Herttzian Mechanics

The profile of each surface in the vicinity of the origin may be expressed in the form

	(8.1)

where, we neglect the higher order terms. Furthermore, we can choose the orientation of the axes such that terms like vanish. Then equation 5.1 may be written as:

	(8.2)

Where and are the principal radii of curvature. Note that they are the minimum and maximum value of the radii of curvature of the surface at the point. If a cross-sectional plane of symmetry exists one principal of curvature lies in that plane.