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APPLICATION OF ACOUSTIC EMISSION IN MONITORING OF FAILURE

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APPLICATION OF ACOUSTIC EMISSION IN MONITORING OF FAILURE IN SLIDE BEARINGS {14 pt Arial, align centre, bold, capital}

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Ireneusz Baran¹, Marek Nowak¹, Wojciech Darski²{12 pt Arial, align centre, bold}

¹Cracow University of Technology, Laboratory of Applied Research, al.Jana Pawla II 37, 31-864 Krakow, Poland; [email protected], [email protected], tel.+48 12 6283250, fax +48 12 6283202

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²Gdansk University of Technology, Ocean Eng. and Ship Technology, ul.G.Narutowicza 11/12, 80-952 Gdansk, Poland; [email protected], tel +48 58 348xxxx, fax +48 58 348xxxx

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Keywords: Frequency analysis, slide bearing, friction factor, bearing bush { 1 line limit }

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Abstract {12 pt Times New Roman, align left, bold}

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The article describes the laboratory tests which make the first stage of the study concerning the use of the AE method to determine the technical state of the slide bearings in engines with self-ignition.

The aim of the presented tests was to compare the recorded signals in relation to the technical state of the material of the bearing bush and to check the possibility of using the AE method when determining the transition moment from the fluid friction into the semi-dry friction in the bearing and signalling the first microdefects of the material of the bearing bush.

The carried out tests do not solve the problem, however they are of a development character and will be continued in the nearest future. {12 pt Times New Roman, justify; 0,5cm [0,2”] indent for paragraph}

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Introduction

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Ship combustion engines with self-ignition have fundamental influence on the profitability of ships and their safety at sea. Therefore, it is very important to ensure the failure-free operation of these engines.

In case of ship engines the maintenance of the sliding abilities of the main bearings and connecting-rod bearings is of special importance because the failures of these bearings constitute almost 30% of the total number of failures in all parts of engines. Since the costs of failures of combustion engines caused by the failures of slide bearings are very high, intensive theoretical and experimental tests of the slide bearings properties have been undertaken. [1, 2] {reference numbers put in [xx], where xx refer to number at end}

The now used methods of monitoring of the technical state of slide bearings signal the state of failure only then, when a considerable degradation of the slide bearings material appears, what in many cases is unsatisfactory in avoiding great defects or failures. Testing by means of the AE method occurs in the real time, therefore this method can be used as a system of the early warning to avoid damage in constructional parts of combustion engines. [3, 4]

The presented tests were carried out on the fully computer controlled laboratory stand PG-2 1Ł type for the examination of slide bearings showed on Fig 1. This stand enables to simulate the real performance conditions of a bearing and to record all the essential parameters, such as: moment of friction, rotational speed, temperatures of the bearing and of the lubricating oil.

Technical data of laboratory stand PG-2 1Ł:

Power of engine: 11kW,
Range of rotation of shaft: 1÷4000 1/min,
Max. transversal load: 150kN,
Diameter of shaft: 76.18_-0.02 or 80.25_-0.100^-0.080 mm,
Length of bush: 36.75_-0.25 or 40,00_-0.2 mm.

There where tested bearing bush MB10 type used in diesel engine C-330 type. This kind of engines are used for drive auxiliary aggregate on ships.

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Technical data of bush MB10 type:

No of catalogue: 1006022010 and 1006021010,
Length: 40,00_-0.2 mm,
Out diameter: 86,00^+0.022 mm,
Thickness of wall: 2.905 mm,
Thickness of steel part: 2.600_-0.2 mm,
Diameter of seating of frame: 86_-0.022 mm.

The trials by the AE method were carried out with the use of the Vallen AMSY5 system as well as with different types of sensors (VS150RIC-Vallen, WD-PAC and others) in order to cover the widest band of frequency measurements. At the same time the AE system enabled to record the test parameters (moment of friction, rotational speed, loading force, temperature) in order to their later correlation with the recorded AE.

The measurement of the bearing with changeable parameters

During the testing of the new bearing a measurement was also taken under the conditions of the changeable rotational speed and step changing of transverse load, what was to lead to the quicker wear of the bearing bush material. After the cyclic changes in rotational speed the AE was recorded during the operation of the bearing under the established conditions. The recorded AE was to detect the appearance of the first damage in the material of the bearing. The sum of distribution of hits in freq band during the changeable rotational speed and step changing of transverse load of the bearing is presented in Fig 2. The visible change in the activity of hits indicated a change in the operation of the bearing. The reason of the sudden increase in the AE activity was the wear of the surface layer of the bearing. These changes were invisible in the parameters (moment of friction, temperature, ...) recorded on the testing lab stand PG-2 1Ł. It was indicated that significantly changing inside slide bearing is dedectable by AE.

It should be noted that these research require a larger number of the carried out trials tests in order to recording AE in a different state of wear of the bearing material.

C
onclusions

The application of the frequency filters allowed to eliminate the majority of noises for the given testing stand, but in the future it will be necessary to determine noises on real objects.

The presented examples illustrate that it is possible to apply the AE method in order to define the state of the bearing material.

The sensitivity of the AE method allows to record the signals which testify the transition from the fluid friction into the mixed friction.

In the future it will be advisable to use the VisualClass application to identify the recorded signals.

References

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1. Burger W. Albers A. Scavino R. Dickerhof M.: Proceedings of WTC2005 World Tribology Congress III, Sept. 12–16, 2005, Washington DC, USA.

2. Scavino R., Burger W., Fritz M., Albers A.: Tribologie Fachtagung 2004, Hungary Academy of Sciences, Kozma: Veszprem, Hungary.

3. Al-Ghambi, Zhechkov D., Mba D.: 26th Europen Conference on Acoustic Emission Testing, Berlin, 2004, Germany.

4. Yoshioka T., Fujiwara T.: Wear, 81 (1), 1994, 183-186.

5. Golaski L., Gebski P., Baran I., Ono K.: Journal of Acoustic Emission, 17 (3-4), 1999, p37.

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