摘要:

AbstractA new method to reduce the solution time of matrices generated by the Boundary Element Method is presented here. The method involves converting the fully populated system into a banded system by lumping certain coefficients of the matrix into fictitious nodes and then constraining these nodes to accurately represent each coefficient. The major advantages of lumping over the substructuring method are that lumping can be applied to arbitrarily shaped geometries and infinite‐domain problems and that it preserves the diagonal‐dominance of the matrix. It is shown here that the proposed algorithm reduces the rate of increase of solution timetof ann‐degree‐of‐freedom problem fromt∝n3tot∝n2. Although the algorithm is for thermal problems, its extension to mechanical problems is straightforward. The procedure can easily be incorporated into existing boundary‐element

ISSN:0029-5981    

DOI:10.1002/nme.1620330602

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA geometrically non‐linear thin shell element made from classical laminated materials is developed from three dimensional continuum concepts that admits arbitrarily large displacements and rotations. The development shows how explicit integration through the thickness of the element can be accomplished without sacrificing significant accuracy of the element.Computations obtained via the present formulation are compared with four test problems for which numerical data are available. All computations were carried out using the Crisfield–Riks arc length continuation algorithm with a full Newton–Raphson iterative scheme. Excellent agreement is observed for each test pr

ISSN:0029-5981    

DOI:10.1002/nme.1620330603

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractDynamic substructuringor modal synthesis is established as a powerful means by which the computational effort required to perform dynamic analyses of large structures comprising many degrees of freedom can be reduced. For the case where the substructures are rigidly connected a method of synthesis is proposed which gives very substantial improvements in efficiency over existing methods both in terms of the number of floating‐point operations which must take place and the on‐board computer memory required. The proposed method makes use of a stable co‐ordinate transformation which reduces the mass matrix for the constrained composite‐system to the identity matrix and makes the stiffness matrix banded. The bandwidth is exactly equal to twice the total number of constraints plus 1. This is usually very small in comparison with the total number of degrees of freedom in the constrained composite‐system. The proposed method is ideal for combining a number of substructures into a single new substructure in an efficient way without necessarily disposing of any degrees of freedom. Approximate formulae are presented which give the ratios of the number of operations required for established methods compared with the number needed for the proposed method. These formulae determine when it is appropriate to use the method prop

ISSN:0029-5981    

DOI:10.1002/nme.1620330604

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new explicit variable time‐integration methodology and architecture which possesses self‐starting attributes, eliminates the need to involve acceleration computations, and which has improved accuracy characteristics in comparison to the traditional central‐difference‐type formulations customarily advocated is described for applicability to computational structural dynamics. To sharpen the focus of the present study, an explicit variable time‐integration architecture which is relatively simple, yet effective, is described. Unlike variable explicit time‐integration formulations adopted in the past, the present self‐starting variable time‐integration architecture and implementation aspects facilitate a simplified representation and a straightforward and effective approach for combining finite element meshes requiring different time steps in a single analysis. Numerical test cases are provided which demonstrate the applicability of the propos

ISSN:0029-5981    

DOI:10.1002/nme.1620330605

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this paper we derive the non‐singular boundary integral representation of the field gradients for two‐dimensional problems of classical potential field theory. Numerical implementation of this representation is developed too. The proposed method eliminates the most inaccurate influence coefficients which arise when singular integral representations are used and the internal point approaches the boundary. Since the integrands in this new method are finite at any internal point, accurate numerical results are achieved even in that portion of a solid which is very close to a discretized boundary. Two test problems are analysed in which the numerical results computed by strongly singular, weakly singular and non‐singular integral representations are compared mutually and with exact solu

ISSN:0029-5981    

DOI:10.1002/nme.1620330606

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractOptimal plastic designs for structural frames can be obtained via static or kinematic considerations, each leading to a mathematical model requiring solution by linear programming. In both cases a mechanism can be found which satisfies the Foulkes optimality condition. However, this mechanism generally has many degrees of freedom and is most unlikely to be the actual collapse mode of the frame. A simple algorithm based on the method of redundant forces is presented for the automatic generation of the alternative optimal collapse mechanisms, any of which may be the actual collapse mode.

ISSN:0029-5981    

DOI:10.1002/nme.1620330607

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this paper, a ring rolling process is analysed by the Arbitrary Lagrangian Eulerian (ALE) finite element method. Phenomena associated with the process, such as large deformations, elastoplastic material behaviour and the friction on the interface, are included in the analysis. Special modelling on driven, idle and guide rolls is given. Results which include the overall shape of the formed ring, the time histories of roll separating force and driving torque, the distribution of the normal pressure on the ring–roll interface as well as the distribution of effective stresses in the formed ring, are also presente

ISSN:0029-5981    

DOI:10.1002/nme.1620330608

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe issue of developing effective and robust schemes to implement a class of the Ogden‐type hypereiastic constitutive models, for large‐strain analysis of rubber‐like materials, is addressed. To this end, explicit forms for the corresponding material tangent‐stiffness tensors are developed, and these are valid for the entire deformation range; i.e. with both distinct as well as repeated principal‐stretch values. Throughout the analysis the various implications of the underlying property of separability of the strain‐energy functions are exploited, thus leading to compact final forms of the tensor expressions. In particular, this facilitated the treatment of the complex cases of uncoupled volumetric/deviatoric formulations for incompressible materials, which are becoming increasingly popular in recent years. The forms derived are also amenable for use with symbolic‐manipulation packages for systematic co

ISSN:0029-5981    

DOI:10.1002/nme.1620330609

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractSeveral old and new tetrahedral elements are tested and compared to some classical hexahedral elements for the solution of three‐dimensional incompressible fluid flow problems. The proposed elements are created by adding velocity degrees of freedom to the basic trilinear velocity, constant pressure tetrahedron so as to satisfy the Brezzi condition. Numerical tests carried out for an artificial divergence‐free flow problem and the lid‐driven cubic cavity up to a Reynolds number of 400 are used to compare the proposed elements and assess their acc

ISSN:0029-5981    

DOI:10.1002/nme.1620330610

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe present paper is concerned with the effective numerical implementation of the two‐dimensional dual boundary element method, for linear elastic crack problems. The dual equations of the method are the displacement and the traction boundary integral equations. When the displacement equation is applied on one of the crack surfaces and the traction equation on the other, general mixed‐mode crack problems can be solved with a single‐region formulation. Both crack surfaces are discretized with discontinuous quadratic boundary elements; this strategy not only automatically satisfies the necessary conditions for the existence of the finite‐part integrals, which occur naturally, but also circumvents the problem of collocation at crack tips, crack kinks and crack‐edge corners. Examples of geometries with edge, and embedded crack are analysed with the present method. Highly accurate results are obtained, when the stress intensity factor is evaluated with theJ‐integral technique. The accuracy and efficiency of the implementation described herein make this formulation ideal for the study of crack growth problems under mixed‐mo

ISSN:0029-5981    

DOI:10.1002/nme.1620330611

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY