Ramberg-Osgood

[Anonymous]

Hello,

I am coupling Abaqus and Moldflow using Helius PFA (AME), when analyzing a fiber reinforced component. Everything was great, but now Im trying to understand how Helius works the Ramberg-Osgood in order to get the elastic and plastic coefficients (n,alpha,beta....).

I found your plasticity model here:

http://help.autodesk.com/view/ACMPAN/2016/ENU/?guid=GUID-F156C59C-37BE-437C-AD98-CD40B72BB89C

however the equation (1) doesnt look like the typical Ramberg-Osgood formulation:

https://en.wikipedia.org/wiki/Ramberg%E2%80%93Osgood_relationship

Where is your parameter alfa ou K from tthe typical formulation? Which E ist that in you plasticity model? E from the matrix or from the homogenized composite?

I cant understand as well a parameter named "Eig" on my Material Data in Helius PFA, what is it?

Im trying to plot the Ramberg-Osgood curve using my material's decomposition data, how can I do it?

Best regards,

André Oliveira

[andrew.morrison · Accepted solution]

Hi André,

K=1 in our formulation. The ramberg-osgood model is excercised at the matrix level so all the material properties are matrix properties. The ramberg-osgood model defines how the matrix effective plastic strain and matrix tangent modulus evolves for a given strain increment. The matrix tangent modulus is than used in the homgoenization process to obtain the composite level stiffness. We pretty much follow the work of "BA Nghiep Nguyen. , Prediction of the Elastic-Plastic Stress/Strain Response for Injection-Molded Long Fiber Thermoplastics."

One difference is that we use a weighted von mises effective stress. Where the matrix stress components are weighted by alpha and beta as described in the documentation. The eig value you refer to is λm,I  in the documentation. It is a represenative largest eigenvalue of the fiber orienation tensors found in the plaque that the experimental data is gathered from.  

-Andrew

[Anonymous]

Hi, @andrew.morrison
I'm have the doubt about  λm,I . How is it calculated? or  what does it depend on?

David Amorim