# Rotations bug. 360º

**URL:** <https://calculix.discourse.group/t/rotations-bug-360/2153>\
**Category:** Uncategorized\
**Created:** [March 18, 2024, 4:59pm UTC](https://calculix.discourse.group/t/rotations-bug-360/2153 "2024-03-18T16:59:03Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [March 18, 2024, 4:59pm UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/1 "2024-03-18T16:59:03Z")

</div>

I have found a weird bug in the solver just by accident.  
The following strip rolls without issue when I request a time step that don’t generate a rotation that pass exactly through the 360º value.  
The rotation boundary condition is built as 360 \* t by means of an amplitude.  
My advancing step is direct to force passing through multiples of 360º if I want.  
Overall time periods of 1, 2 or 3 makes the convergence to fail while .98, 1.98 or 2.98 converges without issue.  
I would say ccx doesn’t like the 360º value.(180º might have the same issue).  
Inp atached

![RollingStrip](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/f/f8a0e6eee1226d91c18d98f239f94c007f451bce.gif)

```auto
** Generated by Mecway 24
*NODE
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*ELEMENT,TYPE=S4R
1,67,17,18,68
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29,121,57,58,122
30,123,59,60,124
31,125,61,62,126
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38,43,75,76,44
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*ELEMENT,TYPE=B31
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*ELSET,ELSET=Default
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*ELSET,ELSET=Component
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*DENSITY
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*BEAM SECTION,ELSET=Component,MATERIAL=Material,SECTION=RECT
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-1,0,0
*BOUNDARY
1,2,,0
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*AMPLITUDE,NAME=A_1
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*STEP,NLGEOM=YES,INC=300,AMPLITUDE=STEP
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*NODE FILE,GLOBAL=YES
U,RF
*EL FILE
S,NOE
*SECTION PRINT,SURFACE=S1,NAME=Reaction_forces
SOF,SOM
*END STEP

```

---

<div class="post-metadata">

**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\
**Post date:** [March 19, 2024, 9:24am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/2 "2024-03-19T09:24:12Z")

</div>

Might be good to report on GitHub. This .inp file runs correctly (converges) in Abaqus.

---

<div class="post-metadata">

**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [March 19, 2024, 5:31pm UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/3 "2024-03-19T17:31:23Z")

</div>

Done. 👍.  
I have also confirm some issues with 180º too.

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [March 20, 2024, 8:26am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/4 "2024-03-20T08:26:48Z")

</div>

it’s not comparable between S4R of Abaqus and CalculiX. It seems a limitation of shell element in CalculiX due to expanded internally to solid, using solid element by meshed properly can solve for similar cases i.e 0deg to 360deg rotations.

![anim0](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/106041b8322451f79de983e3e7d81fcf3f44f581.gif)

---

<div class="post-metadata">

**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [March 20, 2024, 8:52am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/5 "2024-03-20T08:52:10Z")

</div>

How far did you bend “using solid element by meshed properly” ?  
What’s the Mmax value?

> [@xyont](#):
>
> It seems a limitation of shell element in CalculiX due to expanded internally to solid

What’s exactly the limitation? Do you refer to apply multiples of 360º or using moment on the lip to reach large rotations?

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [March 20, 2024, 9:03am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/6 "2024-03-20T09:03:07Z")

</div>

i’m not yet doing further comparison in force and stress, but all results seems reasonable. Currently, in mesh sensitivity study and seeking the possibility using shell element in CalculiX.

---

<div class="post-metadata">

**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [March 20, 2024, 9:05am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/7 "2024-03-20T09:05:22Z")

</div>

> [@xyont](#):
>
> i’m not yet doing further comparison in force and stress, currently in mesh sensitivity study and seeking the possibility using shell element in CalculiX

I’m not even considering solids. The benchmark is stated for shells. We know there are no issues with solid rotations.

Popular Benchmark Problems for Geometric Nonlinear Analysis of **Shells**

That’s what requires some scrutiny to find source of issues and keep moving.

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [March 20, 2024, 9:18am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/8 "2024-03-20T09:18:26Z")

</div>

> [@Disla](#):
>
> We know there are no issues with solid rotations.

are that sure? i did investigate further based on this source [links](https://github.com/calculix/CalculiX-Examples/tree/master/Streifen), even for 90deg rotation it can not convergences.

Mean Rotation MPC

> At 28% of the specified deformation, the incremental time becomes too small and the solution is stopped.

Rigid Body Constraint

> At 74% of the specified deformation, the incremental time becomes too small and the solution is stopped.

Coupling/Kinematic

> At 78% of the specified deformation, the incremental time becomes too small and the solution is stopped.

---

<div class="post-metadata">

**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [March 20, 2024, 9:43am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/9 "2024-03-20T09:43:14Z")

</div>

> [@xyont](#):
>
> i did investigate

Investigate.? Don’t make laught.

> [@xyont](#):
>
> even for 90deg rotation it can not convergences.

Then what are you posting?. You don’t even explain what could be the different aproach proposal or compare your results with known values. What’s the aim of that vid.

Regarding S4R not comparable?. Comparison means comparing **results** , no more no less.  
What’s the aim of a comparison or benchmark?. We do use FEM to get results. I don’t give a shit what the formulation is. Do you understand that? You are becoming very anoying man.

If what you feel is the need to always put something on top of others you can do that, I will not waste time responding.

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [March 20, 2024, 9:57am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/10 "2024-03-20T09:57:06Z")

</div>

are you ANYS in PrePoMax forum and posting similar threads? i’ve been done in given some explanation there about 4 hours ago from now.

don’t want commenting anymore, just ‘wow’ and everyone can judge he/her type of persons.

> **[Geometric Nonlinear Analysis of Shells](https://prepomax.discourse.group/t/geometric-nonlinear-analysis-of-shells/1611/8)**
>
> below, model of solid element with four layer trough thickness of linear hexahedral (reduced) and maximum 2.5mm mesh size. p.s deflected shape is true scale add higher rotation, it seems convergence is related to mesh.

---

<div class="post-metadata">

**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\
**Post date:** [March 21, 2024, 10:10am UTC](https://calculix.discourse.group/t/rotations-bug-360/2153/11 "2024-03-21T10:10:11Z")

</div>

Seems like it fails at lots of angles, 360, 180, less than 90. Maybe the fixed time steps are skipping over the low angles that fail and landing on the higher ones? You get this effect in contact too where you can skip over trouble spots with fixed time steps. All the ways of applying the load - moment, MPC, rotation, rigid body, etc. use MPCs so they’re probably all a bit dicey with shells. I kind of wonder why that is. It seems like they’re so close to working and just pass through a few singularities or something. Seems a pity that the capability is limited by what seems like an unnecessary problem.

I guess you could make a special structure at the tip and apply two pressure loads to form a moment but that’s sort of avoiding the problem and doesn’t generalize very well.