Axisymmetric tension test

[Yaakov]

Dear FEAP Team,

I wrote a input file in FEAP as I want to make a axisymmetric tension test in FEAP.
This input file seems not working.
I have attached the axisymmetric tension test input file.

would you please let me know where is the error in the my FEAP Input File?

Warm regards,
Yaakov

[FEAP_Admin]

Did you bother looking in the output file? and checking for warning?  Please do that first and see if you can answer your own question.

[Yaakov]

Dear FEAP Administrator,

how can I define the rotation axis for axisymmetric  problem FEAP (in this benchmark, U_z is the rotation axis) ?

 I want to make a simulation of three-dimensional necking of a circular bar in FEAP, which is based on the benchmark by Prof. Simo.

Warm regards,
Yaakov

[Prof. R.L. Taylor]

I am not clear about what you are asking.  In a 2-d axisymmetric analysis the axis of rotation is the z-axis in an r-z system.

If you are asking about 3-d then usually we also make z the axis and define the circular cross section in the x-y plane.

[Prof. R.L. Taylor]

Another comment, I would recommend using the HILL plasticity model set for J2 behavior.  It is usually more robust in calculations and also allows for kinematic as well as isotropic hardening.  The user manual should describe how to use the various features of the model.

[Yaakov]

Dear Prof. Taylor,

Many thanks for your answer!

Actually, I want to make a tesion test of a circular bar using the  2-d axisymmetric analysis (3D Model is reduced to 2D Model.)

My  proposed FEAP Input File works, but I can't see any necking effects in output  that I have seen the articles/books  which are written by Prof. Simo or Prof. Miehe.

Is it possible that we could get a typical Benchmark File for 2-d axisymmetric analysis of a circular bar with necking effects?

Many thanks for your help again!

Kind regards,
Yaakov

[Prof. S. Govindjee]

To see necking you need something to trigger it, so a geometric perturbation or a thermal one like in the Miehe and Simo work.

[Prof. R.L. Taylor]

If I added density, then that made the analysis transient and triggered the necking just fine!  It required careful scaling of the time step and I did not let the analysis go to the "static" equilibrium state.

If you read the papers carefully you will find that authors add some perturbation, like a slight geometric taper near the mid-section; indeed such is usual in experimental setups too.

[Yaakov]

Dear Prof. Prof. Taylor and Dear Prof. Govindjee,

many thanks for your answer and support!

Today I have solved this problem in FEAP!

I attach the correct input file for 2-d axisymmetric analysis of a circular bar with necking effects.

Many thanks for your help again!
Kind regards,
Yaakov