Thank you. I had this paper.

Your response is repeated for 3 times. Just for RG score??

Dear Amir,

the initial powder density of the powder during a compaction test can be calculated experimentally. ABAQUS has nothing to do with it. Before you fill the die you need to weight the powder that you intend to fill the die with. After filling the die with the powder you could measure the volume occupied  by the powder and then you can get the density by dividing the powder weight over the volume. The relative density can be obtained by dividing the calculated density over the true density of the powder. The calculated relative density could then be used inside the Drucker-Prager Cap (DPC) model.

Dear Ahmad

Thank you for your response. This question has been posted a long time ago. To define initial relative density in ABAQUS, you can use USDFLD subroutine and relate the material model constants (specially the Young's modulus) to instantaneous relative density (PEQC4).

Amir 

Thanks Amir,

you are right that you need to use USDFLD to change the model parameters with the relative density.

My respond was about how to get the value of relative density at the starting of the simulation where there is no plastic strain and the force has not applied yet.

Regards,

Ahmad

You said: "The calculated relative density could then be used inside the Drucker-Prager Cap (DPC) model"

It is impossible to use relative density in the DPC model. DPC has 6 different plasticity constants like angle of friction, material cohesion , ...