Pavel Grinfeld¹

CMC-Computers, Materials & Continua, Vol.19, No.3, pp. 239-254, 2010, DOI:10.3970/cmc.2010.019.239

Abstract We model viscosity in the framework of the exact nonlinear equations of fluid film dynamics. The proposed approach yields monotonic dissipation of energy and guarantees that viscous forces are not engaged when the film undergoes rigid motion. With the addition of viscosity, the governing system has all the essential elements - inertia, surface tension, interaction with the ambient medium, influence of external fields and, now, viscosity - for accurate prediction and interpretation of experimental observations. The fluid film is modelled as a two-dimensional manifold. The film's thickness is represented by a surface density function. The resulting system is the fluid… More >

Sujoy Mukherjee¹, Ranjan Ganguli^1,2

CMC-Computers, Materials & Continua, Vol.19, No.2, pp. 105-134, 2010, DOI:10.3970/cmc.2010.019.105

Abstract In this study, variational principle is used for dynamic modeling of an Ionic Polymer Metal Composite (IPMC) flapping wing. The IPMC is an Electro-active Polymer (EAP) which is emerging as a useful smart material for `artificial muscle' applications. Dynamic characteristics of IPMC flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. A comparative study of the performances of three IPMC flapping wings is conducted. Among the three species, it is… More >

Lutz Nasdala¹ , Andreas Kempe¹ and Raimund Rolfes¹

CMC-Computers, Materials & Continua, Vol.19, No.1, pp. 57-104, 2010, DOI:10.3970/cmc.2010.019.057

Abstract In order to understand the underlying mechanisms of inelastic material behavior and nonlinear surface interactions, which can be observed on macroscale as damping, softening, fracture, delamination, frictional contact etc., it is necessary to examine the molecular scale. Force fields can be applied to simulate the rearrangement of chemical and physical bonds. However, a simulation of the atomic interactions is very costly so that classical molecular dynamics (MD) is restricted to structures containing a low number of atoms such as carbon nanotubes. The objective of this paper is to show how MD simulations can be integrated into the finite element method… More >

Zone-Ching Lin¹and Ren-Yuan Wang¹

CMC-Computers, Materials & Continua, Vol.16, No.3, pp. 247-272, 2010, DOI:10.3970/cmc.2010.016.247

Abstract The paper establishes a new three-dimensional quasi-steady molecular statics nanoscale abrasive cutting model to investigate the abrasive cutting behavior in the downpressing and abrasive cutting process of a workpiece in chemical mechanical polishing (CMP) process. The downpressing and abrasive cutting process is a continuous process. The abrasive cutting process is done after the single abrasive particle has downpressed and penetrated a workpiece to a certain depth of a workpiece. The paper analyzes the effects of the abrasive particles with different diameters on action force. It also analyzes the action force change of abrasive particles with different diameters on the projected… More >

Hieu H. Pham¹, Tahir Ça ˇgın¹

CMC-Computers, Materials & Continua, Vol.16, No.2, pp. 175-194, 2010, DOI:10.3970/cmc.2010.016.175

Abstract We analyze the lattice dynamics of Fe in different crystal phases (bcc, fcc and hcp) by using density-functional theory. The study on equations of states indicates that bcc Fe is more stable than fcc and hcp Fe at low pressures. However, dynamical instabilities in lattice vibrations of bcc Fe predict a phase transformation from bcc to hcp at higher pressures. We reported a complete set of second-order and third-order elastic constants of Fe in these three phases. We observed a linear variation in the values of second order elastic constant as a function of increased pressures. The phonon spectra were… More >

E. Hayward¹, C. Deo¹

CMC-Computers, Materials & Continua, Vol.16, No.2, pp. 101-116, 2010, DOI:10.3970/cmc.2010.016.101

Abstract Damage cascades representative of those that would be induced by neutron irradiation have been simulated in systems of pure iron and iron containing 0.01 at.% hydrogen. Results from molecular dynamics simulations using three different embedded-atom method (EAM) type potentials are compared for primary knock-on atom energies of 5, 10, and 20 keV to assess the effect of hydrogen on the primary damage state. We examine the influence of hydrogen on the primary damage state due to a single radiation cascade. These results can serve as an atomistic database for methods and simulations for long time scale evolution of radiation damage. More >

Chen Y J^1,2, Huber N^2,3

CMC-Computers, Materials & Continua, Vol.16, No.1, pp. 1-24, 2010, DOI:10.3970/cmc.2010.016.001

Abstract An efficient wear integration algorithm is crucial for the simulation of wear in complex transient contact situations. By rewriting Archard's wear law for two dimensional problems, the wear integration can be replaced by the total contact force. This avoids highly resolved simulations in time and space, so that the proposed method allows a significant acceleration of wear simulations. All quantities, including the average contact velocity, slip rate and total contact force, which are required for the pressure-force transformation, can be determined from geometric and motion analysis, or alternatively, from Finite Element simulations. The proposed CForce method has been implemented into… More >

Luming Shen¹

CMC-Computers, Materials & Continua, Vol.15, No.3, pp. 241-260, 2010, DOI:10.3970/cmc.2010.015.241

Abstract In this study, molecular dynamics (MD) simulations are performed to form glassy silica from meltedb-cristobalite using cooling rates of 2, 20 and 200 K/ps. The resulting glassy silica samples are then shocked at particle velocities ranging from 0.3 to 11 km/s in the MD simulations. The effect of the cooling rate on the shock wave velocity is observed for particle velocities below 2 km/s. Moreover, the simulated pressure and density of the shocked glassy silica increase as the cooling rate increases. As compared with the experimental data, the MD simulation can approximately identify the initiation of densification and predict the… More >

C.M. Hefferan¹, S.F. Li¹, J. Lind¹, U. Lienert², A.D. Rollett³, P. Wynblatt³, R.M. Suter^1,3

CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 209-220, 2009, DOI:10.3970/cmc.2009.014.209

Abstract We have measured and reconstructed via forward modeling a small volume of microstructure of high purity, well annealed nickel using high energy x-ray diffraction microscopy (HEDM). Statistical distributions characterizing grain orientations, intra-granular misorientations, and nearest neighbor grain misorientations are extracted. Results are consistent with recent electron backscatter diffraction measurements. Peaks in the grain neighbor misorientation angle distribution at 60 degrees (∑3) and 39 degrees (∑9) have resolution limited widths of ≈ 0.14 degree FWHM. The analysis demonstrates that HEDM can recover grain and grain boundary statistics comparable to OIM volume measurements; more extensive data sets will lead to full, five… More >

Shu-Feng Lee¹, Che-Wun Hong^1,2

CMC-Computers, Materials & Continua, Vol.12, No.3, pp. 223-236, 2009, DOI:10.3970/cmc.2009.012.223

Abstract Solid oxides, such as ceria (CeO₂) doped with cations of lower valance, are potential electrolytes for future solid oxide fuel cells. This is due to the theoretically high ionic conductivity at low operation temperature. This paper investigates the feasibility of two potential electrolytes which are samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) to replace the traditional yttria-stablized zirconia (YSZ). Molecular simulation techniques were employed to study the influence of different dopant concentrations at different operation temperatures on the ionic conductivity from the atomistic perspective. Simulation results show that the optimized ionic conductivity occurs at 11.11mol% concentration using both dopants of… More >