Hardness Measurement for Metals Using Lightweight Herbert Pendulum Hardness Tester With Cylindrical Indenter

Abstract

A Herbert pendulum was modified to a lightweight pendulum with a cylindrical indenter by Habara in order to measure the hardness of viscoelastic materials such as plastics and rubbers. It is difficult to provide enough strain to evaluate the hardness of hard materials using the Herbert pendulum with a cylindrical indenter because the contact stress between the indenter and the specimen is smaller than that of the original Herbert pendulum. In this study, a modified measurement system is developed to accurately measure the swing angle of a lightweight Herbert pendulum with a cylindrical indenter. Two independent laser displacement meters are installed, to provide a noncontact measurement of the swing angle. The modified Herbert pendulum with a cylindrical indenter is evaluated for measuring the hardness of metals. Four types of Herbert hardness are compared with the Vickers hardness. Good correlation is shown between the damping hardness (one type of Herbert hardness) and the Vickers hardness. The damping hardness measured based on the modified Herbert hardness tester can be used as the hardness parameter of the metals.