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In comsol is it possible to set a BC for a couple of seconds and then release it?

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As states i am running a time-dependent simulation in solid mechanics. I want to set a prescribed displacement to zero for the first 0.05s and then release it to free. Is there any way that I can do it?


2 Replies Last Post 24 feb 2020, 09:30 GMT-5
Magnus Ringh COMSOL Employee

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Posted: 5 years ago 24 feb 2020, 09:13 GMT-5

Hi Boyue,

You should be able to get such an effect by adding a Prescribed Displacement node and choose the General notation option. Then add an expression for the H matrix (really an isotropic scalar value here) like

1*(t[1/s]<0.05)

where t is the time (made dimensionless by [1/s]). When then time is less than 0.05 s, the expression becomes 1, and the displacement is set to 0. When the time is 0.05 or more, the equation for the prescribed displacement is essentially 0 = 0, which does not add any constraint, so the boundary becomes free.

Best regards,

Magnus Ringh, COMSOL

Hi Boyue, You should be able to get such an effect by adding a **Prescribed Displacement** node and choose the **General notation** option. Then add an expression for the **H matrix** (really an isotropic scalar value here) like `1*(t[1/s]

Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago 24 feb 2020, 09:30 GMT-5

See also this blog post :

https://www.comsol.se/blogs/how-to-make-boundary-conditions-conditional-in-your-simulation

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Henrik Sönnerlind
COMSOL
See also this blog post :

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