Single perturbation load vs Linear Buckling Eigenmode Perturbation for Nonlinear Buckling

[Doodler3D]

Hi,

Are there guidelines to implement single perturbation load vs scaled eigenmode perturbation from linear buckling for a nonlinear buckling analysis of pressure vessels (ASME Section VIII Div. 2, type 3 buckling)? PVT-17-1030 does a good job of summarizing different methods, but implementation of single perturbation methods appear to be suited for axial compression of composite cylinders. The software at work does not have the capability to input a scaled eigenmode shape to initiate buckling. Accordingly, is it appropriate to manually define a normal point load at the extremity of the buckled mode that would result in a perturbation that is equivalent to the manufacturing tolerance as shown? How can this manual approach be validated?

Additionally, are cut-outs, manway holes, service hatches, nozzle loads, eccentric loads, asymmetry, etc. sufficient features to initiate a non-linear buckling response without an initial perturbation?

Thank you.

 

[FEA way]

It seems that you are using SolidWorks Simulation which indeed doesn’t have an option to add imperfections in form of scaled linear buckling mode shapes. I don’t know if your code permits this (usually engineering codes are quite specific about such details) but I would rather avoid load imperfection in cases other than the basic ones.

 

[Doodler3D]

FEA way, its Inventor Nastran. The code itself has no specific guidelines on introducing imperfection.

 

[FEA way]

In the case of Inventor Nastran it seems that there are some workarounds that could let you use imperfections based on linear buckling mode shapes. However, you would have to manipulate with output/input files a bit. It might be worth giving a try though.

 

[Doodler3D]

FEA way, that involves a fair bit of manipulation, hence I was checking to see whether a single load perturbation approach would be sufficient.