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1

The monitoring of the bearing joints with excessive axial clearances using the FAM-C AND FDM-A methods

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2010

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nr 27

121-136

EN

The intended aim of the paper is to discuss issues resulting from the observation of thee bearing support elements/components in single-shaft turbine engines with excessive axial clearances. Described are parameters and symptoms of such a condition, probable hazards, as well as capabilities of determining it with the FDM-A1 and FAM-C2 methods. Presented are hypotheses formulated by the Authors on subsequent stages of the wearout of bearing support elements/components in an aircraft turbojet engine, which lead to that excessive axial clearances start to arise. Theory of the issue has been completed with results of diagnostic examination of engines and data from the mechanical inspection of the engines after their disassembly.

2

The FDM-A AND FAM-C methods with regard to effects associated with transmission of rf signals

Gębura A., Mroszkiewicz K.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2010

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nr 27

151-164

EN

The paper deals with issues related to analogies between methods used for conditioning, transmission and reception of diagnostic signals with use of the FAM-C1 and FDM-A2 techniques and corresponding phases that happen to phenomena associated with transmission of information in radio engineering. All these cases include modulation, transmission and demodulation of FM signals. The only difference is the content of information transmitted: for the diagnostic signal with use of FAM-C and FDM-A techniques it is the information about technical condition of kinematic pairs within the driving unit (demonstrated by defined modulation to angular velocity of kinematic pairs) whilst broadcast signals are used to transmit speech, music or specific sequences of sounds (acoustic signals). The transmission medium is also different. In case of RF signals conveyed between the transmitter and the receiver it can be air, vacuum or water whilst transmission with use of FAM-C and FDM-A techniques assumes signal propagation via rigid tension members of the transmission unit deployed between the monitored kinematic pairs and the electric current generator. The difference lies also in ranges of the carrier frequency - for broadcast transmission with FM modulation the carrier frequency is from a dozen of MHz to hundreds of MHz whilst FAM-C and FDM-A techniques assume the frequency from dozens of Hz to several kHz. The last major difference is also in the heterodyne3 frequency, which is from a dozen of MHz to hundreds of MHz for the RF transmission and from several hundreds of Hz up to several kHz for diagnostic purposes (depending on how the electric machine is designed).

3

Metody FDM-A i FAM-C w wykrywaniu i monitorowaniu silnie zaciśniętych łożysk tocznych

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2008

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nr 23

223-235

PL

W artykule przedstawiono badania eksploatacyjne z zastosowaniem metod diagnostycz-nych opartych na wykorzystaniu analizy modulacji częstotliwości prądnic FDM-A i FAM-C. Metod tych użyto do wykrywania i monitorowania ruchu zbyt silnie zaciśniętych łożysk tocznych w węzłach łożyskowych silników turboodrzutowych. Szczególną uwagę poświę-cono obserwacji ruchu tocznego poszczególnych elementów tocznych oraz płynności ruchu koszyka. W wyniku wykonanych badań i diagnoz stwierdzono, że z chwilą powstania zbyt silnego zacisku pierwszym i najważniejszym skutkiem, obserwowanym metodą FDM-A, jest względne zróżnicowanie stochastyczne płynności ruchu poszczególnych ele-mentów tocznych. W wymienionej metodzie zjawisko to obserwowane jest jako niestabil-ność szerokości pasma zbioru charakterystycznego danego łożyska tocznego.

EN

The paper has been intended to present performance tests with the FDM-A and FAM-C diagnostic methods based on the application of analyses of generators' frequency modula-tion. Both the methods have been used to detect and monitor too tightly fitted rolling-element bearings (i.e. bearings that show too large interference fits) in bearing nodes of turbine jet engines. Special attention has been paid to observations of the rolling motion of individual rolling elements and flexibility of motion of the bearing cage. Results of con-ducted tests and diagnosing work allow us to state that as soon as a too tight fit arises, the first and the most important effect observed with the FDM-A method is the relative stochas-tic differentiation of flexibility of motion of particular rolling elements. The phenomenon observed with this method is instability of the bandwidth of a characteristic set of a given rolling-element bearing.