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Prediscribed displacement and additional Force
Posted 2011年4月28日 GMT-4 14:59 Structural Mechanics Version 4.0a 2 Replies
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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 2011年4月28日 GMT-4 16:40
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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
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Posted:
1 decade ago
Thank you very much for your fast reply!