Under the portable hardness tester there are portable Brinell, portable Rockwell, Leeb hardness tester, ultrasonic hardness tester and so on. The main research and development and production of Shenyang TX Testing Instruments Inc. are portable Brinell and portable Rockwell hardness tester. Therefore, the Portable Hardness Tester Working Principle will be divided into Portable Rockwell Hardness Tester Principle and Portable Brinell Hardness Tester.
As illustrated in Fig. 1, the indenter is pressed (diamond cone or carbide ball ) into the specimen surface in two steps. After maintaining the pressure for a predetermined period of time, unload the major test force F1, and measure the remaining indentation depth h under initial test force F0.
Rockwell hardness value is:
In this equation:
N — a constant related to scales; for A, C, D, N and T scales, N=100; for B, E, F, G, H and V scales, N=130.
S — unit indentation depth, for Rockwell hardness it is 0.002mm, for superficial Rockwell hardness it is 0.001mm.
1 — indentation depth under initial test force F0;
2 — indentation depth under total test forces F0+F1;
3 — elastic recovery depth when major test force F1 is removed;
4 — remaining indentation depth h;
5 — test piece surface;
6 — datum plane;
7 — position of indenter
Rockwell hardness portable testers are designed according to the basic principle of Rockwell hardness test. The main differences from the bench-type lie in: the test force is applied by a screw and a calibrated U-shape spring; two indicators are installed on the tester: one indicating dial indicates the test force value by measuring the deformation of the elastomer and one precision screw micrometer used for testing the indentation depth; one barrel dial installed on the micrometer shows the hardness values. The principle and structure of this instrument is in accordance with the American Standard ASTM E110.
Apply a standard test force F to the carbide ball indenter with a diameter of D and press it into the specimen surface; keep on pressing for a set period of time, then remove the test force F and a round indentation with depth h is obtained on the surface of the test piece. Measure the indentation’s average diameter d, the Brinell hardness can be calculated by the quotient of test force divided by indentation’s surface area.
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