Communications in Numerical Methods in Engineering最新文献_第7页

On group-theoretic computation of natural frequencies for spring–mass dynamic systems with rectilinear motion 直线运动弹簧-质量动力系统固有频率的群理论计算

Communications in Numerical Methods in Engineering Pub Date : 2007-04-20 DOI: 10.1002/CNM.1003

A. Zingoni

{"title":"On group-theoretic computation of natural frequencies for spring–mass dynamic systems with rectilinear motion","authors":"A. Zingoni","doi":"10.1002/CNM.1003","DOIUrl":"https://doi.org/10.1002/CNM.1003","url":null,"abstract":"In this article, group theory is employed to simplify the computation of natural circular frequencies for spring–mass dynamic systems with rectilinear motion. The systems are by themselves not physically symmetric (or they exhibit only very weak symmetry properties), but they can be transformed into graphs that preserve all the connectivities between masses and springs, while featuring the maximum possible symmetry. For physical dynamic systems exhibiting symmetry, a well-known group-theoretic approach involves the computation of the full stiffness matrix of the system first, followed by transformation of this matrix in order to cast it into block-diagonal form. The present approach involves the direct assembly of much smaller stiffness matrices within the decomposed subspaces of the problem, and is therefore computationally more efficient. Of particular focus in this study are transformed configurations belonging to ‘triangular’ symmetry groups, whose symmetries are difficult to exploit using conventional methods. It is shown how the repeating eigenvalues associated with the degenerate subspaces of such symmetry groups can easily be obtained. Copyright © 2007 John Wiley & Sons, Ltd.","PeriodicalId":51245,"journal":{"name":"Communications in Numerical Methods in Engineering","volume":"24 1","pages":"973-987"},"PeriodicalIF":0.0,"publicationDate":"2007-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CNM.1003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51531235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 33

Upper bound limit analysis using discontinuous quadratic displacement fields 不连续二次位移场的上限分析

Communications in Numerical Methods in Engineering Pub Date : 2007-03-27 DOI: 10.1002/CNM.998

A. Makrodimopoulos, C. Martin

{"title":"Upper bound limit analysis using discontinuous quadratic displacement fields","authors":"A. Makrodimopoulos, C. Martin","doi":"10.1002/CNM.998","DOIUrl":"https://doi.org/10.1002/CNM.998","url":null,"abstract":"The classical lower and upper bound theorems allow the exact limit load for a perfectly plastic structure to be bracketed in a rigorous manner. When the bound theorems are implemented numerically in combination with the finite element method, the ability to obtain tight bracketing depends not only on the efficient solution of the arising optimization problem, but also on the effectiveness of the elements employed. Elements for (strict) upper bound analysis pose a particular difficulty since the flow rule is required to hold throughout each element, yet it can only be enforced at a finite number of points. For over 30 years, the standard choice for this type of analysis has been the constant strain element combined with discontinuities in the displacement field. Here we show that, provided certain conditions are observed, conventional linear strain triangles and tetrahedra can also be used to obtain strict upper bounds for a general convex yield function, even when the displacement field is discontinuous. A specific formulation for the Mohr-Coulomb criterion in plane strain is given in terms of second-order cone programming, and example problems are solved using both continuous and discontinuous quadratic displacement fields.","PeriodicalId":51245,"journal":{"name":"Communications in Numerical Methods in Engineering","volume":"24 1","pages":"911-927"},"PeriodicalIF":0.0,"publicationDate":"2007-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CNM.998","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51604621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 83

A simple error estimator for extended finite elements 扩展有限元的简单误差估计

Communications in Numerical Methods in Engineering Pub Date : 2007-03-26 DOI: 10.1002/CNM.1001

S. Bordas, M. Duflot, Phong Le

引用次数: 99

Topology and graph products; eigenproblems in optimal structural analysis 拓扑与图积;结构最优分析中的特征问题

Communications in Numerical Methods in Engineering Pub Date : 2007-03-14 DOI: 10.1002/CNM.1000

A. Kaveh, H. Rahami

引用次数: 15

A new approach to avoid excessive numerical diffusion in Eulerian–Lagrangian methods 欧拉-拉格朗日方法中避免过多数值扩散的新方法

Communications in Numerical Methods in Engineering Pub Date : 2007-03-05 DOI: 10.1002/CNM.996

A. Younes, M. Fahs, P. Ackerer

引用次数: 18

Note on the determination of the ignition point in forest fires propagation using a control algorithm 关于用控制算法确定森林火灾传播中着火点的注意事项

Communications in Numerical Methods in Engineering Pub Date : 2007-02-09 DOI: 10.1002/CNM.990

M. Bergmann, O. Séro-Guillaume, S. Ramezani

引用次数: 3

An interpolation‐based local differential quadrature method to solve partial differential equations using irregularly distributed nodes 基于插值的局部微分正交法求解不规则分布节点的偏微分方程

Communications in Numerical Methods in Engineering Pub Date : 2007-01-12 DOI: 10.1002/CNM.978

Hang Ma, Q. Qin

{"title":"An interpolation‐based local differential quadrature method to solve partial differential equations using irregularly distributed nodes","authors":"Hang Ma, Q. Qin","doi":"10.1002/CNM.978","DOIUrl":"https://doi.org/10.1002/CNM.978","url":null,"abstract":"To circumvent the constraint in application of the conventional differential quadrature (DQ) method that the solution domain has to be a regular region, an interpolation-based local differential quadrature (LDQ) method is proposed in this paper. Instead of using regular nodes placed on mesh lines in the DQ method (DQM), irregularly distributed nodes are employed in the LDQ method. That is, any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of irregularly distributed nodes in the local physical domain. The feature of the new approach lies in the fact that the weighting coefficients are determined by the quadrature rule over the irregularly distributed local supporting nodes with the aid of nodal interpolation techniques developed in the paper. Because of this distinctive feature, the LDQ method can be consistently applied to linear and nonlinear problems and is really a mesh-free method without the limitation in the solution domain of the conventional DQM. The effectiveness and efficiency of the method are validated by two simple numerical examples by solving boundary-value problems of a linear and a nonlinear partial differential equation. Copyright © 2007 John Wiley & Sons, Ltd.","PeriodicalId":51245,"journal":{"name":"Communications in Numerical Methods in Engineering","volume":"17 1","pages":"573-584"},"PeriodicalIF":0.0,"publicationDate":"2007-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CNM.978","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51603537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

A simple way to introduce fibers into FEM models 将纤维引入有限元模型的一种简单方法

Communications in Numerical Methods in Engineering Pub Date : 2007-01-11 DOI: 10.1002/CNM.983

L. Vanalli, R. R. Paccola, H. B. Coda

{"title":"A simple way to introduce fibers into FEM models","authors":"L. Vanalli, R. R. Paccola, H. B. Coda","doi":"10.1002/CNM.983","DOIUrl":"https://doi.org/10.1002/CNM.983","url":null,"abstract":"This communication proposes a simple way to introduce fibers into finite element modelling. This is a promising formulation to deal with fiber-reinforced composites by the finite element method (FEM), as it allows the consideration of short or long fibers placed arbitrarily inside a continuum domain (matrix). The most important feature of the formulation is that no additional degree of freedom is introduced into the pre-existent finite element numerical system to consider any distribution of fiber inclusions. In other words, the size of the system of equations used to solve a non-reinforced medium is the same as the one used to solve the reinforced counterpart. Another important characteristic is the reduced work required by the user to introduce fibers, avoiding ‘rebar’ elements, node-by-node geometrical definitions or even complex mesh generation. An additional characteristic of the technique is the possibility of representing unbounded stresses at the end of fibers using a finite number of degrees of freedom. Further studies are required for non-linear applications in which localization may occur. Along the text the linear formulation is presented and the bounded connection between fibers and continuum is considered. Four examples are presented, including non-linear analysis, to validate and show the capabilities of the formulation. Copyright © 2007 John Wiley & Sons, Ltd.","PeriodicalId":51245,"journal":{"name":"Communications in Numerical Methods in Engineering","volume":"24 1","pages":"585-603"},"PeriodicalIF":0.0,"publicationDate":"2007-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CNM.983","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51603670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 31

Comments on: Efficient placement of rigid supports using finite element models 评论:使用有限元模型有效地放置刚性支撑

Communications in Numerical Methods in Engineering Pub Date : 2007-01-01 DOI: 10.1002/cnm.898

M. Friswell

引用次数: 1

Boundary-value recovery by the Trefftz approach in structural inverse problems 结构逆问题的Trefftz方法边值恢复

Communications in Numerical Methods in Engineering Pub Date : 2006-12-29 DOI: 10.1002/CNM.974

M. Karaś, A. Zieliński

{"title":"Boundary-value recovery by the Trefftz approach in structural inverse problems","authors":"M. Karaś, A. Zieliński","doi":"10.1002/CNM.974","DOIUrl":"https://doi.org/10.1002/CNM.974","url":null,"abstract":"The main idea of the Trefftz approach to numerical modelling consists in the application of trial functions identically fulfilling governing partial differential equations of a considered problem. When boundary conditions of the problem are defined a priori (direct formulation), they can be used to calculate the unknown solution coefficients. In structural inverse problems, the above conditions can be partly unknown (its shape is assumed to be unchanged). Instead, we can measure certain quantities inside the investigated structure and then approximately define the whole boundary-value problem. \u0000 \u0000 \u0000 \u0000Usually, solutions of inverse problems are connected with minimization of certain functionals, which results in optimization procedures. This kind of formulation is presented in detail and illustrated by numerical examples. The properties of the Trefftz approach allow to formulate alternative, much more effective, simple direct algorithms, which considerably shorten the time of computer calculations. This is clearly shown in several computational benchmarks for 2D elastic inverse problems. The proposed algorithms can be applied to any inverse boundary-value problem, for which the complete T-function sets are known. Copyright © 2006 John Wiley & Sons, Ltd.","PeriodicalId":51245,"journal":{"name":"Communications in Numerical Methods in Engineering","volume":"24 1","pages":"605-625"},"PeriodicalIF":0.0,"publicationDate":"2006-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CNM.974","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51603387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8