How to select a singular point for fixed constraint boundary condition?

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Hello,

I am simulating a battery model in 2D that involves multiple concentric circles and shells to build the geometry. I am using the Structural Mechanics module and seek to model the deformation in this 2D battery model.

I am trying to apply a fixed constraint boundary condition to prevent rigid body motion. Ideally, I would like to apply the fixed constraint boundary condition on a singular point on the outer shell of my 2D battery model, however I can't find a way to do so. At the minimum, I'm only able to have a quarter of my outermost shell undergo fixed constraint - not a singular point as I seek to do - and this conflicts with the underlying physics of my system.

Any input would be greatly appreciated.

Best, AU



2 Replies Last Post 2026/01/20 19:02 GMT-5
Jeff Hiller COMSOL Employee

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Posted: 3 hours ago 2026/01/20 16:19 GMT-5

Constraining a single point to have no displacement would not be enough to remove all rigid body motions, even in 2D: the rigid body rotation around that point would still be unchecked. In 2D there are 3 rigid body motions, so you need at least 3 constraints on points to eliminate all of three of them. For instance, you could restrict two point on the y=0 axis to have zero y displacement and one point on the x=0 axis to have zero x displacement.

Best,

Jeff

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Jeff Hiller
Constraining a single point to have no displacement would not be enough to remove all rigid body motions, even in 2D: the rigid body rotation around that point would still be unchecked. In 2D there are 3 rigid body motions, so you need at least 3 constraints on points to eliminate all of three of them. For instance, you could restrict two point on the y=0 axis to have zero y displacement and one point on the x=0 axis to have zero x displacement. Best, Jeff

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Posted: 16 minutes ago 2026/01/20 19:02 GMT-5

Hello Jeff,

Thank you for your response. I understand your approach for preventing rigid body motion and will apply the framework. However, I am still unsure how to restrict individual points as I can only select arcs on my geometry (consisting of concentric shells) for the fixed constraint boundary condition.

Best, AU

Hello Jeff, Thank you for your response. I understand your approach for preventing rigid body motion and will apply the framework. However, I am still unsure how to restrict individual points as I can only select arcs on my geometry (consisting of concentric shells) for the fixed constraint boundary condition. Best, AU

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