Homework 4 – Problem 1
Because the loading in the beginning is very low the pin is just touching the surface of the material and
smearing out some of the high points creating a small oxidized layer of material. As the force increases
the real area of contact increases and larger pieces of the material is disturbed and because it is not fast
enough to completely oxidize the debris, the wear rate increases. At the largest forces the contact area
increases further leading to more surface oxidation and because the surfaces harden quickly wear rate is
lower at these forces.
Homework 4 – Problem 2
Seizure – where the mating pieces fuse together and large chucks of material would be broken off.
Melt Wear – due to the high speeds and pressure the friction between the parts increases the local
temperature of the material to its melting point essentially melting the pieces together.
Mild Oxidational Wear – some parts of one of the metals will break into asperities on the other surface
potentially oxidizing in the process
Severe Oxidational Wear – see above, but to a greater extent
Delamination Wear – similar to a fatigue wear, cracks will start at the surface due to impurities in the
material and propagate
Ultra Mild Wear – very low wear not much material is removed