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 in international affairs and the formulation of U.S. foreign and defense policy. A graduate of the University of Redlands, Janka received a master's degree in International Relations and Middle East Studies from the School of Advanced International Studies at Johns Hopkins University. Janka worked for the United States Information Agency from 1964 to 1968 and was Assistant Dean of the School of Advanced International Studies of Johns Hopkins University from 1968 to 1971, when he was appointed Special Assistant to Henry Kissinger on the National Security Council at the White House. Janka became Senior National Security Council Staff Member for