Inertia relief

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi,

 

In Optistruct, for solving inertia relief problems, the reference point is the CG of the model by default. How to change this reference point ?

 

Thanks

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Answers

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited May 2016

    I feel inertia relief is free of CG.See attached screenshot.

    If you want to change RBE center node location you can use translate command.

    <?xml version="1.0" encoding="UTF-8"?>inertia relief.JPG

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2016

    AFAIK, displacements of all the nodes are calculated with respect to some reference node. And I can confirm its neither CG nor geometric center of the model (as somewhere mentioned in your forums). Please can anyone give some insights on this ?

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited August 2016

    This reference point in .out file is that the reference point to calculate the rigid body modes for inertia relief analysis.

    With INREL,-1, the user needs to specify SUPORT point (you may call this reference point also, which could cause some confusion). With INREL,-2, SUPORT is not required and there is no internally defined suport point either but technically the same effect as suport point at CG of the model.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2016

    'This reference point in .out file is that the reference point to calculate the rigid body modes for inertia relief analysis'

    Please elaborate.

     

    And regarding INREL -2, relative displacements between any two nodes would be same only and here your whole body is deforming subjected to combination of applied loads and balancing fictious inertial loads. SInce here all nodes are moving, relative deformation makes sense but I don't understand how the refernce node is calculated? No.. It's not CG either.. You can try running some analysis with 3D elements as well as 1D springs and check the results file.

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