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
Roll hardness tester of the movement, the pawl spring releases the hammer mass. The impact spring contracts causing the hammer mass to strike against the plunger. This is the impact. The hammer mass then rebounds back to the body of the hammer and distance travelled is recorded on the scale. The rebound distance depends directly on the hardness of the roll under test: A softer roll will absorb more of the impact energy and the rebound distance will be less. A harder roll will reflect more of the impact energy and the rebound distance will increase. Roll hardness is one of the most