Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
how to apply linear contrain equation to the node set
Posted Jun 12, 2012, 1:45 a.m. EDT 4 Replies
Please login with a confirmed email address before reporting spam
Hi,
I want to make FEM model of unitcell of viscoelastic composite.
i don't know how to apply linear constraint equation in comsol.
Linear constraint Equation:
-----------------------------------
(ui^a)y - (uj^b)y = 0
where,
superscript a, b are node no.
subscript i, j are degree of freedom
In abaqus
---------------
i have attached 1 jpeg file in that 'x' [set of all node of x=1 plane except common node (1,1,1)].
similarly i have apply linear constrain in y=1 and z=1 surface of cube.
how can i apply same constraint in comsol.
please reply as early as possible.
I want to make FEM model of unitcell of viscoelastic composite.
i don't know how to apply linear constraint equation in comsol.
Linear constraint Equation:
-----------------------------------
(ui^a)y - (uj^b)y = 0
where,
superscript a, b are node no.
subscript i, j are degree of freedom
In abaqus
---------------
i have attached 1 jpeg file in that 'x' [set of all node of x=1 plane except common node (1,1,1)].
similarly i have apply linear constrain in y=1 and z=1 surface of cube.
how can i apply same constraint in comsol.
please reply as early as possible.
4 Replies Last Post Jun 12, 2012, 3:35 a.m. EDT
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
I see I have been using COMSOL for too long, and anyhow I do not know ABAQUS, that that is a typical example of "older" FEM where everything is reported to the mesh element (nodes, edges, boundaries and element volume, inclusive the writing of the equations, and COMSOL witch allows us to remain at the classical math-physics level, we work with the "phsics" at the elementary volume "dx*dy*dz" independently if underneath there are one or many elements or whatever discretization used, and the mesh is only a numerical math artefact to discretize the model and to solve it.
I do not really understand your notation (not knowing ABAQUS) but in COMSOL "solid" physics ( u, v, w ) are the deformation, these are fields hence one should write the vector ( u(x,y,z,t), v(x,y,z,t), w(x,y,z,t) ) you have also their derivatives w.r.t. x,y,z and t time
So I suppose the nest is to addd a weak BC formula for restraining u or v or w, but you have also the ()y in your equation referring to what exactly.
Perhaps it would be easier if you expressed your equation in standard math formulation, thats closer to COMSOL writing.
To learn how COMSOl treats most BCs try studying the underlaying equaitions by turning on the "Equation view" in the preferences
--
Good luck
Ivar
I see I have been using COMSOL for too long, and anyhow I do not know ABAQUS, that that is a typical example of "older" FEM where everything is reported to the mesh element (nodes, edges, boundaries and element volume, inclusive the writing of the equations, and COMSOL witch allows us to remain at the classical math-physics level, we work with the "phsics" at the elementary volume "dx*dy*dz" independently if underneath there are one or many elements or whatever discretization used, and the mesh is only a numerical math artefact to discretize the model and to solve it.
I do not really understand your notation (not knowing ABAQUS) but in COMSOL "solid" physics ( u, v, w ) are the deformation, these are fields hence one should write the vector ( u(x,y,z,t), v(x,y,z,t), w(x,y,z,t) ) you have also their derivatives w.r.t. x,y,z and t time
So I suppose the nest is to addd a weak BC formula for restraining u or v or w, but you have also the ()y in your equation referring to what exactly.
Perhaps it would be easier if you expressed your equation in standard math formulation, thats closer to COMSOL writing.
To learn how COMSOl treats most BCs try studying the underlaying equaitions by turning on the "Equation view" in the preferences
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
thanks for reply
i have attached the document.
can i able to do same in comsol (i.e momentum equilibrium)
the thing i mention in attachment is what exactly achive by contraining node set.
i have attached the document.
can i able to do same in comsol (i.e momentum equilibrium)
the thing i mention in attachment is what exactly achive by contraining node set.
Attachments:
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
my first reaction is to say use the "rigid body connector" and restrict a rotation Rz
or simply the prescribed displacement and select only "y" and block to "0"
--
Good luck
Ivar
my first reaction is to say use the "rigid body connector" and restrict a rotation Rz
or simply the prescribed displacement and select only "y" and block to "0"
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi,
second one is not possible because it will fixed the displacement which i don't want.
may be i will try rigid body connector, but in that how to restrict the rotation Rz (can give me detail step to do this).
can i use periodic condition to fullfill my requirement, can u explain me what is the periodic condition excatly, and how to apply.
second one is not possible because it will fixed the displacement which i don't want.
may be i will try rigid body connector, but in that how to restrict the rotation Rz (can give me detail step to do this).
can i use periodic condition to fullfill my requirement, can u explain me what is the periodic condition excatly, and how to apply.