Contents of Journal of Mechanical Engineering 54, 3 (2003)
MELTZER, G., PHONG DIEN, N.: Some new advances in gear diagnostics
by application of the wavelet transform 129
MIKO, E.: Geometrical microstructure of steel surface faces milled
at a CNC milling machine 149
KOLLAR, P.: Visco-elastic contact problem of a circular plate
and a half-space in steady temperature field (in Slovak) 165
Letter to the Editor
KROPAC, O., MUCKA, P.: Relations between characteristics
of longitudinal unevenness of roads: erratum and amendments 188
Some new advances in gear diagnostics by application of the wavelet transform
GOTTFRIED MELTZER, NGUYEN PHONG DIEN
Time-Frequency Analysis (TFA) as well as Time-Scale Analysis (TSA) are
well-proved and widely applied signal processing methods in communication,
informatics and other fields. Papers from all branches of the mechanical
engineering were until now mostly restricted to application of one (or
comparison of two) processing method in one individual field of demonstration.
This paper will give a short insight into a global attempt to analyze the
effectiveness of TFA and TSA in vibro-acoustical diagnostics of machines. For
this purpose a simple PC-software for signal processing and extraction of
diagnostic features was developed and tested. The advantage of this program is
in its ease of use also for engineers in practice.
During the program test
with the objective of fault-detection, localisation and assessment at helical
spur gears, some new strategies were implemented and interesting results
obtained, which we found worth of publishing. They are improvements of the
visual estimation of TSA plots, especially, by the task-specific balance of
time and frequency resolution and by the display of the ordering spectra vs.
the rotational angle in polar coordinates and additional different approaches
for extracting of quantitative diagnostic features from the TFA or TSA.
Given examples demonstrate a large step towards a better recognition of
machine or process condition.
Geometrical microstructure of steel surface faces milled at a CNC milling
It has been established that machining parameters, such as feed per tooth,
rotational speed, tool path interval, and cutter setting angle influence
surface roughness in ball-end milling. A scanning microscope was used for
registering and analysing the morphology of milled surfaces. SEM photographs
of surfaces with longitudinal and lateral profiles are included and discussed.
The influence of machining factors on the surface geometrical microstructure
is also evaluated. The study is focused on the evaluation of spatial surface
roughness. The results show that the geometrical microstructure of milled
surfaces depends considerably on feed, rotational speed and tool path interval.
Visco-elastic contact problem of a circular plate and a half-space in steady
The paper deals with temperature stresses and deformations of a circular plate
of a medium thickness interacting with Boussinesq half-space being subject of
a long-term thermal load. The material of the plate and foundation creep in
time. The thermal load is a steady temperature field originated in heating of
the plate surface in a distinct area. Time response of the plate and
foundation material is introduced according to the linear hereditary creep
theory of Boltzmann-Volterra. Effects of creep and relaxation, due to their
time discontinuities, are interpreted as, so called, right-sided Schwartz
distributions. Basic functional system of condition equations is solved by an
indirect method in Laplace's transformation region from where the
time-dependent solution is constructed by the inverse procedure of
Erdelyi-Schapery. Numerical calculations with analysis of the obtained
results are demonstrated by a concrete example.
Leter to the Editor
Relations between characteristics of longitudinal unevenness of roads: erratum
OLDRICH KROPAC, PETER MUCKA
The paper complements the previous paper of the same authors [I]. In the first
part, corrections of some wrong statements, which appeared in it, are given.
In the second part, a simulation study is added, which, in some respect,
reflects a less known property of the IRI algorithm and points
the dependence of IRI on the design speed of the particular road
way. A proposal for introducing qualitative classes based on IRI
is also given.