摘要:

AbstractNew basis functions and solution procedures for p‐version finite element analysis are described. They are used in a highly efficient p‐version finite element solver for linear elastostatics and dynamics, which has been used in an industrial environment for over two years. Using two sample applications it is shown that, using the techniques proposed here, p‐version finite element analysis can have a substantially lower computational cost, for given accuracy, than standard finite element methods. This makes the industrial applicability of p‐version finite element analysis much wider than is commonly b

ISSN:0029-5981    

DOI:10.1002/nme.1620362202

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper deals with the application of a parametric quadratic programming (PQP) method to the numerical solution of large‐deflection beams involving frictional contact constraints. The flexibility of the structure is modelled by an intrinsic spatial beam theory which is approximated by transverse‐shear deformable linear beam elements. The linear complementary problem (LCP) without the penalty function resulting from PQP is made part of a Newton‐Raphson search. The tool for solving the complementary equations is Lemke's algorithm, in which frictional contact conditions are enforced and new contact surfaces are updated during iteration. Applying the resulting contact element, a more accurate approximation of the contact point can be guaranteed, and the contact force can be directly computed by the adjacent beam elements. Three numerical examples are analysed to show the effectiveness and validity of the m

ISSN:0029-5981    

DOI:10.1002/nme.1620362203

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractOne possibility of formulating the tinite element method is founded on the principle of virtual displacement, in which we want to include a rate‐independent elastoplastic constitutive model based on the assumption of a yield surface. The constitutive equations result from the assumptions of small deformations, Hooke's law for the elastic domain, the normality rule for the evolution of plastic strains, the von Mises yield condition and a special kind of kinematic hardening due to Armstrong and Frederick,1in which linear kinematic hardening is generalized with a saturation term. We show that it is not generally recommendable to propose large load steps. To this end, we investigate the influences of the non‐linear kinematic hardening model on the stress computation and the resulting consistent elastoplastic tangent operator. The main topics of this paper are: (1) development of a problem‐optimized backward Euler method with regard to the kinematic hardening model, (2) study of the influence of the saturation term on the numerical accuracy through isoerror maps and (3) computation of the consistent elastoplastic tangent ope

ISSN:0029-5981    

DOI:10.1002/nme.1620362204

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe theoretical prediction of elastoplastic behaviour of single crystals is a basic problem which is central to the prediction of the overall behaviour of the crystal aggregate. It is generally well known that quasi‐static and isothermal plastic deformation in single crystals arises almost solely from slip on specific crystallographic planes, and that this process occurs when the resolved shear stress on a critical slip system reaches a certain maximum value. What is not obvious is how one can identify the specific slip systems activated by a given load increment, since the process usually involves selection from a pool of linearly dependent slip systems. In this paper we use small‐deformation multisurface plasticity theory to phrase properly the problem of crystal slips at infinitesimal increments. We then describe an ‘ultimate’ algorithm for systematically identifying the active slip systems at finite increments. We arrive at the following major conclusions when the ultimate algorithm is applied to f.c.c. crystals: For perfectly plastic crystals the combination of active slip systems may or may not be unique; however, the imposition of the discrete Kuhn‐Tucker conditions is sufficient to determine the (unique) final crystal stresses. For Taylor hardening crystals in which active and latent slip systems harden by the same amount, the discrete Kuhn‐Tucker conditions are also sufficient to make the mathematical problem of crystal stress integration well posed, i.e. the final stresses can be determined uniquely albeit the combination of active slip systems may not be unique. To illustrate the latter point, an accurate return‐mapping algorithm for perfectly plastic and Taylor hardening crystals is described and tested against the ultimate algorithm to demoustrate numerically that it is possible to generate different combinations of active slip systems and yet produce identical f

ISSN:0029-5981    

DOI:10.1002/nme.1620362205

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 with the first‐order reliability method, is developed to study probabilistic fatigue crack growth. Due to the high degree of complexity and non‐linearity of the response, direct differentiation coupied with the response‐surface method is employed to determine the response gradient. Three random processes, the mode I and mode II. stress intensity factors and the crack direction angle, are included in the expression of the response gradient. The sensitivity of these random processes is determined using a first‐order response model. An iteration scheme based on the HL‐RF method2is applied to locate the most probable failure point on the limit‐state surface. The accuracy and efficiency of the stochastic boundary element method are evaluated by comparing the cumulative distribution function of the fatigue life obtained with Monte Carlo simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with randomness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variable at the design point is determined to show its role in the fatigue failure. The variation of each primary random variable at the design point with the change of probability of failure is also presented in numeric

ISSN:0029-5981    

DOI:10.1002/nme.1620362206

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn algorithm which combines the techniques of numerical analysis and numerical simulation in the study of transient dynamic structural response is proposed. This is achieved by incorporating the ability to create new surfaces and separate fragments according to a defined failure criterion into a finite element procedure which uses explicit time integration. Thus, the algorithm not only provides accurate prediction of the structural failure and fragmentation pattern, but also evaluates accurate stress, velocity, acceleration and displacement values of each fragmented component.To develop a viable fragmental algorithm, other than the expected modification in storage and node bookkeeping, we found it necessary to introduce an efficient algorithm to handle extremely large displacements resulting from the fracture. In that regard, an updated corotational approach is introduced.

ISSN:0029-5981    

DOI:10.1002/nme.1620362207

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFinite element algorithms for incompressible fluids, in particular the penalty function method, are re‐examined and re‐formulated based on physically consistent approximations to the mass conservation equation. These approximations lead to methods that satisfy all fluid conditions under the assumption of slightly compressible flow and directly yield approximations to the pressure field that are free from spurious oscillations. Penalty function‐type algorithms are developed for direct steady‐state calculations and for time‐dependent simulations of viscous incompressible flows that are based on the bilinear isoparametric quadrilateral element and circumvent the Ladyszhenskaya, Babuska and Brezzi (LBB) condition. Further‐more, methods that eliminate pressure oscillations in the low Mach number region of high‐speed compressible flows are obtained. These methods are tested in examples that show their superior performance in approximating the p

ISSN:0029-5981    

DOI:10.1002/nme.1620362208

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA three‐dimensional multilayer composite finite element method has been developed based on a composite variational functional which takes three in‐plane strains εx, εx, εxyand three transverse stresses σz, σyz, σxzas the basic variables. The continuity of the transverse stresses σz, σyz, σxzacross the laminate thickness is assured aprioriby introducing a partial stress field parameter α which is associated with the lower and upper surfaces of a lamina in a laminate. A method has been developed to form the partial stress field based on the assumed displacement field. With this method, a three dimensional (3‐D) multilayer composite finite element is formulated for stress analysis of composite laminates. A numerical example is given, which shows some advantages of this co

ISSN:0029-5981    

DOI:10.1002/nme.1620362209

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper deals with the numerical integration of a class of rate‐independent elasto‐plastic models. The backward Euler scheme is used to integrate the rate constitutive relations. The non‐linear equations obtained are solved by the Newton method. The consistent tangent modulus is obtained by exact linearization of the algorithm. In the case ofJ2elasto‐plasticity with non‐linear isotropic hardening and non‐linear kinematic hardening (Chaboche‐Marquis model), explicit formulas are derived, without any a

ISSN:0029-5981    

DOI:10.1002/nme.1620362210

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620362211

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY