摘要:

AbstractAn accuracy analysis of a new class of integration algorithms for finite deformation elastoplastic constitutive relations recently proposed by the authors, is carried out in this paper. For simplicity, attention is confined to infinitesimal deformations. The integration rules under consideration fall within the category of return mapping algorithms and follow in a straightforward manner from the theory of operator splitting applied to elastoplastic constitutive relations. General rate‐independent and rate‐dependent behaviour, with plastic hardening or softening, associated or non‐associated flow rules and nonlinear elastic response can be efficiently treated within the present framework. Isoerror maps are presented which demonstrate the good accuracy properties of the algorithm even for strain increments much larger than the characteristic strains at yie

ISSN:0029-5981    

DOI:10.1002/nme.1620230303

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractTo develop geometrically nonlinear, doubly curved finite shell elements the basic equations of nonlinear shell theories have to be transferred into the finite element model. As these equations in general are written in tensor notation, their implementation into the finite element matrix formulation requires considerable effort. The present paper will demonstrate how to derive the nonlinear element matrices directly from the incrementally formulated nonlinear shell equations using a tensor‐oriented procedure. This enables the numerical realization of all structural responses, e.g. the calculation of pre‐ and post‐buckling branches in snap‐through analysis and especially in bifurcation analysis, including the detection of critical points and the consideration of geometric imperfections. To avoid loss of accuracy care is taken for a realistic computation of the geometric properties as well as of the external loads. Finally, the developed family of shell elements will be presented and its efficiency will be demonstrated by some applications to linear and geometrically nonlinear structural ph

ISSN:0029-5981    

DOI:10.1002/nme.1620230304

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractSeven infinite ring elements have been proposed for the stress analysis around opening in an infinite medium. All elements employ trigonometrical series for interpolation in the θ‐direction and decaying function in ther‐direction. Numerical results indicate that all of them can converge for self‐equilibrating force systems, but only the element which was derived from the stress function can converge in the non‐self‐equilibrating external loads. The present study clearly indicates the close relationship between the semi‐analytical element and closed

ISSN:0029-5981    

DOI:10.1002/nme.1620230305

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe fully symmetrical cubature rules developed and presented are at present the most economically available for numerical integration over the unit cube of complete polynomial functions up to and including nineteenth order. Conventional Gaussian triple product integration formulae, by comparison, require more than twice as many integration points and weights.

ISSN:0029-5981    

DOI:10.1002/nme.1620230306

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA new and powerful mathematical programming method is described, which is capable of solving a broad class of structural optimization problems. The method employs mixed direct/reciprocal design variables in order to get conservative, first‐order approximations to the objective function and to the constraints. By this approach the primary optimization problem is replaced with a sequence of explicit subproblems. Each subproblem being convex and separable, it can be efficiently solved by using a dual formulation. An attractive feature of the new method lies in its inherent tendency to generate a sequence of steadily improving feasible designs. Examples of application to real‐life aerospace structures are offered to demonstrate the power and generality of the approach presen

ISSN:0029-5981    

DOI:10.1002/nme.1620230307

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe boundary‐integral equation formulation for two‐dimensional, planar fracture mechanics based on the use of a special Green's function forms the basis of this analytical paper. The Green's function method is extended to problems of anelastic strain distributions (e.g. elastoplasticity, thermal gradients, residual strains) through a volume (area) integral. The role of the elastic Green's function for the crack problem on the distribution of elastoplastic strains is reviewed. Further, new analytical results for elastic stress intensity factor models for the residual strain and thermal gradient problems are presented. Part 2 of this paper outlines the numerical solution strategy and results for several test probl

ISSN:0029-5981    

DOI:10.1002/nme.1620230308

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractPart 1 of this paper reports on the formulation of an advanced boundary—integral equation model for fracture mechanics analysis of cracked plates, subject to elastoplastic behaviour or other, related body force problems. The basis of this formulation contrasts with other BIE elastoplastic formulations in the use of the Green's function for an infinite plane containing a stress free crack. This Green's function formulation assures that the total elastic strain field for the crack problem is accurately imbedded in the numerical model. The second part of this paper reports on the numerical implementation of this algorithm, as currently developed. The anelastic strain field (residual strains, thermal strains, plastic strains, etc.) is approximated as piecewise constant, while the boundary data is modelled with linear interpolations. An iteration solution scheme is adopted which eliminates the need for recalculation of the BIE matrices. The stability and accuracy of the algorithm are demonstrated for an uncracked, notch geometry, and comparison to finite element results is made for the centre‐cracked panel. The data shows that even the crude plastic strain model applied is capable of excellent resolution of crack tip plastic behavi

ISSN:0029-5981    

DOI:10.1002/nme.1620230309

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractWe present a new 6‐node triangular bending element (called DKTP) based on a discrete Kirchhoff model. A corresponding new flat‐shell element, DLTP, having quadratic variation of in‐plane displacement is also presented. This element has 6 degrees‐of‐freedom (u,v,w, θx, θy, θz) at each corner node and 3 degrees‐of‐freedom (u,v,w) at each mid‐side node. Detailed numerical experimentation is presented to demonstrate the efficiency and reliability

ISSN:0029-5981    

DOI:10.1002/nme.1620230310

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractModal synthesis is a method of formulating the equations of motion for complex vibratory systems. This approach has many advantages in modelling systems that consist of an assembly of linear dynamic elements whose modal characteristics are given. Presented in the paper is a procedure for synthesizing linear dynamic models into one dynamic description in a numerically stable way. This task is achieved by an orthogonal co‐ordinate transformation replacing the matrix inversions required when other procedures are used. The modal synthesis approach is formulated as a problem of finding the equations of motion for a linear system subject to a set of linear constraints. The numerical procedure to generate the equations of motion in terms of independent co‐ordinates is presented. The paper concludes with several examples that demonstrate the properties of the proposed method and its application to the modelling of vibratory syst

ISSN:0029-5981    

DOI:10.1002/nme.1620230311

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA connector element for linking planes of two‐dimensional elements to enable approximate multiplane solutions to a class of three‐dimensional problems is developed. This connector element embodies the same displacement fields as assumed by the connected two‐dimensional isoparametric elements. A reduction from the general multiplane formulation to a dual plane model is shown to be appropriate for analysing bodies with uniformly spaced inclusions. Sample solutions are given, including cases with different continuity conditions in each

ISSN:0029-5981    

DOI:10.1002/nme.1620230312

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY