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Hi,

I am doing a mechanical, nonlinear analysis on a microphone's diaphragm. The goal is to perform a time-dependent analysis and see any nonlinearities in the diaphragm's deflection.

Below is a summary.

• 2D axisymmetric model
• Solid Mechanics physics
• Time dependent study
• Sinusoidal pressure input on the diaphragm (diaphragm is stressed)
• Probe at the center of the diaphragm to see the displacement as a function of time

The issue:

• When looking at the sinusoidal deflection as a function of time during the simulation (from the probe), everything looks fine until the deflections reach a certain positive value. For example, I see the bottom half of the sine wave (negative deflections, real numbers) and then the sine wave will stop producing. My probe is showing deflection values of NaN during this period. It will then resume producing the sine wave.

Troubleshooting:

• The problem goes away when I turn off the geometric nonlinearities.
• When I reduce the sound pressure level, the problem also goes away (but I'm unable to generate the nonlinearities I'm looking for).
• I have tried making the mesh finer and I don't believe any major differences occurred.
• I have changed the diaphragm geometry, which changes the point where the NaN's begin, but it doesn't get rid of them.

Does anyone have any advice for how to solve this? The fact that it is able to run and produce portions of the sine wave is something I haven't seen before. Thank you.