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Body load in nonlinear mechanics
Posted Jan 9, 2024, 5:59 a.m. EST Modeling Tools & Definitions, Studies & Solvers, Structural Mechanics Version 6.0 1 Reply
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Hello, This is my first ever entry in the Discussion Forum, though I have been using the software since it was still Femlab 2.1 (circa 1998). I am trying to set up a nonlinear mechanic computation, where a body load at location (x,y,z) or material location (X,Y,Z), is defined as a function of the displacements (u,v,w) at that location (i.e. a function of u(X,Y,Z), v(X,Y,Z) and w(X,Y,Z)), and also (i.e. simultaneously) a function of the displacement at a different location (e.g. a function of u(X,Y,Z0), v(X,Y,Z0) and w(X,Y,Z0), where Z0 is a parameter). How do I go about this? Thank you, David
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Say that you wanted the load to be proportional to the difference in displacement. Then, you could for example write a function of u-at3(X,Y,Z0,u).
Note, however, that any function of the displacement that couples different locations in the structure will fill in the stiffness matrix significantly. This may cause a problematic increase in solution time if the model is large. It may then be beneficial to use the nojac() operator, as in nojac(u-at3(X,Y,Z0,u)). Then, you do not get the stiffness matrix contributions, but as a tradeoff there will be more iterations since the stiffness matrix is not optimal.
-------------------Henrik Sönnerlind
COMSOL