Contents of Journal of Mechanical Engineering 58, 4 (2007) 




RAJI, A., HASNAOUI, M., BAHLAOUI, A., NAÏMI, M., EL AYACHI, R.: 
Mixed convection in inclined channels with localized heating blocks     185

GRZEGOŻEK, W., NOGOWCZYK, P.: Analysis of the influence of 
selected motion parameters of a vehicle on steering effort              201

BALLO, I., CHMÚRNY, R.: Critical speed passage of a flexible slender 
rotor by re-tuning                                                      216

BEDNARCZYK, J., GŁUCH, G.: Stress and strain states of inductor 
coils used for electrodynamic machining of metals                       228

Abstracts



Mixed convection in inclined channels with localized heating blocks

ABDELGHANI RAJI, MOHAMMED HASNAOUI, AHMED BAHLAOUI, MOHAMED NAÏMI, RACHID EL AYACHI

The two-dimensional mixed convection heat transfer in inclined channels containing two heating rectangular sources is numerically studied using the Navier-Stokes equations with the Boussinesq approximation. Results in terms of streamlines, isotherms and heat transfer rate are presented for different combinations of the governing parameters, namely, the relative height of the sources (1/8£ B£ 1/2), the Prandtl number (0.01 £ Pr £ 5), the Reynolds number (10 £ Re £ 50), the inclination of the channel with respect to the horizontal surface (0° £ F £ 90°) and the Rayleigh number (103 £ Ra £ 2 ´ 105). The ratio QCE = QC/QE of the heat quantities, leaving the channel through the cold wall, QC, and through the exit, QE, is presented to identify the most favorable issue to the heat transfer in the studied configuration. The results obtained show that it is possible to control the heat evacuation through the cold wall and the exit of the channel by choosing adequate combinations of the governing parameters.

Analysis of the influence of selected motion parameters of a vehicle on steering effort

WITOLD GRZEGOŻEK, PAULINA NOGOWCZYK

When power steering system is designed, the problem of feeling the motion conditions by a driver occurs among others. Steering effort is one out of quantities used for the evaluation of a steering system. The aim of the research presented in this paper is to determine the influence of vehicle velocity and lateral acceleration on steering effort. This determination can be useful for the elaboration of new methods of adjustment of classical power steering systems or for the determination of the virtual reluctance in steer-by-wire systems in order to make driver's feeling of motion conditions favourable.

Critical speed passage of a flexible slender rotor by re-tuning

IGOR BALLO, RUDOLF CHMÚRNY

The paper analyses the flexural vibration of an elastic rotor with linear elastic supports during its first critical speed passage. Before its critical speed passage, the system will be re-tuned in a linear fashion, i.e. the support stiffness will be linearly decreased.

The mathematical model is formulated using the Large Finite Element Method. The matrix equation thus generated is then transformed to the standard form based on a small parameter theory. The solution of this system of equations yields the transient phenomena time dependence and the corresponding stationary state.

Numerical results are presented in two ways. Firstly, the time dependence of the maximal amplitude of rotor transversal deflection during the passage is given. Secondly, the dependence of the largest amplitude of the rotor transversal deflection at the precise start and termination of the re-tuning is presented.

Stress and strain states of inductor coils used for electrodynamic machining of metals

JÓZEF BEDNARCZYK, GERARD GŁUCH

The paper presents the results of research on strength of inductors used as tools in electrodynamic machining of pipes, carried out at the AGH-University of Science and Technology in Cracow. The paper describes the nature of volumetric Lorentz forces acting on the coils of compressing and expanding inductors, followed by the determination of stress and dislocation patterns formed in coils by Lorentz forces using the methods of numerical finite elements. Discussed issues are essential when designing durable inductors for industrial purposes