎｉｎｔｈｅｐｉｐｅｌｉｎｅｓｙｓｔｅｍ (Ｆｉｇ .1) ,ｗｈｉｃｈａｒｅｕｓｅｄｔｏｃｏｍｐｅｎｓａｔｅｆｏｒｔｈｅａｘｉａｌｍｏｖｅｍｅｎｔ,ｔｈｅｒｏｔａｔｉｏｎａｎｄｔｈｅｄｅｆｌｅｃｔｉｏｎｏｆｔｈｅｐｉｐｅｌｉｎｅｓｄｕｅｔｏｔｈｅｔｈｅｒｍａｌａｃｔｉｏｎ ,ｔｈｅｂａｓｅｕｎｅｑｕａｌｓｅｔｔｌｅｍｅｎｔｓａｎｄｔｈｅｉｎｓｔａｌｌａｔｉｏｎｅｒｒｏｒｓ.Ｔｈｅａｘｉｓｙｍｍｅｔｒｉｃａｌｄｅｆｏｒｍａｔｉｏ…