CMC-Vol. 40, No. 3, 2014

Open Access

ARTICLE

Optimization of Johnson-Cook Constitutive Model for Lead-free Solder Using Genetic Algorithm and Finite Element Simulations
D.S.Liu¹, C.L.Hsu^1,2
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 More >

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ARTICLE

Effect of Gravitational Field and Temperature Dependent Properties on Two-Temperature Thermoelastic Medium with Voids under G-N Theory
Mohamed I. A. Othman¹, Magda E. M. Zidan¹, Mohamed I. M. Hilal¹
CMC-Computers, Materials & Continua, Vol.40, No.3, pp. 179-201, 2014, DOI:10.3970/cmc.2014.040.179
Abstract This investigation is aimed to study the two dimensional problem of thermoelastic medium with voids under the effect of the gravity. The modulus of elasticity is taken as a linear function of the reference temperature and employing the two-temperature generalized thermoelasticity. The problem is studied in the context of Green-Naghdi (G-N) theory of types II and III. The normal mode analysis method is used to obtain the exact expressions for the physical quantities which have been shown graphically by comparison between two types of the (G-N) theory in the presence and the absence of the More >

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Numerical Study on Mechanical Properties of Steel Fiber Reinforced Concrete by Statistical Second-order Two-scale Method
Y. Zhang¹, Y. F. Nie², Y. T. Wu¹
CMC-Computers, Materials & Continua, Vol.40, No.3, pp. 203-218, 2014, DOI:10.3970/cmc.2014.040.203
Abstract The present study aims to evaluate the mechanical properties of steel fiber reinforced concrete (SFRC) by the statistical second-order two-scale (SSOTS) method. At first, the representation for microstructure of SFRC is described by a concept of statistical screen. According to the microstructure representation, the SSOTS method is displayed in a concise way. This method is on the basis of asymptotic expansion homogenization and Monte Carlo method, and can calculate the local strain and stress field through the two-order displacement solution. As the classical homogenization method, the expression of homogenized elastic modulus is derived analytically. Then More >

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Anti-plane Circular Nano-inclusion Problem with Electric Field Gradient and Strain Gradient Effects
Shasha Yang, Shengping Shen¹
CMC-Computers, Materials & Continua, Vol.40, No.3, pp. 219-239, 2014, DOI:10.3970/cmc.2014.040.219
Abstract As well known, gradient theories can describe size effects that are important in nano-scale problems. In this paper, we analyze the Eshelby-type anti-plane inclusion problem embedded in infinite dielectric body by considering both strain gradient and electric field gradient effects to account for the size effect and high-order electromechanical coupling effect. The size-dependent Eshelby and Eshelby-like tensor, strain, stress, electric field and electric displacement components are derived explicitly by means of Green's function method. Theoretical results indicate that strain and electric field are decoupled for anti-plane inclusion problem while stress field and electric displacement are More >

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