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Search Results (24)
  • Open Access



    Zijie Chena , Sanat Modaka, Massoud Kavianya,* , Richard Bonnerb

    Frontiers in Heat and Mass Transfer, Vol.14, No.1, pp. 1-11, 2020, DOI:10.5098/hmt.14.1

    Abstract In dropwise condensation on vertical surface, droplets grow at nucleation sites, coalesce and reach the departing diameter. In biphilic surfaces, when the hydrophobic domain is small, the maximum droplet diameter is controlled by the shortest dimension where the droplets merge at the boundary. Through direct numerical simulations this size-effect heat transfer coefficient enhancement is calculated. Then the 1-D biphilic surface is optimized considering the size-dependent hydrophilic domain partial flooding (directly simulated as a liquid rivulet and using the capillary limit), the subcooling (heat flux) and condenser length effects. The predicted performance is in good agreement with the available experiments. More >

  • Open Access


    Mechanical Properties of Soil-Rock Mixture Filling in Fault Zone Based on Mesostructure

    Mei Tao1, Qingwen Ren1,*, Hanbing Bian2, Maosen Cao1, Yun Jia3

    CMES-Computer Modeling in Engineering & Sciences, Vol.132, No.2, pp. 681-705, 2022, DOI:10.32604/cmes.2022.019522

    Abstract Soil-rock mixture (SRM) filling in fault zone is an inhomogeneous geomaterial, which is composed of soil and rock block. It controls the deformation and stability of the abutment and dam foundation, and threatens the long-term safety of high arch dams. To study the macroscopic and mesoscopic mechanical properties of SRM, the development of a viable mesoscopic numerical simulation method with a mesoscopic model generation technology, and a reasonable parametric model is crucially desired to overcome the limitations of experimental conditions, specimen dimensions, and experiment fund. To this end, this study presents a mesoscopic numerical method for simulating the mechanical behavior… More >

  • Open Access


    Geometrically-Compatible Dislocation Pattern and Modeling of Crystal Plasticity in Body-Centered Cubic (BCC) Crystal at Micron Scale

    Yuxi Xie, Shaofan Li*

    CMES-Computer Modeling in Engineering & Sciences, Vol.129, No.3, pp. 1419-1440, 2021, DOI:10.32604/cmes.2021.016756

    Abstract The microstructure of crystal defects, e.g., dislocation patterns, are not arbitrary, and it is possible that some of them may be related to the microstructure of crystals itself, i.e., the lattice structure. We call those dislocation patterns or substructures that are related to the corresponding crystal microstructure as the Geometrically Compatible Dislocation Patterns (GCDP). Based on this notion, we have developed a Multiscale Crystal Defect Dynamics (MCDD) to model crystal plasticity without or with minimum empiricism. In this work, we employ the multiscale dislocation pattern dynamics, i.e., MCDD, to simulate crystal plasticity in body-centered cubic (BCC) single crystals, mainly α-phase… More >

  • Open Access


    Size-Dependent Behavior of Macromolecular Solids I: Molecular Origin of the Size Effect

    W. Wei1, David C.C. Lam1

    CMES-Computer Modeling in Engineering & Sciences, Vol.64, No.2, pp. 213-226, 2010, DOI:10.3970/cmes.2010.064.213

    Abstract Molecular rotation is the elastic deformation mechanism underpinning macroscopic deformation in macromolecular solid. In this investigation, molecular mechanic simulations are used to investigate the effect of size on the higher order material properties macromolecular solid. The rotational behavior of molecular coils embedded in beams was examined as a function of the beam size in tension, and in bending where the strain gradients in the bent direction are size-dependent. Analysis showed that the effective elastic modulus is size dependent when strain gradients are significant in bending, but not in tension. Analysis of the molecular rotation behavior indicated that the increase in… More >

  • Open Access


    Computational Simulations of Micro-Indentation Tests Using Gradient Plasticity

    Jian Chen1, Huang Yuan2, Folker H. Wittmann3

    CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 743-754, 2002, DOI:10.3970/cmes.2002.003.743

    Abstract Experimental observation confirms that micro-hardness of metallic materials depends significantly on the indentation depth. In the present paper we discuss simulations of micro-indentation tests based on the gradient plasticity model using the finite element method. The role of intrinsic material length parameters in the gradient plasticity model is investigated. The computational results confirm that the gradient plasticity model is suitable to simulate micro-indentation tests and predicts the depth-dependent hardness in micro- and nano-indentations. Variations of micro-hardness is correlated with the intrinsic material length parameters. More >

  • Open Access


    Fracture behavior of plain concrete beams -- experimental verification of one parameter model

    B.K.Raghu Prasad1, Rabindra Kumar Saha1, A.R.Gopalakrishnan1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.14, No.3, pp. 65-84, 2010, DOI:10.3970/icces.2010.014.065

    Abstract Several different models have been proposed to characterize mode-I crack propagation in concrete. The fictitious crack model proposed by Hillerborg et al. and the blunt crack band theory developed by Bazant & Oh are particularly well suited for a finite element analysis. The two-parameter fracture model proposed by Jenq & Shah is found to be applicable only for beams with s/w=4, where s=span & w=depth of the beam. The general applicability of the model for other testing configurations is not published. In the present study an experimental verification of a one-parameter model based on fundamental equation of equilibrium developed by… More >

  • Open Access


    Determination of the Size Effect Law with One-Size Concrete Specimens of Different Notch Depths

    H. Cifuentes1, F. Medina2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.4, pp. 197-202, 2008, DOI:10.3970/icces.2008.007.197

    Abstract The most popular expression that considers the size effect showed in concrete structures is the size effect law of Bazant. This law depends on two coefficients Gf and cf. For the experimental determination of these coefficients is necessary obtaining the ultimate loads, in three points bending tests, of notched beams with different sizes. In this work, a method to determine the coefficients about the results on identical beams varying the deep of the notch, is presented. The necessary values of loads are obtained by a numerical analysis with FEM that considers non linear behaviour of the concrete material. Next the… More >

  • Open Access


    Higher-Order Stress and Size Effects Due to Self Energy of Geometrically Necessary Dislocations

    N. Ohno1, D. Okumura1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 207-214, 2007, DOI:10.3970/icces.2007.004.207

    Abstract The self energy of geometrically necessary dislocations (GNDs) is considered to inevitably introduce the higher-order stress work-conjugate to slip gradient in single crystals. It is pointed out that this higher-order stress stepwise changes in response to in-plane slip gradient and thus directly influences the onset of initial yielding in polycrystals. The self energy of GNDs is then incorporated into the strain gradient theory of Gurtin (2002). The resulting theory is applied to model crystal grains of size D, leading to a D-1-dependent term with a coefficient determined by grain shape and orientation. It is thus shown that the self energy… More >

  • Open Access


    Size effect studies on a notched plain concrete beam using initial stiffness method

    B.K. Raghu Prasad1, T.V.R.L. Rao1, A.R. Gopalakrishnan1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.3, pp. 179-196, 2009, DOI:10.3970/icces.2009.009.179

    Abstract A simple numerical method namely Initial Stiffness Method using finite element method has been employed to study the size effect which is prominent in concrete structures. Numerous experimental investigations performed on notched plain concrete beams subjected to three point or four-point bending have revealed the fracture process to be dependent on size of the structural member. It was found that, the nominal stress at maximum load decreases as the size of the structure increases. The nominal stress at failure on the characteristic dimension of structure is termed as size effect. This has also been explained in energy concepts as, the… More >

  • Open Access


    The Effect of Fiber Diameter on the Compressive Strength of Composites - A 3D Finite Element Based Study

    Ch,ra S. Yerramalli1, Anthony M. Waas2

    CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 1-16, 2004, DOI:10.3970/cmes.2004.006.001

    Abstract Results from a 3D finite element based study of the compression response of unidirectional fiber reinforced polymer matrix composites (FRPC) are presented in this paper. The micromechanics based study was used to simulate the compressive response of glass and carbon fiber reinforced polymer matrix composites, with a view to understanding the effect of fiber diameter on compression strength. Results from the modeling and simulation indicate the presence of a complex three dimensional stress state in the matrix of the FRPC. Results from the simulation highlight the role of fiber diameter on the compressive response of FRPC. In particular, it is… More >

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