Jeremiah Jones
FWLM HW6 Problem 1
Wear Mechanism
Adhesion
Abrasion
Erosion
Polishing
Corrosion
Fretting
Brinelling
Electrical Discharge
Description of Physical or Chemical Process
This occurs when two metal surfaces are brought
in contact with each other and they “stick” to each
other resulting in a shearing of one of the two
surfaces. During contact of the asperities, a bond
is formed with little interdiffusion of atoms.
In this wear mechanism, either the asperities of
the harder material or the foreign particles
embedded in the softer material “plow” and/or
“cut” the top level asperities of the softer material.
Erosion is similar to abrasion however instead of a
harder material pushing a foreign material along
the surface of the softer material, in erosion a fluid
forces the foreign particle to remove asperities
from the soft material.
This is an abrasive wear in which very fine and
particular “foreign particles” are used to wear a
surface. Polishing a surface generally results in
very shiny and very smooth surfaces.
In this wear mechanism, the need be no contact
with another metal. This mechanism occurs
naturally as the material reacts chemically with its
environment. The most common corrosion is the
oxidation of metals in which oxygen reacts with
the metal thereby weakening said metal.
This wear mechanism is a subset of abrasive wear.
Fretting occurs in rotating components with
minimal displacement. What happens is a foreign
particle is introduced to the contact surface but
since the displacement motion is so small, the
foreign particle is not removed from the system
and therefore continues to abrasively wear the
surface.
This wear mechanism occurs in rolling element
applications. As the rolling element is compressed
over a foreign particle, permanent indentations
are created on the surface of the rolling element.
This wear mechanism removes metal when there
is a electrical spark between two surfaces. The
electrical discharge from one surface causes
pitting in the surface of the other metal.
Cavitation
Contact Fatigue
This wear mechanism occurs in high pressure fluid
flow applications. It occurs when there is a sudden
local decrease in pressure which creates a vapor
cavity. This cavity however quickly collapses and
causes significant mechanical stress to the surfaces
moving the fluid.
This wear mechanism occurs when a material
continually experiences contact stresses in similar
locations and therefore can wear or crack due to
the fatigue loading.