ELASTO-PLASTIC PROPERTIES OF SINTERED STEELS MEASURED THROUGH INSTRUMENTED HARDNESS TESTS

摘要

Indentation hardness may be measured by various hardness tests, such as Brinell, Rockwell and Vickers. As everybody knows, the Vickers and Brinell tests require the optical measurement of the indentation, while the Rockwell test requires the measurement of the indentation depth, after load removal, and may be carried out in a completely automatic way. The possibility of automatic testing is really an advantage, but, unfortunately, the range of testing loads is inadequate to measurements localized or focused on very small and selected areas. This requirement may be satisfied by the Vickers test, which presents the advantage of a constant penetration angle, so that hardness results are nearly independent on the used load. The short comparison between Rockwell and Vickers tests points out to a new method, which should include the different advantages of automatic testing and numerical results not influenced by the level of load. This optimum solution is now a reality, because it is now possible to carry out tests of automated hardness, by means of new machines, suitable to measure and to record, continuously, the acting force and the corresponding penetration depth. These two quantities are recorded during the whole test, i.e. during loading and unloading. The main physical property measured by the described method is named universal hardness.