Hello,
I am trying to model the stress-induced curvature of a thin plate with an even thinner coating, each with different CTE, when heated or cooled.
The plate is only ~100um thick, and the coating is only a few microns. I have tested the solid mechanics physics by using two stacked extended 3D elements of similar thickness, and I believe the results make sense. For this, I made two plates of 100 um thickness, assigned materials with two different CTEs, and meshed appropriately so that there was a few elements in the thin direction. For constraints, I prescribed the displacement of the 4 lower edges of the bottom plate to reside in the z=0 plane, and I also fixed a point to have x,y=0 displacement (to prevent translation). This allows the whole system to rotate, but it did not stop the solver from converging. I am using a stationary solver.
Since the real coating is so thin, using the above method seems impractical due to meshing considerations. Instead, I would like to use a shell. So, I have added shell physics and removed the second plate altogether. I have added thermal expansion to both the shell and solid physics, and I have prescribed the same material to all domains (there's only one) and boundaries EXCEPT the top surface, where I want to simulate the coating. After doing some reading on the forums, I have seen that I should do the prescribed displacement constraints in the shell model and not in the solid model (is this correct?).
After doing all this, I am unable to get any results. The solver always returns saying that the relative error is greater than the tolerance. In some cases with the original all-solid model, I got a similar error, but was able to get around this by explicitly selecting a nonlinear solver (not sure if this is a correct thing to do). Doing this in the solid/shell model only makes it run through the full iteration limit (I selected 500) before returning the usual error.
Can you tell me if I am setting up the model correctly? In general, how does one connect shell and solid physics like I am trying to do?
I am trying to model the stress-induced curvature of a thin plate with an even thinner coating, each with different CTE, when heated or cooled.
The plate is only ~100um thick, and the coating is only a few microns. I have tested the solid mechanics physics by using two stacked extended 3D elements of similar thickness, and I believe the results make sense. For this, I made two plates of 100 um thickness, assigned materials with two different CTEs, and meshed appropriately so that there was a few elements in the thin direction. For constraints, I prescribed the displacement of the 4 lower edges of the bottom plate to reside in the z=0 plane, and I also fixed a point to have x,y=0 displacement (to prevent translation). This allows the whole system to rotate, but it did not stop the solver from converging. I am using a stationary solver.
Since the real coating is so thin, using the above method seems impractical due to meshing considerations. Instead, I would like to use a shell. So, I have added shell physics and removed the second plate altogether. I have added thermal expansion to both the shell and solid physics, and I have prescribed the same material to all domains (there's only one) and boundaries EXCEPT the top surface, where I want to simulate the coating. After doing some reading on the forums, I have seen that I should do the prescribed displacement constraints in the shell model and not in the solid model (is this correct?).
After doing all this, I am unable to get any results. The solver always returns saying that the relative error is greater than the tolerance. In some cases with the original all-solid model, I got a similar error, but was able to get around this by explicitly selecting a nonlinear solver (not sure if this is a correct thing to do). Doing this in the solid/shell model only makes it run through the full iteration limit (I selected 500) before returning the usual error.
Can you tell me if I am setting up the model correctly? In general, how does one connect shell and solid physics like I am trying to do?