Materials-Testing measurements

Hardness testing

Hardness tests on materials consist of pressing a hardened ball or point into a specimen and measuring the size of the resulting indentation. The two methods shown are the Brinell method, which utilizes a ball, and the Vicker's pyramid method which utilizes a pyramidal point. Other methods in use are the Rockwell method which uses a ball or diamond cone, and the Shore scleroscope, a portable instrument which measures the
height of rebound of a hammer falling on the surface. Measurement of Brinnel hardness number (BHN)

The ball size is 10 mm for most cases or 1 mm for light work.

Measurement of Brinnel hardness number (BHN)

The ball size is 10 mm for most cases or 1 mm for light work.

Toughness tests:

Toughness testing consists of striking a notched test piece with a hammer and measuring the energy required to cause fracture. The energy is indicated on the dial of the test machine and the force is produced by a swinging mass. Energy to fracture specimen
 

 The energy of the swinging mass The energy of the swinging mass is 163 J for the Izod
impact test and 294 J for the Charpy test.Izod impact test machine and test piece.

Tensile test on steel

Testing machines are used to determine the mechanical properties of materials under tension, compression, bending, shear and torsion.

One of the most important tests is the tensile test, especially that for steel. Typical curves are shown for ductile steel and hard steel. In the case of a ductile steel such as ‘mild steel’, there is a definite yield point above which the steel is no longer elastic. In the case of hard steel the load-extension curve becomes non-linear and it is necessary to specify a ‘proof stress’ for a specified strain, e.g. 0.1%.