Simulating the Tensile Test of an Aluminium Coupon

Introducing the plastic behaviour of a material in a Finite Element Model is not straightforward, but it is not impossible.

In the book “Computational Structural Engineering” at Chapter 13 many hints and tips&tricks are given to succesfully introduce into the model the required material data, from a bilinear (simpler) behaviour up to the full stress-strain curve. Explanation is also given on the difference between true stress-true strain and nominal stress-nominal strain curves.

In general it is not advisable to rely on results above the ultimate strain provided by the material supplier.

Nonetheless, by having some more material data it is possible to extend the simulation beyond that point and try and predict the actual failure of a component. Testing is anyway strongly suggested, if  the component has to really work until its complete failure.

In the animation here below, a uniaxial tensile stress on an aluminium round coupon has been simulated by using the stress-strain curve indicated in the figure; the results obtained by the Finite Element Model match perfectly the experimental curve. Unfortunately it was not possible to get the full stress-strain curve to check if the model can reproduce the actual behaviour at failure. We anyway hihglight that the necking onset is caught quite well and up to the available test data.