中国区域稳定工程地质学产生与发展

区域稳定工程地质学是在中国产生、发展和壮大起来的。自50年代产生以来，历经几代工程地质工作者的不懈努力，现已形成了具有系统理论和系统研究方法、在国民经济建设中正发挥着显着作用的新兴学科。回顾该学科的产生与发展过程，对促进该学科的思维方法、学科理论和进一步发挥学科作用具有重要的意义。     

炮药断裂韧性初探

高膛压炮的问世,对炮药的力学性能提出了更高的要求。本文根据炮药的性质、加工和使用的特点,探讨炮药断裂韧性的测定。     

Fluid Flows Through Two-Dimensional Channels of Composite Materials

The present analysis relates to the study of the full two-dimensional Brinkman equation representing the fluid flow through porous medium. The steady, incompressible fluid flow, with a negligible gravitational force, is constrained to flow in an infinitely long channel in which the height assumes a series of piecewise constant values. The control volume method is used to solve the Brinkman equation which involves the parameter, =/Da, where Da is the Darcy number and is the ratio of the fluid viscosity _f to the effective viscosity . An analytical study in the fully developed section of the composite channel is presented when the channel is of constant height and composed of several layers of porous media, each of uniform porosity. In the fully developed flow regime the analytical and numerical solutions are graphically indistinguishable. A geometrical configuration involving several discontinuities of channel height, and where the entry and exit sections are layered, is considered and the effect of different permeabilities is demonstrated. Further, numerical investigations are performed to evaluate the behaviour of fluid flow through regions which mathematically model some geological structures of various sizes, positions and permeability, for example a fault or a fracture, where the outlet channel is offset at different levels. The effect on the overall pressure gradient is also considered.     

On axisymmetric motion of an incompressible elastic medium under impact loading

The method of matched asymptotic expansions was employed to obtain approximate solutions to the one-dimensional boundary-value problems of nonlinear dynamic elasticity theory of impact loading on the surface of a cylindrical cavity of an incompressible medium that causes antiplane motion or torsion of the medium. The expansion of the solution in the near-front region is based on solutions of evolution equations different from the equations for quasi-simple waves. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 144–151, November–December, 2006.     

Technical stability of stationary automatic control systems of variable structure with switched filters

Sufficient conditions for the technical stability in measure of a nonstationary control system with variable structure are established. The controller of the system has feedback-switched filters functioning together with shaper and actuator. It is assumed that the nonstationary parameters of the system vary within given ranges, at a finite rate, with appropriate control laws, with adjustment against mismatch signal, its derivatives of finite order, and all variable parameters of the filter. The parameters of the switching hyperplane remain constant. This approach for analysis of technical stability does not involve sliding mode conditions. Criteria of technical instability in measure for the control system under consideration are formulated using the properties of systems of comparison from below. The general criteria of technical stability and instability are applied to nonstationary filtered-control systems of variable structure of the third order. The comparison method based on normalized Lyapunov functions is used __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 6, pp. 110–127, June 2006.     

Singular perturbation analysis of dynamic fields in a thermoelastic solid with a small surface-breaking crack

An asymptotic analysis is presented for a dynamic problem of a semi-infinite isotropic thermoelastic solid with a small surface breaking crack. The exterior surface of the solid is subjected to a series of short thermal pulses. The crack surface is traction free and an ideal thermal contact is assumed across the crack. The stress intensity factor is asymptotically evaluated as a function of the crack depth and time. The effect of a boundary layer associated with the diffusive term is identified. The theoretical model is supplied with numerical simulations.     

螺旋槽干气密封微尺度流动场的近似计算及其参数优化

应用PH线性化方法、迭代法,近似求解了螺旋槽内稳态微尺度流动场的非线性雷诺方程,求得了气体动压和速度分布的解析解。继而利用多目标优化方法构建了气膜刚度与泄漏量之比的协调函数,并对该目标函数进行了近似求解,获得了最佳的螺旋槽几何参数值。     

非齐次动力方程Duhamel项的精细积分

提出了不需要矩阵求逆运算的求解Duhamel积分项的精细积分方法.通过将精细积分法的关键思想--加法定理和增量存储--直接应用于Duhamel积分响应矩阵的求解,可给出当非齐次项分别为多项式、正弦/余弦以及指数函数等基本形式时Duhamel积分在计算机上的精确解.特别的,该算法不依赖于系统矩阵(或相关矩阵)的形态.当系统矩阵奇异或接近奇异时,其优越性更为显著.算例验证了该算法的有效性.     

新的复合材料格栅加筋板的平铺等效刚度法

针对薄壁复合材料格栅加筋结构的受力特点,在改进原有力学假设的基础之上,推导了一种新的平铺等效刚度计算方法,它充分考虑了筋条和面板之间的相互作用.通过格栅单元结构布局形式的参数化表示,建立了通用的力学分析模型;该模型可用于分析各种结构布局形式和面板铺层方式下的结构总体屈曲问题,故对于航空航天结构设计非常有用.结合Rayleigh-Ritz方法,推导出了求解格栅加筋板屈曲载荷的通用线性特征方程;最后,分析了多种类型格栅结构的算例,并与现有的各种方法进行了比较,结果更为精确,因而对格栅加筋结构的优化设计具有很好的应用价值.     

高速移动荷载下黏弹性半空间体的动力响应

分别以移动荷载和黏弹性半空间体模拟运动列车荷载和地基,分析了地基在运动列车作用下的动力响应.首先采用Green函数法求解黏弹性半空间体在各种移动荷载模式作用下的动力响应的解析解,包括恒常和简谐移动点源、线源和面源荷载.然后采用IFFT算法和自适应数值积分算法计算解析解中的二维积分,得到了包括低音速、跨音速和超音速移动荷载作用下位移的数值结果.最后分析了速度对位移的分布和最大值的影响,发现当速度大于Rayleigh波速时,位移发生显著变化.