In people with keratoconus, rigid contact lenses improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the lens, thereby creating the effect of a smoother cornea.
Rockwell Hardness Testing Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation.lick here to learn more about hardness testing basics. The Rockwell hardness test method, as defined in ASTM E-18, is the most commonly used hardness test method.
Hardness is a measure of how easily a material can be scratched or indented. Hard materials are often also very brittle - this means they have a low resistance to impact . Well known hard materials include diamond and hardened high carbon steels. Same units as for tensile strength. The methods used for testing hardness are the Brinell test which uses a hardened steel ball and produces a hardness number HB which can be used to compare the hardness of materials.