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An Integrated Design Analysis Methodology to Address Piston Tribological Issues

Keribar, Rıfat
Dursunkaya, Zafer
Venkatesh, Ganapathy
An integrated simulation methodology for the analysis of piston tribology is presented. The methodology is comprised of coupled models of piston secondary dynamics, skirt oil film elastohydrodynamic lubrication and wristpin bearing hydrodynamics, developed earlier by the authors. Models have been further expanded to calculate distributions of cumulative wear load on the skirt and cylinder and to account for details of skirt crankcase end geometry. The skirt elasticity model has also been improved to account for the effects of piston crown and pin boss stiffness in conventional, one-piece pistons. The model predicts piston assembly secondary motions, piston (skirt) friction, skirt and wristpin oil film pressures, transient deformations, skirt-cylinder contact/impact pressures and skirt and cylinder wear loads. As such it constitutes an advanced integrated methodology for addressing key piston tribological design issues, i.e. friction, wear/scuffing, slap noise, through optimization of piston design. The methodology is applied in a series of parametric studies to investigate the effect of design and operating parameters (piston stiffness and mass, engine speed and load, skirt/cylinder temperatures and thermal deformations, skirt-cylinder cold clearance and pin offset) on the behavior of an automotive piston.