Consideration of Test Parameters in Reciprocating Tribometers Used to Replicate Ring-On-Liner Contact

Abstract

The use of horizontal reciprocating tribometers to model ring-on-liner contact in engines is common practice. The steady reduction of lubricant viscosity to improve fuel economy has produced a consequential reduction in film thicknesses at these interfaces. As a result reciprocating tribometer tests are now more often testing the resultant surface film formed in the contact by the lubricant additive package as opposed to the bulk lubricant. This has made understanding the interlinked nature of the parameters that can be set on the tribometer more essential than previously due to the increasing complexity of the tribochemistry. In this article, the parameters that can be set on these reciprocating tribometers are discussed, how they potentially impact upon the test, the interactions between the parameters and the level of representation of the engine conditions that can be achieved. List of Symbols aAcceleration (m/s 2 ) REffective crank radius (m) s Displacement (m) t Time (s)-Note at time t = 0, s = 0. Systems are at mid stroke position u Velocity (m/s)

Simulation of Piston Ring/Cylinder Bore System Using Tribotests - A Review Focused on the Tribochemical Aspect

“…This region is used because is where the system experiments the most sever conditions of load, temperature and the lubrication regime is boundary. According to Lee [3] the parameters to be considered in designing a tribotest to simulate the piston ring/cylinder bore system can be split into two main groups: • Components -geometry (surface profile and finish), materials and lubricant. • System Conditions -speed, load, temperature and, on a reciprocating tribometer, stroke length.…”

“…Therefore the importance of the tribofilm formed from friction modifiers and antiwear additives on friction and wear is increasing. According to Lee [3] this increasing importance of the tribofilms on the piston ring/cylinder bore system performance has been leading to a frequent use of tribotests on the effort of understanding how the tribofilms forms from the additives and behave on the control of friction and wear. Nevertheless, Morina et al [4] showed that results are far from the objective of reproducing using tribometers the same tribofilm formed in an engine.…”

The influence of start–stop transient velocity on the friction and wear behaviour of a hyper-eutectic Al–Si automotive alloy

“…Periods when the vehicle was stationary and in motion were calculated and averaged to produce a regular time dependent velocity interruption. Actual engine velocities are difficult to replicate on a laboratory scale tribometer as discussed by other authors [17,18] and thus a test frequency was chosen which represented a matched idle engine frequency, described in detail elsewhere [16]. Further challenges to simulating conditions experienced in operational engines include lubricant starvation in a vertically sliding contact (and the associated local temperature rise), the influence of lubricant contamination (including soot and fuel) as well as the influence of different ring materials.…”

Piston ring-cylinder liner tribology investigation in mixed lubrication regime: part I-correlation with bench experiment

“…The most difficult condition to reproduce in a laboratory test is the variations of pressure, temperature and gas composition, which occurs in the combustion chamber. Most cannot be practically or safely replicated in a tribometer (Lee and Chittenden, 2010). Indeed, if attempted, the tribometer could become more complicated and expensive to run than a fully fired engine.…”