Uncertainty Analysis of Friction and Wear-Rate of Cylinder Liner–Piston Ring Tribo Pair Under Boundary Lubrication Conditions

Abstract

Uncertainty analyses can improve the reliability and validity of the assessment of friction and wear-rate of tribosystems. This work analyses the various sources of uncertainty in the estimation of friction and wear-rate of liner-ring pairs using a linear reciprocating tribometer (LRT) as per the analytical method suggested by Guide to the Expression of Uncertainty in Measurement (GUM) and simulation approach using Monte Carlo simulation (MCS) method. The uncertainty analysis was conducted by performing sliding wear experiments using a hypereutectic Al–Si cylinder liner specimen against the chrome-coated piston ring as the counter specimen. The experiments were performed to mimic the engine’s condition under a boundary layer lubrication regime. The type A and type B uncertainty components of the tribosystem, such as uncertainty involved in the measurement of mass, linear dimensions of the specimen, radius of the specimen, normal force, stroke length, and frictional force, were evaluated to study their influence on the assessment of the friction and wear-rate. The probability density function of all these uncertainty sources was simulated using the MCS approach to compute the 95% coverage interval for friction and wear-rate directly. The variation in absolute value between the coverage interval limits computed by the GUM framework and predicted by the Monte Carlo method for wear-rate was 11.83%, and for friction coefficient, it was 12.005%.