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Search Results (19)
  • Open Access


    Optimization of Johnson-Cook Constitutive Model for Lead-free Solder Using Genetic Algorithm and Finite Element Simulations

    D.S.Liu1, C.L.Hsu1,2

    CMC-Computers, Materials & Continua, Vol.40, No.3, pp. 165-178, 2014, DOI:10.3970/cmc.2014.040.165

    Abstract To ensure the reliability of microelectronics packages, the high strain rate deformation behavior of the solder joints must be properly understood. Accordingly, the present study proposes a hybrid experimental / numerical method for determining the optimal constants of the Johnson-Cook (J-C) constitutive model for 96.5Sn-3Ag-0.5Cu (SAC305) solder alloy. In the proposed approach, FEM simulations based on the J-C model are performed to describe the load-time response of an SAC305 ball solder joint under an impact velocity of 0.5 m/s. The optimal values of the constitutive model are then determined using an iterative Genetic Algorithm approach based on a comparison of… More >

  • Open Access


    Moving Finite Element Simulation of Various Fracture Path Prediction in Materials Containing Holes and Inclusions

    Nishioka T.1, sugami M.1, Fujimoto T.1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.1, No.3, pp. 119-126, 2007, DOI:10.3970/icces.2007.001.119

    Abstract In this paper, the simulations of fatigue crack propagation and dynamic fracture path prediction are carried out for specimens containing circular holes or inclusions, using the moving finite element method based on Delaunay automatic triangulation. And, we compared the numerical results with the experimental results. More >

  • Open Access


    Prediction of Crack Location in Deep Drawing Processes Using Finite Element Simulation

    S. K. Panthi1, Sanjeev Saxena2

    CMC-Computers, Materials & Continua, Vol.32, No.1, pp. 15-28, 2012, DOI:10.3970/cmc.2012.032.015

    Abstract Sheet metal forming process like deep drawing subjected to large irreversible deformation. It leads to high strain localization zones and then internal or superficial micro defects. The deformation behavior and crack initiation in cylindrical deep drawing of aluminum alloy are simulated by the elasto-plastic finite element simulation. A1100-O and A2024-T4 sheet material are used in the simulation. Material properties based on the tensile and plane strain test is used in the simulation. Six cases are simulated in this study with different blank diameter. The simulated results are compared with the experimental results in terms of the crack location and critical… More >

  • Open Access


    An Enhanced Dipole Model Based Micro-Macro Description for Constitutive Behavior of MRFs

    Chunwei Zhao1,2, Xianghe Peng1,2,3, Jin Huang4, Ning Hu1,5,6

    CMC-Computers, Materials & Continua, Vol.30, No.3, pp. 219-236, 2012, DOI:10.3970/cmc.2012.030.219

    Abstract The validity of the two conventional micro-macro descriptions for MRFs, based respectively on the exact dipole model and the simplified dipole model, is examined with the results obtained with the commercially available finite element (FE) code ANSYS. It is found that although the simplified dipole model can match better the result by FE computation, there is still a marked difference. An enhanced dipole model is then suggested, which takes into account the contribution of the magnetized particles to magnetic field. Making use of a statistical approach and neglecting the interaction between particle chains, a micro-macro approach is developed for the… More >

  • Open Access


    A 3-D Visco-Hyperelastic Constitutive Model for Rubber with Damage for Finite Element Simulation

    Ala Tabiei1, Suraush Khambati2

    CMES-Computer Modeling in Engineering & Sciences, Vol.105, No.1, pp. 25-45, 2015, DOI:10.3970/cmes.2015.105.025

    Abstract A constitutive model to describe the behavior of rubber from low to high strain rates is presented. For loading, the primary hyperelastic behavior is characterized by the six parameter Ogden’s strain-energy potential of the third order. The rate-dependence is captured by the nonlinear second order BKZ model using another five parameters, having two relaxation times. For unloading, a single parameter model has been presented to define Hysteresis or continuous damage, while Ogden’s two term model has been used to capture Mullin’s effect or discontinuous damage. Lastly, the Feng-Hallquist failure surface dictates the ultimate failure for element deletion. The proposed model… More >

  • Open Access


    MicroCT/Micromechanics-Based Finite Element Models and Quasi-Static Unloading Tests Deliver Consistent Values for Young's Modulus of Rapid-Prototyped Polymer-Ceramic Tissue Engineering Scaffold

    K.W. Luczynski1, A. Dejaco1, O. Lahayne1, J. Jaroszewicz2, W.Swieszkowski2, C. Hellmich1

    CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.6, pp. 505-529, 2012, DOI:10.3970/cmes.2012.087.505

    Abstract A 71 volume-% macroporous tissue engineering scaffold made of poly-l-lactide (PLLA) with 10 mass-% of pseudo-spherical tri-calcium phosphate (TCP) inclusions (exhibiting diameters in the range of several nanometers) was microCT-scanned. The corresponding stack of images was converted into regular Finite Element (FE) models consisting of around 100,000 to 1,000,000 finite elements. Therefore, the attenuation-related, voxel-specific grey values were converted into TCP-contents, and the latter, together with nanoindentation tests,entered a homogenization scheme of the Mori-Tanaka type, as to deliver voxel-specific (and hence, finite element-specific) elastic properties. These FE models were uniaxially loaded, giving access to the macroscopic Young's modulus of the… More >

  • Open Access


    Study of the Underfill Effect on the Thermal Fatigue Life of WLCSP-Experiments and Finite Element Simulations

    Shaw-Jyh Shin1, Chen-Hung Huang2, Y.C. Shiah3

    CMES-Computer Modeling in Engineering & Sciences, Vol.40, No.1, pp. 83-104, 2009, DOI:10.3970/cmes.2009.040.083

    Abstract Owing to the CTE (Coefficient of Thermal Expansion) mismatch among solder joints, IC (Integrated Circuit) chip, and PCB (Printed Circuit Board), electronic packages shall experience fatigue failure after going though a period of thermal cycling. As a major means to enhance the reliability of the solder joints, underfill is often dispensed to fill the gap between the die and the substrate. This study aims at investigating how the underfill may affect the thermal fatigue life of WLCSP (Wafer Level Chip Scale Package) by means of FEA (finite element analysis). In this study, the thermal fatigue life of the WLCSP was… 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 >

  • Open Access


    Finite Element Simulations of Four-holes Indirect Extrusion Processes of Seamless Tube

    Dyi-Cheng1, Syuan-Yi Syong1

    CMC-Computers, Materials & Continua, Vol.13, No.3, pp. 191-200, 2009, DOI:10.3970/cmc.2009.013.191

    Abstract Finite element simulations are performed to investigate the plastic deformation behavior of Ti-6Al-4V titanium alloy during its indirect extrusion through a four-hole die. The simulations assume the die, mandrel and container to be rigid bodies and ignore the temperature change induced during the extrusion process. Under various extrusion conditions, the present numerical analysis investigates the effective stress and profile of product at the exit. The relative influences of the friction factors, the temperature of billet and the eccentricity of four-hole displacement are systematically examined. The simulations focus specifically on the effects of the friction factor, billet temperature and eccentricity ratio… More >

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