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Manuel Uhlig

Why and how does the choice of preferred modulus input change my results?

Dear VEDA-Experts,

I’m using the VEDA tool for some F-z-curve plots. If one adds Kelvin-Voigt visco-elastic force, one has to choose the preferred modulus input. I don’t fully understand how this influences the result. As far as I understood, by setting this option I simply define wheter my entered sample modulus is interpreted as Shear (G) oder Young’s (E) modulus.

Since the tip modulus is not affected, the result should be the same if I enter

a) some value X and keep the default setting (shear modulus) or b) enter the same value X multiplied by a factor of 2*(1+v) since G=E/(2*(1+v)) and choosing Young’s modulus

Actually, that works fine for approach-only curves. If it comes to retract, the plots look significantly different.

In the manual’s theory section (page 105) one can find the equations behind the model. Still I don’t see any reason why it should lead to different results, when switching from E to G using G=E / (2(1+v)). As already mentioned, approach parts are identical. That’s why I suppose I’m using the equations properly.

I am grateful for any support, Manuel Uhlig

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    Manuel Uhlig

    To be precise: The value I change is sample modulus, while tip modulus is kept constant.

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