# External pressure Cylinder buckling

Member

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)

• Forum Coordinator

Hi @OguzhanA ,

Regards,

Ashish Khemka

• Member

Hi! @akhemka I have already reviewed this document. And you can see my result with stabilzation.

• Forum Coordinator
edited November 2020

Hi, could you take a look at this link from Help for limitations and best practice of using arclength method? What error/warning message did you encounter with the unconverged case? You might want to adjust the max/min arc radius multiplier using that arclen command. Also, is this a symmetric problem? If it is you can try take advantage of modeling only half/quarter of it for faster solve AND easier convergence.

• Member

thanks for your comment @HuiLiu you can see what I did below. Where exactly am I going wrong?

I added this commands. is it enough for arclength?

Geometry and BC

stabilization settings-off

Should I change the newton raphson setting ?

Regards

Oguzhan