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 The information provided may be out of date.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.
Prediscribed displacement and additional Force
Posted Apr 28, 2011, 2:59 p.m. EDT Structural Mechanics Version 4.0a 2 Replies
Please login with a confirmed email address before reporting spam
Hi community,
i have two little questions: I have a flat spring. Its fixed on one side. On the other side a point of it gets displaced with a prediscribed displacement of 0.2mm. So the spring gets bend, resulting in internal stress and a spring force. Now i want to add an additional force on the SAME point in the bending direction.
Now when the added force gets bigger then the spring force, the spring should bend some more.
The problem is that the mentioned point gets fixed by the prediscribed displacement! Is there any possibility to get the expected result?
And the secound question: How can i get/messure the value of the spring force?
Best regards,
Dirk Niebel
i have two little questions: I have a flat spring. Its fixed on one side. On the other side a point of it gets displaced with a prediscribed displacement of 0.2mm. So the spring gets bend, resulting in internal stress and a spring force. Now i want to add an additional force on the SAME point in the bending direction.
Now when the added force gets bigger then the spring force, the spring should bend some more.
The problem is that the mentioned point gets fixed by the prediscribed displacement! Is there any possibility to get the expected result?
And the secound question: How can i get/messure the value of the spring force?
Best regards,
Dirk Niebel
2 Replies Last Post Apr 28, 2011, 4:40 p.m. EDT
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
forces are best extracted via the "reaction forces" on fixed, or prescribed displacement BC's check the doc and the KB, or via Lagrange Multipliers (turn on weak form for the specific BC, and use direct solving)
For the spring motion, if you prescribe a x,y = 0 displacement and leave z free you allow the point to slide along Z, freely, so ou need to use something else, such as a boundary or point load.
If you say that when you add another force or moment the spring attachment point should move in two direction, the you should only restrain (prescribe) one coordinate, but you need to have 2 stiffness's, one for each free direction, defined some way. By the way "fixed" == "prescribed displacement x=y=z=0 (same BC)
--
Good luck
Ivar
forces are best extracted via the "reaction forces" on fixed, or prescribed displacement BC's check the doc and the KB, or via Lagrange Multipliers (turn on weak form for the specific BC, and use direct solving)
For the spring motion, if you prescribe a x,y = 0 displacement and leave z free you allow the point to slide along Z, freely, so ou need to use something else, such as a boundary or point load.
If you say that when you add another force or moment the spring attachment point should move in two direction, the you should only restrain (prescribe) one coordinate, but you need to have 2 stiffness's, one for each free direction, defined some way. By the way "fixed" == "prescribed displacement x=y=z=0 (same BC)
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Thank you very much for your fast reply!