2. Rebound hardness testing

2.1 Dynamic penetration

As early as 1895, Martel devised a dynamic penetration test involving dropping a penetrator onto the surface of the material and measuring the indentation left after rebound. The hardness number was, by definition, equal to the ratio of the energy of the indenter to the volume of the indentation.

2.2 Shore rebound

The measurement of rebound height was also proposed to measure material hardness. It was taken up by Shore in the form of a small mass of steel terminated by a...