This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Fatigue Life of Diesel Engine Cams in Accelerated Test Environment
Technical Paper
2003-01-0052
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
Surface distress involving pitting, scuffing, frosting, and high friction leads to failure in fuel injector cams. The relationship amongst relative features of these failures is extremely complex. They comprise local plastic straining, cyclic softening/hardening, crack initiation/propagation, impact, skidding, and third body formation. From an industrial application point of view determination of failure probability and service life expectancy are important. Although factors such as operating loads, speeds, number of loading cycles, surface roughness, lubrication conditions, and third body particles are known to affect the life of gears and bearings, the effect of such factors on the life of cam-follower contact is little known. In particular, failure of cams due to pitting under conditions of rolling/sliding friction is unclear. The objective of this research was a) to investigate premature failure of injector cams in Diesel Engines and b) to determine the pitting life of fuel injector cams in terms of number of cycles of the cam, through laboratory test simulation and analysis. Towards the accomplishment of this goal, an instrumented cam-follower test rig facility was designed and fabricated, followed by experimentation to reproduce field failures in a laboratory environment under accelerated test conditions. Different cams were run at contact stresses ranging from 3000 MPa to 3800 MPa. In the first cam, after the initial running in at 3000 MPa, the load was increased to produce a base circle stress of 3800 MPa. Within 5 minutes of running at this loading condition catastrophic failure of the cam occurred, as characterized by squeal, chatter, smoke, and significant increase in the contact loads and accelerations. Examination of the cam surface indicated severe gouging and scoring of the surface, particularly on the ramp-down side of the cam. Similar failures on the ramp-down side of the cam can also be seen in field failures, but the exact mechanism of back sliding in field failures is not clearly known. This experiment was very valuable in terms of replicating the damage that was commonly found on the cams failed in the field. It is noteworthy to mention that it is the first time this backside-sliding phenomenon on cam has been observed in a laboratory environment. A second and third cam were tested for approximately 700 hours (<50,000K loading cycles) before the first signs of failure (pitting) was observed. Results from these tests indicate that normal contact fatigue failure occur after 50 million loading cycles are applied to the cam. Forces, acceleration, power spectral density (PSD) function, surface roughness, and wear measurements at different locations of the cams clearly indicate an increase with increase in loading cycles. Cam surface distress observed from this test is basically mild wear on the base circle with severe pitting on ramp-down side occurring after 50 million contact cycles. The lab tests having been conducted on full size components and operating at or near the field conditions have significant practical value. The findings of this research are useful in extending the understanding of failure of diesel engines primarily due to failure of cams roller-follower system.
Recommended Content
Citation
Shareef, I. and Karmali, A., "Fatigue Life of Diesel Engine Cams in Accelerated Test Environment," SAE Technical Paper 2003-01-0052, 2003, https://doi.org/10.4271/2003-01-0052.Also In
References
- Wolff, R. Nonaka, T. Kubo, A. Matsuo, K. 1992 “Thermal Elastohydrodynamic Lubrication of Rolling/Sliding Line Contacts,” Journal of Tribology 114 706 713
- Alamsyah, C. Dillich, S. Pettit, A. 1989 “Effects of Initial Surface Finish on Cam Wear,” Wear 134 1 28 47
- Zhou, R. S. Cheng, H. S. Mura, T. 1989 “Micropitting in Rolling and Sliding Contact Under Mixed Lubrication,” Journal of Tribology 111 605 613
- Shareef, I. Mirghani, M. M. Karmali, A. D. Cusac, D. A. 2001 “Investigation of Surface Distress in Injector Cams Under Conditions of High Friction,” International Conference on Engineering Education 2001 Friction Session 8D3 Oslo, Norway 10 15
- Love, R. J. Wykes, F. C. 1975 “The Scuffing of Automotive Cams and Followers,” Chartered Mechanical Engineer 22 5 28 47
- Hamilton, G. M 1980 “The Hydrodynamics of a Cam Follower,” Tribology International 13 3 113 119
- Gecim, B. A. 1988 “Lubrication and Fatigue Analysis of a Cam and Roller Follower,” Tribology Series 14 91 100
- Taylor, C. M. 1994 “Fluid Film Lubrication in Automobile Valve Train,” Proc. of the Institution of Mech. Engineers. Part J, Journal of Engineering Tribology 208 4 221 234
- Bell, J. C. Willemse, P. J. 1998 “Mid-Life Scuffing Failure in Automotive Cam-Follower Contacts,” Proc. of the Institution of Mech. Engineers. Part J, Journal of Engineering Tribology 212 4 259 269
- Hugnell, B. A. Björklund, S. Andersson, S. 1996 “Simulation of the Mild Wear in a Cam-Follower contact with Follower Rotation,” Wear 199 2 202 210
- Suslov, A. G. Gorlenko, A. O. Simkin, A. Z. 1997 “Life Increase of Cam Mechanism,” Journal of Friction and Wear 18 3 95 98
- Soejima, M. Ejima, Y. Wakuri, Y. Kitahara, T. 1999 “Improvement of Lubrication for Cam and Follower,” Tribology Transactions 42 4 755 762
- Michalski, J. Marszalek, J. Kubiak, K. 2000 “An Experimental Study of Diesel Engine Cam and Follower Wear with Particular Reference to the Properties of the Materials,” Wear 240 1 168 179