Durometer versus Stiffness of Natural Rubber
Durometer versus Stiffness of Natural Rubber
(OP)
Is it possible for a rubber with a higher durometer to be less stiff than another rubber with a lower durometer? I thought that durometer was a direct indicator of a rubbers hardness and stiffness





RE: Durometer versus Stiffness of Natural Rubber
RE: Durometer versus Stiffness of Natural Rubber
RE: Durometer versus Stiffness of Natural Rubber
http://en.wikipedia.org/wiki/Shore_durometer
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Durometer versus Stiffness of Natural Rubber
Greg's reply is generally correct, i.e. the answer is generally no.
There are a couple of oddball conditions where the above could be answered yes - one is if the rubber was poorly cured, from the o.d. in, and had a relatively soft core, with a harder (more fully cured) outer surface. Can also be done deliberately, i.e. if the core is foamed with a harder outer skin. Since a durometer test measures local stiffness only, the skin may have a higher durometer than the bulk of the material. A second condition is if you are measuring very high elongation in tensile testing relative to the (relatively small) deflections imposed by a Shore A or D penetrator. At high deflections the rubber may show a softer average stiffness than you might expect due to nonlinear elasticity of the rubber, and/or many or most rubbers will undergo strain softening (Mullins effect) with repeated loading, and you will see a decrease in apparent modulus with each load/unload cycle.
RE: Durometer versus Stiffness of Natural Rubber
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Durometer versus Stiffness of Natural Rubber
As it happens for metals, applying a certain hardness measurement procedure to a category of materials which does not belong to the range the procedure has been conceived for, can lead to misleading results.
RE: Durometer versus Stiffness of Natural Rubber
Let me ask another question on this subject. What if the rubber was different - say Nitrile versus Vamac?
RE: Durometer versus Stiffness of Natural Rubber
RE: Durometer versus Stiffness of Natural Rubber
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As you will see for a given value of shore A there is more then one value of shore D and vice versa
RE: Durometer versus Stiffness of Natural Rubber