Find the yield strength for an elastomer

[ac_nex]

Hey,

Just wondering, how would you find the yield strength for an elastomer just from the engineering stress-strain curve. My professor said its complix and different books have different ways of finding it. Any ideas?

 

[Gokul43201]

I know that it is not calculated from a 0.2% offset method. I think for elastomers, the yield stress is usually pretty close to the maximum stress, but this is only a best guess (and doesn't really tell you how exactly to find it). The difference between an elastomer and say, a metal, is the large amount of non-linear elastic deformation. This basically is why the offset method will not work.

 

[PerennialII]

Would think that the yield strength itself is not as important of a material characteristic as it is in metals for example, and they'd use other properties to describe suitability to typical applications ( ). But in order to attain an adequate description of stress-strain response for elastomers one needs to 'calibrate' a nonlinear stress-strain model to the results with all its "weird" 'tilts', which doesn't really make it a simple task (models such as hyperelastic models (for example the Mooney-Rivlin model), where the stress-strain response is given via several coefficients of strain energy potentials which don't really identify with stress or strain measures directly, but rather to a nonlinear fit to the stress-strain response (often done for example using FEA)). Some PDE codes have within them routines which do the fitting on the basis of model examples when inputted with experimental data, but overall getting an accurate result (don't know of any shortcuts with decent accuracy, meaning if you need the stress-strain response) is far more laborious than doing an engineering analysis of a tensile test of a metal.