摘要:

AbstractIn this paper a discussion of volume integral formulations in three‐dimensional non‐linear magnetostatics is presented. Integral formulations are examined in connection with Whitney's elements in order to find new approaches. A numerical algorithm based on a formulation implying properly the continuity conditions of magnetic field strengthH, i.e. anh‐type formulation, is introduced. Results of demanding application problems are shown demonstrating the characteristics of this kind of volume integral approach. In addition, a discussion of the parallelized version of the numerical code based on theh‐type approach is presented appended with numerical results illustrating the advantages of combining integral formulations with concurrent co

ISSN:0029-5981    

DOI:10.1002/nme.1620381602

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA new hybrid algorithm for automatically generating either an all‐quadrilateral or an all‐triangular element mesh within an arbitrarily shaped domain is described. The input consists of one or more closed loops of straight‐line segments that bound the domain. Internal mesh density is inferred from the boundary density using a recursive spatial decomposition (quadtree) procedure. All‐triangular element meshes are generated using a boundary contraction procedure. All‐quadrilateral element meshes are generated by modifying the boundary contraction procedure to produce a mixed element mesh at half the density of the final mesh and then applying a polygon‐splitting procedure. The final meshes exhibit good transitioning properties and are compatible with the given boundary segments which are not altered. The algorithm can support discrete crack growth simulation wherein each step of crack growth results in an arbitrarily shaped region of elements deleted about each crack tip. The algorithm is described and examples of the generated meshes are provided for a representative selection of cracked and uncracked

ISSN:0029-5981    

DOI:10.1002/nme.1620381603

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA novel algorithm for the analysis of contact problems in elasticity has been presented in this paper. The algorithm is based on the boundary element method and a direct approximation of the contact complementarity conditions using linear programming. An incremental loading scheme has been developed to ensure an accurate approximation of the deformation path that the object experiences during the process of contact. Several numerical examples have been analysed to illustrate the validity of the proposed formulations.

ISSN:0029-5981    

DOI:10.1002/nme.1620381604

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the modelling of nonlinear elastic multi‐body systems discretized using the finite element method. The formulation uses Cartesian co‐ordinates to represent the position of each elastic body with respect to a single inertial frame. The kinematic constraints among the various bodies of the system are enforced via the Lagrange multiplier technique. The resulting equations of motion are stiff, non‐linear, differential‐algebraic equations. The integration of these equations presents a real challenge as most available techniques are either numerically unstable, or present undesirable high frequency oscillations of a purely numerical origin. An approach is proposed in which the equations of motion are discretized so that they imply conservation of the total energy for the elastic components of the system, whereas the forces of constraint are discretized so that the work they perform vanishes exactly. The combination of these two features of the discretization guarantees the stability of the numerical integration process for non‐linear elastic multi‐body systems. Examples of the procedure ar

ISSN:0029-5981    

DOI:10.1002/nme.1620381605

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA multivariable optimization technique based on the Monte‐Carlo method used in statistical mechanics studies of condensed systems is adapted for solving single and multiobjective structural optimization problems. This procedure, known as simulated annealing, draws an analogy between energy minimization in physical systems and objective function minimization in structural systems. The search for a minimum is simulated by a relaxation of the statistical mechanical system where a probabilistic acceptance criterion is used to accept or reject candidate designs. To model the multiple objective functions in the problem formulation, a cooperative game theoretic approach is used. Numerical results obtained using three different annealing strategies for the single and multiobjective design of structures with discrete‐continuous variables are presented. The influence of cooling schedule parameters on the optimum solutions obtained is discussed. Simulation results indicate that, in several instances, the optimum solutions obtained using simulated annealing outperform the optimum solutions obtained using some gradient‐based and discrete optimization techniques. The results also indicate that simulated annealing has substantial potential for additional applications in optimization, especially for problems with mixed discrete‐continuous va

ISSN:0029-5981    

DOI:10.1002/nme.1620381606

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe objective of the research presented in this paper was to develop a general computational method for kinematic limit analysis problems that involve the determination of an optimal kinematically admissible velocity field of the studied structure under external loads. With the failure velocity field available, we can obtain a numerical estimate of the limit load exerted to the structure. The general kinematic limit analysis is characterized by the minimization of the plastic potential power dissipation functional of the mechanical system. This minimization problem was approached previously by linear and non‐linear programming schemes. In this paper, a new non‐linear solution scheme is described which is based on previous research on the regularized method. The regularized functional is a convex and non‐linear functional whose minimum represents a viscoplastic potential power dissipation, the velocity which minimizes this functional was proved to be kinematically admissible and can be obtained by the augmented Lagrangian method. This paper demonstrates that the non‐linear programming scheme is applicable to direct limit analysis. The basic idea of using this optimization method is to tranform the functional with a non‐linear term of the first‐order derivatives of the velocity to a functional in which this term is uncoupled with the strain rates, and in consequence the augmented Lagrangian (transformed functional) can be solved more easily. Some special problems related to incompressibility and discontinuity are discussed. A simple and accurate scheme is proposed to deal with the incompressibility problem and the problem of the linear Mohr–Coulomb yield surface in the principal stress space. Examples of plane stress and plane strain problems are given for von Mises and Mohr–Coulomb materials. Numerical results are provided in graphical form which serves to illustrate the kinematic admissibility. The limit loads obtained agreed well with the analytical results, which demonstrates the efficiency and accuracy of the non‐linear computational

ISSN:0029-5981    

DOI:10.1002/nme.1620381607

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAn 8‐noded linear hexahedron element for large strain hyperelastic analysis is presented in this paper. The element is based on a constant deformation gradient interpolation and is formulated using a mixed variational principle of the Hu–Washizu type. Volumetric and isochoric components of the deformation are treated independently to ensure the correct evaluation of the element volume. A simple procedure to control the propagation of spurious hourglass deformation modes is also discussed. This is based on the addition of artificial hourglass forces which vanish under constant deformation gradient conditions, thereby ensuring that the element passes a non‐linear version of the patch test. Applications in the field of neo‐Hookean materials and superplastic forming processes are also con

ISSN:0029-5981    

DOI:10.1002/nme.1620381608

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA general family of single‐step methods for use in first‐order ODEs is presented. This family of methods, called SS3‐methods, embraces generalized trapezoidal methods, SS21‐methods, α‐methods and many other well‐known methods, thus providing a good basis for comparison of these methods. Corresponding parameter values of SS3 methods for these methods are presented. The analysis of SS3‐methods is restricted to linear and symmetric systems. Stability, convergence, accuracy, numerical dissipation and overshoot of the methods are considered. The conditions for algorithm parameters to exhibit good characteristics in these respects are given. It is shown that the optimal subfamily of SS3‐methods coincide

ISSN:0029-5981    

DOI:10.1002/nme.1620381609

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620381610

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620381601

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY