Experimental Investigation of Microdimples for Improving Lubrication and Friction in Piston-Liner Contacts of Internal Combustion Engines

Abstract

Abstract. Surface texture shapes and texturing methods were created to improve the tribological performance of mechanical systems. High-speed conventional micromachining in general and semihemispherical microdimples prepared through ball nose end milling in particular, have recently gained recognition as an effective method for improving tribological performance. The tribological behavior of semihemispherical microdimples created through ball nose end milling was investigated in this research at constant and accelerated sliding speeds. Experiments were conducted using an oscillating pin-on-disc arrangement with varying load (2 and 4 N), lubrication (0.2, 2, and 20 µl), and temperature (50, 100, and 150 °C) to replicate the characteristics of the piston–liner contact in an internal combustion engine. The coefficient of friction decreases with an increase in lubrication and a drop in load, sliding speed, and temperature across all evaluated surfaces. D40 surfaces exhibited better efficiency throughout most tribological test settings, with a mean texture efficiency of 26.86% for the evaluated conditions. Analysis of texture efficacy for the variation of linear speed similar to the piston-ring–liner interface at higher load and temperature suggests a novel approach to study the variation of friction for the variation of lubrication regimes in reciprocating motion. Overall, it was found that the textured surfaces with semihemispherical microdimples of 240 µm in diameter, 40 µm in depth, and 10% area density, created by conventional micromachining, are suitable for piston applications.