Mechanics and Control
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ISSN 2083-6759
e-ISSN: 2300-7079
Issue Date
2012
Volume
Vol. 31
Number
No. 4
Description
Journal Volume
Mechanics and Control
Vol. 31 (2012)
Projects
Pages
Articles
Worm gear analysis in terms of numerical modelling
(2012) Biegaj, Mariusz; Dziedziech, Kajetan; Macheta, Adam
A worm gear mechanism, widely used in numerous mechanical applications, is the essential component in energy efficiency considerations. Compared to traditional gearboxes, worm gear is characterized by lower value of efficiency, provided by the manufacturers as 70-90%. However, the efficiency level can differ depending on the specific conditions of operation such as output torque, input rotational velocity, ambient temperature and type of lubrication. In order to analyse and simulate the worm gear mechanism in mechanical systems, it is essential to establish the actual efficiency value for specific conditions. The following article contains the description of efficiency test performed for the worm gear as a part of tram pantograph system studied in frame of ESTOMAD project. The aim of the experiment was to determine the actual efficiency value of the transmission tested. The worm gear has been tested in an open loop configuration, therefore the efficiency has been determined basing on input and output torque and rotational velocity measurements. The tests have been performed for various output torques and input velocities to obtain view on losses in worm gear under different operational conditions, paying special attention to the velocity that drives the pantograph mechanism. The efficiency changes with the output torque variation, while the impact of rotational velocity level on the mentioned value is minimal. The results of measurements are used in modelling phase of worm gear component in 1D simulation environment, particularly creating new model and its correlation and validation.
Analysis of vibrations generated by the multi-body model of a planetary gear
(2012) Dąbrowski, Dariusz; Adamczyk, Jan
In the paper the dynamic model of an one-stage planetary gear was presented. The model was developed on the basis of a multi-body dynamics method. To conduct dynamic simulations the specialized multi-body dynamics software was used. In the study the tests results for steady state operations of the planetary gear were presented. In the paper the meshing force signals were analyzed. The vibrations generated by the model consist of carrier and gear meshing frequency harmonics. On the spectra the amplitude modulations of the gear meshing frequencies harmonics were observed.
Yield stress modification in the strip yield model
(2012) Machniewicz, Tomasz
From among of the deterministic models for fatigue crack growth predictions suitable for metallic materials a Strip Yield (SY) model can be considered the most general and powerful crack growth prediction tool owing to its applicability to arbitrary variable amplitude load histories. The SY model based on the conception of plasticity at the crack tip according to Dugdale, modified to accounting for the crack closure phenomena. The original Dugdale model is only valid for plane stress state conditions at the crack tip. Accounting for the triaxial stress conditions at the crack tip requires the yield stress modification, what is usually realized by using the suitable constraint factors. In the paper several concepts of the yield stress modification in the SY model have been described and notified. As it has been concluded the another important role of the constraint factors, in addition to accommodating in the SY model the triaxial stress state, is covering indirectly various processes which do affect crack growth, but cannot be treated in a rigorous way.
Multichannel data acquisition system for vibroacoustic signals
(2012) Piechowicz, Janusz; Pawlik, Paweł
The authors have made an attempt to construct a multi-channel data acquisition system for vibroacoustic signals, collected for analysis of acoustic field distributions in enclosed rooms and determination of surface acoustic impedance values at the wall surfaces. The scope of the study required a synchronic registration of acoustic pressure by 24 measurement microphones, determination of the phase-shift angles between the measured signals and determination of the vibration velocity for the loudspeaker diaphragm. The paper presents the first stage of the research, directly related to the multi-channel system for registration and analysis of vibroacoustic signals. The constructed research tools, due to their modular structure, can be adapted to new tasks, extended by adding new elements (further measurement cards, microphones, accelerometers etc.), what ensures greatflexibility and suitability of the system for realization of advanced acoustical measurements. Open source code and users request for specialized acoustic analyses make the developed software packages a highly prospective research tool both for today and tomorrow.
Endurance analysis of Koepe pulleys with peripheral ribs
(2012) Wolny, Stanisław; Ładecki, Bogusław
There are numerous hoisting installations operated in Polish mines that are equipped with winding gear incorporating a Koepe pulley reinforced with peripheral ribs, where the symptoms of fatigue cracking are often revealed. Current repairs of those areas help mitigate for this undesirable phenomenon for a short time only. In order to eliminate this problem, steps have been taken to identify the origins and propagation patterns of fatigue cracks in Koepe pulleys. A numerical model of a Koepe pulley is developed and the endurance analysis is performed by the FEM method, preceded by a dynamic analysis of the normal duty cycle of the hoisting installation. The results of dynamic and endurance analyses are verified through experimental testing on a real object, involving force and stress measurements taken at selected points on the Koepe pulley. Those measurement data provide the background for the fatigue endurance assessment and new redesigns of the Koepe pulley structure.