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bracket contact
Posted 03.06.2014, 12:03 GMT-4 Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 4.4 1 Reply
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Hello,
I am reproducing the model bracket contact and I have a doubt. What is the point in using the spring foundation? I have tried to run the model without it and it is not working.
The model is feasible without it. A solid deformed by a force. In fact the tutorial itself says that the force applied by the spring can be neglected compared to the force defined. Then, why it must be defined?
Thank you.
I am reproducing the model bracket contact and I have a doubt. What is the point in using the spring foundation? I have tried to run the model without it and it is not working.
The model is feasible without it. A solid deformed by a force. In fact the tutorial itself says that the force applied by the spring can be neglected compared to the force defined. Then, why it must be defined?
Thank you.
1 Reply Last Post 04.06.2014, 02:33 GMT-4
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Posted:
1 decade ago
Hi,
Without the spring, the pin can have free rigid body motions.
Even after contact is established, the pin could spin around its axle since there is no friction in the model.
In the initial state (before contact is established) the model is threefold singular. Any numerical disturbance in the first iterations could then send the pin 'into the universe' since it has no constraints againstY-translation, Z-translation or X-rotation.
The very weak spring will remove the singularity, while it still only introduces negligible forces in the converged state when displacements are small.
This method for suppressing singularities in the initial state of contact models is rather standard, and is used also in other models. In the section 'Constraints' under 'Introduction to Contact modeling' in the Structural Mechanics Module documentation a slightly more sophisticated version is described.
Thanks for the comment, we will extend the explanation of the spring in the next release of this model.
Regards,
Henrik
Without the spring, the pin can have free rigid body motions.
Even after contact is established, the pin could spin around its axle since there is no friction in the model.
In the initial state (before contact is established) the model is threefold singular. Any numerical disturbance in the first iterations could then send the pin 'into the universe' since it has no constraints againstY-translation, Z-translation or X-rotation.
The very weak spring will remove the singularity, while it still only introduces negligible forces in the converged state when displacements are small.
This method for suppressing singularities in the initial state of contact models is rather standard, and is used also in other models. In the section 'Constraints' under 'Introduction to Contact modeling' in the Structural Mechanics Module documentation a slightly more sophisticated version is described.
Thanks for the comment, we will extend the explanation of the spring in the next release of this model.
Regards,
Henrik