Large Displacement

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

Hello,

 

I don't know when to use the option LGDISP in the PARAM-Card. The stresses at a simple beam without LGDISP are about 480 MPa, and with LGDISP just 230 MPa. The ultimate displacement of the component is about 22mm, so I don't think that LGDISP is required here. Can you please explain me, when this option should be activated?

 

Greets

Tom

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017

    Hi @Tom94

     

    Small displacement cannot handle geometric non linearity, follower load conditions and elasto plasctic material non linearity. In these case we use LGDISP. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017
    Altair Forum User said:

    Hi @Tom94

     

    Small displacement cannot handle geometric non linearity, follower load conditions and elasto plasctic material non linearity. In these case we use LGDISP. 

     

    Hi Prakash,

     

    the length of my beam is 430mm and the displacement is 22mm. Thats about 5%, so I should take geometric non linearity into account right?

    Is it the same when I do a NLSTAT simulation with LGDISP like doing a NLGEOM (implicit) simulation?

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017

    @Tom94

     

    Yes, but currently OptiStruct with LGDISP has some limitations. 

     

    From help document: Currently, in OptiStruct the large displacement capabilities include large strain elasto-plasticity (MATS1), hyperelasticity of polynomial form (MATHE), contact with small tangential motion, deformation dependent loads (follower loads), and rigid body constraints.

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