摘要:

AbstractPoints on load‐displacement paths of thin shells subjected to proportional loading, at which the second and/or the third derivative of the displacement components with respect to the load parameter vanishes, are termed ‘special points’. Such points represent global characteristics of the state of deformation of the shell in the sense that for the respective values of the load parameter the mentioned rate(s) of all displacement components at all points of the shell must vanish. It will be shown that special points on load‐displacement paths correspond to special points of one order lower on the Det KT–λ diagram, where Det KTis the determinant of the tangent stiffness matrix within the framework of the finite element method and λ is a dimensionless load parameter. Points of inflection on load‐displacement diagrams, for example, correspond to extreme values on the Det KT–λ diagram. The main reason for the occupation with special points on load‐displacement paths is that points of inflection and flat points on these paths correspond to special points on eigenvalue curves in the context of accompanying linear stability analyses of geometrically non‐linear prebuckling analyses of thin shells by the finite element method, investigated

ISSN:0029-5981    

DOI:10.1002/nme.1620310202

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA 4‐node element with 1 integration point is developed for the analysis of elastoplastic large strains. It is based on the Hu‐Washizu principle and uses a co‐rotational formulation. Special care is taken to avoid spurious zero‐energy modes and incompressibility locking.This element successfully passes the large strain patch test. It proves to be accurate and computationally ver

ISSN:0029-5981    

DOI:10.1002/nme.1620310203

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA geometrically non‐linear constant moment triangular finite element is designed under Kirchhoff theory from a Hu–Washizu functional such that it passes the totality of von Kármán patch tests for constant strain and constant curvature. The non‐linear triangle has the same connection properties as in the linear theory where the constant strain triangle is superposed upon the displacement version of the constant moment t

ISSN:0029-5981    

DOI:10.1002/nme.1620310204

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractWe consider large eigenvalue problems for skeletal structures with symmetry. We present an algorithm, based upon a novel combination of group‐theoretic ideas and substructuring techniques, that block‐diagonalizes such systems exactly and efficiently. The procedure requires only the structural matrices of a repeating substructure, together with the symmetry modes, which are obtained from symmetry considerations alone. We first present a simple paradigmatic example and then follow with several non‐trivial applications involving large lattice struc

ISSN:0029-5981    

DOI:10.1002/nme.1620310205

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo different methods of assuming independent strain fields are examined for the nine node degenerate solid shell element. In the first case, the assumed strain field is chosen for the local orthogonal co‐ordinate systems defined at the Gaussian integration points. In the second case, the independent strain is assumed for a local orthogonal co‐ordinate system defined at the origin of the parent co‐ordinates. The results of numerical tests involving simple example problems demonstrate that the second method is capable of exactly representing constant stress or moment states even when element geometries are distorted. In addition, both methods lead to a finite element model which is free of lo

ISSN:0029-5981    

DOI:10.1002/nme.1620310206

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620310207

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA new numerical technique for large deflection elasto‐plastic analysis of stiffened plates is presented. The method uses super finite elements which are macro elements having analytical as well as the usual finite element shape functions, specially designed so that only one plate element per bay and one beam element per span are needed. The large deflection theory by von Karman and the von Mises yield criterion and associated flow rule are employed. The governing equations are derived using the principle of virtual work, integrated numerically using Gauss quadrature and solved by Newton–Raphson iteration. Numerical solutions are presented for simple beams and plates, and plates stiffened in one or two mutually perpendicular directions. Good approximations are obtained with only one‐element representations of each plate bay or beam span with significant savings in computing time, costs and storage requirements as compared with using regular finite ele

ISSN:0029-5981    

DOI:10.1002/nme.1620310208

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAn experimental procedure and a finite element simulation method for rate‐dependent metal forming processes are developed. The development includes the formulation of a tangential stiffness matrix for an axisymmetric solid finite element with four node, eight degree of freedom, quadrilateral cross‐section. The formulation includes the effects of elasticity, viscoplasticity, temperature, strain rate and large strains. The solution procedure is based on a Newton‐Raphson incremental‐iterative method which solves the non‐linear equilibrium equations and gives temperatures and incremental stresses and strains. Three examples are studied. In example 1, finite element simulation for the upsetting of a cylindrical workpiece between two perfectly rough dies is performed and the results are compared with alternative finite element solutions. In examples 2 and 3, both experimental and finite element studies are performed for the upsetting of a cylindrical billet and the forging of a ball, respectively. Annealed aluminium 1100 workpieces are used in both examples. For the finite element analysis, uniaxial compression tests are first performed to provide the material properties. The tests generate elastic moduli and two sets of stress‐strain curves (quasi‐static and constant strain rate), which are used to establish a rate‐dependent material model for input. For both examples 2 and 3, comparisons between the experimental and finite element simulation results for the forming force vs. die displacement relations and also for the deformed configurations show good agreement. The versatility of finite element methods allows for displaying detailed knowledge of the metal forming process, such as the distributions of temperature rise, yield stress, effective stress, plastic strain, plastic strain rate, forming forces and deformed configurations, etc. at any instance during the

ISSN:0029-5981    

DOI:10.1002/nme.1620310209

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAn advanced level development of the boundary element method is presented for the elastic stress analysis of a three‐dimensional solid containing a large number of small diameter, tubular shaped holes. The formulation has been developed such that these holes can be modelled by a system of curvilinear line elements, resulting in substantial savings in both data preparation and computing costs. This is accomplished by assuming a variation in the displacement field along the circumference defined in terms of trigonometric functions together with a linear or quadratic variation of displacements along the longitudinal directio

ISSN:0029-5981    

DOI:10.1002/nme.1620310210

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper introduces three four‐node quadrilateral axisymmetric elements. The first one is an incompatible element while the second one is a modification of the first element by an extended Hellinger‐Reissner principle. The second element is then simplified by incorporating the conceptual idea of free formulation and thus forms the third element. All of the three elements are found to be invariant, insensitive to nodal point numbering, free of locking for nearly incompressible material, able to pass the patch test and do not exhibit the false shear phenomenon. Numerical examples are given and satisfactory predictions are achie

ISSN:0029-5981    

DOI:10.1002/nme.1620310211

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY