摘要:

AbstractA finite element analysis for viscoelastic solids responding to periodic disturbances travelling at constant speed is developed. The disturbance is decomposed into harmonic components using the Discrete Fourier Series, and the viscoelastic material response is determined using the Correspondence principle. The procedure is used to solve two and three dimensional contact problems to demonstrate its effectiveness.

ISSN:0029-5981    

DOI:10.1002/nme.1620260702

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn algorithm is presented for removing hidden lines for isometric and perspective projections of three‐dimensional objects. An object can be regarded as being made up of a number of planes, and the whole picture can therefore be visualized as only a collection of planes. Considering planes as the basic element of a picture, non‐convex polyhedra can be displayed directly without prior subdivisions into convex ones. Lines connecting nodal points are first retrieved from the model to be plotted by a simple but efficient technique. On the picture planes, each unique line is examined in turn to see if it is totally or partially hidden. The intersections between a unique line and a projected plane (with or without openings) are determined by a new method which, even in the presence of numerical errors, will always give correct intersection information. Unlike many classical algorithms, intersections are determined by a single formula without tedious case subdivisions. With little additional calculations, object penetrations can also be tack

ISSN:0029-5981    

DOI:10.1002/nme.1620260703

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe variational‐asymptotic formulation for the edge layer problem is implemented by mixed‐hybrid finite elements. This approach is used to analyse the stress singularity at the free edge in composite laminates. Results indicate that the stress singularity (asr→ 0) is very closely approximated by logrinstead

ISSN:0029-5981    

DOI:10.1002/nme.1620260704

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe singular integral equation governing the opening of a mode I embedded three‐dimensional fracture in an infinite solid was solved by applying the finite element method. The strategy is to formulate the equation into weak form, and to transfer the differentiation from the singular term, 1/r, in the equation to the test function. A numerical algorithm was thus developed. The numerical solutions for circular and elliptical fractures under the action of polynomial pressure distributions were compared with the analytical solutions by Green and Sneddon,12Irwin,13Shah and Kobayashi14and Nishioka and Atluri.16The results have demonstrated that the numerical method reported is accurate and efficien

ISSN:0029-5981    

DOI:10.1002/nme.1620260705

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA new numerical formulation is proposed in this investigation for the solution of parabolic differential equations. The time step parameter λ = 2Δτ/(Δχ)2under consideration is as large as 2000 such that only a few time steps are needed for the entire regime of transient heat conduction. Along with the formulation, a time scaling transformation is introduced to produce an accurate result for the beginning of a transient process. Although the present formulation makes reference only to the transient heat conduction problem, the idea is equally applicable to parabolic differential equations for other physical phenomena such as transformed boundary layer flow equat

ISSN:0029-5981    

DOI:10.1002/nme.1620260706

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn alternative formulation of Kirchhoff's equations is given which is amenable to a standardC0finite element discretization. In this formulation, the potential energy of the plate is formulated entirely in terms of rotations, whereas the deflections are the outcome of a subsidiary problem. The nature of the resulting equations is such thatC0interpolation can be used on both rotations and deflections. In particular, general classes of triangular and quadrilateral isoparametric elements can be used in conjunction with the method. Unlike other finite element methods which are based on three‐dimensional or Mindlin formulations, the present approach deals directly with Kirchhoff's equations of thin plate bending. Excellent accuracy is observed in standard numerical tests using both distorted and undistorted mesh pattern

ISSN:0029-5981    

DOI:10.1002/nme.1620260707

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIt is difficult to analyse a large, complex structure in sufficient detail to obtain accurate results everywhere. One approach is simply to refine the whole structure model in the regions of interest. Another approach is to identify a subregion of the structure and develop a separate refined model of the subregion. It is difficult to assure accuracy in this subregion model because of uncertainties in specifying boundary conditions and loading from the whole structure model solution. In the current literature, three methods other than whole model refinement have been described to deal with this problem. These are called the specified boundary displacement method, the linear constraint method and the zooming method.This paper describes a new approach to this problem of modelling subregions. This approach uses the stiffnesses and forces from the whole model solution at the nodes on the boundary of the sub‐region model. Accurate displacement and stress solutions are obtained with this method as it takes into account the interaction between the new stiffness of the subregion and the rest of the structure. This approach is similar to substructuring; however, the equations outside the subregion are discarded rather than condensed out, which results in much less computation effort.Examples of the application of this method to the problem of a plate with a centre hole in tensile loading are presented. The results compared favourably with the results of the same problem solved using other methods, with significant improvement in accuracy over the specified boundary displacement method. Also presented are some results from design modification of the subregion which illustrate the potential of this method for redesign applicatio

ISSN:0029-5981    

DOI:10.1002/nme.1620260708

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA general method for shape design sensitivity analysis as applied to plane elasticity problems is developed with a direct boundary integral equation formulation, using the material derivative concept and adjoint variable method. The problem formulation is very general and a complete consideration is given to describing the boundary variation by including the tangential component of the velocity field. The method is then applied to obtain the sensitivity formula for a general stress constraint imposed over a small part of the boundary. The accuracy of the design sensitivity analysis is studied with a fillet and an elastic ring design problem. Among the several numerical implementations tested, the second order boundary elements with a cubic spline representation of the moving boundary have shown the best accuracy. A smooth characteristic function is found to be better than a plateau function for localization of the stress constraint. Optimal shapes for the two problems are presented to show numerical applications.

ISSN:0029-5981    

DOI:10.1002/nme.1620260709

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn incremental Total Lagrangian Formulation for curved beam elements that includes the effect of large rotation increments is developed. A complete and symmetric tangent stiffness matrix is obtained and the numerical results show, in general, an improvement over the standard formulation where the assumption of infinitesimal rotation increments is made in the derivation of the tangent stiffness matrix.

ISSN:0029-5981    

DOI:10.1002/nme.1620260710

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA third‐order semi‐implicit five‐point finite difference method is developed to solve the one‐dimensional convection‐diffusion equation, using the ‘weighted’ modified equation method. It is shown to have a large stability region, to be very accurate and computa

ISSN:0029-5981    

DOI:10.1002/nme.1620260711

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY