ISSN:0029-5981    

DOI:10.1002/nme.1620380402

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper, an elastoplastic analysis based on fuzzy mathematics and using finite element method will be described. The Drucker–Prager yield criterion and the elasto‐plastic matrix are fuzzified for the non‐linear analyses which adopt the initial stress method for the solution. A numerical example is given to illustrate the possible variations in the displacements and the extent of plastic zones at the discrete membership functions. A reliability index of a membership grade based on the concept of non‐probabilistic entropy is also p

ISSN:0029-5981    

DOI:10.1002/nme.1620380403

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA return mapping algorithm for a class of cyclic plasticity models is presented. The constitutive model includes a quadratic yield criterion and multi‐component formulations of non‐linear isotropic and kinematic hardening. Thus, both initially isotropic and anisotropic materials can be described, and a proper description of the hysteresis loops and the cyclic hardening response of materials under cyclic loading is obtained. The return mapping algorithm employs the closest point projection scheme in combination with a decomposition method, to obtain an efficient and robust integration of the constitutive model. The consistent tangent operator is derived in closed form, and is found to be unsymmetric due to the non‐linear evolution of the kinematic hardening terms. The accuracy and robustness of the algorithm are assessed through numerical exa

ISSN:0029-5981    

DOI:10.1002/nme.1620380404

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA general algorithm for resequencing equations and finite element meshes is presented. This algorithm incorporates, in a unified form, the most successful resequencing schemes, namely: the Sloan, Gibbs–King (GK) and Gibbs–Poole–Stockmeyer (GPS) algorithms. As well it provides a context within which the development of new algorithms may take place with a minimum of change. It is easily programmed and has been shown to speed up the execution of the original GK algo

ISSN:0029-5981    

DOI:10.1002/nme.1620380405

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe aim of this work is to extend an isotropic elastoplastic damage concept for ductile materials within a generalized micropolar continuum framework. The underlying motivation is on the one hand to model softening behaviour by damage evolution and on the other hand to regularize the impending loss of ellipticity which results in strong mesh dependence of localization computations. To this end, theclassicaldisplacement field is supplemented by anindependentrotation field to yield an enhanced continuum. For the model originally proposed by Lemaitre the damage evolution follows from a dissipation potential and the hypothesis of general associativity. Special emphasis is directed towards the numerical implementation of the constitutive model within the framework of finite element analysis of inelastic boundary value problems. To compare damage evolution and standard strain softening the results are contrasted to the outcome of an analysis with the micropolar version of the classical von Mises model. Thereby, the intriguing correspondence of strain softening and damage evolution is highlighted. Additionally, several planar micropolar finite element formulations are derived within mixed variational principles to enhance the poor performance of the standard bilinear displacement and rotation expansions used so far in the literature. The merits of these new element developments are demonstrated for the example of localization within a compression problem.

ISSN:0029-5981    

DOI:10.1002/nme.1620380406

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents an accurate and efficient method for the treatment of time integrals in time‐domain boundary integral equations for viscoelastic problems. First, the integral equations in space and time are derived for linear viscoelastic and thermo‐viscoelastic problems. Then various quadrature rules are discussed for the computation of time integrals. A modified Simpson's rule is proposed as an effective integration scheme. The proposed procedure requires a small computational effort and it is applicable even in time‐domain boundary element analysis of many different problems. Numerical results of example problems show the accuracy and effectiveness of the proposed m

ISSN:0029-5981    

DOI:10.1002/nme.1620380407

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Galerkin equations relevant to the eddy currents induced in an iron body are considered. These equations are obtained by formulating the field problem in terms of the magnetic vector potential and by applying the Galerkin method. They are shown to have aunique steady‐state solutionif a certain condition on the magnetic constituitive relationship is satisfied. In particular aT‐periodic source gives rise to a uniqueT‐periodic solution to which all other solutions converge asymptotically independently from the initial conditions. Under the same condition the exponential decay of the ‘transients’ is shown, and an explicit lower and upper bound for its rate is given. These structural properties allow us to excludea priorithat qualitatively different asymptotic behaviours, including even chaotic solutions, may occur. Numerical simulation, when based on qualitative information of this type, enables us to obtain the quantitative properties in an efficient manner. In order to demonstrate the practical use of these results some numerical experiments are

ISSN:0029-5981    

DOI:10.1002/nme.1620380408

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractBased on a rational choice of the internal incompatible displacement function and a special formulation of thea priorielimination of the internal non‐conforming displacement parameters, a new refined quadrilateral plane element RQ4has been developed. The present element can be shown to be computationally efficient, accurate and free from locking, and is better than other elements such as the Plan's element HS, the generalized hybrid element QCS6, and the refined hybrid element RGH4, etc. Several numerical examples are given to show the superior performances of the present element RQ

ISSN:0029-5981    

DOI:10.1002/nme.1620380409

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA new multi‐grid (two‐grid) pseudospectral element method has been carried out for solution of incompressible flow in terms of primitive variable formulation. The main objective of the proposed method is to apply the multi‐grid technique solving the incompressible flow problems associated with three commonly encountered multi‐grid environments. In domain decomposition terminology, it includes (I) partially overlapped subdomains, each of which has same types of grids; (II) partially overlapped subdomains, each of which has different types of grids; (III) local adaptive subdomains fully overlapped with the original computational domain (composite grids).The approach for flow problems, complex geometry or not, is to first divide the computational domain into a number of subdomains with the inter‐overlapping area (partially or fully overlapped). In categories I and II, the fine‐grid or coarse‐grid subdomains can be defined by their representation, while in category III the fine‐grid or coarse‐grid subdomains are defined as usual. Next, implement the Schwarz Alternating Procedure (SAP) to exchange the data among subdomains, where the coarse‐grid correction is used to remove the high frequency error that occurs when the data interpolation from the fine‐grid subdomain to the coarse‐grid subdomain is conducted. The strategy behind the coarse‐grid correction is to adopt the operator of the divergence of velocity field, which intrinsically links the pressure equation, into this process. The solution of each subdomain can be efficiently solved by the direct (or iterative) eigenfunction expansion technique or preconditioned method with the least storage requirement, i.e.O(N2) in 2‐D.Numerical results of (i) driven cavity flow (Re= 100,400) with Cartesian grids (category I) in each subdomain, (ii) driven cavity flow (Re= 3200) with local adaptive grids (category III) in each subdomain, and (iii) flow over a cylinder (Re= 250) with ‘O’ grids in one subdomain and Cartesian grids in another (category II) will be presented in the paper to account for the versatility of

ISSN:0029-5981    

DOI:10.1002/nme.1620380410

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper, a class of ‘assumed strain’ mixed finite element methods based on the Hu–Washizu variational principle is presented. Special care is taken to avoid hourglass modes and shear locking as well as volumetric locking. An unified framework for the 4‐node quadrilateral solid and thermal as well as thermomechanical coupling elements with uniform reduced integration (URI) and selective numerical integration (SI) schemes is developed. The approach is simply implemented by a small change of the standard technique and is applicable to arbitrary non‐linear constitutive laws including isotropic and anisotropic material behaviours. The implementation of the proposed SI elements is straightforward, while the development of the proposed URI elements requires ‘anti‐hourglass stresses’ which are evaluated by classical constitutive equations. Several numerical examples are given to demonstrate the performance of the suggested formulation, including static/dynamic mechanical problems, heat conduction and thermomech

ISSN:0029-5981    

DOI:10.1002/nme.1620380411

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY