How to reduce the compressibility of a powder material?

Carlos Fondevila

I'm triying to calibrate a powder material in EDEM, this powder in the empiric experiment, has a compressibility of a 10% under a pressure of 6986Pa. When I want to calibrate the material with EDEM, teorically for to play with the compressibility of the material, I can to adjust the Young Modulus, but even increasing the Young Modulus in a high value, I can't achieve the compressiblity of the 10% under the metioned pressure (I obtain compresibilties of 20-30%).

I'm using doble spheres with a 1,5mm size, and I understand that the major part of the compression that the powder experiments in EDEM comes from intergranular relocation, and not from the stifness of the particles, due this, I can't achieve the specified compressiblity, and increasing the Young Modulus I lead to a very long simulation time.

How can I play with the compressiblity of the powder to achieve the correct value?

Thanks.

Stephen Cole

Hi Carlos,

Which particle-particle physics model are you using?  The standard Hertz-Mindlin is an incompressible model but you can add in the EEPA model which allows compressible (plastic) behaviour:

https://2022.help.altair.com/2022.2/EDEM/Simulator/Creator/Physics/Base_Models/Edinburgh_Elasto-Plastic_Adhesion_Model_(EEPA).htm

The EEPA model allows you to set the plasticity of the model however if you are already using the Hertz model then that is the same as using the fully elastic part of the EEPA.

There may be a question on the starting point when measuring the compressibility, is it loosely poured or tapped/compacted before starting the test?

 

Regards

Stephen

Carlos Fondevila

Stephen Cole_21117 said:

Hi Carlos,

Which particle-particle physics model are you using?  The standard Hertz-Mindlin is an incompressible model but you can add in the EEPA model which allows compressible (plastic) behaviour:

https://2022.help.altair.com/2022.2/EDEM/Simulator/Creator/Physics/Base_Models/Edinburgh_Elasto-Plastic_Adhesion_Model_(EEPA).htm

The EEPA model allows you to set the plasticity of the model however if you are already using the Hertz model then that is the same as using the fully elastic part of the EEPA.

There may be a question on the starting point when measuring the compressibility, is it loosely poured or tapped/compacted before starting the test?

 

Regards

Stephen

Hi Stephen,

The contact model that I'm using is the EEPA

Sorry, I think that I have not used the correct words, my problem is not caused by the plasticity of the material, but it's caused about the stiffness of the material (I think that this can be the correct definition).

In my experiment I drop loosely poured the powder in a cylinder, ant then I aply pressure to the powder with a type of plunger.

In this compression (equivalent to 7000Pa) the powder suffer a decrease in his heigh of 4%, and in my model I am not able to adjust the parameters of the powder to have an equivalent decrease of product height in EDEM, I always have upper to 4%, I deduce, caused due to Interparticular replacement, not about the stiffness of the material, and I think that I can't to avoid it, playing with the stifness of the material, because the gain are low, and it repercutes very negatively in terms of simulation time.