Abstract
Piston rings with radio-active wearing-surfaces were used to study the micro-welding between rings and cylinder wall during “run-in” in a small, water-cooled, internal combustion engine. The results indicated that micro-welding and the accompanying transfer of metal were present under the mildest conditions of engine operation, including motoring with the engine cylinder-head removed.
The distribution of micro-welding along the ring-travel was found to correspond to the wear profile observed in engine cylinders by other workers. Such transferred material may play a part in the formation of the “glazed” layer which is said to be present on “run-in” cylinder walls and rings. The presence of transferred metal at all points along the ring-travel indicates that the piston ring was not fully supported by a hydrodynamic oil film of sufficient thickness to separate completely the surfaces of the ring and the cylinder wall.
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