Hardness test is the most widely used test on vulcanised rubber material , hardness is rubber material property which the engineer will often need to specify when defining his requirements. The term “hardness” as applied to valcanised rubber material mean resistance to deformation, or more precisely, indentation by rigid body The British Standard method of expressing hardness of rubber material has been so devised that the result, express in British Standard and International Rubber Hardness Degree, bears a known relation to the elastic modulus .However from the engineer’s point of view the hardness test serves essentially as an indirect measure of the elastic modulus, of greater or less accuracy according to the circumstances just mentioned. The basis of the British Standard Hardness Test is the following relationship between the elastic modulus of the rubber material and the depth of penetration by rigid ball:
F/E = 0.00017*(r^0.65)*(p^1.35)
where F = the indenting force (kg)
E = Elastic modulus (kg/cm^2)
r = radius of ball (cm)
p = depth of penetration (mm/100)
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