摘要:

AbstractA finite element method to simulate coupled thermal viscous coextrusion is presented, with a power‐law viscosity function obtained from viscometric data on rubber composites. It combines, by successive substitution iterations, some well‐known schemes, such as streamline integration for updating interfaces and Lagrange‐Galerkin treatment of the energy equation. Some details of the implementation are discussed. The method is then applied to a comparison of two pre‐forming plates for the dual tuber head extruder of Farrel Corporation. Both the normal stress and the temperature at the interface suggest that the presence of a deflector deteriorates the adherence properties. This prediction is in agreement with operational exp

ISSN:0029-5981    

DOI:10.1002/nme.1620361302

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAccounts of the symmetric Galerkin approach to boundary element analysis (BEA) have recently been published. This paper attempts to add to the understanding of this method by addressing a series of fundamental issues associated with its potential computational efficiency. A new symmetric Galerkin theoretical formulation for both the (harmonic) heat conduction and the (biharmonic) elasticity problem that employs regularized singular and hypersingular boundary integral equations (BIEs) is presented. The novel use of regularized BIEs in the Galerkin context is shown to allow straightforward incorporation of curved, isoparametric elements. A symmetric reusable intrinsic sample point (RISP) numerical integration algorithm is shown to produce a Galerkin (i.e. double) integration strategy that is competitive with its counterpart (i.e. singular) integration procedure in the collocation BEA approach when the time saved in the symmetric equation solution phase is also taken into account. This new formulation is shown to be capable of employing hypersingular BIEs while obviating the requirement of C1continuity, a fact that allows the employment of the popular continuous element technology. The behaviour of the symmetric Galerkin BEA method with regard to both direct and iterative equation solution operations is also addressed. A series of example problems are presented to quantify the performance of this symmetric approach, relative to the more conventional unsymmetric BEA, in terms of both accuracy and efficiency. It is concluded that appropriate implementations of the symmetric Galerkin approach to BEA indeed have the potential to be competitive with, if not superior to, collocation‐based BEA, for large‐scale probl

ISSN:0029-5981    

DOI:10.1002/nme.1620361303

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA boundary integral formulation is presented for the detection of flaws in planar structural members from the displacement measurements given at some boundary locations and the applied loading. Such inverse problems usually start with an initial guess for the flaw location and size and proceed towards the final configuration in a sequence of iterative steps. A finite element formulation will require a remeshing of the object corresponding to the revised flaw configuration in each iteration making the procedure computationally expensive and cumbersome. No such remeshing is required for the boundary element approach. The inverse problem is written as an optimization problem with the objective function being the sum of the squares of the differences between the measured displacements and the computed displacements for the assumed flaw configuration. The geometric condition that the flaw lies within the domain of the object is imposed using the internal penalty function approach in which the objective function is augmented by the constraint using a penalty parameter. A first‐order regularization procedure is also implemented to modify the objective function in order to minimize the numerical fluctuations that may be caused in the numerical procedure due to errors in the experimental measurements for displacements. The flaw configuration is defined in terms of geometric parameters and the sensitivities with respect to these parameters are obtained in the boundary element framework using the implicit differentiation approach. A series of numerical examples involving the detection of circular and elliptical flaws of various sizes and orientations are solved using the present approach. Good predictions of the flaw shape and location are obtaine

ISSN:0029-5981    

DOI:10.1002/nme.1620361304

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA numerical model for non‐linear static and dynamic analysis of stiffened box structures is presented. The model is based on a new super element formulation which provides completeC1continuity for both plate and beam elements. Geometric and material non‐linearities are included and the temporal equations are solved by the implicit Newmark‐β method with Newton‐Raphson subiteration. The new formulation has been applied to the static, vibration and transient analysis of various structures such as flat plates, folded plates and rectangular boxes. Both isotropic and beam stiffened structures are considered and the results obtained are compared with other available solutions. It is observed that the new super element formulation can provide reasonable solutions to both linear and non‐linear problems of stiffened box structures. The mathematical formulation of the model is presented in this paper, while the numerical verifications are given in the compan

ISSN:0029-5981    

DOI:10.1002/nme.1620361305

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractNumerical investigations are carried out to verify the new super element model developed in Reference 1 for non‐linear analysis of stiffened box structures. The results presented here are obtained from a variety of examples which are chosen to illustrate the accuracy and convergence of the model in various applications. Good agreement is obtained for most of the problems considered and the present formulation is found to be accurate and economical for preliminary engineering desig

ISSN:0029-5981    

DOI:10.1002/nme.1620361306

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe divergence‐free finite element method (DFFEM) is a method to find an approximate solution of the Navier‐Stokes equations in a divergence‐free space. That is, the continuity equation is satisfieda priori. DFFEM eliminates the pressure from the calculations and reduces significantly the dimension of the system to be solved at each time step. For the standard 8‐node velocity and 4‐node pressure DFFEM, an optimal basis for the weakly divergence‐free subspace is constructed such that each basis function has non‐zero support on at most nine contiguous elements. Given this basis, weakly divergence‐free macroelements

ISSN:0029-5981    

DOI:10.1002/nme.1620361307

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA superelement algorithm for the transient dynamic analysis of structural systems is presented. The method represents a generalization of existing static and dynamic superelement (substructure) algorithms. Natural frequencies and modal shapes of a fixed boundary substructure are used to obtain equations of motion of a superelement. An implicit time‐stepping algorithm is presented for the numerical solution of a resulting superelement system of equations of motion. Numerical examples are given to illustrate the presented approach. The method is believed to be effective for large‐scale problems of structural analy

ISSN:0029-5981    

DOI:10.1002/nme.1620361308

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe shape functions of a 6‐noded triangular element have been derived to model power‐type singularities under thermal loads. A number of case studies have been presented, which involve variable‐order singularities under mechanical and thermal loads. The results show the usefulness of the el

ISSN:0029-5981    

DOI:10.1002/nme.1620361309

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA neural network model is proposed and studied for the treatment of structural analysis problems. Both the cases of bilateral and unilateral constraints are considered and Hopfield‐like neural models are proposed. Moreover, new results, generalizing the results of Hopfield and Tank,10are obtained.Numerical applications illustrate the theory and show clearly the advantages of the neural network approach. Finally, the parameter identification problem is formulated and solved as a ‘learning’ problem for a neural ne

ISSN:0029-5981    

DOI:10.1002/nme.1620361310

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620361311

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY