Learning Forum

[lorenzo.loria]

Good evening, I am trying to use the "Transient coupled field" simulation environment for a Thermo-Mechanical simulation. my simulation is divided into 2 steps. The first one which lasts 1 second has both a pressure load (with an axial position array) and a heat load (given by using an APDL command). During the second phase (time step 2) I want to remove both the pressure load and the APDL command. Removing Structural load at different time steps is pretty straightforward since they can be deactivated easily from the "tabular data" with just RMB. Instead, for removing an APDL I used another APDL, defined at time step 2 with the following command line.

Although the actual thermal load has been removed, as can be seen from the following photo showing the temperature over time, something strange happens to

the deformation.

 

In fact, everything is normal up until 1 second when my nozzle is teleported above the assembly.

I don't think the problem is strictly related to the second APDL command line, but I have never had this happen to me using just one. Another interesting view that I have on the probable issue is related to the residual criteria used after the first time step. In fact, if we see the solver output we can see that after the first time step, the residual displacement criteria changed, increasing drastically, while force and heat residual criteria remained unchanged.

 

Do you think the problem relates to the APDL deactivation or the residual criteria? If it is the second one, is there a way to set a different residual value for different time steps? 
Just to provide more information, the geometry is the one shown below and all the contacts are frictionless except for the bluish one which are bonded together

Thank you very much in advance!

[John Doyle]

Not sure, but it looks like you are selecting the surface elements AFTER you execute the SFEDELE command.  Is that intentional?  It seems backwards.  What is the purpose of the selection logic?