*mememe* said:
hi
I have som quest which im havin trouble wid
wat is the difference between, rockwell test , izod test , charpys test (and all the text required 4 HSC) and wat dey are used for,
also wats the difference between hardness, stiffness nd strength (and which method they can be found from)
thx in advance
Rockwell is a hardness test, it uses I think, both a pyramid diamond and a hardened ball (whereas Brinell uses a ball, Vickers a Diamond).
Izod and Charpy are both notch toughness tests, they measure the notch toughness of a material.
Izod holds the test piece vertically and the pendulem hits on the same side as the notch.
Charpy holds the test piece horizontally and hits on the opposite side.
Hardness is: The cohesion of the particles on the surface of a body, determined by its capacity to scratch another, or be itself scratched;-measured among minerals on a scale of which diamond and talc form the extremes.
Knowing hardness itself is no good but it gives a wide indication of other properties, eg there are tensile/hardness graphs for steel on a rockwell scale which means you dont have to destroy the piece if you have heat treated it.
Stiffness is its ability to resist deformation, measured by the gradient of the straight line part on the stress/strain curve.
Strength is abit abstract but it is the ability to resist stress, support a load or resist breaking. You rarely say a material is strong, but you can say eg. Concrete has a high compressive strength, or steel has a high tensile strength.
