TESTING HARDNESS OF METAL ITEMS WITH MET-UD COMBINED PORTABLE HARDNESS TESTER

Abstract A new approach to portable hardness testers has been developed and introduced. It makes it possible to inspect hardness by one and the same hardness tester applying both, the ultrasonic contact impedance method and rebound method. Hardness tester wide possibilities which allow to inspect hardness of metal and alloy products with all standardized scales (Rockwell, Brinell, Vickers and Shore) have been demonstrated. The possibility to improve the precision of portable hardness testers of this type by calibrating them for each of the above listed scales with hardness reference blocks only without any conversion tables has been shown. Experiments and real measurements conducted on cold rolls showed that change in hardness of a hardened layer in depth and surface stresses influence can be disclosed in the process of hardness measurement by portable combined hardness tester by two different methods