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, More >

D. S. Liu¹, C. Y. Tsai¹, S. R. Lyu²

CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 147-164, 2009, DOI:10.3970/cmc.2009.011.147

Abstract This study presents a novel numerical method for extracting the tempe -rature-dependent mechanical properties of the gold and aluminum thin-films. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of the thin substrate nanoindented at temperatures ranging from 300-900 K. A simple but effective procedure involving genetic algorithm (GA) and finite element method (FEM) is implemented to extract the material constants of the gold and aluminum substrates. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus, yield stress and the tangent More >

Yeau-Ren Jeng¹,Ping-Chi Tsai¹,Guo-Zhe Huang¹, I-Ling Chang¹

CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 109-126, 2009, DOI:10.3970/cmc.2009.011.109

Abstract This study performs a series of Molecular Dynamics (MD) and Molecular Statics (MS) simulations to investigate the mechanical properties of single-walled carbon nanotubes (SWCNTs) under a uniaxial tensile strain. The simulations focus specifically on the effects of the nanotube helicity, the nanotube diameter and the percentage of vacancy defects on the bond length, bond angle and tensile strength of zigzag and armchair SWCNTs. In this study, a good agreement is observed between the MD and MS simulation results for the stress-strain response of the SWCNTs in both the elastic and the plastic deformation regimes. The… More >

Baolin Wang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.8, No.2, pp. 81-84, 2008, DOI:10.3970/icces.2008.008.081

Abstract When the size of a physical system is smaller than its characteristic dimensions, the macroscopic viewpoint may not be applicable. In addition, experiments at micro/nanometer scale are difficult and the analysis of nano-experimental data is far from simple. This is mostly due to the lack of effective models that are able to study the structural characteristics and mechanics behavior of the micro/nanometer physical systems. Atomic simulation simulation has been used extensively in the investigation of nanoscale phenomena. However, the size limit of atomic simulation is far short to reach the macroscale because of the limitation More >

V.I. Alshits^1,2, R.K. Kotowski^1,3, P. Tronczyk¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.6, No.4, pp. 207-214, 2008, DOI:10.3970/icces.2008.006.207

Abstract The magnetoplastic effect manifests itself in a transformation of the structure of the impurity pinning centers in crystals exposed to an external magnetic field which modifies their mechanical properties. As a result, an ordinary nonmagnetic crystal becomes a smart material whose physical properties may be controlled by means of the external magnetic treatment. The basic features of this phenomenon and its established physical mechanisms are discussed. A series of results of experimental studies and computer simulations of the magnetoplastic effect are presented. More >

Kazuhiko Kakuda¹, Masayuki Sakai¹, Shinichiro Miura²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.5, No.4, pp. 199-204, 2008, DOI:10.3970/icces.2008.005.199

Abstract The applications of a finite element scheme to three-dimensional incompressible viscous fluid flows around circular cylinders are presented. The scheme is based on the Petrov-Galerkin weak formulation with exponential weighting functions. The incompressible Navier-Stokes equations are numerically integrated in time by using a fractional step strategy with second-order accurate Adams-Bashforth scheme for both advection and diffusion terms. Numerical solutions for flow around a circular cylinder are presented. The parallelization and the performance of the present scheme are also checked. 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, More >

B Radhika¹, S S P,a¹, C S Manohar^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 79-110, 2008, DOI:10.3970/cmes.2008.027.079

Abstract Reliability of nonlinear vibrating systems under stochastic excitations is investigated using a two-stage Monte Carlo simulation strategy. For systems with white noise excitation, the governing equations of motion are interpreted as a set of Ito stochastic differential equations. It is assumed that the probability distribution of the maximum in the steady state response belongs to the basin of attraction of one of the classical asymptotic extreme value distributions. The first stage of the solution strategy consists of selection of the form of the extreme value distribution based on hypothesis tests, and the next stage involves More >

C. Moulinec¹, R. Issa², J.-C. Marongiu³, D. Violeau⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 133-148, 2008, DOI:10.3970/cmes.2008.025.133

Abstract The gridless Smoothed Particle Hydrodynamics (SPH) numerical method is preferably used in Computational Fluid Dynamics (CFD) to simulate complex flows with one or several convoluted free surfaces. This type of flows requires distorted meshes with classical Eulerian mesh-based methods or very fine meshes with Volume of Fluid method. Few 3-D SPH simulations have been carried out to our knowlegde so far, mainly due to prohibitive computational investment since the number of particles required in 3-D is usually too large to be handled by a single processor. In this paper, a parallel 3-D SPH code is More >

Thomas Boeck¹, Alexander Nepomnyashchy^2,3, Ilya Simanovskii²

FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.1, pp. 11-20, 2008, DOI:10.3970/fdmp.2008.004.011

Abstract Anticonvection in a two-layer system of mercury and water is studied using three-dimensional direct numerical simulations with a Fourier-Chebyshev spectral method. The two fluid layers have equal thicknesses and are uniformly heated from above. Interface deformations and surface tension gradients are neglected. The quiescent state is replaced by steady hexagons upon increasing the heating from above. We investigate the destabilization of this primary convective pattern in a small and in a large computational domain upon increasing the temperature difference across the two fluid layers. For the large domain the convection cells become disordered at about More >