# Why do non-interacting cylinders bend in unintuitive direction under identical forces?

**URL:** <https://fenicsproject.discourse.group/t/why-do-non-interacting-cylinders-bend-in-unintuitive-direction-under-identical-forces/16306>\
**Category:** General\
**Created:** [November 15, 2024, 12:51pm UTC](https://fenicsproject.discourse.group/t/why-do-non-interacting-cylinders-bend-in-unintuitive-direction-under-identical-forces/16306 "2024-11-15T12:51:18Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![TomM](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@TomM](https://fenicsproject.discourse.group/u/TomM)\
**Post date:** [November 18, 2024, 12:51pm UTC](https://fenicsproject.discourse.group/t/why-do-non-interacting-cylinders-bend-in-unintuitive-direction-under-identical-forces/16306/5 "2024-11-18T12:51:45Z")

</div>

My full sigma is this:

```auto
def sigma(u):
    return lambda_ * tr(epsilon(u)) * Identity(len(u)) + 2 * mu * epsilon(u)

```

Is this correct and if not what is the mistake?

When changing the mesh by setting these numbers I get better results. Is this the way to go or should I try something else?

```auto
gmsh.option.setNumber("Mesh.MeshSizeMax", 0.1) 
gmsh.option.setNumber("Mesh.MeshSizeMin", 0.0001)  

```

 ![better_mesh](https://global.discourse-cdn.com/free1/uploads/fenicsproject1/original/2X/7/7ac219ffaa4fa6d867a099a65fa80a6210807db8.png)  
Thanks for helping me with this!

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