In Rockwell hardness testing method, the hardness of a material is measured by-

Explanation

Explanation: Hardness It is the measure of materials localized plastic deformation. Hardness test are performed by forcing a small indentor into the surface of a material to be tested and under controlled conditions of load and rate of application. The size of the resulting indentation is related to hardness numbers. Rockwell hardness test: Rockwell hardness testers use a number of indenters in combination with a variety of loads. It has 1/16, 1/8, 1/4, 1/2 inch diameter spherical steel indenter as well as conical diamond indenter which is used for the hardest material. Each of the indenters can be used with a major load of 60, 100, or 150 kg, and a minor load of 10 kg. The hardness number is the difference between the penetrations caused by major and minor load applications. Based on these load and indenters scales are developed, Rockwell A scale , 60 kg with diamond indenter is used for steels and similar hard alloys . Rockwell B scale , 100 kg with 1/16 inch diameter sphere indenter are used for aluminum alloys. Rockwell C scale , 150 kg with the diamond pyramid indenter are used for steel and similar hard alloys . Copper alloys are measured in k scales. Polymers are measured in the Rockwell E and M scales. M scales are used for hard polymers. Brinell hardness Scale: In Brinell hardness test a hard spherical indenter of 10 mm diameter is used, and the load varies between 500 and 3000 kg. Harder materials require greater applied load.