月牙肋钢岔管结构模型试验与计算结果的比较

结合实际工程，采用比尺为1∶6的结构模型试验和有限元的方法对月牙肋明钢岔管的受力分布进行分析。结果表明：对于这类均质钢壳结构，模型试验与计算结果基本吻合，采用计算方法所得出的结果能够满足工程的要求。     

A note on Hopf bifurcations in a delayed diffusive Lotka-Volterra predator-prey system

The diffusive Lotka-Volterra predator-prey system with two delays is reconsidered here. The stability of the coexistence equilibrium and associated Hopf bifurcation are investigated by analyzing the characteristic equations, and our results complement earlier ones. We also obtain that in a special case, a Hopf bifurcation of spatial inhomogeneous periodic solutions occurs in the system.     

非线性强迫系统的分叉

本文通过对传统的IHB方法进行推广和形式的变化，将其应用于非线性动力系统的分叉现象。得到了分叉方程，并作出了分叉图，该方法扩大了IHB方法的应用范围以及提高了可靠性。     

Bifurcation of cavitation solutions for incompressible transversely isotropic hyper-elastic materials

In this paper, the bifurcation problem of void formation and growth in a solid circular cylinder, composed of an incompressible, transversely isotropic hyper-elastic material, under a uniform radial tensile boundary dead load and an axial stretch is examined. At first, the deformation of the cylinder, containing an undetermined parameter-the void radius, is given by using the condition of incompressibility of the material. Then the exact analytic formulas to determine the critical load and the bifurcation values for the parameter are obtained by solving the differential equation for the deformation function. Thus, an analytic solution for bifurcation problems in incompressible anisotropic hyper-elastic materials is obtained. The solution depends on the degree of anisotropy of the material. It shows that the bifurcation may occur locally to the right or to the left, depending on the degree of anisotropy, and the condition for the bifurcation to the right or to the left is discussed. The stress distributions subsequent to the cavitation are given and the jumping and concentration of stresses are discussed. The stability of solutions is discussed through comparison of the associated potential energies. The bifurcation to the left is a `snap cavitation'. The growth of a pre-existing void in the cylinder is also observed. The results for a similar problem in three dimensions were obtained by Polignone and Horgan.     

内加强月牙肋钢岔管新型结构

内加强月牙肋钢岔管具有水头损失小、受力比较均匀、外部无明显突出构造物、洞室开挖断面较小等优点 ,因此广泛应用于地下埋藏式压力管道。但布置在地面上的明式月牙肋钢岔管尚不多见 ,特别是当钢岔管承受的水头和直径较大时。以某水电工程钢岔管为例 ,以满足结构受力和水力条件为前提 ,优化岔管体形 ,然后按照钢衬钢筋混凝土岔管结构进行了有限元计算 ,得到了一些有益的结论。     

上海粘性土剪切带形成的平面应变试验研究

采用可进行边界变形局部化量测的平面应变仪 ,对上海典型硬粘性土 ( 2层褐黄色粉质粘土、6层暗绿色粉质粘土 )进行平面应变不排水剪切试验 ,研究局部化变形的初始分叉点、剪切带倾角随固结应力 σ3 之间的变化规律 ,评价 Columb和 Roscoe理论对剪切带倾角的预估 ,初步研究了剪切带内的变形机理。     

A rigorous method for the analysis of localization of axisymmetric buckling patterns in thick cylindrical shells

This paper theoretically investigates the localization of axisymmetric buckling patterns in cylindrical shells because this phenomenon has a large influence on the strength degradation in the post-buckling range. The localization behavior is caused by a plastic bifurcation on the decreasing equilibrium path subsequent to the maximum load point. Thus, we first show a rigorous numerical method based on the finite-element method technique for analysis of plastic bifurcation under two-axial stresses. Then, using this method, we examine how the structural parameters, constitutive models and boundary conditions affect the deformation capacity of cylindrical shells.     

干摩擦作用下贮液器的非线性振动与分岔

研究了干摩擦作用下贮液器的非线性振动，利用非线性振动理论与实验模态分析相结合的方法，求出了该系统的极限环和Ｈｏｐｆ分岔解，分析了干摩擦粘滑系数及搓动速度在非线性振动中的作用。本文的方法和结论对同类非线性振动的研究具有一定的参考价值。     

Smooth stabilizing feedback for a class of mechanical systems with a pitchfork bifurcation

We consider the problem of local stabilization of a class of mechanical systems depending on a physical parameter, and which exhibit an open-loop pitchfork bifurcation. Furthermore, at the critical value of the parameter the tangent linearization of the system contains two zero uncontrollable modes. Our goal is to find a nonlinear stabilizing feedback law.     

Application of the Duffing Chaotic Oscillator Model for Early Fault Diagnosis- Ⅰ.Basic Theory

In this paper, the well-known Duffing equation and the nonlinear equation de-scribing vibration of the human eardrum are introduced from elastic nonlinear system theory. According to the fact that the human ear can distinguish weak sound with small difference , the idea that the Duffing oscillator can be used to detect a weak signal and diagnose early fault of machinery is proposed. In order to obtain a model for weak signal detection via the Duffing oscillator, the first step is to week all forms of solutions of the Duffing equation. The second step is to study global bi furcations of the Duffing equation using qualitative analysis theory of a dynamic system. That is to say, a series of bi furcations thresholds of the Duffing equation can be analyzed by the Melnikov function and a subharmonics Melnikov function. Then the three types of bifurcations thresholds varying with damping and external exciting amplitude are discussed. The analysis concludes that the bi furcation threshold corresponding to the ma