Clarification of a Semi-Empirical Approach in Piston Ring-Cylinder Bore Conformability Prediction

Abstract

This technical brief clarifies origins of the piston ring conformability bounds presented by Dunaevsky (1990, Tribol. Trans. 33(1), pp. 33–40) and provides their correct expression. The subject has strong practical significance in the field of piston engines and compressors, and it is currently getting additional prominence due to stringent emission regulations. The bounds stem from an earlier version, developed by the authors using a semi-empirical approach, and published in the 1970s in Russian technical journals. A semi-empirical background of the bounds was inadvertently missed in the aforementioned Tribology Transactions’ publication. This fact, and the virtual inaccessibility of Russian sources to the English reader, interfere with the proper use of the bounds and cloud their authorship. In this technical brief, the correct expression of these conformability bounds, the development process, and uses are highlighted.

Direct and quantitative evidence for buckling instability as a mechanism for roughening of polymer during plasma etching

“…Considerable care is needed in extracting the effective modulus of the combined tip-film system from the measured force curves; we followed the procedure suggested by Lin et al 8,9 It uses the relation between the measured tip displacement (D pd ) and the tip penetration (d) into the film to determine the zero tip-sample force point, the adhesion force (F ad ), and the contact point. It makes use of the PietrementTroyon (P-T) force-penetration relationship, 10 (2) where a 0 is the contact radius at zero load, R is radius of the AFM tip, and F is the load.…”

A Dual Grid Curved Beam Finite Element Model of Piston Rings for Improved Contact Capabilities

“…The curvature of a plane curve in polar coordinates is given by: (7) θ is the polar and angle and r is the radial coordinate of the ring neutral axis. In engine operation, the ring neutral axis deformation is small compared to the cylinder radius and the curvature can be approximated by: (8) Here, y is the ring neutral axis radial displacement from its original position at radius R. The expression of ring curvature and free shape can be substituted in equation (6) to obtain a relation between ring deformation and contact force distribution: (9) The contact force distribution, f c , is a function of ring-liner clearance as well as lubricating conditions. Piston rings experience boundary contact near the top and bottom dead centers and transition to mixed or hydrodynamic lubrication regimes depending on engine speed during the rest of the stroke.…”

“…Mueller [5] developed an analytical criterion to calculate the maximum admissible bore distortion for a given ring configuration. A similar analytical approach and a statistical treatment of bore distortion was used by Dunaevsky et al to suggest different bore distortion limits [6,7,8]. Tomanik later proposed a new conformability criterion based on experimental measurements of ring conformability limits [9,10].…”