A flexible multi-body dynamics model for piston pin-connecting rod-crank pin was established with a six cylinder diesel engine as the research object. Moreover based on the thermal elastic hydrodynamic(TEHD) lubrication and the asperity contact theory

a TEHD model for connecting rod small end bearing was established to analyze the influence of the bearing clearance and surface roughness on lubricity under thermal load. Results show that under the influence of thermal load

the maximum oil film pressure increases by 7.5%

the minimum oil film thickness decreases by 8.1%

the friction power loss increases by 10.1%

and the rough peak contact increases by 6.0%

and hence the maximum temperature of the bearing rises to 20.1 ℃. With the increase in bearing gap

the maximum oil film pressure increases by 55%

and the decrease of minimum oil film thickness remains constant. Moreover

with the increase of surface roughness

the maximum oil film pressure amplification increases by 50%

and the minimum oil film thickness decreases by 55%. The thermal elastic hydrodynamic model adopted in this study provides a feasible way for the analysis of the failure mechanism of the friction pairs of power machinery under thermal load conditions. What's more

the results of this study have a certain guiding role in making the machining precision of sliding bearing friction pair.