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
Walter Janka Walter Janka Walter Janka (born in Chemnitz 29 April 1914, died in Kleinmachnow 17 March 1994) was a German communist, political activist and writer who became a publisher. Janka is notable for having spent time incarcerated as a political prisoner under the rule of the Nazis and later imprisoned under suspicion of counter-revolutionary activities by the Supreme Court of East Germany, in both cases serving most of his sentence at Bautzen prison. Walter Janka was one of six children born to a Tool and die maker called Adalbert Janka. He attended junior school from 1920 till 1928. Between 1928 and