共查询到20条相似文献，搜索用时 15 毫秒
1.
K. M. Liew J. Ren J. N. Reddy 《International journal for numerical methods in engineering》2005,63(7):1014-1040
2.
Kiyoung Yi K. K. Choi Nam H. Kim Mark E. Botkin 《International journal for numerical methods in engineering》2006,68(2):231-266
A continuum‐based shape and configuration design sensitivity analysis (DSA) method for a finite deformation elastoplastic shell structure has been developed. Shell elastoplasticity is treated using the projection method that performs the return mapping on the subspace defined by the zero‐normal stress condition. An incrementally objective integration scheme is used in the context of finite deformation shell analysis, wherein the stress objectivity is preserved for finite rotation increments. The material derivative concept is used to develop a continuum‐based shape and configuration DSA method. Significant computational efficiency is obtained by solving the design sensitivity equation without iteration at each converged load step using the same consistent tangent stiffness matrix. Numerical implementation of the proposed shape and configuration DSA is carried out using the meshfree method. The accuracy and efficiency of the proposed method is illustrated using numerical examples. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
Gye‐Hee Lee Heung‐Jin Chung Chang‐Koon Choi 《International journal for numerical methods in engineering》2003,56(3):331-350
In this paper, an adaptive analysis of crack propagation based on the error estimation by the element‐free Galerkin (EFG) method is presented. The adaptivity analysis in quasi‐static crack propagation is achieved by adding and/or removing the nodes along the background integration cells, those are refined or recovered according to the estimated errors. These errors are obtained basically by calculating the difference between the values of the projected stresses and original EFG stresses. To evaluate the performance of the proposed adaptive procedure, the crack propagation behaviour is investigated for several examples. The results of these examples show the efficiency and accuracy of the proposed scheme in crack propagation analysis. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
Weimin Han Gregory J. Wagner Wing Kam Liu 《International journal for numerical methods in engineering》2002,53(6):1323-1336
Implementation of Dirichlet boundary conditions in mesh‐free methods is problematic. In Wagner and Liu (International Journal for Numerical Methods in Engineering 2001; 50 :507), a hierarchical enrichment technique is introduced that allows a simple implementation of the Dirichlet boundary conditions. In this paper, we provide some error analysis for the hierarchical enrichment mesh‐free technique. We derive optimal order error estimates for the hierarchical enrichment mesh‐free interpolants. For one‐dimensional elliptic boundary value problems, we can directly apply the interpolation error estimates to obtain error estimates for the mesh‐free solutions. For higher‐dimensional problems, derivation of error estimates for the mesh‐free solutions depends on the availability of an inverse inequality. Numerical examples in 1D and 2D are included showing the convergence behaviour of mesh‐free interpolants and mesh‐free solutions when the hierarchical enrichment mesh‐free technique is employed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
5.
Dan Wang Weihong Zhang 《International journal for numerical methods in engineering》2012,90(13):1598-1617
Simultaneous shape optimization of thin‐walled curved shell structures and involved hole boundaries is studied in this paper. A novel bispace parameterization method is proposed for the first time to define global and local shape design variables both in the Cartesian coordinate system and the intrinsic coordinate system. This method has the advantage of achieving a simultaneous optimization of the global shape of the shell surface and the local shape of the openings attached automatically on the former. Inherent problems, for example, the effective parameterization of shape design variables, mapping operation between two spaces, and sensitivity analysis with respect to both kinds of design variables are highlighted. A design procedure is given to show how both kinds of design variables are managed together and how the whole design flowchart is carried out with relevant formulations. Numerical examples are presented and the effects of both kinds of design variables upon the optimal solutions are discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
7.
A new formulation of the element‐free Galerkin (EFG) method is presented in this paper. EFG has been extensively popularized in the literature in recent years due to its flexibility and high convergence rate in solving boundary value problems. However, accurate imposition of essential boundary conditions in the EFG method often presents difficulties because the Kronecker delta property, which is satisfied by finite element shape functions, does not necessarily hold for the EFG shape function. The proposed new formulation of EFG eliminates this shortcoming through the moving kriging (MK) interpolation. Two major properties of the MK interpolation: the Kronecker delta property (?I( s J)=δIJ) and the consistency property (∑In?I( x )=1 and ∑In?I( x )xIi=xi) are proved. Some preliminary numerical results are given. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
8.
Anh-V&#x; Phan Subrata Mukherjee J. R. Ren Mayer 《International journal for numerical methods in engineering》1998,42(8):1391-1407
This paper presents new formulations for computing stresses as well as their sensitivities in two-dimensional (2-D) linear elasticity by the Boundary Contour Method (BCM). Contrary to previous work (e.g. Reference 1), the formulations presented here are established directly from the boundary contour version of the Hypersingular Boundary Integral Equation (HBIE) which can provide accurate numerical results and is very efficient with regard to numerical implementation as well as computational time. The Design Sensitivity Coefficients (DSCs) computed from the above formulations are then coupled with a mathematical programming method, here the Successive Quadratic Programming (SQP) algorithm, in order to solve shape optimization problems. Numerical examples are presented to demonstrate the validity of the new formulations for calculation of DSCs. Also, based on these formulations, shape optimization examples by the BCM are presented here for the first time. © 1998 John Wiley & Sons, Ltd. 相似文献
9.
Wei-Hong Zhang Pierre Beckers Claude Fleury 《International journal for numerical methods in engineering》1995,38(13):2283-2292
This paper presents a general parametric design approach for 2-D shape optimization problems. This approach has been achieved by integrating practical design methodologies into numerical procedures. It is characterized by three features: (i) automatic selection of a minimum number of shape design variables based on the CAD geometric model; (ii) integration of sequential convex programming algorithms to solve equality constrained optimization problems; (iii) efficient sensitivity analysis by means of the improved semi-analytical method. It is shown that shape design variables can be either manually or systematically identified with the help of equality constraints describing the relationship between geometric entities. Numerical solutions are performed to demonstrate the applicability of the proposed approach. A discussion of the results is also given: 相似文献
10.
Ashok V. Kumar Premdheepak S. Periyasamy 《International journal for numerical methods in engineering》2012,91(5):472-490
Mesh independent analysis is motivated by the desire to use accurate geometric models represented as equations rather than approximated by a mesh. The trial and test functions are approximated or interpolated on a background mesh that is independent of the geometry. This background mesh is easy to generate because it does not have to conform to the geometry. Essential boundary conditions can be applied using the implicit boundary method where the trial and test functions are constructed utilizing approximate step functions such that the boundary conditions are guaranteed to be satisfied. This approach has been demonstrated for two‐dimensional (2D) and three‐dimensional (3D) structural analysis and is extended in this paper to model shell‐like structures. The background mesh consists of 3D elements that use uniform B‐spline approximations, and the shell geometry is assumed to be defined as parametric surfaces to allow arbitrarily complex shell‐like structures to be modeled. Several benchmark problems are used to study the validity of these 3D B‐spline shell elements. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
11.
E. Parente L. E. Vaz 《International journal for numerical methods in engineering》2001,50(9):2127-2142
The accuracy problem of the semi‐analytical method for shape design sensitivity analysis has been reported for linear and non‐linear structures. The source of error is the numerical differentiation of the element internal force vector, which is inherent to the semi‐analytical approach. Such errors occur for structures whose displacement field is characterized by large rigid body rotations of individual elements. This paper presents a method for the improvement of semi‐analytical sensitivities. The method is based on the element free body equilibrium conditions, and on the exact differentiation of the rigid body modes. The method is efficient, simple to code, and can be applied to linear and non‐linear structures. The numerical examples show that this approach eliminates the abnormal errors that occur in the conventional semi‐analytical method. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
12.
Yan Liu Ted Belytschko 《International journal for numerical methods in engineering》2010,82(6):699-715
A new support integration technique is proposed, which is similar to those used in truly mesh‐free methods. The contribution of this paper is to exploit the divergence‐free condition for the support integrals to construct quadrature formulas that only require three integration points per particle in two dimensions. Numerical examples show that the proposed integration method can achieve results that agree with manufactured closed‐form solutions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
13.
Eckhard Kirchner Rainer Immel 《International journal for numerical methods in engineering》2000,48(2):185-209
A novel approach towards fully stressed designs in hyperelasticity is discussed leading to closed‐form expressions for the sensitivities of the objective and displacements with respect to design variations. The key idea is the modification of the classical approach coupled with a so‐called design element method offering a lot of parallelism to standard finite element methods. We bypass implicit constraints on dependent quantities and derive an explicit linearly constrained optimization problem solved by means of first‐order procedures. The results obtained with the proposed method are adequate from an engineering point of view though being computed with a simple method. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
14.
L. FOURMENT T. BALAN J. L. CHENOT 《International journal for numerical methods in engineering》1996,39(1):51-65
This paper is the second part of a two-part article about shape optimization of metal forming processes. This part is focused on numerical applications of the optimization method which has been described in the first paper. The main feature of this work is the analytical calculations of the derivatives of the objective function for a non-linear, non-steady-state problem with large deformations. The calculations are based on the differentiation of the discrete objective function and on the differentiation of the discrete equations of the forging problem. Our aim here is to show the feasibility and the efficiency of such a method with numerical examples. We recall the formulation and the resolution of the direct problem of hot axisymmetrical forging. Then, a first type of shape optimization problem is considered: the optimization of the shape of the initial part for a one-step forging operation. Two academic problems allow for checking the accuracy of the analytical derivatives, and for studying the convergence rate of the optimization procedure. Both constrained and unconstrained problems are considered. Afterwards, a second type of inverse problem of design is considered: the shape optimization of the preforming tool, for a two-step forging process. A satisfactory shape is obtained after few iterations of the optimization procedure. 相似文献
15.
Kenjiro Terada Mao Kurumatani 《International journal for numerical methods in engineering》2005,63(15):2102-2123
In this paper an integrated procedure for three‐dimensional (3D) structural analyses with the finite cover method (FCM) is introduced. In the pre‐process of this procedure, the geometry of a structure is modelled by 3D‐CAD, followed by digitization to have the corresponding voxel model, and then the structure is covered by a union of mathematical covers, namely a mathematical mesh independently generated for approximation purposes. Since the mesh topology in the FCM does not need to conform to the physical boundaries of the structure, the mesh can be regular and structured. Thus, the numerical analysis procedure is free from the difficulties mesh generation typically poses and, in this sense, enables us to realize the mesh‐free analysis. After formulating the FCM with interface elements for the static equilibrium state of a structure, we detail the procedure of the finite cover modelling, including the geometry modelling with 3D‐CAD and the identification of the geometry covered by a regular mesh for numerical integration. Prior to full 3D modelling and analysis, we present a simple numerical example to confirm the equivalence of the performance of the FCM and that of the standard finite element method (FEM). Finally, representative numerical examples are presented to demonstrate the capabilities of the proposed analysis procedure. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
16.
Z. Y. Gao R. V. Grandhi 《International journal for numerical methods in engineering》1999,45(10):1349-1373
In complex forging processes, it is essential to find the optimal deformation path and the optimal preform shape that will lead to the desired final shape and service properties. A sensitivity analysis and optimization for preform billet shape in thermo‐mechanical coupled simulation is developed in this work. Non‐linear sensitivity analysis of temperatures, flow‐stresses, strains and strain‐rates are presented with respect to design variables. Both analytical and finite‐difference gradients are employed to validate the effectiveness of sensitivity analysis developed in this work. Numerous iterations of coupled thermo‐mechanical analysis are performed to determine an optimum preform shape based on a given criterion of minimizing the objective function on effective strain variance within the final forging. The design constraints are imposed on die underfill, material scrap, folding defects and temperatures. In addition, a method for material data processing is given in order to determine the flow stress and its derivatives. The shape optimization scheme is demonstrated with the preform designs of an axisymmetric disk and a plane strain problem. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
17.
A novel Lagrangian gradient smoothing method (L‐GSM) is developed to solve “solid‐flow” (flow media with material strength) problems governed by Lagrangian form of Navier‐Stokes equations. It is a particle‐like method, similar to the smoothed particle hydrodynamics (SPH) method but without the so‐called tensile instability that exists in the SPH since its birth. The L‐GSM uses gradient smoothing technique to approximate the gradient of the field variables, based on the standard GSM that was found working well with Euler grids for general fluids. The Delaunay triangulation algorithm is adopted to update the connectivity of the particles, so that supporting neighboring particles can be determined for accurate gradient approximations. Special techniques are also devised for treatments of 3 types of boundaries: no‐slip solid boundary, free‐surface boundary, and periodical boundary. An advanced GSM operation for better consistency condition is then developed. Tensile stability condition of L‐GSM is investigated through the von Neumann stability analysis as well as numerical tests. The proposed L‐GSM is validated by using benchmarking examples of incompressible flows, including the Couette flow, Poiseuille flow, and 2D shear‐driven cavity. It is then applied to solve a practical problem of solid flows: the natural failure process of soil and the resultant soil flows. The numerical results are compared with theoretical solutions, experimental data, and other numerical results by SPH and FDM to evaluate further L‐GSM performance. It shows that the L‐GSM scheme can give a very accurate result for all these examples. Both the theoretical analysis and the numerical testing results demonstrate that the proposed L‐GSM approach restores first‐order accuracy unconditionally and does not suffer from the tensile instability. It is also shown that the L‐GSM is much more computational efficient compared with SPH, especially when a large number of particles are employed in simulation. 相似文献
18.
M. S. Joun S. M. Hwang 《International journal for numerical methods in engineering》1998,41(2):311-335
A new approach to die shape optimal design in shape extrusion is presented. In this approach, the design problem is formulated as an optimization problem incorporating the three-dimensional finite element analysis model, and optimization of the die shape is conducted on the basis of the design sensitivities. The approach is applied to the determination of the die shapes for extrusion of parts with various cross sections including polygons and T sections. © 1998 John Wiley & Sons, Ltd. 相似文献
19.
Kiyoung Yi K. K. Choi Nam H. Kim Mark E. Botkin 《International journal for numerical methods in engineering》2007,71(12):1483-1511
The springback is a manufacturing defect in the stamping process and causes difficulty in product assembly. An impediment to the use of lighter‐weight, higher‐strength materials in manufacturing is relative lack of understanding about how these materials respond to complex forming processes. The springback can be reduced by using an optimized combination of die, punch, and blank holder shapes together with friction and blank‐holding force. An optimized process can be determined using a gradient‐based optimization to minimize the springback. For an effective optimization of the stamping process, development of an efficient design sensitivity analysis (DSA) for the springback with respect to these process parameters is crucial. A continuum‐based shape and configuration DSA method for the stamping process has been developed using a non‐linear shell model. The material derivative is used to develop the continuum‐based design sensitivity. The design sensitivity equation is solved without iteration at each converged load step in the finite deformation elastoplastic non‐linear analysis with frictional contact, which makes sensitivity calculation very efficient. Numerical implementation of the proposed shape and configuration DSA method is performed using the meshfree method. The accuracy and efficiency of the proposed method are illustrated by minimizing the springback in a benchmark S‐rail problem. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
20.
该文利用罚函数法施加边界条件,建立了Reissner-Mindlin板壳无网格法的离散形式,通过数值锁死试验,探讨了EFG法、RPIM以及基于节点积分的无网格法在解决Reissner-Mindlin板壳闭锁问题中所存在的优缺点。所得结果表明,基于匹配近似场和节点积分方案的无网格法在处理剪切闭锁问题时具有优越性。然后以SCNI-MLS无网格法为基础,对Reissner-Mindlin板壳结构的尺寸、形状和轮廓设计进行了统一的设计灵敏度分析,结合约束变尺度序列二次规划法,完成了SCNI-MLS无网格法壳结构优化设计的算例,算例结果验证了所建立灵敏度分析的精度和优化方法的可行性。 相似文献