Re: [Getfem-users] Shrink fit problem

[Miikka Väntänen]

Hi Kostas, and thank You for your immidiate reply!

My current os is CentOS linux, 6.5 release, with x86x64 (also 32 bit available). At the time being I'm using only one cpu (no mpi atm), which I suppose ought to be enough as the model is not a huge one and I'm not in a hurry...

I had some problems with getfem version 4.3 (with the nodal contact brick, actually) and changed to 4.2 just because of that. Now that you recommended the integral contact, I might give it another go. The contact is what I was actually interested in, so I was planning to fiddle with different contact bricks anyway once I get the model working with any one of them.

I tried the superlu solver but ended up with eating up all the memory and hence crashing the script. I might try mumps, once I get it installed. The model has 16500 nodes and I'm using linear hexahedron (8-node) elements so there should be around 50 k dofs.

I would like to avoid modifying the mesh geometry because I'm planning on comparing the getfem contact results with results from other fem software, and changing the mesh would affect the outcome. But if I that's the only reasonable way to do it, would I just modify the meshes so that they would overlap by 5 mm and then let the contact brick handle the rest? Would it force the surfaces into a contact and apply the contact pressure that is respective to the overlap distance?

Br.

Miikka

2014-08-19 16:43 GMT+03:00 Konstantinos Poulios <address@hidden>:

Hi Miikka,

some questions/comments/recommendations:

- Which version of getfem++ do you use, which operating system?

- Why don't you use "add_integral_contact_between_nonmatching_meshes_brick"? It is normally superior to nodal contact.

- Why don't you use a direct solver like superlu or even better mumps? How many degrees of freedom do you have?

- The easiest way of accounting for the interference fit is by modifying the meshes so that they incorporate the fit. You can modify the mesh in your mesher software or within getfem, e.g. by using the functions pts() and set_pts() of the mesh object in python.

Best regards

Kostas

On Tue, Aug 19, 2014 at 2:59 PM, Miikka Väntänen <address@hidden> wrote:

Hi all,

 

I’m relatively new to GetFem, but I’ll try to do my best in explaining what I’m struggling with…

 

I’m trying to solve a linear elastic problem that consists of two parts, a shaft and a bush. Between the two parts I use a contact “add_nodal_contact_between_nonmatching_meshes_brick” (in python api). I’m using a linear gmres solver with either ILU or ILUT preconditioning (probably ilut works better with saddle point problems?). There’s also some loading implemented to the shaft, but I reckon that’s irrelevant at this point.

 

The real problem I’m currently facing is with the shrink fit. The actual shaft-bush contact should have a shrink fit with 5 mm radial difference between the two parts. Is there any way in getfem to implement the shrink fit? Should I, for example, use temperature change to shrink/expand the parts in an individual step before calculating the actual static problem? Or should I implement a radial displacement to either of the faces in contact? Is there any way to do any of this?

Br.

Miikka V.

_______________________________________________
Getfem-users mailing list
address@hidden
https://mail.gna.org/listinfo/getfem-users