A question about the force and moment calculation in Rocky.

- March 21, 2023 at 3:48 am
  
  志仁朱
  Subscriber
  
  I have a question about Rocky and would like to ask the technical team: In Rocky's "DEM Technical Manual", it is stated that the force of shell particles is calculated at the joint connecting two shell units, as shown in the diagram. The green part represents the shell particles in Rocky, and the yellow part represents the sphere particles. Sphere particles Ball-1 and Ball-2 are in contact with Shell-0 and Shell-3 at points P1 and P2, respectively. I would like to ask about the forces and moments at these 7 joints: Joint-01, Joint-02, Joint-03, Joint-34, Joint-35, Joint-56, and Joint-57. The "DEM Technical Manual" and other Rocky manuals do not discuss the transmission of forces within the same shell unit and between different shell units.
- March 21, 2023 at 11:14 am
  
  Rob
  Ansys Employee
  
  I suspect it's the same as when a single particle strike is calculated. All that happens is there are more forces to resolve. Unfortunately we're only able to discuss what's in the documentation, so if it's not covered I can't comment in any detail.
  - March 21, 2023 at 11:24 am
    
    志仁朱
    Subscriber
    
    Thank you for your reply. I asked this question because the user manual does not specify the mechanism of force transfer on the Shell element. I would like to implement some custom function via the API, but I can’t start my work due to the lack of this information. I have read ‘DEM Technical Manual’, 'API Solver Manual'and 'Rocky Help 22.1.2'. However, there is no example of a Shell element here. 。･ﾟ･(つд`ﾟ)･ﾟ･ I just want to know how the force is distributed when a contact force is applied to the Shell element. The DEM technical manual says that the force of the Shell element is calculated on the joints connecting the two entities. So I was wondering, if the Shell element is subjected to a contact force, how is this force distributed to the three joints?
- March 22, 2023 at 5:08 pm
  
  Rob
  Ansys Employee
  
  Having checked, the particle strikes the surface facet, and any other strikes etc are calculated within that timestep. Then the facet positions and joints are updated as per the image and other documentation. I can't expand on that at present, but have requested a documentation improvement for the future.
  - March 23, 2023 at 12:42 am
    
    志仁朱
    Subscriber
    
    Thanks again for your reply and I'm looking forward to the updates on the documentation.

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