摘要:

AbstractApplications of the boundary element method for two‐ and three‐dimensional structural shape optimization are presented. The displacements and stresses are computed using the boundary element method. Sub‐structuring is used to isolate the portion of the structure undergoing geometric change. The corresponding non‐linear programming problem for the optimization is solved by the generalized reduced gradient method.B‐spline curves and surfaces are introduced to describe the shape of the design. The control points on these curves or surfaces are selected as design variables. The design objective may be either to minimize the weight or a peak stress of the component by determining the optimum shape subject to geometrical and stress constraints. The use of substructuring allows for problem solution without requiring traditional simplifications such as linearization of the constraints. The method has been successfully applied to the structural shape optimization of plane stress, plane strain and three‐dimensional elastici

ISSN:0029-5981    

DOI:10.1002/nme.1620260903

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA finite element velocity method for analysing the superplastic sheet metal forming process is presented. This method is developed from the principle of virtual work and is based on the use of isoparametric continuum elements. The large inelastic deformation of the superplastic material is modelled as the behaviour of an incompressible non‐linear viscous flow material. The contact and friction problem is solved by using thecompatibility load stepmethod, which is an extension of an earlier work. The finite element method is applied to selected problems to illustrate the applicability of the solution procedur

ISSN:0029-5981    

DOI:10.1002/nme.1620260904

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA nine node finite element is presented for the analysis of thin shell structures undergoing large deflection. The finite element formulation is based on the concept of degenerate solid shell element and the Hellinger‐Reissner principle with independent strain. Three versions of assumed independent strain are selected to suppress spurious kinematic modes. One version leads to a finite element model which is kinematically stable at element level while the other two give globally stable models. Numerical tests indicate that the finite element model which is stable at element level may reveal the locking effect in certain cases. However, the other two models are free of lockin

ISSN:0029-5981    

DOI:10.1002/nme.1620260905

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe constitutive relationship between fields in electromagnetic media is cast in error form. For well‐posed static problems, the error splits systematically into complementary functionals. Error minimization provides a universal variational principle that generates complementary and dual solution formulations. The error, which is wholly attributed to the numerical constraints in approximate solutions, is always defined and computable locally and globall

ISSN:0029-5981    

DOI:10.1002/nme.1620260906

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn efficient implementation of finite element methods for free boundary parabolic problems in general two dimensional space domains is presented. The Stefan problem, the Hele‐Shaw problem and the porous medium equation are included. Backward differences or linearization techniques are used for the time discretization of the problem. The performances of these schemes are discussed with several numerical test

ISSN:0029-5981    

DOI:10.1002/nme.1620260907

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe reason for looking in some depth at locking of Mindlin shell elements is introduced.A simple example of straight beam locking is examined in detail.The observations about reduced integration that emerge are subsequently unified with some other facts the writer has come across.A simple curved beam element is then formulated and examined under inextensional bending. The performance of this element under reduced integration is predicted for both the ‘undistorted’ and ‘distorted’ configurations (see text) and for a selective‐very reduced integration scheme.The previous predictions are then verified through the performance of an 8 node Mindlin shell element in a suitable cylindrical shell test.The paper finally concludes with a set of important observations that so easily could be drawn from such a simple

ISSN:0029-5981    

DOI:10.1002/nme.1620260908

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractMinimum principles in velocities, stress rates and plastic strain rates are extended in order to derive formulations for finite increments of displacement, stress and plastic strain fields defining complete numerical methods. Kinematical, statical and mixed principles are developed from a new variational formulation of the elastic‐plastic work‐hardening constitutive relation.The consequences of this time discretization are discussed independently of any discretization of the continuum. In particular, the incremental formulations derived from extended rate principles account for local elastic unloading and produce stress field approximations complying with equilibrium and plastic admissibility without any additional procedure, at least for piecewise linear yield functions. These properties are not fulfilled when the incremental analysis is based on direct discrete versions of classical rate principles.Finally, FEM approximations are formally introduced and the solution of the resulting finite dimensional quadratic optimization problem is conside

ISSN:0029-5981    

DOI:10.1002/nme.1620260909

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIn this paper a discrete element matrix formulation for the analysis of linear and non‐linear bifurcation problems of some elastic structures is introduced. This, combined with a discrete perturbation technique, is implemented into a computer code to solve buckling and initial postbuckling problems of elastic strut

ISSN:0029-5981    

DOI:10.1002/nme.1620260910

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractNew two‐ and three‐dimensional boundary element formulations are developed for steady‐state and transient uncoupled thermoelasticity. These new procedures differ from previous work in that additional surface or volume integration is not required to incorporate thermal loads in the analysis. Instead, thermal body forces are introduced in the boundary element system via particular integrals.The present formulation is implemented in a general purpose, multi‐region system, and examples are presented to demonstrate the accuracy and versatility of the

ISSN:0029-5981    

DOI:10.1002/nme.1620260911

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractNew two‐ and three‐dimensional boundary element formulations are developed for elastoplastic stress analysis. These new procedures differ from previous work in that volume integration is not required to incorporate the non‐linear effects in the analysis. Instead, initial stess rates are introduced in the boundary element system via particular integrals.The present formulation is implemented in a general purpose, multi‐region system, and examples are presented to demonstrate the accuracy and versatility of the

ISSN:0029-5981    

DOI:10.1002/nme.1620260912

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY