pin insertion and modal analysis

[JeroenDevos]

Hello,

My problem is the following: I have to simulate the frequency response function of system consisting of a prosthesis pushed into a bone like structure.

I've got several questions regarding to modal analysis and pin insertion problems

1. Is it possible in Ansys to use the outcome of a 'pin insertion like' problem (outcome = stress configuration) as prestressed structure for a modal analysis?

2. Is it possible to simulate plastic deformation (for this pin insertion problem)

3. Has anybody got a tutorial on pin insertion?

4. Has anyone got some useful tips on how to do a modal analysis on a system consisting of 2 seperate bodies (one inserted into the other).

5. For the insertion: do I have to use gap elements, conact elements,...

thanks in advance,
Jeroen

 

[meshparts]

Hi Jeroen,

I can't answer you all the questions, but I will try some of them.

To 1. See Chapter 12. Fracture Mechanics in the Help of Ansys. I've neve done such a simulation (pin insertion) but if I should, I would try with fracture mechanics.

To 2. Platic deformation is no problem for Ansys.

To 4. If one body is not bouded on the other one, you will not be able to do a modal analysis of such a system, since this system has geometry nonlinearity. Modal analysis works just for linear systems.

Hope it helps!

Regards,
Alex

 

[cbrn]

Hi,
in addition to Alex's reply:
1- yes, the stress field coming from a static analysis can be input in the modal analysis as "prestress" condition. Only thing, you have to activate "prestress effects" BEFORE doing the static analysis. The static analysis can then be linear or not, elastic or plastic, it doesn't matter.
2- No problem. Contact/targets can be highly non-linear in Ansys, only make sure you choose a "good" contact algorithm for what you're doing (read the help, it's a complex matter...)
3- Sorry I haven't got any. But it may be looked at as a "shrink-fit" problem in plastic field
4- If I'm not wrong, contacts are allowed in modal analysis; only, being the eigenproblem linear, the contact status is evaluated at the start of the analysis and then never updated. So, if your configuration is so that the two parts are "blocked" together by the shrink-fit, then the modal analysis will "see" the two parts as bonded. Otherwise, you will get RBMs as the two parts will become totally independent. As I understand your problem, if the pin insertion is such as to overcome plastic limit of one of the two parts, it's very likely that the shrink-fit is "totally bonded" (no slipping possibility), so why not simplify everything and "glue" the two parts together for the modal analysis?

Regards