Basit Harmonik Harekete Sahip Kam Profilinin Aşınma Modeli

Öz

Makine sistemi içinde ömür tahmini, dizayn açısından teknik ve maddi kayıplardan dolayı oldukça önemlidir. Birbirine sürtünen yüzeylerin aşınması elemanın ömür süresini kısaltan önemli bir parametredir. Aşınma sıradan bir olay olmasına rağmen aşınmanın teorisi ve mekanizması, malzeme özellikleri, hız, pürüzlülük, yağlama, yük v.s. gibi sınır şartlarını kapsayan karmaşık bir yapıdır. Ancak bu kadar çok bileşeni bir matematik model üzerinde sisteme dahil etmek mümkün değildir. Literatürde, kam yüzeyinde atalet kuvvetini ihmal edebilmek adına, kamın hızının ve sistemin kütlesinin sınırlı tutularak sadece yay kuvvetinin modele dahil edildiği analitik ve deneysel sonuçları kapsayan çalışmalar mevcuttur. Bu araştırmada ise, kam mekanizmasını etkileyen yay kuvveti ve izleyicinin ivmelenmesinden doğan atalet kuvvetleri de modelleme çalışmasına dahil edilmiştir..Archard’ın, aşınmanın yük ile ilişkisini ortaya koyan ve aşınma derinliğini veren denklemi mevcut çalışmanın temelini oluşturmuştur. Kurulan matematik model için belirlenen kamın devir sayıları, PTFE (Teflon) olarak belirlenen kam malzemesi ve toplam tur sayısı için kurulan deney düzeneğinde aşınma işlemi yapılmıştır. Daha sonra aşınmış profil üzerinden CMM (koordinat ölçüm makinesi) yardımıyla ölçüm alınarak, kamın üzerinde her 5° lik noktalarda aşınma derinlikleri belirlenmiştir. Matematik model ile tahmin edilen aşınma derinlikleri, deneysel olarak gözlemlenen sonuçlar ile kıyaslanmış ve modelin güvenilir olduğu görülmüştür.

Anahtar Kelimeler

• aşınma
• kam
• aşınma katsayısı

Wear Modeling of Cam Profile with Simple Harmonic Motion

Abstract

Life estimation within the machine system is very important in terms of design due to technical and financial losses. Wear of surfaces rubbing against each other is an important parameter that shortens the life of the element. Although wear is an ordinary phenomenon, the theory and mechanism of wear is affected by material properties, speed, roughness, lubrication, load, etc. It is a complex structure that includes boundary conditions such as However, it is not possible to include so many components in a mathematical model. In the literature, there are studies covering analytical and experimental results in which only the spring force is included in the model by keeping the speed of the cam and the mass of the system limited in order to ignore the inertial force on the cam surface. In this research, the spring force affecting the cam mechanism and the inertia forces arising from the acceleration of the follower were also included in the modeling study. Archard's equation, which reveals the relationship between wear and load and gives the wear depth, formed the basis of the current study. Wearing process was carried out in the experimental setup established for the number of revolutions of the cam determined for the mathematical model, the cam material determined as PTFE (Teflon) and the total number of revolutions. Then, measurements were taken on the worn profile with the help of CMM (coordinate measuring machine) and the wear depths were determined at every 5° points on the cam. The wear depths predicted by the mathematical model were compared with experimentally observed results and the model was found to be reliable.

Keywords

• wear
• cam
• wear coefficient

Kaynakça

1. Archard, J.F., (1980). Wear Theory and Mechanism, ASME Wear Control Handbook.
2. Blanchet, T.A., (1997). The Interaction of Wear and Dynamics of a Simple Mechanism, Journal of Tribology, 119:597-599.
3. Cheng vd., (1994). Wear and Life Prediction of Cam Roller Follower, SAE, 940822:468-479.
4. Czichos, H., (1978). Tribology- a System Approach to the Science and Technology of Friction, Lubrication and Wear, Elseiver.
5. Dickrell III, D.J., Dooner, D. B. ve Sawyer, W. G., (2003). The Evolution of Geometry for a Wearing Circular cam:Analytical and Computer Simulation With Comparison to Experiment, Journal of Tribology, 125:187-192.
6. Dinc, O.S.,Cromer, R. ve Calabrese, S.J., (1995). Redesigning Mechanical Systems for Low Wear Using System Dynamics Modeling,Journal of tribology, 35:1-8.
7. Fries, R.H. ve Rogers, C.A., (1988). Predictions of Cam Wear Profiles, Proceedings of the 15 th Leeds-Lyon Symposium on Tribology, 6-9 September 1988, Leeds.
8. Hugnell, A., Andersson, S., (1994). Simulating Follower Wear in a Cam-Follower Contact, Wear, 179:101-107

9. Hugnell,B.-J. A., Björklund, S. ve Andersson, S., (1996). Simulation of the Mild Wear in a Cam-Follower Contact with Follower Rotation,Wear, 199:202-210.
10. I Bell, J.C., vd., (1985). Prediction of Automotive Valve Train Wear Patterns with Simple Mathematical Models, 1985, Proceedings of the 12 th Leeds-Lyon Symposium on Tribology, 6-9 September 1985, Lyon, France.
11. Jain, V.K. ve Bahadur, S., (1980). Development of a Wear Equaition for Polymer-Metal Sliding in Terms of the Fatigue and topography of the Sliding Surfaces, Wear:237-248.
12. Kar, M.K. ve Bahadur, S. (1980). Estimation of Wear Particle Thickness in Polymer-Metal Sliding, Wear:105-112.
13. Keskin, İ., (2012). Yürek mekanizmalarında Aşınma ve Elastohidrodinamik Yağlama, Doktora tezi,Y.T.Ü., Fen Bilimleri Enstitüsü.
14. Lacey, P.ve Torrance, A.A., (1991). The calculation of Wear Coefficients for Plastic Contacts,Wear145:367-383.
15. Mehenny ve Taylor, (2001). Analysis of the influence of cam surface waviness on the lubrication of an automotive cam and flat faced follower, in:Tribology Research: From Model Experiment to Industrial Problem, Elsevier.
16. Meng, H., (1994). Wear Modeling: Evaluation and Categorization of Mear models, Ph.D., The University of Michigan.
17. Michalski, J., Marszalek, J. Ve Kubiak, K., (2000). An Experimental Study of Diesel Engine Cam and Follower Wear with Particular Reference to the Properties of the Materials, Wear, 240:168-179.
18. Nayak,N., Lakshminarayanan, P.A., Gajendra Babu, M.K., Dani A.D., (2006). Predictions of cam follower wear in diesel engines,Wear, 260:181-192.
19. Özmen, Y., (2004). Makine elemanlarının Tribolojik Hasarları ve Uygun Malzeme Seçimi, Makine Teknolojileri Elektronik Dergisi, 2004(1):31-37.
20. Podra, P. ve Andersson,S., (1999). “Simulating Sliding Wear With Finite Element Method”, Tribology International, 32:71-81.
21. Podra, P. ve Andersson,S., (1999).Finite Element Analysis Wear Simulation of a Conical Spinning Contact Considering Surface Topography, Wear, 224:13-21.
22. Rabinowicz, E., (1965). Friction and Wear of Materials, New York, Wiley. Sawyer, W. G., (2003). Wear Predictions for a Simple-Cam Including the Coupled Evolution of Wear and Load, Lubrication Engineering, 57:31-36.
23. Shigley, J.E. ve Uicker, J.J.,(1995),. Theory of Machines and mechanisms, McGraw-Hill.
24. Soejima,M., vd., (1994).Experimental Studies on Friction and Wear of Cam and Tappet,JSAE Review,23:140-146.
25. Soejima, M., Wakuri, Y. Ve Ejima, Y., (1997). Experimental Studies on Improvement of Lubrication for Cam and Follower, JSAE Review, 18:301-305.