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Piezoelectric cantilever based energy harvester- body load notation query

Posted 2021/10/06 5:59 GMT-4 MEMS & Nanotechnology, Piezoelectric Devices Version 5.0 2 Replies

K Naveen Kumar
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Hello everyone,

I have desined a 3D multilayered cantilever piezoelectric structure. I have clearly defined the materials and assigned it to its respective domain.

I have to simulate it for vertical body acceleration.

In the existing piezoelectric energy model (this is in 2D) in application library, the body load is given as solid.rho*g_const*acc.

I have done the same for my 3D structure. But I am getting the error showing "undefined variable" "failed to evaluate variable".

Can anyone solve this query??

2 Replies Last Post 2021/10/06 9:43 GMT-4
Magnus Ringh COMSOL Employee

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Posted: 3 years ago 2021/10/06 7:44 GMT-4

Hi,

You get this error because the Solid Mechanics interface in the model is called Solid Mechanics 2, with the tag solid2. So, changing the expression to -solid2.rho*g_const*acc in the Settings window for the Body Load node makes the simulation run.

Best regards,

Magnus

Hi, You get this error because the Solid Mechanics interface in the model is called **Solid Mechanics 2**, with the tag `solid2`. So, changing the expression to `-solid2.rho*g_const*acc` in the Settings window for the **Body Load** node makes the simulation run. Best regards, Magnus
K Naveen Kumar
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Posted: 3 years ago 2021/10/06 9:43 GMT-4

Hi Magnus,

Thank you very much for the reply.

But now, it showing error as "There are 1 void equations (empty rows in matrix) for the variable comp1.es.term1.Q0_ode. at coordinates: (0,0)" and "return solution is not converged"

I have connected the ground to the lower face of PZT and other terminal at the top face of PZT. And i have included the electric circuit as well.

Thanks.

Hi Magnus, Thank you very much for the reply. But now, it showing error as "There are 1 void equations (empty rows in matrix) for the variable comp1.es.term1.Q0_ode. at coordinates: (0,0)" and "return solution is not converged" I have connected the ground to the lower face of PZT and other terminal at the top face of PZT. And i have included the electric circuit as well. Thanks.

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