Perhaps they are talking about elongation?
Could it be the secant or tangent modulus at 300% elongation?
Youngs (tensile) modulus can be described as the pressure to extend a section 100% so that it ends up twice as long as it started. For many materials, this is a theoretical construct, because they waist and or fracture between 1 and 5% elongation. For rubber however, it is entirely conservative, because some rubbers can extend to 7X their starting length.
Brian Whatcott Altus OK
Thanks for your responses, everyone. I'm working on an RC car simulator for Serpent Model Cars and due to a lack of tire test data, I'm trying a different approach for a new tire model. The tires are foam rubber, very high friction coefficient, and I've found some formulae that theoretically give friction coefficient of soft, deformable materials given Young's modulus and surface roughness, which is fantastic because we're trying to find how stiffness and grip should change given different shore ratings. I've also read that Young's modulus isn't what you really want to be dealing with when it comes to rubber. Seems that different sources have different thinking on this subject.. Surprise surprise...
Just to make sure I'm understanding this correctly: Young's modulus (and shear modulus too, I presume, which is important for this too) are not constant, but instead change with deformation, right?
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Great, thanks Mr. Whatcott.
Todd Wasson Racing Software
I think, from my past experience (limited, but I have used rubber) the
300% modulus is essentially Young's Modulus at 300% elongation. Whereas metals such as steel, aluminum, and titanium exhibit linear stress/strain relationships up to yield, rubber is highly non-linear. For something such as a rubber band, 300% is pretty much the working deflection (judging from the rubber bands we use on model aircraft). For your application, you're going to need more data...RW Gu>>From: Brian Whatcott snipped-for-privacy@sbcglobal.net
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