摘要:

AbstractA series of finite element algorithms for the calculation of the post‐buckling behaviour of structures are proposed. The algorithms represent a finite element implementation of a variational principle for nonlinear eigenvalue problems. Incremental amplitude solution schemes are defined. Numerical results are presented for the post‐buckling behaviour of specific structures with linear and nonlinear pre‐buckling s

ISSN:0029-5981    

DOI:10.1002/nme.1620150702

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractFor the case of free edges which are loaded, follower forces remaining normal to the middle surface of a shell throughout the deformation history do not have a load potential. In finite element analysis, this results in an unsymmetric pressure stiffness matrix. Depending on the structure of the available computer program, implementation of an equation solver permitting solution of unsymmetric simultaneous systems of algebraic equations may be a tedious task. This explains the significance of the topic of symmetricability of pressure stiffness matrices, turning out to be of special importance in the case of static buckling under the assumption of a linear prebuckling path.At first, incremental equations for tracing the nonlinear load–displacement path are derived. Thereafter, the buckling condition is deduced. Then, it is demonstrated that symmetrization of the pressure stiffness matrix is admissible if the so‐obtained ‘buckling pressure’ differs ‘very little’ from the ‘buckling pressure’ resulting from an alternative symmetric ‘buckling matrix’, as is shown to be the case for a simply supported cylindrical shell with a free upper edge, subjected to hydrostatic external pressure. The alternative symmetric ‘buckling matrix’ is a consequence of deleting the virtual work term, causing the unsymmetry of the pressure stiffness matrix, in the expression for the external virtual work. A mechanical interpretation of this virtual work term is given. It is shown to be equal to the difference of virtual work of the original pressure load and of a ‘substitute pressure‐field’, of the form of a Fourier series of the former. This explains why, normally, the buckling coefficient resulting from the ‘substitute pressure‐field’ represents a good approximation to the buckling coefficient stemm

ISSN:0029-5981    

DOI:10.1002/nme.1620150703

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThis paper presents isoparametric formulation for the three‐dimensional transition finite elements. The transition finite elements are necessary for applications requiring the use of three‐dimensional isoparametric solid elements and the curved shell elements. These elements provide proper connections between the two portions of the structure modelled with three‐dimensional solids and the curved shell elements. The element properties are derived and presented in detail. Numerical examples are also presented to demonstrate the accuracy and the applications of such elements in three‐dimensional stress a

ISSN:0029-5981    

DOI:10.1002/nme.1620150704

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA new approach to the generation of near‐optimum finite element meshes is presented. Like other current methods, the procedure presented uses the results of a previous analysis to improve the idealization, but unlike other procedures a new element mesh is generated in each cycle with the aid of interactive computer graphics. The procedure generates near‐optimum two‐dimensional meshes on one cycle employing a grid optimization criterion based on variations in the strain energy density and using a software system which operates like an interactive finite element preprocessor. The example problems presented demonstrate the efficiency and flexibility of the app

ISSN:0029-5981    

DOI:10.1002/nme.1620150705

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620150706

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractAn analysis procedure for the plane strain contained plastic deformation problem is proposed. It is shown that, when piecewise‐linear elastic–plastic laws are adopted, the plane strain problem can be formulated in terms of exactly the same variables appearing in a plane stress problem, even if the transverse stress and plastic strain components do not vanish in general. The two problems are governed by the same equilibrium and compatibility equations and the only difference is in the elastic–plastic material constitutive laws, in complete analogy with the linear elastic case.The problem is discretized by using a compatible finite element model on which basic elastic‐plastic constitutive laws for an element in plane strain conditions can be obtained. When the assemblage is performed, the resulting set of governing relations presents a mathematical structure which enable, for solution, techniques efficiently used for truss and frame problems. Some solutions for axisymmetric tubes subjected to pressure and temperature gradients are illu

ISSN:0029-5981    

DOI:10.1002/nme.1620150707

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA detailed study is made of the error growth associated with explicit difference schemes for a conduction‐convection problem. It is shown that the error can become arbitrarily large after a finite number of time steps even though it ultimately decays to zero. Certain ambiguities reported in the literature can thereby be resolve

ISSN:0029-5981    

DOI:10.1002/nme.1620150708

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the solution of the three‐dimensional potential problem for electromagnetic river gauging. It extends previous ideas of joining finite elements in an interior region to one infinite external element treated by the boundary integral method1,2to this case where there are two external infinite elements representing the river and the ground. The boundary continuity conditions on the infinite river–ground interface, as well as the internal–external interfaces, are dealt with by introducing a variational principle with relaxed continuity require

ISSN:0029-5981    

DOI:10.1002/nme.1620150709

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractIn this paper, a procedure for obtaining a fully stresses shape of elastic continuum under arbitrary design conditions is proposed, by using the optimum distribution of the material properties such as the Young's modulus or the plate thickness. By using this technique, the optimum multiple‐connected shape can be created from the original shape of simply body. The optimum shape of a road‐pole subjected to an uniformly distributed load is determined by using the technique, and from the results the effectiveness of the technique is examined numerica

ISSN:0029-5981    

DOI:10.1002/nme.1620150710

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620150711

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY