The traditional methods are based on well-defined physical indentation hardness tests. Generally, impact device types are optimized for certain application fields. Hardness comparison The indenter is forced into the test material under a minor load, usually 10 kgf. A magnetic impact body permits the velocity to be deduced from the voltage induced by the body as it moves through the measuring coil. Other Hardness Scales The Rockwell, Brinell, and Vickers are the most common hardness scales, but there are many others: Deformation parameters, such as the indentation depth in the Rockwell method, are recorded to give measures of hardness.
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In this dynamic test method, the ratio of rebound velocity to impact velocity of a moving impact body is used to determine the hardness. The impact velocity lies between 1. It is a rebound test method, i. The ratio of the impact velocity to the rebound velocity is the measure of the dynamic Leeb hardness of a test specimen.
Shape and material of the impact body: Tungsten carbide cobalt, ceramic or diamond, ball-shaped indenter with different radii. Test Procedure In the Leeb hardness test conducted according to ISO , an impact device accelerates an impact body using spring force.
The velocity of the impact body is broken down into three phases: Approach phase, during which the impact body is accelerated towards the test surface by means of the spring force.
Impact phase, during which the impact body and the specimen are in direct contact. The specimen is thereby elastically and plastically deformed and the impact body is brought to a complete standstill. The elastic spring-back of impact body and specimen causes the impact body to rebound.
Rebound phase, during which the impact body is again accelerated out of the impact phase with the remaining energy. The velocities are measured contact-free by means of an induced voltage, generated by a moving magnet in a defined coil in the impact device. The induced voltage signal is recorded electronically and the peak values, the point of the impact phase and the point of the rebound phase, are used to calculate the Leeb hardness, see also figure below.
The ratio of rebound velocity vr to impact velocity vi, multiplied by a factor of , gives the Leeb hardness see formula.
Hardness Conversion Table