JKR Model- Surface Energy to geometry?

Ella_22416
Ella_22416 Altair Community Member
edited September 2022 in Community Q&A

Hello everyone,

I have a question about the JKR Model. I do not know how to set the surface energy of particles-particle vs. surface energy of particle-geometry. My understanding is the surface energy of a particle to particle will give us cohesion, and the surface energy of a particle to geometry will give us adhesion.

I know we need to calibrate the powder, but I'm working on a parametric study of surface energy on heat transfer therefore, I'm not calibrating any powder. I know that Increasing the surface energy of particles will give me more cohesive behavior, but I'm not sure how to set the surface energy of particles to geometry in each case. Can I pick any number and have the parametric study for this, too? or Are there any relationships that I need to follow between Particle-Particle surface energy Vs. Particle-Geometry surface energy?

I would appreciate any help in this regard

Thanks!

 

 

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Answers

  • PrasadAvilala
    PrasadAvilala
    Altair Employee
    edited September 2022

    Hi Ella,

     

    It is difficult to suggest any other method without knowing the objective of the problem. 

    Can you please share some more details about your objective and answers to below questions

    1)What do you mean by parametric study of surface energy?

    2) why are you doing surface energy study against heat transfer?

     

    Thanks,

    Prasad A

     

  • Stefan Pantaleev_21979
    Stefan Pantaleev_21979
    Altair Employee
    edited September 2022

    Hi Ella,

    If you are modelling at the physical particle scale, the sruface energy can be related to the Hamaker constant of the two materials in contact by the Frenkel relation (equation 4 in below paper).

    Capece, M. et al. (2015) ‘Prediction of powder flow performance using a multi-component granular Bond number’, Powder Technology. Elsevier B.V., 286, pp. 561–571. doi: 10.1016/j.powtec.2015.08.031.

    This book is a good reference in general on tribological forces:

    Israelachvili, J.N., 2011. Intermolecular and surface forces. Academic press.

    If you are not modelling at the physical particle scale, the strict definition of surface energy is violated and an appropriate value needs to be indirectly determined for a given set of macro-mechanical properties via calibration. This is the case for both the particle-particle and particle-geometry interactions.

    A good way to pick a reasonable range for the surface energy is to keep the Bond number (ratio of adhesive force to particle weight) within the range 0 - 30. The above paper discusses calculations for the Bond number as a function of surface energy and you can also use the parameter estimator in the EEPA contact model, keeping the pull-off force = 0 and changing the surface energy only.

    image

    The surface energy may affect the heat flux trhough the granular assembly through a change in the packing state (a reduction in solid fraction with increasing surface energy) but this would be primarily controlled by the particle - particle interaction so I do not expect particle - geometry interactions to be signifficant (provided the Bond number is within a reasonable range as above so that the affect of adhesive force on contact area is negligible).

     

    Best regards,

    Stefan 

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