Estimation of residual stress by finite element analysis

[meetsrivatsan]

I am trying to do a finite element analysis ofcold extrusion process of a tube wherein the steel tube is reduced from a larger outer diamter to a smaller one by extrusion process.The tube is held stationary and the die is pushed into the tube for a particular length and then retrieved.I am interested in finding the residual stress distribution after extrusion. Do i have to take the stress state after the removal of die as residual stress or do i have to perform a spring back analysis after removing the die and then consider the resulting stress state as residual stress? Is there a procedure to estimate the residual stress by FEA.Any help in this regards will be highly appreciated.

 

[Mech_Engineer]

This will be a very challenging FEA problem to solve, and it would depend on very accurate material properties of the bar being extruded.

You could however estimate the stress by simply looking at the the size difference (strain) between the two tubes.

 

[meetsrivatsan]

Thank you for the reply.As the material behaviour is non linear during plastic deformation,i have to rely on FEA only.

Also the input billet for the extrusion in this case is also a tube and not a bar.Typical size of the billet is a tube of OD 76mm and thickness of 6mm which has to be extruded to 70mm OD .

I have come across some documents wherein after simulating the extrusion process,they do a spring back analysis to find the residual stress.I am not able to understand why spring back analysis has to be done separately after extrusion simulation.Any clarification in this regard will be of great help to me in understanding the FE simulation procedure.

I have the mechanical properties obtained from tensile tests and i am planning to use von mises yield criteria with isotropic hadening behaviour in the FE simulation.