A hemispherical ring of copper with radius = 30 mm rotates on a flat ring of steel with inner radius = 50 mm and outer radius = 150 mm. The hemispherical ring touches the flat ring at the center from the axis of rotation (at 100 mm).

The hemispherical ring is subjected to a pressure load of 4000 N/mm² and is rotating with a frequency of 100,000 revolutions/sec. Sliding of the hemispherical ring on the flat ring causes wear in the rings.