Error (excessive pivot ratios) while applying MPC on 3D elements (Hex)

I have created two solid bodies with a gap between them and meshed it with HEX elements. I want to connect nodes on adjacent sides of the gap using MPC (RBAR or rigid). SOL 101 is performed but I keep on getting error excessive pivot ratios (elements failed directions occur on rotational DOFs) . When I performed SOL 103 I got rigid body motions in rotational DOFs. Can anyone help me troubleshoot this problem? .bdf and f06 file has been attached for reference.

Do solid elements support application of MPCs?

Attached Files (2)

MPC_3D_element.bdf.zip

MPC_3D_element.f06.zip

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0 Dave Popejoy over 5 years ago

The issue is the rotational DOFs. The 3D solid elements do not have stiffness in those DOFs, so the RBE2s act as if they're connected via ball joints. There are different ways to add in the rotational stiffnesses; one way is to coat the solids with thin shell elements, which I've done in the attached file.

Attached Files (1)

MPC_3D_element_add_shells.bdf.zip
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0 Dave Popejoy over 5 years ago

The issue is the rotational DOFs. The 3D solid elements do not have stiffness in those DOFs, so the RBE2s act as if they're connected via ball joints. There are different ways to add in the rotational stiffnesses; one way is to coat the solids with thin shell elements, which I've done in the attached file.

Attached Files (1)

MPC_3D_element_add_shells.bdf.zip
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