(Received November 24, 2006; revised March 19, 2007; accepted March 23, 2007; published online July 26, 2007)
Examination methods of industrial hardnesses such as Vickers hardness and Rockwell hardness are used for the characteristic measurement of materials. These methods assume that the length of the plastic deformation is a reliable index of hardness. Since the indenters used in these methods produce deformation imprints and the methods themselves are difficult to perform, they cannot be used for the ready measurement of hardness. Recently, a nondestructive ultrasonic hardness tester that is capable of measuring the hardness of materials has been developed by the authors. This tester can measure small areas rapidly and accurately. Another advantage of this tester is that it can measure a wide range of hardness. Therefore, we consider that it is highly advantageous to replace conventional hardness testers with ultrasonic hardness testers. In this study, ultrasonic hardness was compared with micro-Vickers hardness. As a result, it was clarified that micro-Vickers hardness was in proportion to the 4.25th power of the index of ultrasonic hardness.
KEYWORDS:elastic modulus, hardness tester, ultrasonic vibrator, resonance frequency, micro-Vickers hardness