摘要:

AbstractA self‐correcting forward gradient time integration procedure is formulated for the integration of a new unified visco‐plastic constitutive model for an eutectic solder alloy using a tensorial internal state variable. The procedure has been implemented numerically into a commercial FE code through a user‐material subroutine and is well suited to deal with numerically stiff constitutive equations. This is accomplished through an automatic subincrementation procedure controlled by a maximum allowed equivalent inelastic strain increment per time step.For illustration purposes, two examples are discussed: (i) uniaxial test simulations to reveal the optimum combination of the user‐specified tolerance and the prescribed load step size to obtain a desired accuracy at a minimum cost, (ii) a large‐scale three‐dimensional analysis of an integrated circuit (IC) package's solder joint to show the capability of the proposed procedure to deal with thermomechani

ISSN:0029-5981    

DOI:10.1002/nme.1620370402

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA contact algorithm has been developed and implemented in a non‐linear dynamic explicit finite element program to analyse the response of three‐dimensional shell structures. The contact search algorithm accounts for initial contact, sliding, and release through the use of a parametric representation of the motion of points located on the surface of the structure combined with a contact surface representation which approximates the actual surface by means of triangular search planes. The mechanics of contact is handled by taking advantage of the fact that an explicit time integration scheme results in very small displacements during a time step. The amount of overlap of the discrete representation of the surfaces which occurs at contact is taken as a measure of the approach of the surfaces. Hence, experimental data which relates approach to normal contact pressure can be used to determine the contact pressure applied to the finite element model of the surface as contact evolves. The friction model also incorporates experimental data on the dependence of the coefficient of friction on both the relative sliding velocity and on the relative tangential displacement between surfaces in contact observed in friction tests. The parallel implementation of this contact algorithm and its performance on a 128‐processor distributed‐memory multiprocessor computer is discussed in Part II of thi

ISSN:0029-5981    

DOI:10.1002/nme.1620370403

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA parallel implementation of the contact algorithm discussed in Part I of this paper has been developed for a non‐linear dynamic explicit finite element program to analyse the response of three‐dimensional shell structures. The parallel contact algorithm takes advantage of the fact that in general only some parts of the structure will actually be in contact at any given time. Special interprocessor communication routines and a method which enables individual processors to dynamically build local contact domains during execution have been developed. The performance of the parallel contact algorithm has been studied by executing the program on 128 processors of a distributed‐memory multiprocessor com

ISSN:0029-5981    

DOI:10.1002/nme.1620370404

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the present paper, we analyse the computational performance of the Lanczos method and a recent optimization technique for the calculation of thep(p≤ 40) leftmost eigenpairs of generalized symmetric eigenproblems arising from the finite element integration of elliptic PDEs. The accelerated conjugate gradient method is used to minimize successive Rayleigh quotients defined in deflated subspaces of decreasing size. The pointwise Lanczos scheme is employed in combination with both the Cholesky factorization of the stiffness matrix and the preconditioned conjugate gradient method for evaluating the recursive Lanczos vectors. The three algorithms are applied to five sample problems of varying size up to almost 5000. The numerical results show that the Lanczos approach with Cholesky triangularization is generally faster (up to a factor of 5) for small to moderately large matrices, while the optimization method is superior for large problems in terms of both storage requirement and CPU time. In the large case, the Lanczos–Cholesky scheme may be very expensive to run even on modern quite powerful comput

ISSN:0029-5981    

DOI:10.1002/nme.1620370405

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAn upwind flux vector splitting algorithm which utilizes the moments of the Boltzmann equation to derive the Euler equations for inviscid compressible flow has been used with a variety of grid types. Although the upwind approach offers the potential for accurate flow simulations, it is necessary to ensure that such procedures can be utilized on realistic grids. In this paper, an upwind algorithm is used with structured multiblock grids, unstructured grids of triangles and hybrid structured/unstructured grids to solve realistic compressible flow problems in two dimensions.

ISSN:0029-5981    

DOI:10.1002/nme.1620370406

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractStability and convergence analysis of finite element approximations of Biot's equations governing quasistatic consolidation of saturated porous media are, discussed. A family of decay functions, parametrized by the number of time steps, is derived for the fully discrete backward Euler–Galerkin formulation, showing that the pore‐pressure oscillations, arising from an unstable approximation of the incompressibility constraint on the initial condition, decay in time. Error estimates holding over the unbounded time domain for both semidiscrete and fully discrete formulations are presented, and a post‐processing technique is employed to improve the pore‐pressure a

ISSN:0029-5981    

DOI:10.1002/nme.1620370407

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe following is a summary of several years' research work devoted to the development of a sheet metal forming computer program. A few aspects of the membrane formulation are discussed, leading to the conclusion that instability problems cannot be avoided. Then a complete formulation including bending, based on the large‐displacement equations of plates, is developed. An expression for the tangent matrix is obtained. Elastic behaviour, yield equation and the plastic flow rule are reformulated in a suitable basis. A reliable method for stress projection on the yield surface, based on a ‘dichotomic’ algorithm, is presented. Many other features of the simulation problem are discussed: contact and frictional effects, thickness updating and geometry definitions. Finally, three illustrative test cases are pres

ISSN:0029-5981    

DOI:10.1002/nme.1620370408

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA method using techniques of computational geometry for generating tetrahedral finite element meshes in three‐dimensional polyhedral regions is presented. The input to the method consists of the boundary faces of the polyhedral region and possibly internal and hole interfaces, plus the desired number of tetrahedra and other scalar parameters. The region is decomposed into convex polyhedra in two stages so that tetrahedra of one length scale can be generated in each subregion. A mesh distribution function, which is either automatically constructed from the first‐stage convex polyhedron decomposition or supplied by the user, is used to determine the tetrahedron sizes in the subregions. Then a boundary‐constrained triangulation is constructed in each convex polyhedron, with local transformations being used to improve the quality of the tetrahedra. Experimental results from triangulations of three regions are pro

ISSN:0029-5981    

DOI:10.1002/nme.1620370409

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620370410

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620370401

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY