In-Plane and Out-of-Plane Elastodynamics of Thin Rings and Seals

Thin curved rings used mostly as seals, including in internal combustion engines undergo complex elastodynamic behavior when subjected to a combination of normal radial loading and tangential shear with friction. In turn, their complex modal behavior often results in loss of sealing, increased friction, and power loss. This paper presents a new finite difference approach to determine the response of thin incomplete circular rings. Two interchangeable approaches are presented; one embedding mass and stiffness components in a unified frequency-dependent matrix, and the other making use of equivalent mass and stiffness matrices for the ring structure. The versatility of the developed finite difference formulation can also allow for efficient modification to account for multiple dynamically changing ring support locations around its structure. Very good agreement is observed between the numerical predictions and experimental measurements, particularly with new precision noncontact measurements using laser Doppler vibrometry. The influence of geometric parameters on the frequency response of a high performance motorsport engine's piston compression ring demonstrates the degree of importance of various geometrical parameters on ring dynamic response.