HW3
Problem 7
Reference (1) Fundamentals of Tribology and Bridging the Gap Between the Macro- and
Micro/Nanoscales
Keszthely, Hungary
August 25,2000
Edited by Bharat BHushan
The reference material depicts a crystal lattice. Lattice orientation were determeined prior to friction
testing, and this knowledge enabled Hirano et al.(1991) to use their test apparatus to study the effects
of lattice misfit angle on friction the lattice misfit angle, theta, can be defined as the angle between
crystal lattices of two opposing surfaces when they are in contact with one another. The schematic
diagram included in the Reference (fig.6 pg 287) shows the crystal lattice of one surface sliding against
the crystal lattices of two opposing when they are in contact with one another. As shown in figure 6
when the misfit angle is approximately 0degrees or 60degrees the two specimens are said to be in
commensurate contact, which means the crystal lattice orientation of the surfaces, is the same. If the
misfit angle is 30degrees the mica materials are said to be in incommensurate contact. This means that
the crystal surface of one surface is rotated 30degrees with respect to the other surface. Commensurate
contact at a misfit angle leads to an increase in friction, whereas incommensurate contact at 30degrees
leads to a reduction of friction between the surfaces.