Hello

 I need to propagate a crack by releasing nodes with an MPC subroutine. So first I wrote an MPC subroutine to constrain the nodes of the crack path to a node on which a symmetry boundary condition with respect to z is applied ( U3=R1=R2=0). However, it doesn't work and I don't know where the error comes from. Can you please help me? Thanks in advance 

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