| 摘要 |
A hardness tester for metals and alloys is capable of providing comparative values of hardness in Vickers or Brinnel scale by direct reading utilizing an indenter (17) of conducting material having a high resistivity. The size of the indentation produced determines a certain electrical contact resistance between the indenting point (20) and the sample (21), which may be measured by an appropriate measuring apparatus, e.g. a Wheatstone bridge (W). By trimming the apparatus using a blank or master sample of known hardness, the indenter (17) is loaded so as to penetrate in the test sample (21) until attaining again the same electrical contact resistance condition as on the master sample. The difference between the applied loads provides a comparative evaluation of the hardness which may be read directly on a suitable scale without the need of microscope measurements of the size of the indentation. The hardness tester is particularly suited for field use and for testing internal surfaces. |
