Menu

Discussion Forum

New Discussion
Filtern

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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.

can not apply Torque load in 3D, Comsol 4.1

Posted 09.06.2011, 07:27 GMT-4 Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers, Structural Mechanics Version 4.1 3 Replies

a k
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello everyone,
Could some one please take this model and apply a small torque load on one free end so that I know how to apply such loads?
the geometry is basically a rotating joint fixed on the outter side on one side and under torsional loading causeing the free end to rotate. pretty much like a single bar fixed at one end and under applied force from at the free end.
i have gone through all i could on the internet and that one toturial that Ivan recommends in comsol 3.5 but i just cant get it done.
Any helps or hints is appreciated, And I am really sorry that comsol simply does NOT provide enough litrature so that we dont have to creat a new thread for just every single problem. and while i am at it, the dynamic help is more like a bumper sticker than a real help!

Ali
3 Replies Last Post 10.06.2011, 09:08 GMT-4
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 09.06.2011, 08:49 GMT-4
In finite element analysis of solids, there are no degrees of freedom associated with rotations, only with displacements, and for that reason, you cannot apply concentrated torques at nodes. Rather, you need to apply a distributed force load that results in the torque you want.
In finite element analysis of solids, there are no degrees of freedom associated with rotations, only with displacements, and for that reason, you cannot apply concentrated torques at nodes. Rather, you need to apply a distributed force load that results in the torque you want.
a k
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10.06.2011, 05:28 GMT-4
Thanks for the hint Jean, but I just mentioned that because if you design a geometry in 2D you will have an option to define your boundary load directly in N.m dimensions, maybe i didn not address it right.
I did , however, got around the problem and I am posting it here for others with the same problem.
I defined stress parameters (Tx,Ty,Tz) in [Pa] and also a Radius (r=sqrt(x^2+y^2)) and included a time variable
(para=1-0.2*t) to fade my force out in 5 seconds of my analysis (Time dependant).
next i defined the boundary load as (Tax*y-Tay*x)*r*para. pay attention that the dimensions of this load is N.m.s but I am guessing it is a way of making it time dependant. the expression turned red when i entered it but i neglected that and moved on to the computation.
the results seem pretty logical and It simulates what I want perfectly. examining the reaction forces and displacement values also suggest that the solution is correct.

I should thank Ivan too, his posts are really helpful.
Thanks for the hint Jean, but I just mentioned that because if you design a geometry in 2D you will have an option to define your boundary load directly in N.m dimensions, maybe i didn not address it right. I did , however, got around the problem and I am posting it here for others with the same problem. I defined stress parameters (Tx,Ty,Tz) in [Pa] and also a Radius (r=sqrt(x^2+y^2)) and included a time variable (para=1-0.2*t) to fade my force out in 5 seconds of my analysis (Time dependant). next i defined the boundary load as (Tax*y-Tay*x)*r*para. pay attention that the dimensions of this load is N.m.s but I am guessing it is a way of making it time dependant. the expression turned red when i entered it but i neglected that and moved on to the computation. the results seem pretty logical and It simulates what I want perfectly. examining the reaction forces and displacement values also suggest that the solution is correct. I should thank Ivan too, his posts are really helpful.
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10.06.2011, 09:08 GMT-4
1/ In 2D you can provide a boundary load in N.m if you are providing it as a force per unit length, but that has little to do with applying a torque.

2/ Don't ignore your entries if they turn red. That's COMSOL's way of telling you that you are providing an input with the wrong dimensions. What you should be doing is providing a boundary load (in Pa) selected such that it is equivalent to the torque you want.

1/ In 2D you can provide a boundary load in N.m if you are providing it as a force per unit length, but that has little to do with applying a torque. 2/ Don't ignore your entries if they turn red. That's COMSOL's way of telling you that you are providing an input with the wrong dimensions. What you should be doing is providing a boundary load (in Pa) selected such that it is equivalent to the torque you want.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content