Dynamic Hardness of Porous and Nonporous Materials Using a Dropped Ball
R B. Clough
A method for measuring the dynamic hardness of materials using a dropped ball is developed and applied to nonporous cold-rolled plain carbon (1018) steel. A new feature of the method is that it corrects the hardness measurement for the effects of pile-ups or sink-ins around the indentation through incorporation of the Norbury-Samuel constant. The results thus obtained extend the currently available dynamic flow stress data on plain carbon steel to higher stresses and strain rates. The analysis shows that if the Norbury-Samuel constant C = 0.5, deformation occurs through constant volume plasticity. If C < 0.5, the material has densified, either through retention of an elastic strain field or through plastic closing of pores if such are present. Thus the method is in principle applicable to porous materials as well.