Identyfikatory
Warianty tytułu
Experimental investigation of slide bushes fatigue strength under conditions of rotary load vector
Języki publikacji
Abstrakty
W referacie przedstawiono wyniki badań warstw ślizgowych z wybranych stopów łożyskowych obciążonych wirującą reakcją łożyskową. Taki sposób obciążenia wywołuje w warstwie ślizgowej stan zmiennych naprężeń o asymetrycznym przebiegu w ramach cyklu. Prezentowane przypadki pęknięć zmęczeniowych panwi łożyskowych uzyskano w testach zmęczeniowych prowadzonych na stanowisku MWO (maszyna z wirującym obciążeniem) skonstruowanym i zbudowanym w laboratorium tribologicznym Politechniki Gdańskiej w ramach grantu KBN. Jest to jedyne tego typu stanowisko badawcze w kraju, spełniające wymagania badawcze określone w normie ISO 7905 w zakresie badań zmęczeniowych cienkościennych panwi ślizgowych łożysk poprzecznych. W referacie wyjaśniono metodykę testów zmęczeniowych i analizy ich wyników oraz przedstawiono rezultaty badań panwi wykonanych na bazie stopów AlSn20Cu1 i CuPb30.
Results of research on fatigue strength of dynamically loaded hydrodynamic journal bearing slide bushes are presented in the paper. Investigations have been made in MWO testing machine with rotary load vector at tribological laboratory of the Gdansk University of Technology. A rotary load of the bearing was adjusted by proper selection of unbalanced masses fixed to the machine shaft. A feature of loading pattern i the MWO machine is that not only the bearing reaction but also the whole generated oil film rotates synchronously with rotation of test journal. In the result the identical variable normal stresses occur at each point of slide layer in given cross-section during the loading cycle. These are pulsating compressive radial stresses and variable tangential stresses that alternate from tension to compression. A constant parameter of fatigue tests was rotational speed n = 4000 rpm. A basis of fatigue test on the MWO rig was assumed as 3.6xl000 000 000 of load cycles. An objective of testing was achievement of fatigue failures on the specimen surface within the specified number of load cycles. In fatigue investigation it has been assumed that tested bearing lining reaches its critical state when any macroscopically visible disarrangement of the surface structure, such as first local fissures, a net of cracks (no matter how long) or lining breakouts, appears. Methodology of fatigue tests and pertinent data handling was based on the two-point strategy. Programme of experimental research has included fatigue investigation of thin-walled multilayer half-bearings made of some selected metallic bearing materials. Bimetallic half-bushes consisted of steel shell and lining made of sintered CuPb30 or AlSn20Cu1 alloy. A three-layer variant of the bearing had additionally an overlay of PbSn10Cu3 soft alloy. All bearings were subjected to standard fatigue test in MWO machine. Bearings were lubricated with typical IC engine oil Selectol SAE 20W/40. Feed oil pressure was about 0.55 MPa. Fatigue ratings expressed in terms of critical tangential stresses in slide layer of AlSn20Cu1 and CuPb30 (and overlay) bearing materials were evaluated. Values of critical stresses in investigated bearings, corresponding to the rotary load leading to fatigue cracks, were calculated with the procedure recommended by ISO 7905/1 standard. Mean stress and alternating stress amplitudes at the same circumferential location of the bearing surface layer have been evaluated. Mean stress is normal negative (compressive) stress. It has been proved that the MWO bearing machine fully meets the requirements as a device for testing the journal bearing resistance to fatigue. It results from the analysis of computation of bearing investigated in the MWO machine that at each point of slide surface (and lining layer) in given cross-section of the bush there is generated an identical asymmetric tensile-compression pattern of tangential stresses fluctuating within the load cycle. Thus the mechanism of fatigue damages initiation and propagation in bushes tested in the MWO machine differs from the one that occurs in the bearing investigated in testing machines with other patterns of load generation where only varying negative stresses (radial, tangential and axial) occur in the zone of fatigue cracks observed during the test.
Czasopismo
Rocznik
Tom
Strony
293--305
Opis fizyczny
Bibliogr. 5 poz., rys., tab.
Twórcy
autor
- Politechnika Gdańska, ul. Narutowicza 11/12, 80-952 Gdańsk
Bibliografia
Typ dokumentu
Bibliografia
Identyfikator YADDA
bwmeta1.element.baztech-article-BPS1-0012-0106
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