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#1 2021-04-23 22:31:05

Bragadesh_Srivatsan
Member
Registered: 2021-04-23
Posts: 17

Singularity error when trying to simulate 3D 3 point Bending.

Hello,

I am new to Code aster and I am trying to simulate 3 point bending of Beam in 3D.

I get a matrix singular error when I try to run the case. I learned from the forum that this error is due to the Rigid body motion of one of the components.

Here I have the displacement load in the negative y-direction and I get the error that I have not constrained the beam in the DY direction. I want the beam to be supported by the support pins in the y-direction and thus do not want to constraint in the DY direction.

The simulation ran successfully if the Beam nodes fixed in the DY direction, but this defeats the purpose of support pins in 3 point bending assembly.

I have attached the message file and mesh file and .comm file for reference.

Thanks in advance

Last edited by Bragadesh_Srivatsan (2021-04-23 22:31:35)


Attachments:
3pbend_beam.zip, Size: 607.04 KiB, Downloads: 80

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#2 2021-04-24 08:42:05

sameer21101970
Member
Registered: 2019-09-06
Posts: 353

Re: Singularity error when trying to simulate 3D 3 point Bending.

ADD Below steps as well as per your contact groups, It should work or re-send .comm file after making changes

mesh = MODI_MAILLAGE(reuse=mesh,
                     MAILLAGE=mesh,
                     ORIE_PEAU_3D=_F(GROUP_MA=('pincont', 'rackcon')))

mesh = DEFI_GROUP(reuse=mesh,
                  CREA_GROUP_MA=_F(NOM='tout',
                                   TOUT='OUI'),
                  CREA_GROUP_NO=_F(GROUP_MA=('tout', )),
                  MAILLAGE=mesh)

mesh0 = CREA_MAILLAGE(CREA_POI1=_F(GROUP_NO=('tout', ),
                                   NOM_GROUP_MA=('ressorts', )),
                      MAILLAGE=mesh)

model = AFFE_MODELE(AFFE=(_F(MODELISATION=('3D', ),
                             PHENOMENE='MECANIQUE',
                             TOUT='OUI'),
                          _F(GROUP_MA=('ressorts', ),
                             MODELISATION=('DIS_T', ),
                             PHENOMENE='MECANIQUE')),
                    MAILLAGE=mesh0)

elemprop = AFFE_CARA_ELEM(DISCRET=_F(CARA='K_T_D_N',
                                     GROUP_MA=('ressorts', ),
                                     VALE=(0.1, 0.1, 0.1)),
                          MODELE=model)

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#3 2021-04-24 18:27:06

Bragadesh_Srivatsan
Member
Registered: 2021-04-23
Posts: 17

Re: Singularity error when trying to simulate 3D 3 point Bending.

Thank you, Sameer for your help.

I have included the above command in the model to add spring elements, and I do not get the singularity error but the contact iteration does not converge even after 50 iterations. Is this because of contact condition or am I missing something else?


I have attached the mesh file, .comm file and message file for your reference.


Attachments:
3pbend_beam_modified_1.zip, Size: 620.86 KiB, Downloads: 95

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#4 2021-04-26 10:01:48

sameer21101970
Member
Registered: 2019-09-06
Posts: 353

Re: Singularity error when trying to simulate 3D 3 point Bending.

the attached .comm is working. first make simple load steps then tune .comm to complexity.
you can modify on attach .comm file.


Attachments:
3pb_3D_beam_updated_1.comm, Size: 5.96 KiB, Downloads: 116

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#5 2021-04-26 15:10:57

Bragadesh_Srivatsan
Member
Registered: 2021-04-23
Posts: 17

Re: Singularity error when trying to simulate 3D 3 point Bending.

Thank you, Sameer.  The file works now.

The problem with my file was the contact. Thank you very much.

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