Contents of the Journal of Mechanical Engineering 49, 1 (1998)

KALKER, J. J.: Wheel-rail contact. Theory, algorithms, applications       
(Review paper)                                                            1


RUJBROVA, B., CHMURNY, R.: Detection of rotating machinery failures  
using a simulation method (in Slovak)                                    27


WISZT, E., WISZTOVA, E.: Comparison of acoustical and mechanical 
couplings of vibrating mechanical oscillators                            40


JILEK, M.: Stress transients propagation in a viscoelastic
conical bar. I. Formulation and analysis (in Czech)                      52


ISTENIK, R., KUKUCA, P.: Analysis of OHV distribution mechanism as 
a mass continuum (Engineering note) (in Slovak)                          64

The technology of rail vehicles consists of three parts: vehicle technology, track technology, and the contact between wheel and rail. This paper, on wheel-rail contact, also consists of three parts:
1. The theory of contact (not necessarily wheel-rail)
2. Algorithms
3. Applications

Digital signal processing of mechanical vibration creates new possibilities in vibration-based condition monitoring systems. Orbit and vector analyses of measured mechanical vibration and simulated signals are applied. For orbit analysis, non-recursive digital filters are used. The simulation method of mean averaging with control parameter of shaft vibration displacement that is used in the shaft orbit analysis can gain a new knowledge of a vibration-based diagnostic system.

In the paper the problem of quantitative comparison of acoustical coupling of two mechanical oscillators with purely mechanical coupling between them is solved, and an answer to the question, to what extent there exists an analogy between these two types of coupling, is searched for. Finally, in the case of external harmonic excitation, the method of introducing the acoustical mass and acoustical stiffness is presented and is complemented by numerical calculations for particular cases of the acoustical coupling. Comparison of such relatively simple systems should above all contribute to the clarification of the universal physical substance of acoustical-structural phenomena, though the similar systems can also model to some extent certain dynamic phenomena, e.g. in piston machines, hydraulic devices, etc.

The paper is the first part of an analysis dealing with the axial impact of a slender viscoelastic conical bar upon a rigid half-space. One-dimensional approach and a generalized Maxwell rheological model comprising z parallelly coupled string-piston groups is considered. The equation of motion is solved using the Laplace transform technique resulting in expressions for displacements, velocities, strains, and stresses. Limiting procedures to a viscoelastic cylindrical bar and to an elastic conical bar are provided to be confronted with the solutions and results to those simpler cases at the same initial and boundary conditions.

The distribution mechanism is a very important part of a combustion engine. It influences reliability and life-time of the engine as well as its properties from the point of view of operational economy and impact on the environment.

This paper deals with the distribution mechanism from the point of view of its dynamic properties. It examines a possibility of calculating of the natural frequency of vibrations as a mass continuum in comparison with a usual method of a calculation model with discrete masses.