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  • Open Access


    Modeling of the Inhibition-Mechanism Triggered by `Smartly' Sensed Interfacial Stress Corrosion and Cracking

    Sudib K. Mishra1, J. K. Paik2, S. N. Atluri1

    CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 67-96, 2009, DOI:10.3970/cmes.2009.050.067

    Abstract We present a simulation based study, by combining several models involving multiple time scales and physical processes, which govern the interfacial stress corrosion cracking (SCC) in grain boundaries, layered composites or bi-materials, and the mechanisms of inhibition using `smart' agents. The inhibiting agents described herein, automatically sense the initiation of damage, migrate to the sites and delay the corrosion kinetics involved in the process. The phenomenon of SCC is simulated using the lattice spring model (for the mechanical stresses), coupled with a finite difference model of diffusing species, causing the dissolution of the interfacial bonds. The dissolution is expressed through… More >

  • Open Access


    Energy-Conserving Local Time Stepping Based on High-Order Finite Elements for Seismic Wave Propagation Across a Fluid-Solid Interface

    Ronan Madec1, Dimitri Komatitsch1,2, Julien Diaz3

    CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 163-190, 2009, DOI:10.3970/cmes.2009.049.163

    Abstract When studying seismic wave propagation in fluid-solid models based on a numerical technique in the time domain with an explicit time scheme it is often of interest to resort to time substepping because the stability condition in the solid part of the medium can be more stringent than in the fluid. In such a case, one should enforce the conservation of energy along the fluid-solid interface in the time matching algorithm in order to ensure the accuracy and the stability of the time scheme. This is often not done in the available literature and approximate techniques that do not enforce… More >

  • Open Access


    An Improved Quadrilateral Flat Element with Drilling Degrees of Freedom for Shell Structural Analysis

    H.Nguyen-Van1, N.Mai-Duy1 and T.Tran-Cong1

    CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 81-112, 2009, DOI:10.3970/cmes.2009.049.081

    Abstract This paper reports the development of a simple and efficient 4-node flat shell element with six degrees of freedom per node for the analysis of arbitrary shell structures. The element is developed by incorporating a strain smoothing technique into a flat shell finite element approach. The membrane part is formulated by applying the smoothing operation on a quadrilateral membrane element using Allman-type interpolation functions with drilling DOFs. The plate-bending component is established by a combination of the smoothed curvature and the substitute shear strain fields. As a result, the bending and a part of membrane stiffness matrices are computed on… More >

  • Open Access


    Computational Framework for Durability Design and Assessment of Reinforced Concrete Structures Exposed to Chloride Environment

    Gang Lin1, Yinghua Liu1,2, Zhihai Xiang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.47, No.3, pp. 217-252, 2009, DOI:10.3970/cmes.2009.047.217

    Abstract Deterioration of reinforced concrete (RC) structures due to chloride ingress followed by reinforcement corrosion is a serious problem all over the world, therefore prediction of chloride profiles is a key element in evaluating durability and integrity of RC structures exposed to chloride environment. In the present paper, an integrated finite element-based computational framework is developed for predicting service life of RC structures exposed to chloride environment, which takes environment temperature and humidity fluctuations, diffusion and convection, chloride binding, as well as the decay of durability of structures caused by coupled deterioration processes into account. The decay of RC structures due… More >

  • Open Access


    A Three-Point BVP of Time-Dependent Inverse Heat Source Problems and Solving by a TSLGSM

    Weichung Yeih1,2, Chein-Shan Liu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.2, pp. 107-128, 2009, DOI:10.3970/cmes.2009.046.107

    Abstract We consider an inverse problem for estimating an unknown time dependent heat source H(t) in a heat conduction equation ut(x,t) = uxx(x,t) + H(t). First this inverse problem is formulated as a three-point boundary value problem (BVP) for ODEs discretized from the transformed homogeneous governing equation. To treat this three-point BVP we develop a two-stage Lie-group shooting method (TSLGSM). The novel approach is examined through numerical examples to convince that it is rather accurate and efficient; the estimation error is small even for identifying discontinuous and oscillatory heat sources under noise. More >

  • Open Access


    Investigation of Inherent Deformation in Fillet Welded Thin Plate T-joints Based on Interactive Substructure and Inverse Analysis Method

    Rui Wang1, Jianxun Zhang1, Hisashi Serizawa2, Hidekazu Murakawa2

    CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.1, pp. 97-114, 2009, DOI:10.3970/cmes.2009.044.097

    Abstract In this paper, the inherent deformation of fillet welded thin plate T-joints is studied. The prediction procedure of inherent deformation consists of three parts: part one, a three dimensional (3D) thermo-elastic-plastic analysis using an in house finite element (FE) code of interactive substructure method (ISM) is utilized to obtain the welding distortions; part two, corresponding experiments are carried out to verify the computational results of ISM; part three, using the verified computational results, the inverse analysis is utilized to evaluate the welding inherent deformation. Based on the results in this study, an inherent deformations database of fillet welded thin plate… More >

  • Open Access


    Variational formulation and Nonsmooth Optimization Algorithms in Elastostatic Contact Problems for Cracked Body

    V.V. Zozulya1

    CMES-Computer Modeling in Engineering & Sciences, Vol.42, No.3, pp. 187-216, 2009, DOI:10.3970/cmes.2009.042.187

    Abstract The mathematical statement for contact problem with unilateral restrictions and friction is done in classical and weak forms. Different variational formulation of unilateral contact problems with friction based on principles of virtual displacements and virtual stresses are considered. Especially boundary variational functionals that are used with boundary integral equations have been established. Nonsmooth optimization algorithms of Udzawa type for solution of unilateral contact problem with friction have been developed. Some theoretical results of existence and uniqueness in elastostatic unilateral contact problem with friction are outlined. More >

  • Open Access


    High-Fidelity Tetrahedral Mesh Generation from Medical Imaging Data for Fluid-Structure Interaction Analysis of Cerebral Aneurysms

    Yongjie Zhang1, Wenyan Wang1, Xinghua Liang1, Yuri Bazilevs2, Ming-Chen Hsu2, Trond Kvamsdal3, Reidar Brekken4, Jørgen Isaksen5

    CMES-Computer Modeling in Engineering & Sciences, Vol.42, No.2, pp. 131-150, 2009, DOI:10.3970/cmes.2009.042.131

    Abstract This paper describes a comprehensive and high-fidelity finite element meshing approach for patient-specific arterial geometries from medical imaging data, with emphasis on cerebral aneurysm configurations. The meshes contain both the blood volume and solid arterial wall, and are compatible at the fluid-solid interface. There are four main stages for this meshing method: 1) Image segmentation and geometric model construction; 2) Tetrahedral mesh generation for the fluid volume using the octree-based method; 3) Mesh quality improvement stage, in which edge-contraction, pillowing, optimization, geometric flow smoothing, and mesh cutting are applied to the fluid mesh; and 4) Mesh generation for the blood… More >

  • Open Access


    A rotation free formulation for static and free vibration analysis of thin beams using gradient smoothing technique

    X.Y. Cui1,2, G. R. Liu2,3, G. Y. Li1,4, G. Zheng1

    CMES-Computer Modeling in Engineering & Sciences, Vol.38, No.3, pp. 217-230, 2008, DOI:10.3970/cmes.2008.038.217

    Abstract In this paper, a gradient smoothed formulation is proposed to deal with a fourth-order differential equation of Bernoulli-Euler beam problems for static and dynamic analysis. Through the smoothing operation, the C1 continuity requirement for fourth-order boundary value and initial value problems can be easily relaxed, and C0 interpolating function can be employed to solve C1 problems. In present thin beam problems, linear shape functions are employed to approximate the displacement field, and smoothing domains are further formed for computing the smoothed curvature and bending moment field. Numerical examples indicate that very accurate results can be yielded when a reasonable number… More >

  • Open Access


    Assessment of Mixed Uniform Boundary Conditions for Predicting the Mechanical Behavior of Elastic and Inelastic Discontinuously Reinforced Composites

    D. H. Pahr1, H.J. Böhm1

    CMES-Computer Modeling in Engineering & Sciences, Vol.34, No.2, pp. 117-136, 2008, DOI:10.3970/cmes.2008.034.117

    Abstract The combination of heterogeneous volume elements and numerical analysis schemes such as the Finite Element method provides a powerful and well proven tool for studying the mechanical behavior of composite materials. Periodicity boundary conditions (PBC), homogeneous displacement boundary conditions (KUBC) and homogeneous traction boundary conditions (SUBC) have been widely used in such studies. Recently Pahr and Zysset (2008) proposed a special set of mixed uniform boundary conditions (MUBC) for evaluating the macroscopic elasticity tensor of human trabecular bone. These boundary conditions are not restricted to periodic phase geometries, but were found to give the same predictions as PBC for the… More >

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