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Adding a Point Load Without a Geometrical Point

Posted May 31, 2018, 1:32 p.m. EDT Structural Mechanics Version 5.2a 3 Replies

Ben Pang
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Hello, I'm a new learner about COMSOL. Now I'm modeling a bending beam and want to simulate its stress. I create a 3D model and build a block(cuboid) suppose it's a beam. Then I fix one side of block, and add force on another side(opposite fixed side). Now I want to add force on this side in different point (suppose I select ten points) to see the stress. I try to use Points in Physics, but it only can be selected on block's eight corners. Could someone please help me to solve this? Thank you very much.

3 Replies Last Post Jun 5, 2018, 9:47 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 1, 2018, 1:57 a.m. EDT
Updated: 6 years ago Jun 1, 2018, 2:00 a.m. EDT

Hi Ben,

A Point Load can only be applied to a geometrical point, so you will to add more points to your geometry.

There is however a way to add a load at an arbitrary location (not necessarily even a mesh node). This requires using some more advanced features. In the attached example model, look for

Definitions->Domain Point Probe
Solid Mechanics->Weak Contribution

Regards,
Henrik

P.S. To make it easier for others to find this solution, I will change the title of your thread.

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Henrik Sönnerlind
COMSOL
Hi Ben, A **Point Load** can only be applied to a geometrical point, so you will to add more points to your geometry. There is however a way to add a load at an arbitrary location (not necessarily even a mesh node). This requires using some more advanced features. In the attached example model, look for Definitions->Domain Point Probe Solid Mechanics->Weak Contribution Regards, Henrik P.S. To make it easier for others to find this solution, I will change the title of your thread.
Ben Pang
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Posted: 6 years ago Jun 4, 2018, 4:15 p.m. EDT

Hello Henrik,

Thanks for helping me. Your attachments are really helpful. But when I compute, it has an error. I think it's the expression of point probe. Could you please help me to check this? I attached my screenshot.

Hello Henrik, Thanks for helping me. Your attachments are really helpful. But when I compute, it has an error. I think it's the expression of point probe. Could you please help me to check this? I attached my screenshot.

Attachments:

Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 5, 2018, 9:47 a.m. EDT
Updated: 6 years ago Jun 5, 2018, 9:47 a.m. EDT

Hi,

The Point Probe Expression should be the displacement component in the direction of the load. In my example, the Y-direction displacement 'v' was used.

More generally speaking (in case someone would like to add a heat source, for example), it should be the degree of freedom which is energetically conjugate to the prescribed 'load' or 'point source'.

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi, The Point Probe Expression should be the displacement component in the direction of the load. In my example, the Y-direction displacement 'v' was used. More generally speaking (in case someone would like to add a heat source, for example), it should be the degree of freedom which is energetically conjugate to the prescribed 'load' or 'point source'. Regards, Henrik

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