External pressure Cylinder buckling

I study the buckling loads of cylinders. I need to find critical buckling, overall buckling, and collapse buckling loads. First, I did a linear buckling analysis and used mode-1 as a geometric imperfection (scale factor = 0.1). I applied 0.03 Mpa of pressure to the cylinder. I obtained a graph using Newton Raphson and the stabilization settings but could not model the behavior exactly. Then I tried the Arc-Length method. It didn't happen again.

Eigenvalue multiplier is 20,306 for 0,001 mpa . So my critical buckling have to be lower 0,0203. Finally ı wanted to see my model behavior for overall buckling and collapse buckling.

Can you help?

Model - R(radius)=500 mm h=1250 mm t(thickness)=1 mm

Top and Bottom simply supported (displacement x=y=z=0)

1-ansys model

2-eigenvalue multiplier

3-newton raphson -stabilization energy constant 0,001 (initial 200 min 100 max 2000 substeps) result

4-arclength commond

5-my arclength result(finished 0,63 sn and not converged)

6-true arc length grafic (wanted)


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