B.B. Karki¹, R. Kumar¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 35-42, 2007, DOI:10.3970/icces.2007.003.035

Abstract We report important preliminary results from atomistic simulations of grain boundaries in minerals. The recently developed parallel PCMD (polycrystal molec-ular dynamics) program was used to perform structural optimization. In particular, we have simulated the {310}/[001] symmetric tilt grain boundary of MgO as a function of pressure. The simulation cell containing about 55,000 atoms was used. Visualization of the atomic position-time series data show that the structure changes dramatically on compression from a simple open-structure at zero pressure to a highly dense structure containing high coordination state and a screw-like dislocation at high pressure, consistent with More >

Erik T. Thostenson¹, Chunyu Li¹, Tsu-Wei Chou¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 29-34, 2007, DOI:10.3970/icces.2007.003.029

Abstract With their well-known novel mechanical and electrical properties, carbon nanotubes are inherently multifunctional. Toward the development of multifunctional composite materials we have experimentally and theoretically investigated the use of carbon nanotubes as sensors and actuators. In this research work, we consider the nanotube within an external electric field with non-uniform charge distribution. Subsequently the charge induced deformations are investigated. We also demonstrate that conducting carbon nanotube networks formed in an epoxy polymer matrix can be utilized as highly-sensitive sensors for detecting the onset, nature and evolution of damage in advanced polymer-based composites. Using direct-current measurements More >

K.G. Wang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 21-28, 2007, DOI:10.3970/icces.2007.003.021

Abstract A framework of applications of multiscale modeling to property prediction of advanced materials will be briefly presented. A methodology will be shown to link micro-scale to the continuum scale, integrating micro-scale modeling of microstructure with the large Thermo-Calc© database. This paradigm is successfully applied to the case of Fe-12Ni-6Mn maraging steel. We predict the mechanical properties of the maraging steel such as hardness. We found that our predictions in hardness is in agreement with experimental data. More >

S.P. Xiao¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 15-20, 2007, DOI:10.3970/icces.2007.003.015

Abstract A bridging domain method for coupling continuum models with molecular models is described. In this method, the continuum and molecular domains are overlapped in a bridging subdomain, where the Hamiltonian is taken to be a linear combination of the continuum and molecular Hamiltonians. We enforce the compatibility in the bridging domain by Lagrange multipliers or by the augmented Lagrangian method. An explicit algorithm for dynamic solutions is developed. In this paper, the bridging domain multiscale method is employed to study nanotube-based composites. More >

L. Roy Xu¹, Charles M. Lukehart², Lang Li², Huacheng Kuai¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 9-14, 2007, DOI:10.3970/icces.2007.003.009

Abstract Graphitic carbon nanofibers were used to reinforce epoxy resin to form nanocomposite adhesive bonding. Good dispersion and polymer wetting of the GCNF component is evident on the nanoscale. Tensile and shear joint strength measurements were conducted for metal-metal and polymer-polymer joints using pure epoxy and nanocomposite bonding. Very little bonding strength increase, or some bonding strength decrease, was measured. More >

Jie Wang¹, Tong-Yi Zhang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.1, pp. 1-8, 2007, DOI:10.3970/icces.2007.003.001

Abstract Two-dimensional phase field simulations of stress-free ferroelectric nanoparticles with different long-range (LR) electrostatic interactions are conducted based on the time-dependent Ginzburg-Landau equation. Polarization patterns and the toroidal moment of polarization are found to be dependent on the LR electrostatic interaction and the size of the simulated nanoparticle. Phase field simulations exhibit vortex patterns with purely toroidal moments of polarization and negligible macroscopic polarization in the stress-free ferroelectric nanoparticles when the LR electrostatic interaction is fully taken into account. However, a single-domain structure without any toroidal moment of polarization is formed in small particles if the More >

S. Okamoto¹, H. Noguchi²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.4, pp. 131-136, 2007, DOI:10.3970/icces.2007.002.131

Abstract This paper presents a control of walking robot by using inverse dynamics of link mechanisms, which has already been proposed and applied in several in-plane motions. In this method, FEM is used for the discretization of equations of motion. This method calculates nodal forces by evaluating equations of motion in a matrix form, and thus information from the entire system can be handled efficiently, and the torques input to each joint of link mechanisms to achieve required motion are calculated easily. This method is suitable to the feed-forward control of closed-loop or continuously link mechanisms. More >

Zhenguo Tu¹, Fuxing Miao¹, Guojun Sun¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.4, pp. 125-130, 2007, DOI:10.3970/icces.2007.002.125

Abstract In this paper the reverberation ray matrix method, which was developed recently by Professor Pao and his colleagues for analyzing dynamic response of elastic trusses or frames, is extended and used to solve the transient response of frames made of viscoelastic bars. Originally for the solution of elastic structure the matrix (I-R)-1 is expanded into Neumann series to circumvent the difficulty of singularity in reversing the matrix in frequency domain. However, it is not necessary to expand this matrix since there is no singularity problem for viscoelastic frame due to viscous damping. The accuracy and More >

M.V. Hosur¹, F.H. Chowdhury¹, S. Jeelani¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.4, pp. 119-124, 2007, DOI:10.3970/icces.2007.002.119

Abstract In the present study, Nanomer® I-28E, organically modified montmorillonite nanoclay supplied by Nanocor Inc., was used to modify SC-15, a toughened epoxy system using sonication route. Different weight percentage ranging from 1-3% of nanoclay was used. The modified epoxy was then used to fabricate 15-layer plain weave carbon/epoxy composite laminates using vacuum assisted resin transfer molding (VARTM) method. Samples of size 100 x 100 mm were cut from the laminates and were subjected to low-velocity impact loading using an instrumented drop-weight system (Dynatup Model 8210) at three different energy levels of 10, 20 and 30J. More >

M-A Lavoie¹, A. Gakwaya¹, M. Nejad Ensan², D.G. Zimcik²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.4, pp. 111-118, 2007, DOI:10.3970/icces.2007.002.111

Abstract This paper reviews numerical methods that are currently available to simulate bird strike as well as the theory of the event. It also summarizes important parameters and provides guidelines as to how to set up the analysis and how to evaluate a model. The information provided is based on physical properties and available results regarding a bird and its behaviour upon impact. The simulations have been performed with LS-DYNA 970 but can be done in similar dynamic finite elements analysis codes. More >