非线性周期波及破碎波对杆件的作用力

本文采用十五阶 Stokes 波的 Pade 逼近,获得了与实验较为一致的流场,并且利用已有的破碎波的速度、加速度场,计算了非线性波和破碎波对各种杆件作用力,比较了它们的主要特征,为海洋工程设计提供依据。     

二维地表局部不规则区域对P,SV波传播的影响

本文将转换矩阵法加以推广,用来求解半空间表面局部不规则区域所引起的P、SV波的散射透射问题。计算讨论了孤突山丘和沉积谷地对地震波的放大作用,结果与实际震害调查中观测到的现象基本一致。     

BIFURCATIONS OF TRAVELLING WAVE SOLUTIONS FOR GENERALIZED DRINFELD-SOKOLOV EQUATIONS

Ansatz method and the theory of dynamical systems are used to study the traveling wave solutions for the generalized Drinfeld-Sokolov equations. Under two groups of the parametric conditions, more solitary wave solutions, kink and anti-kink wave solutions and periodic wave solutions are obtained. Exact explicit parametric representations of these travelling wave solutions are given.     

弹塑性波的研究现状与趋势

本文系统总结了弹塑性波理论的研究现状,并介绍了当前在弹塑性波理论和相关的工程领域中的重要课题。分析并指出了今后弹塑性波问题的研究趋势。     

促进其线性频散特征另一种形式的Bousinesq方程

Ｂｏｕｓｉｎｅｓｑ方程能够用于模拟表面重力波传播过程中的折射、绕射、反射以及浅化，非线性作用等现象．用不同垂直积分方法所得到的二维Ｂｏｕｓｓｉｎｅｓｑ方程形式具有不同的线性频散特征．采用两个不同的水深层的水平速度变量组合，推导出一个新形式的Ｂｏｕｓｉｎｅｓｑ方程．通过对其参数的设置可得到精确的线性频散解Ｐａｄｅ近似４阶精度．其适用范围已由原来的浅水，向深水拓进．相速误差小于２％，其拓展适用范围可达到０８个波长水深．应用所得到的新型Ｂｏｕｓｉｎｅｓｑ方程，采用有限差分法，对经典工况进行了数值模拟，其计算结果表明，计算值与物模实验值吻合较好．这说明本文新形式的Ｂｏｕｓｓｉｎｅｓｑ方程对变水深非线性效应所产生的能量频散有着较为精确的描述     

波涡相互作用研究的某些进展(Ⅱ)

<正> 5 波涡共振 从第3节的感受性问题再前进一步,自然要问在什么条件下入射波激发起涡中之波的最大响应.这就导致了入射波与层状或轴状涡中受激波之间共振的概念,简称波涡共振.一般说来,在流体内部若有两个或多个波相会,它们将互相穿透而沿原来的方向离去.但若它们的波矢量和频率满足一定的关系(参见Craik 1985),就会在相会点产生新的波.2阶扰动的振幅可达到1阶扰动振幅的量级,而且流场中会出现一些重要的独特性质.这就是流体内部波共振,波涡共振是其一类情形.     

弹性半空间内中心简单波的反射问题

本文研究弹性体内中心简单波的特征平面和广义特征线。并利用特征线方法求解中心简单波在自由界面上的反射,得到了中心无旋波和中心等容波速度分量的边界放大系数及其某些数值结果。     

Variational analysis of thermomechanically coupled steady-state rolling problem

A steady-state, rigid-plastic rolling problem for temperature and strain-rate dependent materials with nonlocal friction is considered. A variational formulation is derived, coupling a nonlinear variational inequality for the velocity and a nonlinear vari- ational equation for the temperature. The existence and uniqueness results are obtained by a proposed fixed point method.     

FLEXURAL WAVE PROPAGATION IN NARROW MINDLIN＇S PLATE

Appling Mindlin＇s theory of thick plates and Hamilton system to propagation of elastic waves under free boundary condition, a solution of the problem was given. Dispersion equations of propagation mode of strip plates were deduced from eigenfunction expansion method. It was compared with the dispersion relation that was gained through solution of thick plate theory proposed by Mindlin. Based on the two kinds of theories, the dispersion curves show great difference in the region of short waves, and the cutoff frequencies are higher in Hamiltonian systems. However, the dispersion curves are almost the same in the region of long waves.     

各向异性介质中SH波引起的裂纹扩展

本文利用Green函数法,求解各向异性介质中半无限长裂纹在SH波作用下,以任意速度扩展的问题。首先,利用Laplace变换和Cagniard-de Hoop反演法求解各向异性介质中反平面问题的Green函数,并利用它建立了求解裂纹扩展问题的积分方程。因为方程为Abel型的,所以可得到在SH波作用下,半无限长裂纹扩展问题的解析解。还可求得裂纹端点附近的应力和裂纹表面上位移的表达式。并对裂纹端点附近的奇异性进行讨论。最后讨论了裂纹尖端附近任一点的能量关系。并应用Griffith的能量准则,对裂纹扩展规律进行了讨论。     

A SPECIAL SOLUTION OF WAVE DISSIPATION BY FINITE POROUS PLATES

The reflection and transmission of water waves caused by a small amplitude incident wave through finite fine porous plates with equal spacing and permeability in an infinitely long open channel of constant water depth and zero slope are studied. A special solution is obtained when the distance between the two neighbouring plates is an integral multiple of the half-wavelength of the incident wave. It is found, that when the dimensionless porous-effect parameter G_0 is equal to half the total plate number, the wave dissipation reaches a maximum, and only 50% of the incident wave energy remains in the reflected and transmitted waves. Meanwhile, the reflected and transmitted waves have the same amplitude.     

Specific features of incident and reflected blast waves

On the basis of numerical modeling specific features of shock wave reflections were analyzed. It was found, that after diaphragm rupture self-modeling pressure and velocity distributions nearby the shock front establish. But in some special cases the temperature behind the shock front can rise. This peculiarity should be taken into account when performing experiments with high reactive gaseous mixtures. The temperature on the shock front and the velocity gradient behind it are uniform in the case of strong blast wave reflections. This effect is observed in the zone with an elevated temperature profile behind the incident blast wave. The reflected triangular waves conserve a quasi-self-modeling character by pressure. Typical experiments were carried out to verify the theoretical predictions. The effects of reflected wave acceleration in the case of triangular waves and the self-similar character of the pressure profiles were observed.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

深水波理论的新进展

大海是令人神往的。诗人们愿意用大海来抒发感情。更重要的是,在大海中蕴藏着丰富的能量、矿物和生物资源。即使在交通十分发达的今天,它仍不失为沟通世界各大洲的重要渠道之一。但是,大海并不总是那样平静那样驯服。咆哮起来,惊涛骇浪可以折断巨轮,倾覆平台;海啸和风暴潮可以冲决堤坝,破坏海工建筑,吞噬成千上万人的生命。要征服大海不是一件轻而易举的事。人们尊敬古代那些开拓海上通道的先驱者。在中国历史上就有这样     

The Smooth and Nonsmooth Travelling Wave Solutions in a Nonlinear Wave Equation

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｅｘｉｓｔｅｎｃｅｏｆｐｅａｋｏｎＴＷＳｏｆａｎｏｎｌｉｎｅａｒｗａｖｅｅｑｕａｔｉｏｎρｔ =ｂｕｘ 12 [(ｕ2 ±ｕ2 ｘ) ρ] ｘ,　ρ =ｕ±ｕｘｘ ( 1 )ｗａｓｃｏｎｓｉｄｅｒｅｄｂｒｅｉｆｌｙｂｙＰ .Ｒｏｓｅｎａｕ (ｓｅｅ [1 ] ) .Ｅｑ.( 1 )ｉｓｆｏｕｎｄｂｙ“ｒｅｓｈｕｆｆｌｉｎｇ”Ｈａｍｉｌｔｏｎｉａｎｏｐｅｒａｔｏｒｏｆｂｉ＿ＨａｍｉｌｔｉｏｎｉａｎｓｔｒｕｃｔｕｒｅｉｎＫｄＶａｎｄｍＫｄＶｅｑｕａｔｉｏｎ (ｓｅｅ [2 ] ) .ＢｅｃａｕｓｅＥｑ.( 1 )ｈａｓｓｔｒｏｎ…     

损伤介质中波传播特性的研究

本文研究了弹性波在损伤介质中传播的基本理论，建立了基本动力学方程式，并根据其边界条件和连续性条件求得末端接收波位移的时域曲线。接收波则综合携带了损伤介质内部特性信息，可通过这些信息研究损失介质损坏的程度及位置。通过实例计算，定量地分析了结构内部损伤度、损伤位置和损伤区域大小对接收波幅值和波到达时间的影响。通过分析可知损伤对波传播的影响较大；并且可以根据给定的曲线图，直接由测得的接收波峰值及到达时间探测到结构内部损伤大小与分布。这为无损检测的定量化反分析提供了可靠的依据。     

冲击压缩下玻璃样品后自由表面速度的过冲现象

实验发现当飞片碰撞玻璃样品产生的冲击载荷超过一定值后 ,玻璃样品后自由表面速度时程曲线上有过冲现象 ,即速度上升到最大值后 ,立即开始下降 ,其时间的开始部分类似于三角波。通过高速摄影和VISAR等测试手段对这一现象进行了较系统的研究 ,发现其与玻璃样品后自由表面附近的破碎有关 ,建立了描述这一破坏现象的损伤演化方程 ,并进行了数值模拟。计算结果和实验结果吻合 ,表明对这个现象的解释是合理的。     

Exact Explicit Peakon and Periodic Cusp Wave Solutions for Several Nonlinear Wave Equations

Using the method of dynamical systems for six nonlinear wave equations, the exact explicit parametric representations of the solitary cusp wave solutions and the periodic cusp wave solutions are given. These parametric representations follow that when travelling systems corresponding to these nonlinear wave equations has a singular straight line, under some parameter conditions, nonanalytic travelling wave solutions must appear. Dedicated to Professor Zhifen Zhang on the occasion of her 80th birthday     

玻璃样品对表面对失效波萌生的影响

实验首次发现经过酸（5％HCl)处理的玻璃样品表面以及飞片表面粗糙度的变化均对失效液（failure wave)形成的载荷阈值有明显影响。这说明失效波的形成机制与玻璃样品表面固有微裂纹。碰撞瞬间由于样品表面与其内部力学性质差异导致的微裂纹形核、长大等因素有直接关系。从而对进一步研究失效波的萌生机制和建立相关理论模型提供重要的支持。     

Interaction of a gasdynamic shock with small disturbances

The stability of shock wave based on the definition of Landau and Lifschitz^[1] is treated in this paper. This is tantamount to solving the problem of interaction of small disturbances with a shock wave. Small disturbances are introduced on both sides of a steady, non-dissipative, plane shock wave. Landau et al.^[1] obtained the stability criterionM ₁>1,M ₂<1 for small disturbances which are travelling in the direction perpendicular to the shock wave. In the present paper, we assume that the small disturbances may be two dimensional, i.e. they may be propagating in the direction inclined to the shock wave. The conclusions obtained are: regardless of whether the incident wave and diverging wave are defined according to the direction of the phase velocity or the group velocity, the shock wave is unstable for some frequencies and longitudinal wave lengths of the disturbances, even if the conditionsM ₁>1,M ₂<1 are fulfilled. Then several experiments are proposed, and the problem of ways to define the incident wave and diverging wave is discussed. The meaning of this problem is illustrated. The same results can be obtained for the steady shock wave in a tube.