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Search Results (316)
  • Open Access

    ARTICLE

    Effect of QWR Shape on the Induced Elastic and Piezoelectric Fields

    E. Pan1, X. Jiang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 77-90, 2004, DOI:10.3970/cmes.2004.006.077

    Abstract It is of great importance to understand the factors that contribute to the strain and electrical distributions, which are induced by the misfit strain between a buried quantum wire (QWR) and its surrounding matrix. One of the important factors is the shape or geometry of cross section of the QWR. Utilizing a recent exact closed-form solution [Pan (2004)], we study the model system of QWRs with different shapes and calculate both the surface and internal elastic and piezoelectric fields induced by QWRs embedded in semiconductor GaAs substrates by properly setting the size and location of More >

  • Open Access

    ARTICLE

    Stress Concentrations Caused by Embedded Optical Fiber Sensors in Composite Laminates

    Kunigal Shivakumar1, Anil Bhargava2

    CMC-Computers, Materials & Continua, Vol.1, No.2, pp. 173-190, 2004, DOI:10.3970/cmc.2004.001.173

    Abstract The fiber optic sensor (FOS) embedded perpendicular to reinforcing fibers causes an `Eye' shaped defect. The length is about 16 times fiber optic radius (RFos) and height is about 2RFos. The eye contains fiber optics in the center surrounded by an elongated resin pocket. Embedding FOS causes geometric distortion of the reinforcing fiber over a height equal to 6 to 8 RFos. This defect causes severe stress concentration at the root of the resin pocket, the interface (in the composite) between the optical fiber and the composite, and at 90° to load direction in the composite. The… More >

  • Open Access

    ARTICLE

    PDE-Driven Level Sets, Shape Sensitivity and Curvature Flow for Structural Topology Optimization

    Michael Yu Wang1, Xiaoming Wang2

    CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.4, pp. 373-396, 2004, DOI:10.3970/cmes.2004.006.373

    Abstract This paper addresses the problem of structural shape and topology optimization. A level set method is adopted as an alternative approach to the popular homogenization based methods. The paper focuses on four areas of discussion: (1) The level-set model of the structure’s shape is characterized as a region and global representation; the shape boundary is embedded in a higher-dimensional scalar function as its “iso-surface.” Changes of the shape and topology are governed by a partial differential equation (PDE). (2) The velocity vector of the Hamilton-Jacobi PDE is shown to be naturally related to the shape… More >

  • Open Access

    ARTICLE

    Numerical modeling of shape-memory alloys in orthodontics

    F. Auricchio1, L. Petrini2, R. Pietrabissa3, E. Sacco4

    CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.3&4, pp. 365-380, 2003, DOI:10.3970/cmes.2003.004.365

    Abstract Since 80’s many devices were developed to exploit the unique blend of mechanical and biocompatibility properties of shape memory alloys in orthodontic applications. It results in a high clinical effectiveness, but also in a spreading of technical knowledge on the properties of the single appliances. The goal of the present contribution is to contrast this sense of bewilderness and to prepare the basis for a simulationtool able to support the orthodontist choice. In particular a finite-element beam with a one-dimensional constitutive law, able to describe the SMA super elasticity and shape memory effect, is presented: More >

  • Open Access

    ARTICLE

    Shape Optimization of Elastic Structural Systems Undergoing Large Rotations: Simultaneous Solution Procedure

    Adnan Ibrahimbegovic1, Catherine Knopf-Lenoir2

    CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.2, pp. 337-344, 2003, DOI:10.3970/cmes.2003.004.337

    Abstract In this work we present an unconventional procedure for combining the optimal shape design and nonlinear analysis in mechanics. The main goal of the presented procedure is to enhance computational efficiency for nonlinear problems with respect to the conventional, sequential approach by solving the analysis and design phases simultaneously. A detailed development is presented for the chosen model problem, the 3d rod undergoing large rotations. More >

  • Open Access

    ARTICLE

    Shape Optimization of Body Located in Incompressible Navier--Stokes Flow Based on Optimal Control Theory

    H. Okumura1, M. Kawahara1

    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 71-78, 2000, DOI:10.3970/cmes.2000.001.231

    Abstract This paper presents a new approach to a shape optimization problem of a body located in the unsteady incompressible viscous flow field based on an optimal control theory. The optimal state is defined by the reduction of drag and lift forces subjected to the body. The state equation used is the transient incompressible Navier--Stokes equations. The shape optimization problem can be formulated to find out geometrical coordinates of the body to minimize the performance function that is defined to evaluate forces subjected to the body. The fractional step method with the implicit temporal integration and More >

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