Study on the Preparatory Method of Specimens for Micro-Hardness Test

Abstract

In order to perform the precise micro-hardness testing, it is very important to understand the basic effect of method of preparing specimens. So investigations on the conventional methods of preparation have been conducted. Using three kinds of metals, experiments on the mounting of specimen, the grinding, the polishing and the micro-hardness testing have been done. The results are as follows. (1) Polyester resin is better than others to mount specimens. But the initial stress becomes about -450 kg/cm² for mild steel and -150 kg/cm² for aluminum. Accordingly low strength materials such as single crystal metal and aluminum had better not be mounted. (2) Residual compressive stresses occur near the surface ground by the emery papers. On the other hand, residual tensile stresses occur near the surface polished by the lapping wheel with a well piled polishing cloth. (3) It is very reasonable to practise polishing after grinding, because the residual compressive stresses near the surface reduce remarkably.