摘要:

AbstractAn explicit finite element solution procedure for the three dimensional Euler equations is presented. The solution domain is automatically meshed using a tetrahedral mesh generator which is an extension of our previous two dimensional work. Several examples are included to illustrate the performance of the generator and solver. An adaptive mesh regeneration procedure is used for the first time in three dimensions.

ISSN:0029-5981    

DOI:10.1002/nme.1620261002

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractRate‐independent plasticity and viscoplasticity in which the boundary of the elastic domain is defined by an arbitrary number of yield surfaces intersecting in anon‐smoothfashion are considered in detail. It is shown that the standard Kuhn‐Tucker optimality conditions lead to the only computationally useful characterization of plastic loading. On the computational side, an unconditionally convergent return mapping algorithm is developed which places norestrictions(aside from convexity) on the functional forms of the yield condition, flow rule and hardening law. The proposed general purpose procedure is amenable to exact linearization leading to a closed‐form expression of the so‐calledconsistent (algorithmic) tangent moduli.For viscoplasticity, aclosed‐formalgorithm is developed based on the rate‐independent solution. The methodology is applied to structural elements in which the elastic domain possesses a non‐smooth boundary. Numerical simulations are presented that illustrate the excellent performance o

ISSN:0029-5981    

DOI:10.1002/nme.1620261003

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA new method is proposed for studying the effects of various microstructural material discontinuities, within a body, in a finite element analysis. The material discontinuities are accounted for by introducing a transformation strain in those regions. This formulation leads to two matrix equations; the first corresponds to the finite element analysis of the body without material discontinuities, and the second accounts for the microstructure. An important feature of the new method is that the first equation is solved only once, then the second equation can be solved repetitively for different microstructures. Thus, it is possible to study the effect of different microstructures within the body without reanalysing the entire body. It is expected that this method will be particularly useful in materials research to study the mechanisms that occur in materials at the microstructural level.The transformation strain formulation is reviewed, and the matrix equations for the new method are derived. Several numerical examples are presented to illustrate the versatility of the new method.

ISSN:0029-5981    

DOI:10.1002/nme.1620261004

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractElement consistency is generally checked using the patch test on an element patch of finite size. This condition may in certain cases be too restrictive, and disqualifies elements that appear to be convergent. A method termed ‘fractal patch test’ is presented, in which the patch size is maintained constant while the distorted mesh is refined. Examples are given for four‐node quadrilateral elements used in plane stress and strain analysis, and for plate bending ele

ISSN:0029-5981    

DOI:10.1002/nme.1620261005

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA substructure synthesis formulation is presented that permits use of established flexible multibody dynamic analysis computer codes to account for structural geometric non‐linear effects. Large relative displacement is permitted between points within bodies that undergo small strain elastic deformation. Components are divided into substructures, on each of which the theory of linear elasticity relative to a body reference frame is adequate to describe deformation and its coupling with system motion. Normal vibration and static correction deformation modes are used to account for elastic deformation within each substructure. Compatibility conditions are derived and imposed as constraint equations at boundary points between substructures. System equations of motion that include geometric non‐linear effects of large rotation, in terms of generalized co‐ordinates of a reference frame for each substructure and a set of deformation modes that are defined within the substructure, are assembled. The method is implemented in an industry standard flexible multibody dynamics code, with minimal modification. Use of the formulation is illustrated on the classical problem of a spinning beam with geometric stiffening and on a space structure that experiences large deform

ISSN:0029-5981    

DOI:10.1002/nme.1620261006

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA complete mathematical model is formulated to analyse the effects of mean flow incidence angle on the unsteady aerodynamics of an oscillating airfoil in an incompressible flow field. A velocity potential formulation is utilized. The steady flow is independent of the unsteady flow field. However, the unsteady flow is coupled to the steady flow field through the boundary conditions on the oscillating airfoil. The numerical solution technique for both the steady and unsteady flow fields is based on a locally analytical method. In this method, analytical solutions are incorporated into the numerical technique, with the discrete algebraic equations which represent the differential flow field equations obtained from analytic solutions in individual local computational grid elements. This flow model and locally analytic numerical solution method are then verified through the excellent correlation obtained with the Theodorsen oscillating flat plate and Sears transverse gust classical solutions. The effects of mean flow incidence on the steady and oscillating airfoil aerodynamics are then investigated.

ISSN:0029-5981    

DOI:10.1002/nme.1620261007

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA finite element model for the non‐linear analysis of flexibly connected steel frames is proposed. The element is regarded as an assemblage of individual parts whose behaviour is described in terms of generalized stresses and strains. Displacements and plastic strain fields are independently modelled. The former are a function of 13 nodal parameters and constitute a typical application of a hierarchical procedure. The latter are modelled over the cross section, along the element and in the six springs located at the ends of the beam. Examples to show the importance of considering the non‐linear behaviour of the connections in the frame analysis are propo

ISSN:0029-5981    

DOI:10.1002/nme.1620261008

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractWe present a simple calculation which seems at first to yield erroneous results when natural boundary conditions are not enforced. Our example is the static deformation of a cantilever beam under uniform loading. The corresponding variational principle is established and two applications of the Rayleigh–Ritz–Galerkin method are made.(1)The deflection is expanded in a series of cosines. The energy is rendered stationary subject to all boundary conditions, geometric and natural (they are imposed through Lagrange multipliers). The resulting function is exactly the Fourier cosine expansion of the true deflection–which is a fourth‐degree polynomial.(2)The deflection is again expanded in a cosine series but now the natural boundary conditions are ignored.The resulting series does not converge to the true solution.Owing to the simplicity of the coefficients, exact summations are possible and the discrepancy is clear. The disagreement is large, and the object of the paper is to decide which method i

ISSN:0029-5981    

DOI:10.1002/nme.1620261009

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA geometric stiffness formulation is presented for thin‐walled open section beams using semiloof elements. The validity of the formulation is confirmed by performing torsional and lateral initial stability (buckling) analyses of beams. Results are compared with classical solution

ISSN:0029-5981    

DOI:10.1002/nme.1620261010

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn important limiting factor in the accurate modelling of fluid flow problems is the numerical representation of the convection terms in the Navier‐Stokes equations. This paper reviews several approaches used to approximate the convection terms and reduce the so‐called false‐diffusion errors, within the context of finite‐difference and finite‐volume methods. Numerical errors are characterized as those due to discretization of the differential terms and those due to the influence of the multidimensional nature of the flow. Necessary criteria are identified which a numerical scheme must satisfy, if it is to be a candidate, at least in terms of accuracy and practicality, for the successful solution of the Navier‐Stokes equations. One of the criteria is the need of the scheme to account explicitly for the multidimensionality of the flow in the transport of scalar variables. All schemes except Raithby's SKEW approximation are deficient in this respect. However, the SKEW scheme does not satisfy some of the other criteria and does not always perform well. A new scheme called CUPID (CornerUPwInDing), which is based on the ideas of the SKEW scheme, yet obeys more of the criteria identified above, is described. The scheme is tested on a series of discriminating test problems which, the authors contend, demonstrate its potential for practical use in solving accurately the Navier‐Sto

ISSN:0029-5981    

DOI:10.1002/nme.1620261011

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY