## Buckling Analysis

## Buckling Analysis

(OP)

I created a simply tube made up of plate elements and ran two buckling cases:

1. One end is fixed

2. One end is pinned

Now according to Eulers simple equation for linear buckling, the effetive length changes with the type of constraint. In Nastran, both cases yield the same eigenvalue. Am I doing something wrong? Does Nastran account for the type of constraint like the theoretical formula?

Thanks,

Brian

1. One end is fixed

2. One end is pinned

Now according to Eulers simple equation for linear buckling, the effetive length changes with the type of constraint. In Nastran, both cases yield the same eigenvalue. Am I doing something wrong? Does Nastran account for the type of constraint like the theoretical formula?

Thanks,

Brian

## RE: Buckling Analysis

## RE: Buckling Analysis

## RE: Buckling Analysis

## RE: Buckling Analysis

## RE: Buckling Analysis

## RE: Buckling Analysis

Using equation (4) in SP-8007 you have the critical stress. I would use this and then

Sigma-x = axial stress

E = Young’s Modulus

nu = poisson’s ratio

t = thickness

r = radius

to get the total buckling load, just multiply by area (2*pi*r*t).

When you run an FEA linear buckling analysis, the lowest "positive" mode (eigenvalue) times the total applied load is the buckling load. Multiple this by your knock down and you have the max allowable load for the structure. Knock down factors are more critical in cylindrical shell buckling than for other types of structures. SP-8007 should cover this.