Hardness

The technological employ of material has made the term hardness extremely common except then it still keeps a poorly explained material property. Still a layman can differentiate between a softer and harder material, except then it may be complex to designate a material via its quantitative hardness since it is complex to correlate the property along with strain or stress. In general hardness might be understood like a property that offers resistance to permanent plastic deformation. That deformation may leave a permanent impression upon the material surface. For engineering reasons the property of hardness is explained as resistance to scratching or indention. Based on these two methods of hardness measurement name are:

(a)     Scratch hardness, and

(b)     Indentation hardness is employed.
Capability of material to resist abrasion, penetration or cutting is attributed also to hardness.