Abaqus Standard: Nonlinear Buckling Example (Cylinder buckling)

It is a hands-on example to model buckling with Abaqus.

In the tutorial they made a mistake at the upper boundary-conditions:
The upper boundary does not rotate in the real example.

The input-files are: (Not copyrightable, because below the Threshold of originality, therfore Public Domain)

Linear Buckling for the perfect structure with
*Buckle
[.…]
*NODE FIL
U,

*Heading
** Job name: Linear_Buckling Model name: CylinderBuckle
** Generated by: Abaqus/CAE 2021.HF8
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Cyl
*Node
*Element, type=S4R
*Nset, nset=Set-1, generate
    1,  7850,     1
*Elset, elset=Set-1, generate
    1,  7693,     1
*Nset, nset=TopSet, generate
   50,  7850,    50
*Nset, nset=BottomSet, generate
    1,  7801,    50
** Section: Section-1al2mm
*Shell Section, elset=Set-1, material=AL
2., 5
*End Part
**  
**
** ASSEMBLY
**
*Assembly, name=Assembly
**  
*Instance, name=Cyl-1, part=Cyl
*End Instance
**  
*Node
      1,           0.,           0.,           0.
*Node
      2,           0.,           0.,         500.
*Nset, nset=Set-5
 1,
*Nset, nset=Set-6
 2,
*Nset, nset=Set-7
 2,
*Nset, nset=t_Set-2, instance=Cyl-1, generate
    1,  7801,    50
*Elset, elset=t_Set-2, instance=Cyl-1, generate
    1,  7645,    49
*Nset, nset=t_Set-4, instance=Cyl-1, generate
   50,  7850,    50
*Elset, elset=t_Set-4, instance=Cyl-1, generate
   49,  7693,    49
*Nset, nset=_PickedSet6, internal
 2,
*Nset, nset=_PickedSet8, internal
 1,
** Constraint: BottomConstraint
*Rigid Body, ref node=_PickedSet8, tie nset=t_Set-2
** Constraint: TopConstraint
*Rigid Body, ref node=_PickedSet6, tie nset=t_Set-4
*End Assembly
** 
** MATERIALS
** 
*Material, name=AL
*Elastic
73100., 0.35
*Plastic
160.,  0.
340., 0.3
** 
** BOUNDARY CONDITIONS
** 
** Name: BC-1Bottom Type: Symmetry/Antisymmetry/Encastre
*Boundary
Set-5, ENCASTRE
** Name: BC-2Top Type: Symmetry/Antisymmetry/Encastre
*Boundary
Set-6, ZASYMM
** ----------------------------------------------------------------
** 
** STEP: Linear_Buckling
** 
*Step, name=Linear_Buckling, nlgeom=NO, perturbation
*Buckle
8, , 16, 3000
** 
** BOUNDARY CONDITIONS
** 
** Name: BC-1Bottom Type: Symmetry/Antisymmetry/Encastre
*Boundary, op=NEW, load case=1
Set-5, ENCASTRE
*Boundary, op=NEW, load case=2
Set-5, ENCASTRE
** Name: BC-2Top Type: Symmetry/Antisymmetry/Encastre
*Boundary, op=NEW, load case=1
Set-6, ZASYMM
*Boundary, op=NEW, load case=2
Set-6, ZASYMM
** 
** LOADS
** 
** Name: Load-1   Type: Concentrated force
*Cload
Set-7, 3, -1.
** 
** OUTPUT REQUESTS
** 
*Restart, write, frequency=0
** 
** FIELD OUTPUT: F-Output-1
** 
*Output, field, variable=PRESELECT
*NODE FIL
U,
*End Step

I would use the replace-Button for switching from Permuation-Buckle to Nonlinear-Riks-Method

Nonlinear (nlgeom=YES) Buckling for realistic bucklingloads with
*IMPERFECTION,FILE=Linear_Buckling,STEP=1
1,0.2
2,0.1
3,0.05

*Heading
** Job name: Nonlinear_Buckling_Vertical Model name: CylinderBuckle
** Generated by: Abaqus/CAE Unofficial Packaging Version
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Cyl
*Node
** REMOVED
*Element, type=S4R
** REMOVED
*Nset, nset=Set-1, generate
    1,  7850,     1
*Elset, elset=Set-1, generate
    1,  7693,     1
*Nset, nset=TopSet, generate
   50,  7850,    50
*Nset, nset=BottomSet, generate
    1,  7801,    50
** Section: Section-1al2mm
*Shell Section, elset=Set-1, material=AL
2., 5
*End Part
**  
**
** ASSEMBLY
**
*Assembly, name=Assembly
**  
*Instance, name=Cyl-1, part=Cyl
*End Instance
**  
*Node
      1,           0.,           0.,           0.
*Node
      2,           0.,           0.,         500.
*Nset, nset=Set-5
 1,
*Nset, nset=Set-6
 2,
*Nset, nset=Set-7
 2,
*Nset, nset=Set-8
 2,
*Nset, nset=Set-9
 2,
*Nset, nset=t_Set-2, instance=Cyl-1, generate
    1,  7801,    50
*Elset, elset=t_Set-2, instance=Cyl-1, generate
    1,  7645,    49
*Nset, nset=t_Set-4, instance=Cyl-1, generate
   50,  7850,    50
*Elset, elset=t_Set-4, instance=Cyl-1, generate
   49,  7693,    49
*Nset, nset=_PickedSet6, internal
 2,
*Nset, nset=_PickedSet8, internal
 1,
** Constraint: BottomConstraint
*Rigid Body, ref node=_PickedSet8, tie nset=t_Set-2
** Constraint: TopConstraint
*Rigid Body, ref node=_PickedSet6, tie nset=t_Set-4
*End Assembly
** 
** MATERIALS
** 
*Material, name=AL
*Elastic
73100., 0.35
*Plastic
160.,  0.
340., 0.3
** 
** BOUNDARY CONDITIONS
** 
** Name: BC-1Bottom Type: Symmetry/Antisymmetry/Encastre
*Boundary
Set-5, ENCASTRE
** Name: BC-Top Type: Displacement/Rotation
*Boundary
Set-9, 1, 1
Set-9, 2, 2
Set-9, 4, 4
Set-9, 5, 5
Set-9, 6, 6
*IMPERFECTION,FILE=Linear_Buckling,STEP=1
1,0.2
2,0.1
3,0.05
4,.02
5,.01
6,.005
7,.002
8,.001
** ----------------------------------------------------------------
** 
** STEP: Nonlinear_Buckling
** 
*Step, name=Nonlinear_Buckling, nlgeom=YES, inc=1000
*Static, riks
0.0001, 1., 1e-06, 0.1, , 
** 
** LOADS
** 
** Name: Load-1Top   Type: Concentrated force
*Cload
Set-8, 3, -1e+06
** 
** OUTPUT REQUESTS
** 
*Restart, write, frequency=0
** 
** FIELD OUTPUT: F-Output-1
** 
*Output, field, variable=PRESELECT
** 
** HISTORY OUTPUT: H-Output-1
** 
*Output, history, variable=PRESELECT
*End Step

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