The hardness of a moving body is determined using the ASTM A956 Leeb Hardness testing method, which uses the ratio of rebound velocity to impact velocity. It's a nondestructive testing technique. The Leeb hardness test utilizes the dynamic or rebound property, which primarily depends both on the plastic and on the elastic properties of the material being tested.
The Leeb hardness test, ASTM A956, is a dynamic or rebound method that determines the Leeb hardness by comparing the rebound velocity to the impact velocity of a tungsten carbide ball or a diamond-tipped impact body. This portable approach is mostly used for determining whether or not a workpiece is sufficiently large. It calculates the restitution coefficient. The Leeb hardness of steel, cast steel, and cast iron is determined by ASTM A956, and the results are indicative of strength and depend on the heat treatment of the material examined.
During a hardness test, an impact body with a spherically shaped tungsten carbide, silicon nitride, or diamond tip impacts, after being propelled to the specified velocity, the test surface from which it rebounds. The impact and rebound velocities are measured when the impact body is approximately 0.039 inches [1 mm] from the test surface. This is accomplished utilizing a permanent magnet mounted in the impact body which, during the test, moves through a coil in the impact device and induces an electric voltage on both the impact and rebound movements. The quotient of these measured voltage values derived from the impact and rebound velocities, multiplied by the factor 1000 produces a number that constitutes the Leeb hardness value.
Test pieces, with curved surfaces, may be tested on their convex or concave surfaces providing the radius of curvature of the test specimens not less than 1.181 inches (30 mm) for impact devices.
Leeb hardness is reported in SI unit or Inch-pound and is considered as standard separately. Leeb Hardness is calculated as :