TRIBOLOGY TEST QUESTIONS AND
ANSWERS
Key components of a tribological system - ANSWER Solid components A &
B, interfacial medium, environment
What is Ra - ANSWER Average roughness, mean deviation of surface height
from the mean line through surface profile
Mean line - ANSWER Area of profile above equals area of profile below
Issue with Ra value - ANSWER Identical values for surfaces with very
different profiles
Tribology - ANSWER Study of interacting surfaces in relative motion
W - ANSWER Normal load
F - ANSWER Tangential force causing restive motion
What are the typical four layers making up a materials surface - ANSWER
Adsorbed molecules, oxide layers, deformed surface zone, bulk material
Two methods to measure surface roughness - ANSWER Stylus method, non
contact optical method
Issue with non contact optical measuring technique - ANSWER Reflectance of
the material (oxide layer vs metallic surfaces)
Amplitude density function p(z) - ANSWER Probability of finding a point at
height x above or below the mean line
R(sk) - ANSWER Skewness
Negative skewness - ANSWER Isolated valleys below mean line
ANSWERS
Key components of a tribological system - ANSWER Solid components A &
B, interfacial medium, environment
What is Ra - ANSWER Average roughness, mean deviation of surface height
from the mean line through surface profile
Mean line - ANSWER Area of profile above equals area of profile below
Issue with Ra value - ANSWER Identical values for surfaces with very
different profiles
Tribology - ANSWER Study of interacting surfaces in relative motion
W - ANSWER Normal load
F - ANSWER Tangential force causing restive motion
What are the typical four layers making up a materials surface - ANSWER
Adsorbed molecules, oxide layers, deformed surface zone, bulk material
Two methods to measure surface roughness - ANSWER Stylus method, non
contact optical method
Issue with non contact optical measuring technique - ANSWER Reflectance of
the material (oxide layer vs metallic surfaces)
Amplitude density function p(z) - ANSWER Probability of finding a point at
height x above or below the mean line
R(sk) - ANSWER Skewness
Negative skewness - ANSWER Isolated valleys below mean line
