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Difference between Reaction Force and Total Reaction Force

Posted May 17, 2021, 12:43 p.m. EDT 1 Reply

Timothy Russell
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I'm doing a displacement prescribed 3-point bend test (a negative y-displacement is applied at the center of a horizontal beam). I want to determine the reaction force at the point where I've applied the displacement and noticed that solid.RFy is not the same thing as solid.RFtotaly. What is the difference between these terms? solid.RFy seems to give me what I want in this case, but I don't understand what solid.RFtotaly is...

1 Reply Last Post May 18, 2021, 3:52 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 3 years ago May 18, 2021, 3:52 a.m. EDT

solid.RFy is the reaction force to prescribed displacements in the y direction. Actually, it is the same as reacf(v). It has a value in each constrained node, so if you want to see the total reaction force over a certain set of constrained boundaries, you need to do a summation (this is done using an integration operator).

solid.RFytot is the sum of the reaction forces for the whole model. If you are loading by displacement control, it will be zero. If you load by forces, it will equal the total applied loads.

There is, however, one more difference: solid.RFy is only the reaction to pointwise Dirichlet conditions. solid.RFytot includes some other types of reaction forces, for example from elastic supports (Spring Foundation).

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Henrik Sönnerlind
COMSOL
solid.RFy is the reaction force to prescribed displacements in the y direction. Actually, it is the same as reacf(v). It has a value in each constrained node, so if you want to see the total reaction force over a certain set of constrained boundaries, you need to do a summation (this is done using an integration operator). solid.RFytot is the sum of the reaction forces for the whole model. If you are loading by displacement control, it will be zero. If you load by forces, it will equal the total applied loads. There is, however, one more difference: solid.RFy is only the reaction to pointwise Dirichlet conditions. solid.RFytot includes some other types of reaction forces, for example from elastic supports (Spring Foundation).

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