Method of testing the hardness of material and device for making the same

1485218 Measuring hardness PROCEQ SA 31 Oct 1975 [7 Nov 1974.] 45554/75 Headings G1N and G1S The hardness characteristic of a material is determined by causing a test tip to be impacted with the surface of the test material and calculating the ration of the test tip velocities immediately before and after impact. As shown, Fig. 1, a test tip 1 consisting of a hard steel ball embedded in an impact mass 2 is initially drawn back from the test material 15 by virtue of the mechanical coupling between the resilient bottom portion 8 of a rod 7 and an upper bore 2a of the mass 2. The portion 8 has four longitudinal slots 8b, so that by pressing down the upper ports 10, 11 of the assembly shown the rod 7 enters and is retained in the bore 2a. The upper parts 10, 11 are then withdrawn by a spring 12 until the coneshaped upper part 9a of the portion 8 abuts against an end-face 6a of a bushing 6. This squeezes the end of portion 8 and the impact mass 2 is released to be forced by spring 5 on to the surface 15 of the test material. The mass 2 carries a permanent magnet 3 which co-operates with a coil 14 externally located at the bottom of the housing 4 to produce an output voltage which has a positive maximum just before impact and a negative maximum just after impact, these voltages being proportional to the corresponding velocities of the impact mass 2. In another embodiment the test tip is separated from the impact mass, and the maximum velocities of either are measured.