Homework 4
Problem 2
A wear map plots the different wear mechanism a material goes through as the velocity and pressure on
the material changes. The topographic type lines within the graph represent the wear rate at that
pressure and velocity. With the smallest pressure and velocity, steel experiences ultra mild wear. Here
only small particles break loose and some are rapidly oxidized. This only exists if the wear rate is under
10-9 mm3/m.
With increasing pressure, velocity or both steel moves into delamination wear. In this regime, voids
appear near the surface and grow parallel. Once the void reaches a critical length a long, thin piece of
steel breaks off. This occurs for normalized pressures up to about 0.1 and normalized velocities up to
102.
If velocity is increased above 102 but below 104 steel enters mild oxidational wear. Here some small
particles oxidize as they break free and become an abrasive medium further increases the wear rate. At
higher velocities, steel enters severe-oxidational wear and more and more particles because oxidized.
At the upper right hand corner of the map is melt wear which is known as a minor wear mechanism
which doesn’t cause many large problems. Melt wear is when high velocities cause the materials to melt
and bond together.
Finally at high pressures steel enters seizure, also known as adhesive bonding. In this realm material is
lost due to localized bonding of asperities.