Novel boundary element method for resolving plate bending problems

INTRODUCTIONTheboundaryelementmethodisanefficientnumericalmethodforsolvingpracticalengineer ingproblems ,andisparticularlyattractivefortheanalysisofelasticmechanicsproblems,asonlytheboundaryoftheproblemisrequiredtobediscretized .Themainadvantageofthebound…     

纵横载荷联合作用下弯曲薄板的功的互等定理

本文将功的互等定理应用于形状、大小和材料均相同又处于真实状态的两个薄板系统之间，得出了纵横载荷联合作用下弯曲薄板的功的互等定理，并给出了简洁的数学表达式。该式既可以用于横向载荷作用下弯曲薄板问题的求解，又可以用于薄板稳定问题的求解。定理推导过程中没有对薄板的形状和边界条件加以限制，因而使该定理具有较广的适用范围。     

Pure bending of simply supported circular plate of transversely isotropic functionally graded material

INTRODUCTION In recent years, functionally graded materials (FGMs) have attracted more and more attention. Due to their continuously varying material properties in space on the macroscopic scale, FGMs, therefore, are usually superior to conventional fiber-matrix materi-als in mechanical behavior, especially for perform-ance under thermal loading. Now FGMs have been widely used in various fields including electronics, chemistry, optics, biomedicine, etc. Heretofore, volumes of literatu…     

基于“网孔法”的点云数据边界提取技术的应用

根据零件表面的数字化数据提取零件表面的边界是反求工程的关键步骤.针对完全散乱的、无组织的"点云"数据,首先,利用网格法得到边界网孔和非边界网孔,把所有相邻的边界网孔相互连接起来,得到边界网孔环;把边界网孔环中每个边界网孔的最小凸边求出来就得到一段边界线,把各个分段的边界线连接起来就得到初始边界线,然后利用B样条技术对边界线进行光顺处理,得到理想的曲面边界.实践证明,通过该方法得到的边界曲线能满足工程应用的需要.     

Stress analysis of anisotropic thick laminates in cylindrical bending using a semi-analytical approach

Semi-analytical elasticity solutions for bending of angle-ply laminates in cylindrical bending are presented using the state-space-based differential quadrature method (SSDQM). Partial differential state equation is derived from the basic equations of elasticity based on the state space concept. Then, the differential quadrature (DQ) technique is introduced to discretize the longitu- dinal domain of the plate so that a series of ordinary differential state equations are obtained at the discrete points. Meanwhile, the edge constrained conditions are handled directly using the stress and displacement components without the Saint-Venant principle. The thickness domain is solved analytically based on the state space formalism along with the continuity conditions at interfaces. The present method is validated by comparing the results to the exact solutions of Pagano’s problem. Numerical results for fully clamped thick laminates are presented, and the influences of ply angle on stress distributions are discussed.     

弹性力学中混合变量的极值变分原理

本文建立了弹性力学空间问题混合变量的最小势能原理和最小余能原理，并根据该最小势能原理给出了弯曲薄板混合变量的最小势能原理。应用该势能原理计算了一复杂边界条件矩形板的弯曲。     

Numerical simulation of interaction between laminar flow and elastic sheet

A numerical simulation of the interaction between laminar flow with low Reynolds number and a highly flexible elastic sheet is presented. The mathematical model for the simulation includes a three-dimensional finitevolume based fluid solver for incompressible viscous flow and a combined finite-discrete element method for the three-dimensional deformation of solid. An immersed boundary method is used to couple the simulation of fluid and solid. It is implemented through a set of immersed boundary points scattered on the solid surface. These points provide a deformable solid wall boundary for the fluid by adding body force to Navier-Stokes equations. The force from the fluid is also obtained for each point and then applied on the boundary nodes of the solid. The vortex-induced vibration of the highly flexible elastic sheet is simulated with the established mathematical model. The simulated results for both swing pattern and oscillation frequency of the elastic sheet in low Reynolds number flow agree well with experimental data.     

A numerical method for orthogonal grid generation by Laplace system

A new method for the generation of orthogonal body-fitted grids is presented in this paper. The positions of boundary points in the physical domain are adjusted to obtain orthogonal curvilinear grids without changing the value of ξ and η during the numerical process. The densities of ξ and η are given in advance. Good results were achieved in the application of this method on the cooling system of an internal combustion engine and a trail duct.     

Studies on solar flat plate collector evaporation systems for tannery effluent （soak liquor）

INTRODUCTION The tannery effluent (soak liquor) spewed out by tanneries to the surroundings has been polluting the land and water bodies in and around the tanneries and is evaporated over a period of time. The rate of evaporation over this period is small in the natural evaporative ponds and so large area is required. But land in urban and semi-urban sectors is scarce and very costly. Hence, it is required to augment the evaporation rate by adopting some suitable techniques. The rate of e…     

九参拟协调元的误差估计

给出了双参数九参拟协调元在求解四阶板弯曲问题时的误差估计式,并对其节点参数扰动量进行了分析,文中的方法也适用于其他双参数非协调元的误差分析.     

折弯时发生表面压痕现象的分析及解决方法

为了避免数控折弯机加工板材工件时的表面压痕发生,实验中从板材工件的折弯方式、材料硬度、凹模结构、选择机床与模具的精度4个方面来分析板材工件折弯时的产生表面压痕的原因。结果表明,通过使用防压痕胶垫、单V凹模防压痕胶套、块状优力胶＋AT垫衬、硬质橡胶凹模和无压痕折弯凹模的方法来解决数控折弯时工件表面的压痕,达到产品质量要求。     

Learning as boundary-crossing in school–university partnership

This paper points out that globalization has raised fundamental questions about knowing and learning and that it is essential for educators to engage in collective knowledge generation by crossing community boundaries. Drawing on the theoretical framework of Activity Theory, this paper reports on a study on the expansive learning that was afforded by a school–university partnership as university tutors, mentor teachers and student teachers engaged in a new activity system mediated by lesson study. The study showed that in the course of resolving contradictions that were inherent in the boundary zone, they negotiated the mediating tool and consequently, the activity system was transformed from helping student teachers learn to teach into learning for all participants. This paper concludes that it is essential for teachers and teacher educators to develop the capability to engage in expansive learning through tackling ill-defined problems in boundary zones.     

Shape optimization of plate with static and dynamic constraints via virtual laminated element

The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM, only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE (finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named “behavior model technique” can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method. Project (No. 50075083) supported by National Natural Science Foundation of China     

一类变系数二阶非线性常微分方程的边界层问题

主要研究了一类变系数二阶非线性常微分方程的边界层问题。先确定边界层的位置,然后用匹配渐近展开法来求得该问题的一阶近似解。     

Dynamical stability of finite anisotropic panels with elliptical cutouts and cracks

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Solution of stress intensity factors of multiple cracks in plane elasticity with eigen COD formulation of boundary integral equation

The concept of eigen crack opening displacement (COD) can be defined as the COD of a crack in infinite plate under the tractions acting on the crack surface. By introducing this concept, the eigen COD formulation of boundary integral equation is proposed in this paper, together with the solution procedures for multiple crack problems in plane elasticity. With the proposed approach, the multiple crack problems can be solved with the conventional displacement discontinuity boundary integral equations in an it...     

近自由面细长体的振荡问题

本文引进细长体的假定,把三维的流体运动问题化成了二维的非定常问题。前面剖面对后面剖面的干扰作用用积分表示,对物体作了适当近似以后,改善了切片理论。根据物面条件把整个问题的求解分解为兴波问题和振荡问题,而振荡问题可由兴波问题的适当组合表示出来。这样,大大简化了问题的求解。作为例子,本文数值计算了细长体的水动力导数,给出了结果。     

Boundary Element Method with Non—overlapping Domain Decomposition for Diffusion Equation

A boundary element method based on non-overlapping domain decomposition method to solve the time-dependent diffusion equations is presented.The time-dependent fundamental solution is used in the formulation of boundary integrals and the time integratioin process always restarts from the initial time condition.The process of replacing the interface values,which needs a summation of boundary integrals related to the boundary values at previous time steps can be treated in parallel parallel iterative procedure,Numerical experiments demonstrate that the implementation of the present alogrithm is efficient.     

Quasi-static and dynamical bending of a cantilever poroelastic beam

Based on the theory of porous media, the quasi-static and dynamical bending of a cantilever poroelastic beam subjected to a step load at its free end is investigated, and the influences of its permeability on bending deformation is examined.The initial boundary value problems for dynamical and quasi-static responses are solved with the Laplace transform technique,and the deflections, the bending moments of the solid skeleton and the equivalent couples of the pore fluid pressure are shown in figures. It is shown that the dynamical and quasi-static behavior of the saturated poroelastic beam depends closely on the permeability conditions at the beam ends. Under the different permeability conditions, the deflections of the beam may oscillate or not. The Mandel-Cryer effect also exists in liquid-saturated poroelastic beams.     

An adaptive finite element procedure for crack propagation analysis

INTRODUCTION The finite element method (FEM) has proved to be very well suited for the study of fracture mechanics. Nevertheless, modelling the propagation of a crack through a finite element mesh turns out to be difficult because of the modification of the mesh topology. Use of crack propagation laws based on stress inten-sity factor range is the most successful engineering application of fracture mechanics. The stress intensity factors are a very important parameter in fracture analys…