the Hertz-Mindlin with JKR contact model: A question about the negative overlap.

Yu Mu
Yu Mu Altair Community Member
edited July 2022 in Community Q&A

Hello everyone,

In the EDEM 2020.2 document, the normal force-negative normal overlap is described as follows:

image

In the description of the document, the negative overlap is allowed, and will still produce cohesion after particle separation. But the document mentioned at the end:

image

Does this mean that it is impossible to calculate the case where the overlap is negative?

I also see the following figure in the case of EDEM Tutorial： Transfer Chute and JKR Model:

image

The above figure shows the force won't be calculated if the overlap is negative in EDEM.

I'm confused about this. Can this model calculate the force of negative overlap, as described in the document?

Tagged:

Best Answer

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited July 2022 Answer ✓

    Hi,

     

    The JKR v1 model doesn't correctly calculate the force if the overlap is -ve at the point of first contact.  The attractive force at -ve overlap should really only happen after the physical contact has happened.  In the v1 model this force will happen as soon as the contact radii overlap, in the v2 JKR model this attractive force will only occur after the physical contact has occurred and the particles are pulling apart.


    Regards

    Stephen

Answers

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited July 2022 Answer ✓

    Hi,

     

    The JKR v1 model doesn't correctly calculate the force if the overlap is -ve at the point of first contact.  The attractive force at -ve overlap should really only happen after the physical contact has happened.  In the v1 model this force will happen as soon as the contact radii overlap, in the v2 JKR model this attractive force will only occur after the physical contact has occurred and the particles are pulling apart.


    Regards

    Stephen

  • Yu Mu
    Yu Mu Altair Community Member
    edited July 2022
    Stephen Cole_21117 said:

    Hi,

     

    The JKR v1 model doesn't correctly calculate the force if the overlap is -ve at the point of first contact.  The attractive force at -ve overlap should really only happen after the physical contact has happened.  In the v1 model this force will happen as soon as the contact radii overlap, in the v2 JKR model this attractive force will only occur after the physical contact has occurred and the particles are pulling apart.


    Regards

    Stephen

    Hi,

     

    Thank you for your answer! I also want to know, if the contact radius is not turned on, will the attraction of negative overlap is also not calculated when using the JKR V1 model?

     

    Sincerely,

    Yu

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited July 2022
    Yu Mu said:

    Hi,

     

    Thank you for your answer! I also want to know, if the contact radius is not turned on, will the attraction of negative overlap is also not calculated when using the JKR V1 model?

     

    Sincerely,

    Yu

    That's correct,  if the contact radius is not turned on (for any model) the contact will never be detected if the particles are not physically in contact.  Then if the contact is not detected the physics model will never be entered and no force calculated.


    Regards

    Stephen

  • Yu Mu
    Yu Mu Altair Community Member
    edited July 2022
    Stephen Cole_21117 said:

    That's correct,  if the contact radius is not turned on (for any model) the contact will never be detected if the particles are not physically in contact.  Then if the contact is not detected the physics model will never be entered and no force calculated.


    Regards

    Stephen

    Thank you for your patience! It helps me a lot.

     

    Sincerely,

    Yu

Categories