Three-Dimensional Engineering Approach to Conformability Analysis of Piston Rings

Abstract

The work describes a mathematical model for calculation of conformability of piston rings with nonsymmetrical cross section. (Conformability is defined as the limit of bore distortion at which the contact pressure, which the piston ring exerts on the bore, is positive.) Conformability analysis of these rings is more complex than that of rings with symmetrical or rectangular cross sections because of a three-dimensional (3D) deformation experienced by these rings during installation in the bore. To address this complexity, a solution is based on the general theory of 3D deformation of thin elastic rods. The solution also utilizes elements of a two-dimensional treatment employed previously in conformability analysis of the splitless rings. The main difference between the methods of mathematical theory of elasticity applied to the thin rods and the present solution is that in the latter the assumption of inextentional deformation of the centerline (typical assumption accepted in application of the aforementioned theory) is not adopted because the ring is assumed to be splitless. Overall, the present solution is an extension of the two-dimensional analysis of a piston ring deformation to 3D deformation. In the absence of the contemporary solution for conformability of the split rings (numerical calculations based on the latest Society of Automotive Engineers paper of the authors on the subject showed no convergence when the assumption of full conformability for split, initially circular, rings was accepted) a present work offers a viable alternative.

KEY WORDS:

• Piston Rings
• Seals
• Conformability
• Three-Dimensional Deformation
• Cylinder Bore Distortion
• Engines
• Compressors
• Emission Reduction

Notes

Presented at the 59th Annual Meeting in Toronto, Ontario, Canada