Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

methods for constraining wire to solid object, selecting geometry?

Status
Not open for further replies.

MrSamuel

Bioengineer
Oct 13, 2011
45
I need to constrain the end of a wire to a solid. I'm using coupling. Here are the two methods for specifying the geometry I have tried and their short comings:

1. First select the end node of the wire, then specify the closet element node on the solid(I had to create a set for that element node). This method hasn't worked well as the wire seems to float around in space during the simulation and it takes a long time to solve.

2. First select the end node of the wire, then select the face on the solid body on which it lies. This method eliminates the floating around and it solves fast, but the face is very large and seems like a vague thing to attach the wire too. Does the solver just ensure that the end of the wire remains the same distance from all points on the surface that it was initially?

I need the precision of attaching to a node from method 1, but the quality and speed of attaching the wire to a face on the body from method 2. Any suggestions? Whats the best practice here?

Also, is coupling a good technique to join a wire with a solid, or is fixing better, or some kind of MPC constraint?

Those are my questions, here's a little more background information in case its helpful:
I'm attaching a ligament to a bone. The ligament uses an elastic material with compression turned off and a T3D2 element with two nodes. The bone is elastic with tetrahedral elements.

Thank you kindly,
Sam
 
Replies continue below

Recommended for you

I'm still totally stuck on this one...
Hoping to get a response, even if you don't know the best way to do it, please give me your thoughts, keep this post alive until someone comes along who knows the answer!

Thanks,
Sam
 
Normal practice is to connect points via geometry. For that you'd need to partition the solid so that there was a point formed on the surface that you could attach to. You'd also have to make sure that the wire was prevented from spinning rotationally as the solid has no rotational degrees of freedom.

 
I have a lot of ligaments to model, it would be really difficult to partition the model enough time so I can connect ligaments at partitions...
Coupling the tendon to the closest geometry seems to work, but I'm worried this is too much of an approximation. How does coupling to an edge work for instance, does the solver just ensure the coupled point remains the same average distance from all points on the edge?

Thanks,
Sam
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor