concrete prism under compression

[aminjamali]

I am trying to simulate a concrete prism under compression. It's a 1" by 1" by 1" which is to be loaded axially. The concrete has a typical nonlinear stress-strain behavior i.e. an almost parabolic ascending portion and a linear descending branch (please see the attachment). I assume that since the prism is under pure compression, its load-contraction curve must be essentially the same as the concrete stress-strain curve and I wanted to examine this hypothesis.
To define the concrete stress-strain data, I used Inelastic>Rate Independent>Isotropic Hardening Plasticity>Mises Plasticity>Multilinear.
I also introduced the Elastic E and Poisson ratio accordingly.
It should be a simple problem, but surprisingly I get very weird results. For example, I can apply contractions as much as 1" to the cube!

Am I missing something? How would you simulate this problem?

Thanks

 

[aminjamali]

I am still awaiting responses. Any tip is appreciated.

 

[omidomidi]

the problem is a nonlinear problem. you have to apply adequate number of substeps in the solution control window. load has to be applied gradually not at once.you may apply a small load on your model at first and restart your analysis to keep on the analysis in another load step with another amout of load.
also second part of your stress-strain curve is descending which makes the analysis impossible to converge. you have to use true stress-strain curve in stead of engineering one.

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[aminjamali]

Thank you for your help...