摘要:

AbstractAn advanced formulation of the boundary element method has been developed for inelastic analysis based on an initial stress approach. The iterative solution algorithm makes use of an accelerated initial stress approach in which the past history of initial stresses are used to obtain an initial estimate for the current increment. In the present analysis the geometry and functions are represented by higher order (quadratic) shape functions to model complex geometries and rapid functional variations accurately. The methods of numerical integration of the kernels, particularly the singular type, are substantially improved by devising suitable automatic sub‐segmentation routines that incorporate the recent developments in mapping procedures. The formulations have been implemented for two‐dimensional plane stress, plane strain and three‐dimensional elasto‐plasticity p

ISSN:0029-5981    

DOI:10.1002/nme.1620230602

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe problem of non‐linear superconducting magnet and electrical protection circuit system transients is formulated. To enable studying the effects of coil normalization transients, coil distortion (due to imbalanced magnetic forces), internal coil arcs and shorts, and other normal and off‐normal circuit element responses, the following capabilities are included: temporal, voltage and current‐dependent voltage sources, current sources, resistors, capacitors and inductors. The concept of self‐mutual inductance, and the form of the associated inductance matrix, is discussed for internally shorted coils. This is a Kirchhoff's voltage loop law and Kirchhoff's current node law formulation. The non‐linear integrodifferential equation set is solved via a unique hybrid finite difference/integral finite element

ISSN:0029-5981    

DOI:10.1002/nme.1620230603

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA new algorithm for solving transient thermal problems in a reduced subspace of the original space of discretization is described. The basis of the subspace is formed by using the system response at the first time step (or an approximation to it) and a set of orthogonal vectors obtained by the algorithm of Lanczos. Derivatives of these vectors are included when treating non‐linear cases. The method allows one to handle the sharp gradients that appear in thermally loaded structures, and the response is accurately predicted by using only a small number of degrees of freedom in the reduced system. The algorithm is specially well suited for treating large‐scale problems. Examples dealing with one‐, two‐ and three‐dimensional cases of linear and non‐linear conduction problems ar

ISSN:0029-5981    

DOI:10.1002/nme.1620230604

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA fast vectorized algorithm is presented for a sparse matrix‐vector multiply. It can be used when the matrix,A, can be represented as a multiplitting,A= ∑Ae. In particular, it can be applied to a matrix‐vector multiply arising in finite element techniques where the matricesAeare associated with the individual element contributions to the global matrixA. The algorithm presented here uses a data structure which is based on the individual matricesAeand can be applied both to symmetric and to non‐symmetric matrices. This algorithm would be attractive for vector architecture similar to either the CYBER 205 or the CRAY and has been implemented for both regular and irregular finite element grids on the CYBER 205. Execution times and storage requirements are compared to standard sparse and band matrix‐vector multiply a

ISSN:0029-5981    

DOI:10.1002/nme.1620230605

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA new integral method is proposed here to solve the diffusion equation (confined flow) and the Boussinesq equation (unconfined flow) in a two‐dimensional porous medium. The method, based on Green's theorem, derives its integral representation from the portion of the original differential equation with the highest space derivatives so that the resulting kernel of the integral representation is not time dependent. Compared to an earlier integral formulation, namely the direct Green function, based on the same theorem, the kernel is simpler so that the present theory provides a more efficient numerical model without compromising accuracy. An iterative scheme is employed along with the theory to achieve solutions to the non‐linear Boussinesq equation. Concepts used in the finite difference and finite element methods enable simplification of the temporal derivative. The method is tested with success on a number of numerical examples from groundwater f

ISSN:0029-5981    

DOI:10.1002/nme.1620230606

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the method for solving the vibration problem of coil springs of arbitrary shape. In the analysis the exact field transfer matrix is derived from the solution of the fundamental equation of the three‐dimensional curved beam theory. The transfer matrix is given by combining this field transfer matrix and the point transfer matrix. The analysis derives the frequency equation which is applicable to coil springs of general shape. Numerical calculations have been carried out for hyperboloidal springs and barrel springs. Experimental tests also have been carried out to verify the present result

ISSN:0029-5981    

DOI:10.1002/nme.1620230607

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAn incomplete factorization iterative scheme with ORTHOMIN acceleration is evaluated for three‐dimensional finite element applications. Both heat conduction and combined heat and fluid flow are investigated. Computational efficiency is investigated for both linear (8 node) and quadratic (27 node) elements as well as for various degrees of LU Decomposition. The factorization schemes worked well with both types of elements, and a variable factorization scheme, which distributes the level of factorization, performed well on difficult heat and fluid flow problem

ISSN:0029-5981    

DOI:10.1002/nme.1620230608

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA method to efficiently solve the problem of minimum weight design of plane and space trusses with discrete or mixed variables is developed. The method can also be applied to continuous variables. The original formulation leads to a non‐linear constrained minimization problem with inequality constraints, which is solved by means of a sequence of approximate problems using dual techniques. In the dual space, the objective function is to be maximized, depends on continuous variables, is concave and has first and second order discontinuities. In addition, the constraints deal simply with restricting the dual variables to be non‐negative. To solve the problem anad hocalgorithm from mathematical programming has been adapted.Some examples have been developed to show the effectiveness of the met

ISSN:0029-5981    

DOI:10.1002/nme.1620230609

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractNumerical analysis of difference schemes often reveals the presence of eigenmodes which do not feature in the continuum solution. An examination of the dispersion relation shows how the spurious and physical modes interact. The behaviour of certain wave‐profiles was predicted using this analysis and the results confirmed by numerical experimen

ISSN:0029-5981    

DOI:10.1002/nme.1620230610

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractIn this paper, the formulation of six‐point and nine‐point finite element equations for the solution of the diffusion‐convection equation is presented. The six‐point equation requires the solution of a tridiagonal system of equations and the nine‐point centred equation is treated as a solution of a boundary value problem which leads to a large linear system of equations.Some numerical experiments are presented and the comparison with existing methods is

ISSN:0029-5981    

DOI:10.1002/nme.1620230611

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY