Learning Forum

[Talla]

hi guys

I have a question regarding the contact type in ansys. For example for a model of two blocks tighten by for bolts( A bolt in each corner). So normally I can’t have a sliding between the two blocks. When I do some research in the internet many people use a frictional contact between the two blocks to model this situation but when I try it I get a sliding between them. I were thinking that when I use a pretention bolt + a frictional contact normally the pretention load will create a limited zone between the two block (clamping cone) in which the two blocks will be bonded and so avoid the gliding. I notice that when I use the rough contact I have no more gliding between them. I think that this is due to the fact that the rough contact is with an infinite frictional coefficient.

Any explanations will be really appreciate

Thank you!

[jj77]

If you can upload your model then someone might be able to have a closer look. Go to file/archive in WB and save it as a .wbpz, and then use the attach button next to your post above to attach it here

[Talla]

Hi jj77, thank you for your response i can't share my real model because its confidential but this is a quick model with the same problem. you will see that because of the sliding there is non continuty in the displacement between the two blocks. thank you for you help

[jj77]

I saw that you are doing a pre-stressed modal analysis so you need to have in mind that modal is linear and contacts are nonlinear. Thus contacts are linearised.

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v193/wb_sim/ds_eigen_apply_pre_stress.html%23ds_restarts_mult_results

Also the perturb command shows how contacts are treated - search for that in help or google (PERTURB and ansys)

The sticking option valid for frictional contacts generates a frictional tangential contact stiffness at the interface thus the closed contact can not slide that much depending on the tangential contact stiffness.

 

 

 

For more info on this see:

https://www.simutechgroup.com/tips-and-tricks/fea-articles/160-fea-tips-tricks-ansys-14-pre-stressed-modal-analysis-nonlinear-static-analysis

 

As for your set up and the behaviour it seems realistic  and behaves normal, and as one would expect. Also leave the contacts to default if you are not sure 100% what you are doing. Say bonded could be more ok with MPC not with penalty.

[Talla]

thank you jj77 and sorry for the late response i were out of th office. i will take a look into the link that you sent and let you know after

[Talla]

Helllo jj77 can you explain how to use this command please

 

[jj77]

To set it to sticking in WB go to the the initial conditions/pre-stress effect in the modal analysis and at the bottom there is something about contact treatment - change it to sticking

[Talla]

thank you jj77, thats works if I force the contact status to sticking. But i am still wondering something, actually i must have a sticking part just inside the clamping cone and if I force contact to sticking all surface will have the sticking status

[jj77]

read through the documentation on that part as I said:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v193/wb_sim/ds_eigen_apply_pre_stress.html%23ds_restarts_mult_results

Also the perturb command shows how contacts are treated - search for that in help or google (PERTURB and ansys)

The sticking option valid for frictional contacts generates a frictional tangential contact stiffness at the interface thus the closed contact can not slide that much depending on the tangential contact stiffness.