Homework 4
Question 1
A disk subjected to a normal load from a moving pin experiences differing wear rates as the load
increases. For a small normal load, say under 1 N, the disk experiences a very small wear rate, about 10-5
mm3/m. This is called mild wear. Here fine particles are removed and some of them are quickly oxidized.
These oxide particles then become an abrasive medium encouraging further wear.
If the normal load is increased to about 10 N the resulting wear rate is 10-1 mm3/m. Here the wear
mechanism is severe wear. Larger particles are being dislodged yet oxidation due to the flash
temperature can’t fully oxidize these particles.
Finally the normal load reaches 100 N and but the wear rate actually decreases to 10-3 mm3/m. This
regime is called high temperature mild wear. Here high flash temperatures cause rapid formation of
oxides and create a hard, tempered layer on the surface of the disk. This hard layer reduces the wear
rate.