Spicer Drive Axles Failure Analysis Service Manual - Manual (Page 8)

Glossary and Nomenclature
7
Glossary
Abrasion - The process of rubbing, grinding, or wearing away
of material from a surface by friction.
Backface Runout - The total amount of movement in the back-
face surface of the ring gear during one revolution.
Backlash - The total amount of movement between two mating
gears.
Beach Marks - Contour lines on a somewhat smooth failed
surface that indicate fatigue. Beach marks occur as a part suc-
cessfully resists, for a time, the advance of a fatigue crack.
Bending Fatigue - Characterized by beach marks on the frac-
tured area. The phenomenon leading to fracture under repeat-
ed or fluctuating stresses having a maximum value less than
the tensile strength of the material. Fatigue fractures are pro-
gressive, beginning as minute cracks that grow under the ac-
tion of the fluctuating stress. Fatigue results from load and
time.
Brinelling, False - Depressions produced when bearings are
subjected to vibration or low radial-angle oscillation, or to
both, while not rotating. The bearing surfaces are either pol-
ished or show a characteristic red-brown stain.
Brinelling, True - Indentation produced by plastic flow when
rolling elements are forced against the bearing raceway surfac-
es by stationary overload or, especially, by impact during
mounting. Original surface features such as machine marks
are usually visible at the bottom of the indentations.
Burnishing - In sliding contacts, the oxidation of a surface due
to local heating in an oxidizing atmosphere.
Bruising - A type of damage caused by foreign material or hard
particles passing though the rollers and the races. Damage ap-
pears as small indication and or denting.
Burning - Permanent damage to metal or alloy by overheating.
Carrier - The primary casting that supports and houses the
rest of the components of the head assembly.
Coking - A lubricant that has been overheated for an extended
length of time may cause the carbon in the lube to separate and
collect on internal components. The build up will have the ap-
pearance of black paint.
Fatigue Strength - The maximum stress that can be sustained
for a specified number of cycles without failure.
Final Fast Fracture Zone - The part of a breakthrough cross
section that has a rough, crystalline appearance. It could be the
entire area in a shock failure or a small part of a cross section
area in a fatigue failure.
Flaking - See Surface Fatigue Progression.
Fretting - An action that results in surface damage, especially
in a corrosive environment where there is a relative motion be-
tween solid surfaces in contact under pressure.
Frosting - See Surface Fatigue Progression.
Galling - The transfer of material between two moving compo-
nents at extremely high temperatures.
Grooving - Chips of metal particle contaminates become
wedged in the softer cage material and cut grooves in the roll-
ers resulting in the grooving of the cup and cone races.
Head Assembly - The entire drive unit consisting of the D-
Head and the R-Head. The axle housing and wheel equipment
are not included in the head assembly.
I.A.D. - Inter-axle differential.
Lubrication Break Down - When a lubricant is thermally
stressed, the viscosity is lowered and the lube can no longer
maintain a barrier between metal parts.
Oil Contamination - Pollution of lubricating oil by a foreign
substance.
Overloading - A load or torque that is greater than the design
load or torque specification of a particular component.
a. Shock Load - Instantaneous overload. A very rapidly
applied force that causes immediate component
damage.
b. Sustained Overload - A consistent application of
force that is greater than the part can withstand.
Pitting - See Surface Fatigue Progression
Plastic Deformation (Plastic Flow) - Deformation that re-
mains permanent after removal of the load which caused it. An
example of plastic deformation is metal flow on the surface ex-
tending over the tips of gear teeth. This condition can quickly
become destructive pitting.