Q.W. Ma^1,2, J.T. Zhou¹

CMES-Computer Modeling in Engineering & Sciences, Vol.43, No.3, pp. 277-304, 2009, DOI:10.3970/cmes.2009.043.277

Abstract Following our previous work, the Meshless Local Petrov-Galerin me -thod based on Rankine source solution (MLPG_R) will be extended in this paper to deal with breaking waves. For this purpose, the governing equation for pressure is improved and a new technique called Mixed Particle Number Density and Auxiliary Function Method (MPAM) is suggested for identifying the free surface particles. Due to complexity of the problem, two dimensional (2D) breaking waves are only concerned here. Various cases are investigated and some numerical results are compared with experimental data available in literature to show the newly developed method is robust. More >

E. Majchrzak¹, B. Mochnacki², A. L. Greer³, J. S. Suchy⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.41, No.2, pp. 131-146, 2009, DOI:10.3970/cmes.2009.041.131

Abstract Multi-layered thin metal film subjected to a short-pulse laser heating is considered. Mathematical description of the process discussed bases on the equation in which there appear the relaxation time and the thermalization time (dual-phase-lag-model). In this study we develop a three level implicit finite difference scheme for numerical modelling of heat transfer in non-homogeneous metal film. At the interfaces an ideal contact between successive layers is assumed. At the stage of computations a solution of only one three-diagonal linear system corresponds to transition from time t to t + Δt. The mathematical model, numerical algorithm and examples of computations are… More >

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 >

Chun-Lang Yeh¹

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.2, pp. 179-200, 2009, DOI:10.3970/cmes.2009.039.179

Abstract In this research, the atomization process of a nanojet is investigated by molecular dynamics simulation. Liquid argon nanojet made of 44000 Lennard-Jones molecules is examined under various simulation parameters to study their influence on the nanojet atomization process. Snapshots of the molecules, evolution of the density field, and evolution of the intermolecular force are analyzed. The present simulation results can provide insight into the fundamental mechanism of the atomization process and will be helpful for the design of nanojet devices such as nano-printer or nano-sprayer. More >

Shang Ma¹, Xiong Zhang^1,2, Yanping Lian¹, Xu Zhou³

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.2, pp. 101-124, 2009, DOI:10.3970/cmes.2009.039.101

Abstract Numerical simulation of high explosive explosion problems is a big challenge to traditional numerical methods because explosion usually involves extremely large deformation and multi-material interaction of different phases. Recently developed meshfree methods show much advantages over mesh-based method for problems associated with very large deformation. Some of them have been successfully applied to impact and explosion problems, such as smoothed particle hydrodynamics (SPH). Similar to SPH, material point method (MPM) is an efficient meshfree particle method solving continuum problems. With combination of the advantages of Eulerian and Lagrangian methods, MPM is a promising numerical tool for solving large deformation problems,… More >

Fuping Zhou¹, Suresh G. Advani², Eric D. Wetzel³

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 49-66, 2009, DOI:10.3970/cmes.2009.039.049

Abstract Slow drag of a cylinder through a confined, pressurized bed of granules is studied using two-dimensional discrete element method (DEM) simulations. The time-dependent total drag force experienced by the circular cylinder is calculated from the normal and tangential contact forces between the surfaces. To evaluate the role of the granule shape and the aspect ratio on the drag force, the simulation is performed for cylindrical granules, dumbbell-shaped granules, and elliptical granules of three different aspect ratios. Simulation results show that the drag in dumbbell-shaped granules is higher than that in cylindrical granules. In contrast, the drag in elliptical granules decreases… More >

D. S. Liu¹, C.Y. Tsai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 29-48, 2009, DOI:10.3970/cmes.2009.039.029

Abstract Utilizing a thin copper substrate for illustration purposes, this study presents a novel numerical method for extracting the thermo-mechanical properties of a thin-film. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of a thin copper substrate nanoindented at temperatures ranging from 300~1400 K. The load data are then input to an artificial neural network (ANN), trained using a finite element model (FEM), in order to extract the material constants of the copper substrate. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus and the plastic… More >

J. P. Xu¹, Y. Q. Liu^1,2, S. Q. Li³, S. C. Wu⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.38, No.3, pp. 201-216, 2008, DOI:10.3970/cmes.2008.038.201

Abstract For the first time, a special-purpose finite element simulation system CoinForm is developed to analyze the embossing process of commemorative coin, in which one-point reduced integration approach is used in solid element finite element dynamic explicit program. Viscous damping hourglass control algorithm can effectively suppress the spurious modes activated by reduced integration and the computational effort is saved about 93% compared with other method that evaluate anti-hourglass force using stabilization matrix. The embossing process of commemorative coin is then simulated and compared with results from the DEFORM 3D software, which verify the excellent performance of present CoinForm system. According to… More >

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 >

C. Gato and Y. Shie¹

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.3, pp. 269-292, 2008, DOI:10.3970/cmes.2008.033.269

Abstract Numerical simulations of large deformation dynamic fracture in thin shell structures using 3-D meshfree method is presented. Due to the smoothness of the meshfree shape functions, they are well suited to simulate large deformation of thin shell structures while avoiding ill-conditioning as well as stiffening in numerical computations. Dynamic fracture is modeled by simple criterion, i.e. removing connectivity between adjacent nodes once a fracture criterion is met. The main advantage of such 3-D meshfree continuum approach is its simplicity in both formulation and implementation as compared to shell theory approach, or degenerated continuum approach. Moreover, it is believed that the… More >