Piston Rings: Friction, Sealing, and the Physics of Things That Touch
A piston ring is a small part solving a brutal problem: maintain a gas-tight seal in a cylinder that’s changing pressure by 50–100 bar every 10 milliseconds, while moving at 10–20 m/s, while bathed in hot oil of varying viscosity, for 200,000 km. The fact that this works at all is a minor engineering miracle. The fact that it can be optimized requires understanding what’s actually happening at the ring-liner interface — and that interface is where three different physical regimes collide. ...