ERROR # 312 *** In static load case 1 the compliance is negative or large 1.52002e+09. Optimization/buckling analysis cannot be performed. due to possible rigid body model.

Moawez Zamir Awan
Moawez Zamir Awan Altair Community Member
edited September 6 in Community Q&A

Hi! When performing size optimization I am getting this error message. I have read on this forum two possible explanations but both aren't correcting my error. Please let me know what to do.

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Answers

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited May 2020

    Hi,

    This error occurs when a model is under constrained or incorrect material property definition or contact definitions are incorrect or missing.

    error 312.JPG

    In your case (the units are tonne, MPA, mm) the pressure loading of 24000 MPA is causing excessive deformations.  You should review the unit consistency and/or pressure load magnitude.

  • Moawez Zamir Awan
    Moawez Zamir Awan Altair Community Member
    edited May 2020

    Hi! Thanks for answering my query. I wanted to ask for the Moment my units would be Nmm or Nm? Because I figured it would be Nmm since length is in mm but this is giving me an error due to large static compliance. 

    Also when I apply pressure should I calculate according to units in tonnes and mm? or I can directly apply the MPa unit as PA in N/m^2? I am a little confused by the units here.

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited October 2020

    Glad to help.

     

    Hypermesh is unitless and it is the user's responsibility to follow a consistent set of units.

    Force unit? - Altair HyperMesh - Altair Forum

    https://www.altairuniversity.com/wp-content/uploads/2012/04/Student_Guide_55-57.pdf

    Since the material properties are consistent with the tonne, MPA, mm unit system, the model dimensions and loads should follow the same units. So yes, the moment should be Nmm. You are getting a compliance error because of the unrealistically high pressure load of 24000 MPa. Applying only the moment load in the model you shared, the displacement is actually minimal (0.0068 mm). The pressure load should be calculated according to unit system (1 MPa = 1 N/mm2 = 1000000 Pa)

    https://community.altair.com/community?id=community_question&sys_id=e5860c3a1b2bd0908017dc61ec4bcb96

     

  • Adriano_Koga
    Adriano_Koga
    Altair Employee
    edited June 2020

    please, always check if your model is properly constrained, as suggested.

    Large compliance is often related to lack of constraints.

     

    Always perform an analysis only run to check your model, before going to optimization.

     

    In a few scenarios, lrge compliance might also be related to use of gap elements.

  • Vero_ortenzi
    Vero_ortenzi Altair Community Member
    edited September 5

    I have the same problem with the optimization attached. Can you help me solve this error?

  • Rajashri_Saha
    Rajashri_Saha
    Altair Employee
    edited September 6
    Vero_ortenzi said:

    I have the same problem with the optimization attached. Can you help me solve this error?

    Hi Vero,

    I just reviewed your file and realized that your design and non-design parts are not connected.

    Once I equivalenced the nodes, it runs without any issue and gives feasible result.

    Attached is the .out file of this run for reference.

    If this answers your query, mark this as correct answer so that it will go to solved status.

    Thanks

    Rajashri

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