Singularity Error in Frequency Response Analysis

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

Hi,

I am running a Frequency Response Analysis.

When I change the EIGRL entry to EIGRA, I get following error.

 

 *** ERROR # 3432 ***
 Singularity found in construction of constraint equations.
 Usually this happens when a dof is defined as slave in more than 
 one constraints. For inertia relief analysis this problem may be 
 overcome with SUPORT definitions and/or PARAM,COUPMASS,1.
  
 This error occurs in module 'asmbdrv'.
  

How this can be resolved ?

Answers

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited March 2019

    There has to be some issue with the mpc/rbe constraints.This error usually happens when for some reason a slave dof cannot be assigned to a constraint equation, because all the dofs in the equations are already spced are defined as slaves in other equations. Please also review the autospc table.
    If it is possible to share the model then please share, we will take a look.

  • chetanwable
    chetanwable Altair Community Member
    edited March 2019

    @Rahul R 

    1. there are no SPC/MPCs,

    2. also I just changed card from EIGRL to EIGRA, run with EIGRL is ok, but run with EIGRA isn't ( there is absolutely no other change )

    3. Also, same model with EIGRA - Normal modes is also ok.

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited March 2019

    can you please share the .out file of the run?

  • chetanwable
    chetanwable Altair Community Member
    edited March 2019

    @Rahul R I shared it.

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited March 2019

    Thanks for sharing the out files. I am not pretty sure on the reason of error unless we take a look in to the fem file.Why you don't have any SPC/MPCs for analysis. Please also check the comments section of EIGRA card.

    Unable to find an attachment - read this blog