*MPC Plane

PaulFlynn

I'm trying to keep a surface of a model in a plane.  I thought I had this fixed, but now it doesn't work.

The *MPC Plane instructions are pretty simple.  

I define Top_Nodes as a named group and put this in the CCX Model window.

*MPC

Plane,Top_Nodes

Also, I tried with individual node numbers.  Same results.

and I get this in the input file

*MPC

Plane,Top_Nodes

*STEP

*STATIC

*CLOAD

134,2,-100

*NODE FILE,GLOBAL=YES

U,RF

*EL FILE

S

*END STEP

I get these warnings in the output file and no results. I've checked and there are no duplicates between SPC's and the MPC Plane dof's

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 *WARNING in nonlinmpc: coefficient of

          dependent node in PLANE MPC is zero

 Decascading the MPC's

 Determining the structure of the matrix:

 number of equations

 1395

 number of nonzero lower triangular matrix elements

 79958

 Using up to 1 cpu(s) for the stress calculation.

 Using up to 1 cpu(s) for the symmetric stiffness/mass contributions.

 Factoring the system of equations using the symmetric spooles solver

 Using 1 cpu for spooles.

Victor

One problem is that the first 3 nodes in the node set that Mecway generates for Top_Nodes lie on a line, which isn't allowed by *MPC.

Another problem which I can't explain, is that it works when your scale up the size of the mesh by a factor of 10. Maybe it's a CCX bug.

Here's a working model but it's 10x longer and has one node moved out of the line.

Andrea

With *Rigid Body card you can find a solution.
All surface nodes partecipates to rigid body

There is a difference of stresses and deformations respect *MPC plane