It is difficult to observe the detail of motion of the Shore hammer, dropping and rebounding in the closed measuring tube of the Shore hardness tester in very short time, and the detail of motion of the hammer has not yet been observed. In this report, the behaviour of motion of the hammer, especially the distribution of frictional energy loss in the rebounding process, has been made clear by electronic measurement, using an experimental device similar to the present D-type Shore hardness tester. As the result, it has been found that the dropping motion is steady, accompanied with no energy loss, while the rebounding motion is unsteady accompanied with a considerably large energy loss, especially in a short range after impact. And also, difference in characteristics of the hardness scale between high hardness and low hardness has been pointed out and discussed here.
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