Development of a Multiphysics Tribological Model for the Prediction of Adhesive Wear in Journal Bearings of Large Diesel Engines Under Contaminated Lubricant Conditions in Nigeria

Adhesive wear and scuffing failure in the journal bearings of large diesel engines used in Nigerian power generation and transportation applications are significantly accelerated by the widespread use of fuel-contaminated, thermally degraded, and particle-laden lubricating oils that deviate substantially from the clean oil assumptions of existing tribological models, creating a critical gap between theoretical predictions and the failure experience of engine operators across the country. This research develops a multiphysics tribological model for the prediction of adhesive wear in engine journal bearings operating with contaminated lubricants representative of conditions in Nigerian diesel engine maintenance practice. The model framework integrates mixed lubrication hydrodynamics incorporating surface roughness contact mechanics with a thermomechanical model for frictional heat generation at asperity contacts, a contamination transport model for particle migration and embedment in the bearing surface, and an adhesive wear kinetics model based on the modified Archard equation with temperature and contamination-dependent wear coefficients. Experimental characterisation of contaminated lubricant viscosity-temperature behaviour, particle size distributions from field-sampled used lubricants, and wear coefficients from pin-on-disc tribometer tests under contaminated lubrication conditions provide model inputs and calibration data. The fully coupled multiphysics model is implemented in a custom finite element solver and validated against bearing wear measurements from a specially instrumented engine test rig operated under controlled contamination levels. The model demonstrates prediction accuracy within 20 percent of measured bearing wear depths across five contamination test conditions, establishing a theoretically grounded tool for bearing material selection and lubricant change interval optimisation in the Nigerian diesel engine context. Keywords: journal bearing, adhesive wear, multiphysics tribology, contaminated lubricant, diesel engine Nigeria.