Hardness Hardness Hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. Some materials (e.g. metals) are harder than others (e.g. plastics, wood). Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, there are different measurements of hardness: "scratch hardness", "indentation hardness", and "rebound hardness". Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter. There are three
Les Janka Les Janka Leslie A. Janka is President-Saudi Arabia for Quincy International LLC, resident in Riyadh Saudi Arabia.. He has more than 25 years experience as an international affairs specialist in the U.S. Government, business consulting and academic institutions. Prior to joining Quincy International, Janka was President of Raytheon Arabian Systems Company in Riyadh, Saudi Arabia. Prior to managing his independent consulting firm, Les Janka International from 1995 to 2007, he directed the international practice of the energy utility and telecommunications specialty consulting unit of Arthur Andersen, LLP. Janka is a frequent writer and lecturer on the Washington political scene, specializing