BS EN ISO 2039-2:2000,Plastics – Determination of hardness – Part2:Rockwell hardness.
BS EN ISO 2039-2:2000 specifies a method for determining the indentation hardness of plastics by means of the Rockwell hardness tester using the Rockwell M, L and R hardness scales.
For materials having high creep and recovery the time-factors involved in application of the major and minor loads have a considerable effect on the results of the measurements.
An alternative method of using the apparatus to give hardness on the Rockwell-a hardness scale is specified in the annex which shows how this scale may be related to the hardness measurement of ISO2039-1.
This is a method for determining hardness in which a constant minor load is applied to a steel ball resting on the material to be tested, followed by application of a major load, and then followed by a return to the same minor load, all at specified limits for times of loading The actual measurement is based on the total depth of penetration, minus the elastic recovery after a fixed time following removal of the major load, minus the penetration resulting from the minor load. The rockwell hardness number is derived from the net increase in depth of impression as the load on an indentor is increased from a fixed minor load to a major load and then returned to the same minor load.

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