Rebound hardness testing of material using a new coil arrangement that has improved accuracy as for a considerable measurement stretch the signal amplitude is entirely dependent on rebound velocity

摘要

Method for measuring material hardness using the rebound measurement method in which a ball bearing type penetration body (4) is dropped in a pipe towards the surface of a body under test. The body has an attached magnet and its falling and rebound velocities are measured using coils (5, 6). The coils are connected together and have separation distances set such that measurement accuracy is optimized. The first induction coil is positioned so that its maximum induction signal is reached after the time an impact with a test body would occur if it was placed in the pipe, when the test body is allowed to fall through the empty pipe for compensating purposes. In a similar way the second induction coil has its maximum temporally before the impact time. The coils are positioned together such that a resultant signal from a combination of the two signals has a sufficiently long region in which its signal amplitude is entirely dependent on the body's velocity.