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

Abstract

The growing use of tribotest has been helping the researches to understand the actuation mechanisms of additives on the friction and wear control of engine parts. But, it is common to observe differences between the tribofilms formed in real situation from that obtained using tribotests. Furthermore, the automakers have difficulty to correlate the results obtained using tribotests with that performed using engines in dynamometers. For the piston ring/cylinder bore tribosystem is almost impossible to reproduce its real tribosystem using tribotests. Therefore simplifications are necessary and they affect the tribochemical behavior of the tribosystem. To understand how these simplifications and the test parameters affect the tribochemical behavior of the simplified tribosystem is critical to design a tribotest that correlate well with the real situation.

Effect of an Aftermarket Additive in Powertrain Wear and Fuel Consumption of Small-Capacity Motorcycles: A Lab and Field Study

“…This situation is similar to that observed at the beginning of tooth gearing, in which high levels of sliding occur [26]. Furthermore, boundary lubrication (Λ < 1), high contact pressure, and sliding motion across the texture direction are ideal conditions to test additives' performance [20,21,27], particularly anti-wear and extreme pressure additives, which are the main constituents of most aftermarket additive packages for engine oils [1,9]. Under these conditions, metal contact under higher stress occurs, leading to asperity deformation and wear, which in turn trigger the additives [23].…”

“…Surprisingly, to the best of the authors' knowledge, there was no peer-reviewed reference about MC performance in powertrains, even though that is its primary application. Contrastingly, there are thousands of papers evaluating the performance of base or fully formulated oils with the addition of additives or nanoparticles using standardized and tribological tests [11,[18][19][20][21][22]. Although lab tests (pin-on-disk, four-ball, copper corrosion, etc.)…”

“…provide evidence and insights into lubricants' performance, it is challenging to evaluate engine conditions in the laboratory [18,22,23]. In fact, it has been shown that elaborate tests fail to reproduce the tribofilms observed in engine parts [18,21]. Furthermore, lab tests often do not evaluate lubricant degradation over time and its impact on system performance [22].…”

Influence of steadite on the tribological behavior of cylinder liners

“…It is important pointing out that tribotests that simulates piston ring/cylinder bore, such as the HFRR used in this work, present limitations that restrict correlations from real condition, such as the impossibility to properly replicate the ring motion. This affects shear rate and flash temperature, even though the selected operating conditions (P 0 ≤H, Ψ ≫ 1 and Λ ≪ 1) were able to reasonably mimic the ones observed at the top-dead-center of cylinder liners (Siebert and Sinatora, 2016).…”

“…The used operating conditions were chosen to simulate the top dead center of Otto engines and to ensure ZDDP tribofilm formation. Detail information about the required conditions is given in Siebert and Sinatora (2016).…”