Wobbly,
That “English” translation of the paper is a sorry mess, and it is not surprising that it is hard to understand. In fact, I would consider it incoherent and essentially useless for any number of reasons. It almost seems like the translation was made from an original that was missing a few pages. The “conclusion” section seems to have dropped out of the blue, with little relationship to the body of the paper. Something must be missing there. This really seems like somebody had a problem with worn camshafts and gave it to a graduate student to study as a project.
The only interesting thing is the graphical representation showing how the maximum stress locations move from the nose of the cam to the flank and from the center of the lifter to its outer region, depending on the rpm. And even that is misleading in that it shows it as symmetrical when, in actuality, the loading on the lifting ramp is going to be greater than the closing ramp.
No mention is ever made of how they supposedly would change the cam contour to lessen the problem.
In the end, a cam is necessarily designed to actuate the valves with the contour arranged to minimize the contact loading while still achieving the desired motion. Nothing in this paper gives any guidance on how to do that other than the hint about the momentary non-hydrodynamic (or near non-hydrodynamic) lubrication situation that may coincidentally arise at or near the location of maximum contact stress (on the cam flank and outer region of the lifter) during valve lift at higher rpm’s.
Your cam/lifter wear problem is really one of material chemistry, comparative harnesses, surface conditions, and lubrication. Can you fit any oil squirters in there?
(The second, sciencedirect, article is said to be unavailable)
