Herbert Hardness Test Using Accelerometer for Swing Angle Detection

A Herbert pendulum hardness tester can measure the hardness of a sample with a complex shape, such as a drill bit. Hardness is evaluated based on the free decay curve of the Herbert pendulum in the hardness test. The accuracy of a conventional Herbert hardness test is low because the swing of the pendulum is measured using a level gauge attached to the pendulum. The authors previously proposed a Herbert hardness tester that comprises a Herbert pendulum and two laser displacement sensors for swing angle detection. In this study, to increase portability, an accelerometer is used for swing angle detection. A prototype of the proposed Herbert pendulum equipped with an accelerometer is fabricated and its accuracy is evaluated. The damping hardness accuracy of the prototype Herbert hardness tester is equivalent to that of the previously proposed tester. The results show that using an accelerometer for swing angle detection reduces size, weight, and cost of a Herbert pendulum hardness tester without decreasing accuracy.