摘要:

AbstractThe mode of collapse in many metallic shells is, oftentimes, one of localized collapse, wherein severe plastic deformation and high displacement gradients are localized within some region. The combined material and geometric non‐linearity emanating from this local region is the predominant cause of instability in shells of revolution. In such a situation a local‐global strategy is very useful for an efficient analysis. This strategy consists of employing two dimensional degenerated isoparametric shell elements with non‐linear capability in a well defined 'local' zone where all the non‐linearities are expected to be localized and which also contains some form of local deviation from axisymmetry such as a circumferential imperfection, cutouts, cracks, etc. Linear elastic ring type elements are employed in the remaining axisymmetric zone and the two zones are linked through a transformation between the degrees of freedom involved. The solution of the non‐linear problem is achieved by appropriate condensation procedures to reduce the number of active degrees of freedom and the load incrementation is achieved by the well known 'arc length' iterative procedure. Numerical exampies are presented to demonstrate that this strategy is very efficient and accurate for problems with well defined non‐linear local zones. The capability of this strategy for treating problems with local material discontinuities such as cracks, cutouts, etc. as an efficient alternative to a complete two dimensional discretization is

ISSN:0029-5981    

DOI:10.1002/nme.1620350602

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe outline here a finite element technique for the creep of solids whose constitutive equation contains one or more random parameters. In contrast to other finite element techniques for the prediction of random structural response, the present method is based upon exact relations from the theory of probability. It yields, at a given value of time, the probability density function for the field variable of interest, e.g. stress or displacement components. The method is illustrated by a simple creeping beam problem, using a power‐law creep constitutive equation. The calculated distributions are found to be highly skewed, and in excellent agreement with the results of Monte Carlo simulatio

ISSN:0029-5981    

DOI:10.1002/nme.1620350603

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe dispersive properties of finite element semidiscretizations of the three‐dimensional second‐order scalar wave equation are examined for both plane and spherical waves. This analysis throws light on the performance and limitations of the finite element approximation over the entire spectrum of wavenumbers and provides guidance for optimal mesh discretization as well as mass representation. The 8‐node trilinear element, 20‐node serendipity element, 27‐node triquadratic element and the linear and quadratic spherically symmetric elements are c

ISSN:0029-5981    

DOI:10.1002/nme.1620350604

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper develops analytical expressions and numerical for reducing the structural matrices which are used in the Force Method of structural analysis. Two simple examples illustrate the calculations for pin‐jointed trusses.Two advanced applications, a beam cross consisting of two coplanar beams which are linked by a shear connector, and an equilibrium linear‐stress finite element, are also presen

ISSN:0029-5981    

DOI:10.1002/nme.1620350605

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper is devoted to the numerical analysis of bidimensional bonded lap joints. For this purpose, the stress singularities occurring at the intersections of the adherend‐adhesive interfaces with the free edges are first investigated and a method for computing both the order and the intensity factor of these singularities is described briefly. After that, a simplified model, in which the adhesive domain is reduced to a line, is derived by using an asymptotic expansion method. Then, assuming that the assembly debonding is produced by a macro‐crack propagation in the adhesive, the associated energy release rate is computed. Finally, a homogenization technique is used in order to take into account a preliminary adhesive damage consisting of periodic micro‐cracks. Some numerical results are pres

ISSN:0029-5981    

DOI:10.1002/nme.1620350606

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTypical brick‐based finite elements in current use are the 8‐and 20‐node members of the serendipity group. For displacement analyses of solids the 8‐node element can be quite stiff in certain deformation modes, while the 20‐node element can be quite expensive to use, involving as it does 60 degrees of freedom and a fairly high order of quadrature to avoid spurious eigenmodes of the element stiffness. In this paper a family of intermediate 14‐node elements is investigated. Derivation of their properties can be considerably assisted by computer algebra. Performance is evaluated for elastic and elastoplast

ISSN:0029-5981    

DOI:10.1002/nme.1620350607

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to obtain accurate results and to reduce computation time, we have proposed in this paper a new strategic method, where quadratic elements are used at the corner points and linear elements at the points off the corner points. A computer program using this method has been developed and applied to several problems of various shapes. The usefulness of this method was illustrated by the application results.

ISSN:0029-5981    

DOI:10.1002/nme.1620350608

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA model based on the penalty method for 3‐D contact problems with friction is proposed. The friction forces are assumed to follow the Coulomb law, with a slip criterion treated in the context of a standard return mapping algorithm. Consistent linearization of the field equations is performed which leads to a fully implicit scheme with non‐symmetric tangent stiffness which preserves asymptotic quadratic convergence of the Newton‐Raphson method. Numerical results are obtained for some representative examples and compared with existing solu

ISSN:0029-5981    

DOI:10.1002/nme.1620350609

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractPreconditioning techniques based on incomplete LU‐decomposition are described for large, sparse, non‐symmetric matrix systems in which the largest part of the coefficient matrix is a symmetric M‐matrix with a very regular sparsity pattern. Some methods are described in which a small part of the matrix with an irregular sparsity pattern is treated very efficiently. The methods are combined with CGSTAB and tested on a non‐stationary diffusion problem in three dimensions. For this type of problems the modified incomplete decomposition as suggested by Gustafsson performs significantly better than the standard incomplete factorization.Also some methods are described to construct preconditioners for large, sparse, non‐symmetric matrices with arbitrary sparsity patterns. Methods in which the sparsity pattern of the preconditioning matrix is based on a drop tolerance are very effective and relativ

ISSN:0029-5981    

DOI:10.1002/nme.1620350610

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new finite element method is devised for the numerical solution of elliptic boundary value problems with geometrical singularities. In it, the singularity is eliminated form the computational domain in an exact fashion. This is in contrast to other common methods, such as those which use a refined mesh in the singularity region, or those which use special singular finite elements. In them, the singularity is treated as a part of the numerical scheme. The new method is illustrated on an elliptic differential equation in a domain containing a re‐entrant corner. Numerical experiments show that the new method yields result which are generally much more accurate than those obtained by using the standard finite element method with mesh refinement in the singularity region. Both methods require about the same computing tim

ISSN:0029-5981    

DOI:10.1002/nme.1620350611

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY