5-2010 T R I B O L O G I A 253 Krzysztof SICZEK, Maciej KUCHAR RESEARCH ON THE TRIBOLOGICAL PARAMETERS FOR MATERIALS COUPLES USED FOR VALVES, VALVE GUIDES AND SEAT INSERTS BADANIA PARAMETRÓW TRIBOLOGICZNYCH SKOJARZEŃ MATERIAŁÓW STOSOWANYCH NA ZAWORY, PROWADNICE I GNIAZDA Key words: TiAl alloys, valve, valve guides, seat insert, tribotester, model Słowa kluczowe: stop TiAl, zawór, prowadnica, gniazdo, tribotester, model symulacyjny Summary Research on the tribological properties of TiAl alloys used for valves mating with valve guides and seat inserts, made of cast iron, has been done. The aim of the research has been to obtain values of the coefficient of friction for such tribological pairs and to simulate the dynamics of the The Chair of Precise Design, Technical University of Lodz. Department of Vehicles and Fundamentals of Machine Design, Technical University of Lodz.
254 T R I B O L O G I A 5-2010 material sample rotating plate assembly, characteristic used in the research stand. The modified research stand is presented in the article. During research the values of the coefficient of friction, the temperature of sample, the level of sound and the acceleration of material sample were measured. The model of the research stand was for the simulation of the dynamics for the material sample rotating plate assembly. The plots of the coefficient of friction vs. loading, slide velocity, and the duration of the motion of material sample in respect to the rotating plate are presented in the article. Using simulation results, the values of the damping coefficient were estimated, which allow one to obtain the value for the amplitude of the modelled motion for the material sample in respect to the rotating plate near to the value of the amplitude for the real motion. This estimation allows one to forecast the dynamics of the mentioned assembly for other values of velocity and loading. Fig. 1. MAN tribotester: 1 case, 2 motor, 3 coupling, 4 bearing of plate, 5 plate, 6 sample holder, 7 weights, 8 cantilever, 9 axis of cantilever, 10 blocking Rys. 1. Tribotester MAN: 1 korpus, 2 silnik, 3 sprzęgło, 4 ułoŝyskowanie tarczy, 5 tarcza, 6 uchwyt próbki, 7 obciąŝniki, 8 wspornik, 9 oś wspornika, 10 blokada RESEARCHES ON THE MAN TRIBOTESTER Research conditions All researches have been made on the MAN tribotester. The first analyzed sample has been made of Ti6Al4V alloy. Its diameter and height
5-2010 T R I B O L O G I A 255 have been equal 12.5 mm. The sample has mated with the plate made of cast iron GJL250 (with 1.2% Cr), rotating with 200 rpm. The second analyzed sample has been made of TiAl6Zr4Sn2Mo2 alloy. Its diameter has been equal 5.98 mm and height has been equal 12.5 mm. The sample has mated with the rotating plate made of cast iron GJL250 (with 1.2% Cr), rotating with (200 1000) rpm. The loading for each sample has been equal 22 N. The contact couple has been lubricated by kerosene. The initial value of environment temperature has been equal 294.5 K. The roughness of sample has equaled Ra = 0.8 µm and of the plate has equaled Ra = 0.68 µm. Results of researches Results of friction force, acceleration of the sample in respect to the plate, of sound level, have been presented in Fig. 2 6, for Ti6Al4V, in Fig. 7 10 for TiAl6Zr4Sn2Mo2. 0,6 coefficient of friction [-] 0,5 0,4 0,3 0,2 0,1 µ min µ max µ min incidental mi max incidental µ mean 0 0 10000 20000 30000 40000 50000 60000 number of rotation [-] Fig. 2. The measured coefficient of friction vs. number of rotation Rys. 2. Mierzony współczynnik tarcia w funkcji liczby obrotów
256 T R I B O L O G I A 5-2010 0,3 coefficient of friction [-] 0,25 0,2 0,15 0,1 0,05 0 0 10 20 30 40 50 loading [N] µ min µ max µ min incidental µ max incidental µ mean Fig. 3. The measured coefficient of friction vs. loading of sample Rys. 3. Mierzony współczynnik tarcia w funkcji obciąŝenia próbki temperature [K] 303 298 293 0 10000 200003000040000 5000060000 number of rotation [-] sample environment Fig. 4. Measured temperature of sample vs. number of rotation Rys. 4. Mierzona temperatura w funkcji liczby obrotów sound level [dba] 30 25 20 15 0 10000 20000 30000 40000 50000 number of rotation [-] Fig. 5. The difference between the measured and of the environment sound level vs. rotation Rys. 5. RóŜnica między poziomem hałasu zmierzonym i otoczenia w funkcji liczby obrotów
5-2010 T R I B O L O G I A 257 acceleration [m/s 2 ] 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0.0 0 10000 20000 30000 40000 50000 60000 number of rotation [-] Fig. 6. Mean acceleration of sample in respect to rotating plate vs. number of rotation Rys. 6. Średnie przyspieszenie próbki względem wirującej tarczy w funkcji liczby obrotów µ [ ] 0,5 0,45 0,4 0,35 0,3 0,25 0,2 0,15 0,1 0,05 0 0 200 400 600 800 1000 1200 rpm µ min µ max µ min incidental µ max incidental µ mean Fig. 7. The measured coefficient of friction vs. plate rpm Rys. 7. Mierzony współczynnik tarcia w funkcji liczby prędkości obrotowej tarczy temperature [K] 298 297,5 297 296,5 296 295,5 295 294.5 294 0 2 00 400 600 800 1000 1200 sample environment rpm Fig. 8. Measured temperature of sample vs. plate rpm Rys. 8. Mierzona temperatura próbki w funkcji liczby prędkości obrotowej tarczy
258 T R I B O L O G I A 5-2010 sound level [dba] 25 20 15 0 200 400 600 800 1000 1200 rpm Fig. 9. The difference between the measured and of the environment sound level vs. plate rpm Rys. 9. RóŜnica poziomów hałasu mierzonego i otoczenia w funkcji prędkości obrotowej acceleration [m/s 2 ] 13.13 12.50 11.88 11.25 10.63 10.00 9.38 8.75 8.13 7.50 0 200 400 600 rpm 800 1000 1200 Fig. 10. Mean acceleration of sample in respect to rotating plate vs. plate rpm Rys. 10. Średnie przyspieszenie próbki względem tarczy w funkcji jej prędkości obrotowej SIMULATION The model of research stand, (Fig. 11), similar to [L. 2], has been elaborated for the simulation of dynamic parameters for the material sample rotating plate assembly. Basing on simulation results the values of damping coefficient have been estimated (c = 10 N s/mm), which allow to obtain the value for the amplitude of the modeled motion for the material sample in respect to the rotating plate near to the value of the amplitude for the real motion. The estimation of such damping coefficient allows to forecast the dynamic parameters of the mentioned earlier assembly for other values of slide velocity and loading.
5-2010 T R I B O L O G I A 259 Fig. 11. MAN model: 1 lever, 2 sample, 3 contraweight, 4 plate, 5 bearing, 6 weight Rys. 11. MAN model: 1 wahacz, 2 próbka, 3 odciąŝnik, 4 tarcza, 5 łoŝyska, 6 cięŝar Simulation results for the TiAl6Zr4Sn2Mo2, mating with the plate rotating with 1000 rpm have been shown in Fig. 12 14. The dependency for the coefficient of friction between sample and plate vs. velocity of sample in respect to the plate, has been shown in the Fig. 15. 0.6 µ [-] 0.4 0.2 0 0 2 4 6 8 10 time [s] Fig. 12. The coefficient of friction between the sample and the rotating plate vs. time Rys. 12. Współczynnik tarcia między próbką i wirującą tarczą w funkcji czasu
260 T R I B O L O G I A 5-2010 angular velocity [rd/s] 2 1 0-1 -2 0 2 4 6 7 8 10 time [s] Fig. 13. The angular velocity of the sample in respect to the rotating plate vs. time Rys. 13. Prędkość kątowa próbki względem wirującej tarczy w funkcji czasu 20,000 acceleration [m/s 2 ] 15,000 10,000 5,000 0,000 0 1 2 3 4 5 6 7 8 9 10 time [s] Fig. 14. The tangent acceleration of the sample in respect to the rotating plate vs. time Rys. 14. Przyspieszenie prostopadłe próbki względem wirującej tarczy w funkcji czasu 0,35 0,3 µ [-] 0,25 0,2 0,15 Fig. 15. The coefficient of friction between sample and plate vs. velocity of sample Rys. 15. Współczynnik tarcia między próbką i tarczą w funkcji prędkości próbki CONCLUSION 0,1 1,8 3,8 5,8 7,8 9,8 velocity [m/s] 1. The coefficient of friction between sample made of Ti6Al4V alloy and rotating plate made of cast iron has changed with the increase of number of rotation. After initial increasing up to 0.4, it has decreased below 0.2. The first increasing could result from permanent wear of
5-2010 T R I B O L O G I A 261 friction couple. Next the observed wear debries of cast iron mixed with kerosine could make the kind of the tribological film, what could allow to decrease the coefficient of friction. 2. The coefficient of friction between Ti6Al4V sample and rotating plate has initially decreased with increase of loading the contact area has been greater due plastic deformation. Next the wear debries could increase the coefficient of friction with the increase of loading. 3. The measured and simulated coefficient of friction between TiAl6Zr4Sn2Mo2 sample and rotating plate has increased with the increase of plate rpm. It could be caused by centrifugal force acted on the kerosene, making smaller portion of hydrodynamic friction. REFERENCES 1. Lewis R., Dwyer-Joyce R.S.: Automotive Engine Valve Recesion, Willey, 2001. 2. Mortelette L.: Impact of Mineral Fibres on Brake Squeal Occurances, SAE Brake Coloquium 2009, Tampa, Paper No 2009-01-3050. Acknowledgement The financial support of Ministry of Science and Higher Education by the grant No NN502394535 is greatly appreciated. Streszczenie Recenzent: Marek WIŚNIEWSKI Przeprowadzono badania własności tribologicznych stopów TiAl, uŝywanych dla zaworów współpracujących z Ŝeliwnymi prowadnicami i gniazdami. Celem badań było uzyskanie wartości współczynnika tarcia dla tych par ciernych i symulacja dynamiki układu próbka materiału wirująca tarcza, odpowiadającej wykorzystywanemu stanowisku badawczemu. W artykule przedstawiono zmodyfikowany tribotester typu pin-on-disc. Podczas badań mierzono wartości współczynnika tarcia, temperatury próbki, poziomu hałasu i przyspieszenia próbki materiału, a ich zaleŝności od prędkości, obciąŝenia i liczby obrotów przedstawiono na wykresach. Opracowano model tribotestera do symulacji parametrów dynamicznych układu
262 T R I B O L O G I A 5-2010 próbka materiału wirująca tarcza. W oparciu o wyniki symulacji oszacowano wartości współczynników tłumienia, pozwalające uzyskać symulowana amplitudę ruchu próbki względem wirującej tarczy zbliŝoną do amplitudy rzeczywistego ruchu. Określenie tego współczynnika tłumienia pozwala przewidywać parametry układu przy innych wartościach prędkości i obciąŝenia.