FEAP User Forum
FEAP => Input File Issues => Topic started by: Yaakov on May 27, 2017, 02:48:09 PM
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Dear FEAP TEAM & Users,
I would ask, how can I define bending moments in the FEAP input file in a simple way (see the JPG in the attachment)?
Kind Regards,
Yaakov
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If you use frame elements, then you should just place a node at the location of interest and include a "force" in the third dof, this will give you a moment at that point (assuming this is a 2D analysis).
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Here is a simple example. BCs are fully clamped; adjust as needed.
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Dear FEAP Administrator,
Thanks very much for your answer!
If I use 2d-plate (plane stress/ plane strain) elements, how can I define a "force" here (the third dof should be other field (temperature field...)...)?
Warm Regards,
Yaakov
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If you want to apply a moment to model that uses 2D elastic elements, then you will need to apply a force couple as 2D elasticity does not admit point moments in its theoretical formulation (unless you decide to implement a polar media/Cosserat theory).
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Dear Prof. Govindjee,
Thanks very much for your reply!
If I use "force couple", which nodes should I chose for the moment loading as the definition of moment is $M = F*L$?
If I apply a "force" on a node, perhaps I will get a singular value of stress on the node.
Warm Regards, Yaaakov
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If you apply a force at a node in a solid element then you get a higher stress there. If you keep refining the mesh with the same force at the node, yes, the stress will get larger. Thus, if you wish to apply a moment to the end of a mesh of solid elements you would use a distributed traction to represent the moment and avoid singular stress. However, if you apply only over part of the boundary then where the traction becomes discontinuous there is again the possibility of a stress singularity. You should study an elasticity book to learn basic aspects of stress behavior.
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Dear Prof. Taylor,
Thanks very much for your reply, I think too simple that I just choose two nodes and give moment loadings for $M=F*L%. I should study strength of materials again.
Warm Regards, Yaakov
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This is not a question of strength of materials. This is an issue of elasticity theory. Try looking at the classic book of Timoshenko and Goodier (Theory of Elasticity).
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Dear Prof. Govindjee and Dear Prof. Taylor,
I just buy this book, I will read this book carefully.
Warm Regards, Yaakov