Wyniki wyszukiwania - BazTech

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Out-of-round tram wheels – current state and measurements

Staśkiewicz T., Firlik B.

Archives of Transport

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2018

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Vol. 45, iss. 1

93--103

EN

Railway or tram wheel is never perfectly round and its surface is not ideally smooth, even at the very moment after manufacturing. This induces dynamic interaction between wheel and rail while rolling, which may result in accelerated wear, fatigue cracking, corrugation formation (both on wheels and rails) and intensified vibroacoustic emission. This paper is an attempt of summarising the current scientific achievements concerning out-of-round (OOR) tram wheels. The gathered research may provide an introduction to the broader analysis of this issue in tram technology. However there is still very little scientific works dedicated directly to light rail vehicles such as trams. The measuring methodology of out-of-round tram wheels is also described in this article. Appropriate measurements were made on the wheels of selected vehicles operated by municipal tram company in Poznań. The obtained results allowed to learn the characteristic forms of out-of-round tram wheels, among which, several forms of polygonization (ovalization, triangularization, etc.) were observed. Therefore we confirmed the thesis, that the method of fixing tram wheel rims in the lathe has a significant effect on formation of the unevenness of its rolling surface, both when new (just after turning) and, after some mileage of use, when even small irregularities become amplified. We observed also that the amplitude values from 5th up to 10th harmonic orders were increased during the operation. The initial out-of-round shape of the wheel should be likely present on the worn wheel, but with increased amplitudes of irregularities. Wheel out-of-roundness should be identified and removed at the soonest possible state to prevent its development and generating issues in the future operation, that are for example: rolling stock and infrastructure damage, impaired comfort of passengers and city inhabitants. It makes out-of-round wheels a serious problem to cope with for the vehicle operators, which can lead even to a catastrophe.

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Static Characteristics of Air Gauges Applied in the Roundness Assessment

Jermak C. J., Rucki M.

Metrology and Measurement Systems

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2016

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Vol. 23, nr 1

85--96

EN

In the article, analysis of the work conditions and the metrological characteristics of the air gauges dedicated for the roundness assessment is described. To reach the required accuracy of the acquired data, the phenomena of gas dynamics had to be analyzed in the whole flow through elements of the air gauge. A model based on the second critical parameters was used, because it reflects the true processes of the air flow. As a result, fast and accurate simulations provided series of the characteristics to be considered. Nevertheless, the chosen air gauge configuration underwent the experimental verification of its metrological characteristics. Finally, the entire measurement system Geoform with the gauge head based on the chosen air gauges underwent the accuracy test in order to make sure of its overall measurement quality.

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Dynamics of the non-contact roundness measurement with air gages

Jermak C. J., Rucki M.

Acta Mechanica et Automatica

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2016

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Vol. 10, no. 3

227--232

EN

The paper presents the results of investigations on the air gages dynamic characteristics in the measurement of the round profiles of motor cylinders. The principle of the measuring device is explained, and the analysis of the air gages dynamics is described. The results of dynamic calibration enabled to eliminate those configurations of air gages that may not meet the requirements of the measurement they were designed for. After the proper air gages were chosen, the entire system underwent the accuracy test and passed it successfully revealing the method accuracy better than 10% compared to the reference measurement.

4

Journal bearing performance and metrology issues

Sharma S., Hargreaves D., Scott W.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 32, nr 1

98-103

EN

Purpose: In this paper, a radial clearance of a journal bearings and the metrology of the radial clearance measurement is described. Design/methodology/approach: In this experimental study out-of-roundness and radial clearance of journal bearings were measured with high precision and the impact of their metrology was examined on the specific oil film thickness of the bearing. Some metrological issues were emerged and these should be taken into account when bearings are designed. Findings: An investigation showed that the radial clearance measurements can vary from one measuring device to another and the specified clearance may not necessarily meet the design criteria of specific oil film thickness. The study indicates that the radial clearance measurement can differ from one measuring device to another depending upon the precision that can be achieved by the device. The radius of the bearing or the shaft also varies along the circumference, mainly due to out-of-roundness. The out-of-roundness contributes to the error in radial clearance measurement and hence similar to the cut off length specified with the surface roughness, the out-of-roundness needs to be specified with the radial clearance. Practical implications: The radial clearance of a journal bearing is a key design parameter and bearing performance mainly depends upon this parameter. In this paper was showed that the metrology of the radial clearance measurement plays a significant role and not only that the bearing manufacturer or the user of the bearing is aware of this fact but the bearing designer must also take this fact into account while designing bearings Originality/value: This paper showed that The radial clearance is a sensitive micro-geometry parameter and hence metrology plays a vital role in making decisions.