Learning Forum

[ssagar]

I am doing a tensile test with a combination of SPH particles for the gage length and shell elements for the moving and fixed heads. To save computation effort and time, I made the shell elements rigid bodies in LS-DYNA. I am not able to determine the reaction on the fixed side (rigid body). Does anyone know how to if at all one can extract the reactions on a rigid body in LS-DYNA.

[Andreas Koutras]

You can restrain the rigid body by prescribing zero displacement using *BOUNDARY_PRESCRIBED_MOTION_RIGID, instead of using the fields CON1, CON2 in *MAT_RIGID. Then you can obtain the forces at the restrained dof through *DATABASE_BNDOUT.

[ssagar]

Thank you very much Andreas I did just that. Only thing now is that how do I constrain in all degrees of freedoms? At the moment the BOUNDARY_PRESCRIBED_MOTION_RIGID card only has options per DOF. Do I need to specify this 6 times for the fixed end for each DOF? Moving rigid body is fine as I used CON 1 and CON2 in MAT_RIGID. I really want to find the reaction in the fixed support only.
Thanks.

[Andreas Koutras]

You can use BOUNDARY_PRESCRIBED_MOTION_RIGID to just restrain the DOF you are interested in and for the remaining DOFs you can specify CON1, CON2 such that they don't conflict the BOUNDARY_PRESCRIBED_MOTION_RIGID.

[ssagar]

Thank you again so much Andreas. Did it and it worked perfectly :-)
SS