Contents of Journal of Mechanical Engineering 57, 2 (2006) 




SUMELKA, W., LODYGOWSKI, T.: Substitute acoustic boundary 
impedance conditions for boundaries with periodic geometry
in computer simulations of acoustic planar wave travelling               59

HAZEM ALI ATTIA:  Hall effect on transient Hartmann flow and 
heat transfer of a power-law fluid between parallel porous 
plates under exponentially decaying pressure gradient                    71

KIREITSEU, M., TOMLINSON, G. R., HUI, D., BOCHKAREVA, L., 
RONGONG, J. A.: Advanced design and modelling of nanoparticle-
-reinforced damping materials                                            95

ALTENBACH, H., NAUMENKO, K., PYLYPENKO, S., RENNER, B.: 
On the free particle rotation in a polymer melt                         112

Abstracts



Substitute acoustic boundary impedance conditions for boundaries with periodic geometry
in computer simulations of acoustic planar wave travelling

WOJCIECH SUMELKA, TOMASZ LODYGOWSKI

In the paper the substitute acoustic boundary impedance conditions for boundaries with periodic geometry are considered. The complex geometry of boundary is treated as planar one with the equivalent impedance conditions obtained from the process of numerical homogenization. The computer simulations used the finite element method (FEM) and all analysis took into consideration the sinusoidal acoustic planar waves. Homogenized boundaries significantly decrease number of degrees of freedom in acoustic analysis, what, in many cases, is the only way to overcome extremely high hardware requirements.

Hall effect on transient Hartmann flow and heat transfer of a power-law fluid
between parallel porous plates under exponentially decaying pressure gradient

HAZEM ALI ATTIA

The transient Hartmann flow of an electrically conducting viscous incompressible non-Newtonian power-law fluid between two parallel horizontal non-conducting porous plates is studied with heat transfer without neglecting the Hall effect. A sudden uniform and exponential decaying pressure gradient, an external uniform magnetic field that is perpendicular to the plates, and uniform suction and injection through the surface of the plates are applied. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are taken into consideration. Numerical solutions for the governing nonlinear momentum and energy equations are obtained using finite difference approximations. The effects of the Hall term, the parameter describing the non-Newtonian behaviour, and of the velocity of suction and injection on both the velocity and temperature distributions, as well as on the dissipation terms are examined.

Advanced design and modelling of nanoparticle-reinforced damping materials

MAKSIM KIREITSEU, GEOF R. TOMLINSON, DAVID HUI, LIYA BOCHKAREVA, JEM A. RONGONG

The focus in this paper is to provide a multiscale modelling and computational tools towards the development of the next generation vibration damping materials/systems that are light-weight, vibration and shock resistant. The research work concentrates on an investigation related to theoretical and experimental dynamic characterization of carbon nanotube-reinforced materials across the length scales. The outcome of the research work is expected to have wide-ranging technical benefits with direct relevance to industry in areas of transportation (aerospace, automotive, rail), precise engineering and civil infrastructure.

On the free particle rotation in a polymer melt

HOLM ALTENBACH, KONSTANTIN NAUMENKO, SERGIY PYLYPENKO, BARBARA RENNER

For the reason of weight reduction nowadays in engineering applications many load transmitting structures are of polymeric materials and can be manufactured by injection molding. Their mechanical properties can significantly be improved if the polymer is reinforced by short fibers. From experiments it is known that the fiber orientation is usually not constant. Already during the design of structures it is necessary to predict the fiber orientation and thereby the mechanical properties like stiffness and strength.

A fiber can be regarded as a rigid particle. One basic aspect considering the motion of fibers in the polymer melt during the injection molding process is their rotation. For a single particle it is analyzed based on the laws of dynamics. The geometry of the particle is defined, its tensor of inertia is assumed to be transversally isotropic. Since friction with the medium must be taken into account, a model is developed with which its influence on the particle can be described. For this purpose a moment of viscous friction is introduced.