Simulation of 3D motion on rigid body master node

rea2
rea2 Altair Community Member
edited October 2020 in Community Q&A

We have a modell consisting of a femur and an acetabulum (hip bones), both modelled as as a shell and put into a rigid body. I'd like to simulate a gait cycle, so I created an imposed displacement on the rigid body master node of my femur. It however does not work, Radioss Block tells me there are incompatible kinematic conditions on this node, even if I just have one imposed displacement on that node. When I run it through Radioss and display the result in Hypermesh, no motion can be seen. Can anyone help? I've attached the rad files.

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Answers

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited September 2018

    Hi, 

     

    I think the issue is because kinetic relaxation option is turned on (/KEREL), which is effective for settling under gravity load (see dummy positioning example), but is not appropriate for imposed displacements. In the model you have shared there are no incompatible kinematic conditions. However, there are some minor issues with the set up of simulation:

    -tied interface are referring to default type2 interface definition, which is not given

    -there are a total of 33 nodes for which no master surface is found during starter

    -the mass scaling is turned on but no timestep is defined (1e-2 will give mass error below 2%)

    -there are no boundary conditions (constraint) applied to Acetabulum, however the simulation still gives some displacements (in the order of 5e-3)

     

  • rea2
    rea2 Altair Community Member
    edited September 2018
    Altair Forum User said:

    Hi, 

     

    I think the issue is because kinetic relaxation option is turned on (/KEREL), which is effective for settling under gravity load (see dummy positioning example), but is not appropriate for imposed displacements. In the model you have shared there are no incompatible kinematic conditions. However, there are some minor issues with the set up of simulation:

    -tied interface are referring to default type2 interface definition, which is not given

    -there are a total of 33 nodes for which no master surface is found during starter

    -the mass scaling is turned on but no timestep is defined (1e-2 will give mass error below 2%)

    -there are no boundary conditions (constraint) applied to Acetabulum, however the simulation still gives some displacements (in the order of 5e-3)

     

     

    Thank you for your input! 

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