Question

List the 4 different types of harness tests, the types of indenters each uses and the range of loads applied.

Answer 1

1. Brinell Hardness Test-In this test a hardened steel ball of 2.5, 5 or 10 mm in diameter is used as indenter.The loading force is in the range of 300N to 30000N (300N for testing lead alloys, 5000N for testing aluminum alloys, 10000N for copper alloys, 30000N for testing steels). The Brinell Hardness Number (HB) is calculated by the formula:

2. Rockwell Hardness Test -In the Rockwell test the depth of the indenter penetration into the specimen surface is measured. The indenter may be either a hardened steel ball with diameter 1/16”, 1/8” or a spherical diamond cone of 120º angle (Brale).Loading procedure starts from applying a minor load of 10 kgf (3kgf in Rockwell Superficial Test) and then the indicator, measuring the penetration depth, is set to zero. After that the major load (60, 100 or 150 kgf)is applied. The penetration depth is measured after removal of the major load.

3. Vickers Hardness Test-The principle of the Vickers Hardness method is similar to the Brinell method. The Vickers indenter is a 136 degrees square-based diamond pyramid. The impression, produced by the Vickers indenter is clearer, than the impression of Brinell indenter, therefore this method is more accurate. The load, varying from 1kgf to 120 kgf, is usually applied for 30 seconds.

4. Knoop Hardness Test-A diamond pyramid indenter with angles 130º and 170º30’ is used in this method.The loading force in the Knoop method are usually in the range of 10 gf to 1000gf (micro-hardness range).The Knoop Hardness Test is applied for testing soft material and thin coating, since the penetration depth is very small (about 1/30 of the impression length).