Characterize cohesive powder product without success

Carlos Fondevila
Carlos Fondevila Altair Community Member
edited April 3 in Community Q&A

Hi guys,

I'm trying to characterize a powder regarding an empiric experiment. The experiment consist in compress powder in a cylinder with a tapped hole, and when the powder is consolidated, untap the hole, and increase a force acting in the upper surface of the powder to achive the collapse of the consolidated powder, to obtain the value of force needed to "brake" the consolidated product. You can see the sequence bellow:

image

I'm working with the EEPA contact model, and as I understand, to increase the capabilty of the product to hold loads once consolidated, I need to increase the value of Surface Energy, this give the force that we need to "separate" particles after consolidated.

Well, I'm trying to increase the value up tu exagerated values, (50-100) and the product falls throw the hole in the setep 4, it seems that the product has not enough cohesion force to suppert de load.

As I understand, increasing the value of Surface Energy, you can increase (in negative way) the Minimum force (fcp, bellow), and theorically, the particles, after compression, should need more force to separate between them. Is this approach not correct?

image

Tagged:

Answers

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited April 3

    Hi Carlos,


    Increasing the Surface Energy (used in fcp) value or setting a larger negative constant pull-off force (f0) will increase the cohesivity of the material.  The Surface Energy input is typically a +ve value and the constant pull off force a -ve.

    It maybe the values are too high making the simulation unstable, the EEPA model gives some Estimated properties including the recommended time-step.  I would not recommended increasing the cohesion too much so that the bond number is excessively large as this may make the simulation unstable.  Also best to make sure you don't exceed the recommended time-step for the EEPA model.


    Regards

    Stephen

Categories