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New methods for finite element model updating problems

AIAA JOURNAL 2006年第6期44卷 1310-1316页

作者： Kuo, Yuen-Cheng Lin, Wen-Wei Xu, Shufang Natl Univ Kaohsiung Dept Appl Math Kaohsiung 811 Taiwan Natl Tsing Hua Univ Dept Math Hsinchu 300 Taiwan Peking Univ Sch Math Sci Beijing 100871 Peoples R China

We consider two finite element model updating problems, which incorporate the measured modal data into the analytical finite element model, producing an adjusted model on the (mass) damping and stiffness, that closely matches the experimental modal data. We develop two efficient numerical algorithms for solving these problems. The new algorithms are direct methods that require O(nk(2)) and O(nk(2) + k(6)) flops, respectively, and employ sparse matrix techniques when the analytic model is sparse. Here n is the dimension of the coefficient matrices defining the analytical model, and k is the number of measured eigenpairs.

关键词： Finite Element Modeling numerical algorithms Lagrange Multipliers Proportional Damping Boeing Distributed Parameter System Frequency Response Functions Conjugate Gradient Method Gaussian Elimination Structural Dynamics

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A Toeplitz algorithm for polynomial J-spectral factorization

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AUTOMATICA 2006年第7期42卷 1085-1093页

作者： Zuniga, Juan Carlos Henrion, Didier CNRS LAAS F-31077 Toulouse France Czech Tech Univ Fac Elect Engn Dept Control Engn Prague 16627 Czech Republic

A block Toeplitz algorithm is proposed to perform the J-spectral factorization of a para-Hermitian polynomial matrix. The input matrix can be singular or indefinite, and it can have zeros along the imaginary axis. The key assumption is that the finite zeros of the input polynomial matrix are given as input data. The algorithm is based on numerically reliable operations only, namely computation of the null-spaces of related block Toeplitz matrices, polynomial matrix factor extraction and linear polynomial matrix equations solving. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： polynomial matrices spectral factorization numerical algorithms computer-aided control system design

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On stabilization of energy for Hamiltonian systems

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COMPUTER PHYSICS COMMUNICATIONS 2006年第1期175卷 15-24页

作者： Wu, X. Zhu, J. F. He, J. Z. Zhang, H. Nanchang Univ Dept Phys Nanchang 330047 Peoples R China Nanjing Univ Dept Astron Nanjing 210093 Peoples R China

We study post-stabilization of numerical integrators for an autonomous Hamiltonian system in the form H = H-1 + H-2, where H-1 and H-2 are two constants of motion. It is better to stabilize the two energies H-1 and H-2, respectively. As a particular case, the effectiveness of post-stabilization by the total energy is equivalent to one by the two independent energies when the splitting Hamiltonian becomes isotropic. (C) 2006 Elsevier B.V. All rights reserved.

关键词： numerical algorithms symplectic integrators energy conservation post-stabilization

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Macroscopic behavior and field fluctuations in viscoplastic composites:: Second-order estimates versus full-field simulations

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2006年第5期54卷 1029-1063页

作者： Idiart, MI Moulinec, H Castañeda, PP Suquet, P Univ Penn Dept Mech Engn & Appl Mech Philadelphia PA 19104 USA Ecole Polytech Mecan Solides Lab CNRS UMR 7649Dept Mecan F-91128 Palaiseau France CNRS LMA UPR 7051 F-13402 Marseille 20 France

This work presents a combined numerical and theoretical study of the effective behavior and statistics of the local fields in random viscoplastic composites. The full-field numerical simulations are based on the fast Fourier transform (FFT) algorithm [Moulinec, H., Suquet, P., 1994. A fast numerical method for computing the linear and nonlinear properties of composites. C. R. Acad. Sci. Paris 11 318, 1417-1423], while the theoretical estimates follow from the so-called "second-order" procedure [Ponte Castaneda, P., 2002a. Second-order homogenization estimates for nonlinear composites incorporating field fluctuations: I-Theory. J. Mech. Phys. Solids 50, 737-757]. Two-phase fiber composites with power-law phases are considered in detail, for two different heterogeneity contrasts corresponding to fiber-reinforced and fiber-weakened composites. Both the FFT simulations and the corresponding "second-order" estimates show that the strain-rate fluctuations in these systems increase significantly, becoming progressively more anisotropic, with increasing nonlinearity. In fact, the strain-rate fluctuations tend to become unbounded in the limiting case of ideally plastic composites. This phenomenon is shown to correspond to the localization of the strain field into bands running through the composite along certain preferred orientations determined by the loading conditions. The bands tend to avoid the fibers when they are stronger than the matrix, and to pass through the fibers when they are weaker than the matrix. In general, the "second-order" estimates are found to be in good agreement with the FFT simulations, even for high nonlinearities, and they improve, often in qualitative terms, on earlier nonlinear homogenization estimates. Thus, it is demonstrated that the "second-order" method can be used to extract accurate information not only for the macroscopic behavior, but also for the anisotropic distribution of the local fields in nonlinear composites. (c) 2005 Elsevier Lt

关键词： creep inhomogeneous material viscoplastic material homogenization numerical algorithms

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Start vector generation for implicit Newmark time integration of the wave equation

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IEEE TRANSACTIONS ON MAGNETICS 2006年第4期42卷 631-634页

作者： Skarlatos, A Clemens, M Weiland, T Tech Univ Darmstadt Inst Theorie Elektromagnet Felder D-64289 Darmstadt Germany Helmut Schmidt Univ Univ Fed Armed Forces Hamburg Dept Elect Engn Chair Theory Elect Engn D-22043 Hamburg Germany

Different extrapolation strategies are presented for the construction of starting values in implicit Newmark time-stepping schemes used for the solution of the electromagnetic wave equation. The implicit character of this schemes implies the solution of a system of linear equations in each time step. The choice of a good start value derived from the extrapolation of the equation system is shown to improve the convergence of the iterative conjugate gradient solver which reduces the total simulation time.

关键词： electromagnetic wave propagation numerical algorithms time-domain methods

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The performance of parallel matrix algorithms on a broadcast-based architecture

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CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2006年第3期18卷 271-303页

作者： Katsinis, C Hecht, D Zhu, M Narravula, H Drexel Univ Dept Elect & Comp Engn Philadelphia PA 19104 USA

Due to advances in fiber-optics and very large scale integration (VLSI) technology, interconnection networks which allow multiple simultaneous broadcasts are becoming feasible. This paper summarizes one such multiprocessor architecture called the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus). It also presents enhancements to the network interface and the cache and directory controllers which support cache block combining, capture and prefetch, and allow complete overlap of processing time with the communication time due to compulsory misses. The paper uses two fundamental matrix algorithms to characterize the impact of each enhancement on performance. Cache miss analysis and results from the execution of these programs on a SOME-Bus simulator show that block capture and prefetch combined with an effective block replacement policy succeed in significantly reducing the miss rate due to compulsory misses as the cache size increases, while a similar increase of cache size in traditional architectures leaves the miss rate due to compulsory misses unaffected. Copyright (c) 2005 John Wiley & Sons, Ltd.

关键词： multiprocessors broadcast architectures numerical algorithms

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algorithms for model reduction of large dynamical systems

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LINEAR ALGEBRA AND ITS APPLICATIONS 2006年第2-3期415卷 322-343页

作者： Penzl, Thilo Univ Calgary Dept Math & Stat Calgary AB T2N 1N4 Canada

Three algorithms for the model reduction of large-scale, continuous-time, time-invariant, linear, dynamical systems with a sparse or structured transition matrix and a small number of inputs and outputs are described. They rely on low rank approximations to the controllability and observability Gramians, which can efficiently be computed by ADI based iterative low rank methods. The first two model reduction methods are closely related to the well-known square root method and Schur method, which are balanced truncation techniques. The third method is a heuristic, balancing-free technique. The performance of the model reduction algorithms is studied in numerical experiments. (c) 2006 Elsevier Inc. All rights reserved.

关键词： dynamical systems Lyapunov equation model reduction balanced truncation Schur method square root method numerical algorithms sparse matrices

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A weight function methodology for the assessment of embedded and surface irregular plane cracks

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ENGINEERING FRACTURE MECHANICS 2006年第17期73卷 2662-2684页

作者： Montenegro, Hugo Lopez Cisilino, Adrian Otegui, Jose Luis Univ Mar del Plata Inst Mat Sci & Technol Welding & Fracture Div INTEMA RA-7600 Buenos Aires DF Argentina

A low cost numerical tool for the calculation of mode I stress intensity factors K in embedded and surface irregular cracks is presented in this paper. The proposed tool is an extension of the O-integral algorithm due to Oore and Burns for the assessment of embedded plane cracks using the weight function methodology. The performance of the O-integral is assessed first by comparing its K results to exact solutions for embedded elliptical and rectangular cracks. From the analysis of this data it is found that the error in the K results systematically depends on the crack aspect ratio and the local crack front curvature. Based on this evidence a corrective function is derived in order to remediate the limitations of the O-integral. Solutions due to Newman and Raju are used to account for the effects of free surfaces and finite thickness. The accuracy of the proposed procedure is assessed by solving a number of examples and by comparing the obtained results to those available in the literature. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： fracture mechanics stress intensity factor three-dimensional cracks numerical algorithms surface cracks

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New one terminal digital algorithm for adaptive reclosing and fault distance calculation on transmission lines

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IEEE TRANSACTIONS ON POWER DELIVERY 2006年第3期21卷 1231-1237页

作者： Radojevic, ZM Shin, JR Konkuk Univ Dept Elect Engn Seoul 143701 South Korea

This paper presents a new numerical spectral domain algorithm devoted to blocking unsuccessful automatic reclosing onto permanent faults and fault distance calculation. Are voltage amplitude and fault distance are calculated from the fundamental and third harmonies of the terminal voltages and currents phasors. The electric arc is modeled with its voltage waveshape defined numerically on the basis of a number of arc voltage records obtained in the high-voltage laboratory. From the calculated arc voltage amplitude, it can be concluded whether the fault is a transient arcing fault or a permanent arcless fault. If the fault is permanent, automatic reclosure should be blocked. The algorithm can be applied for adaptive autoreclosure, distance protection, and fault location. The results of algorithm testing through computer simulation and real field record are given.

关键词： arc resistance electric power systems fault location numerical algorithms protection spectral analysis transmission lines

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A continuum analysis of charge induced ferroelectric domain wall motions

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2006年第1期54卷 86-112页

作者： Kessler, H Balke, H Framatome ANP GmbH FGTM Mech Design D-91050 Erlangen Germany Tech Univ Dresden Inst Solid Mech D-01062 Dresden Germany

A continuum model is presented for the motion of a domain wall in a plane 90 degrees-domain configuration subjected to an isolated extrinsic charge near the surface of a ferroelectric single crystal. Local pinning is postulated for the kinetic law. Before the appearance of the extrinsic charge, all polarization surface charges are taken to be neutralized by environmental charges. The domain wall motion after the appearance of the extrinsic charge is assumed to proceed sufficiently fast without any significant conductive currents on the surface or in the interior of the crystal such that new surface and interface polarization charges remain unscreened and contribute to the ferroelectric anisotropy energy. A non-admissible divergence of the electric field and consequently of the local thermodynamic driving force and of the domain wall velocity appears in the model if the domain wall charged by interface polarization charges intersects the crystal surface charged by surface polarization charges under an arbitrary angle. The physically possible domain wall angle is identified using the condition of a non-divergent driving force. The ferroelectric anisotropy energy and an intrinsic surface energy of the domain wall, however, do not provide stability of the domain wall trajectory against an unlimited increase of its curvature at the surface. The problem has been solved conceptually by proper account of the domain wall bending energy. numerical and dimensional analysis explain also why domain walls driven by extrinsic charges remain almost straight in soft ferroelectrics. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： electromechanical processes ferro-electric material analytic functions numerical algorithms

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