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

Abstracts

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 machine

EDWARD MIKO

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 temperature field

PAVOL KOLLAR

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 and amendments

OLDRICH KROPAC, PETER MUCKA