Young's modulus height dependent

[cobram]

Hello!

First I want to apologize for my broken english.

The problem I don't understand is this.
We have rod porous materials and we want to measure modulus. We made compression tests and if I have diferent height of tablet or rod for example, the diameter is about 12mm and height is 2,3,6,9,15,...mm we got always diferent modulus. The material is not plastic, it goes back to original size after 2-3 days.

How can we obtain modulus of elasticity for our material???

Aleš

 

[tarrat]

I am just wondering that you have considered the plane theory of elasticity.

I mean, if you have a sample with a small height, you should consider two dimmensions as infinite compared to the height, which means that you carry out your test in plane strain mode.
If the height is significantly higher, it means that you are plane stress mode.

In first case, you have to consider the shearing occuring at the contact surface, but you can neglect the dimmension changes. In the second case, you can neglect the shear stresses occurinig, but you have to consider the dimmension changes in each direction.

Anyway, with ABAQUS it is possible to carry out the simmulation adequately in each case.