摘要:

AbstractA shear flexible (i.e. Timoshenko) quadratic isoparametric beam element with two degrees of freedom per node is critically examined from the point of view of the consistency of the constrained strain fields that arise in the thin‐beam limits. The errors, in terms of convergence of displacement fields and violent oscillations of stress fields, that emerge when exactly integrated elements are used are predicteda prioriand confirmed with numerical experiments. The rationale behind the use of optimal stress sampling at Gaussian points is also derived directly from these argument

ISSN:0029-5981    

DOI:10.1002/nme.1620231102

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractStructure optimization for problems of solid mechanics is gaining in importance. Of special interest to the ship and aeroplane designer is optimizing changes in sections and hols in such a way that the largest value of the von Mises stress becomes as small as possible, to optimize the use of material. Also, the temporal beginning of crack propagation should be delayed as long as possible. Adynamic programmingformulation for structure optimization is presented and mechanical theorems fix an iterative solution process.

ISSN:0029-5981    

DOI:10.1002/nme.1620231103

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAfter a short introduction the possibilities and limitations of polynomial simple elements withC1continuity are discussed with reference to plate bending analysis. A family of this kind of elements is presented. These elements are applied to simple cases in order to assess their computational efficiency. Finally some conclusions are shown, and future research is also proposed.

ISSN:0029-5981    

DOI:10.1002/nme.1620231104

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractRecently, several methods of time integration of the equations of motion have been proposed. Many of them result in square mass, damping and stiffness matrices. The space–time finite element method is an extension of the FEM, familiar to most engineers, over the time domain. A special approach enables the use of triangular, tetrahedral and hyper‐tetrahedral elements in time and space. By special division of the space–time layer the triangular matrix of coefficients in the system of equations can be obtained. A simple algorithm enables the storage of non‐zero coefficients only. Dynamic solution requires a small amount of the memory compared to other methods, and ensures considerable reduction of arithmetic operations. The method presented is also efficient in solving both linear and non‐linear problems. Matrices for a beam and plane stress/strain element are derived. Exemplary problems solved by the method described have proved the effectiveness of the application of triangular and tetrahedral space–time elements in vibrati

ISSN:0029-5981    

DOI:10.1002/nme.1620231105

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe direct boundary element method based on the Rayleigh‐Green identity is employed for the static analysis of Kirchhoff plates. The starting point is a slightly modified version of Stern's equations. The focus is on the implementation of the method for linear elements and a Hermitian interpolation for the deflectionw. The concept of element matrices is developed and the Cauchy principal values of the singular integrals are given in detail. The treatment of domain integrals, the handling of internal supports, the properties of the solution and the effect of singularities are discused. Numerical examples illustrate the various techniques. In the appendix the influence functions for the second and third derivatives of the deflectionware give

ISSN:0029-5981    

DOI:10.1002/nme.1620231106

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractShakedown analysis of axisymmetric elastic–perfectly plastic sandwich shells is performed here using a new upper bound formulation based on a special form of Koiter's theorem concerning piecewise linearized yield surfaces. Starting from finite element techniques and the Tresca sandwich yield condition, shakedown analysis is reduced to a linear programming problem which is solved by a powerful simplex algorithm. Numerical results are given for a number of examples and a comparison is made with a previously computed lower bound formulatio

ISSN:0029-5981    

DOI:10.1002/nme.1620231107

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA sixth‐order method is developed and analysed for the numerical solution of the linear fourth‐order boundary value problem for which the boundary conditions are given in terms of functional values and (i) first‐order derivatives (the clamped‐clamped beam problem) or (ii) second‐order derivatives (the simple‐simple beam problem). The method is tested on a number of problems from the

ISSN:0029-5981    

DOI:10.1002/nme.1620231108

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe value of the permissible pressure in torispherical heads is usually judged from the size of the permanent deformations after the first load cycle. The difficulty always lies in the determination of the maximum permanent strain caused by the pressure, as the strain depends on the changes of the elastic‐plastic state. The elastic‐plastic state of the heads can be, for example, found and well followed by the finite element method. Values obtained in this way are naturally valid only for the case examined. However, by extending the numerical investigations and by appropriately processing and evaluating the results certain regularities and generalizations can be recognized. On this basis certain approximations can be made, leading to a very simple and reliable calculation proc

ISSN:0029-5981    

DOI:10.1002/nme.1620231109

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe quality of solution obtained using the boundary element method (BEM) is dependent on how the boundary is discretized. This is particularly true in domains of complex geometry. A rule for grid optimization for the BEM is derived on the bases of an asymptotic measure of the boundary element error that preserves the number of elements (degrees of freedom). Three example problems are provided to show the advantages of grid optimization in terms of accuracy and cost.

ISSN:0029-5981    

DOI:10.1002/nme.1620231110

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFirst the Cholesky factorization is extended to cover uniformly partitioned banded positive definite matrices of ranknwhich may be real symmetric or Hermitian. Then two stratagems are given for the use of the algorithm in concurrent machines where the number of processing elements is less than required to factor the matrix in as few serial steps as possible, and where uniformly high efficiency is expected from all processing elements. Expressions are given for the efficiency factoreappearing in the speed‐up expressiong=eN, and these are specialized for theNnode hypercube machine as a function of partition sizes, the numberNof processing elements of the hypercube machine, and the cost μ of interelement transmission relative to computation. It is shown that efficiency factoreis inversely proportional to μ/s, and thateis almost independent ofNwhenNis large and μ/s= 0. The task is completed inn/sserial steps with no limit onn. The half bandwidthbof the matrix is

ISSN:0029-5981    

DOI:10.1002/nme.1620231111

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY