TONDL, A. PUST, L.: On the phenomenon "Parametric anti-resonance" 125 KOMPIŠ, V., MURČINKOVÁ, Z., FERENCEY, V.: Computational simulation of composite materials reinforced by fibres with large aspect ratio 139 JIN XU-XING: Optimum synthesis method of mechanical press driven by non-circular gears 155 ELBASHBESHY, E. M. A., EMAM, T. G., SAYED, E. A.: Effect of pressure work on free convection flow from a vertical circular cone with variable surface heat flux 169
A. TONDL, L. PUST
The aim of this contribution is to present a survey of the main research results dealing with the phenomenon "parametric anti-resonance" and to stimulate the interests of designers for its application in engineering practice especially in machinery and for devices where vibrations are undesirable for the safe run. It is interesting that this phenomenon can be used for vibrations suppressing for all kind of excitations, i.e. not only externally, but also for self-excitation and undesirable parametric resonance.
V. KOMPIŠ, Z. MURČINKOVÁ, V. FERENCEY
A new type of mechanical press which has a crank-slider mechanism and a pair of non-circular
gears is presented in this paper. The crank is attached to the driven gear, so that the motion law of the
slider is determined by the non-\linebreak
-circular gears, and the displacement curve of the slider can be easily
changed to meet different processing requirements, which is necessary for the multi-variety and
small batch manufacturing.
The purpose of this study is to achieve excellent motion characteristics of the press; firstly, a quintic polynomial curve is suggested for defining the desired motion of the slider. Then, an optimal method is proposed to obtain the pitch curves of the non-circular gears, the object function and constraints for optimization are discussed and suggested to obtain feasible design. Finally, an example is introduced to illuminate the press performance; the results demonstrate that the optimum synthesis method is effective.
E. M. A. ELBASHBESHY, T. G. EMAM, E. A. SAYED
The effect of pressure work on free convection flow from a vertical circular cone with variable surface heat flux is considered. Similarity solutions for boundary layer equations are found to exist when the surface heat flux is proportional to xn (where x is distance measured from the leading edge). The governing system of partial differential equations is reduced to a system of ordinary differential equations. Mathematica has been used to solve such system after obtaining the missed initial conditions. Comparison of numerical results is made with previously published results under the special cases, the results are found to be in a good agreement. The solutions are presented in terms of local skin-friction, local Nusselt number, velocity and temperature profiles for values of Prandtl number, pressure work parameter and heat flux gradient parameter.