Buckling Analysis of a Compressed Straight Tube (surface)

Let's review the buckling analysis of a straight tube compressed with an pressure q. The tube has length L, middle radius R and wall thickness h, both ends being simply supported. Sought is the load factor corresponding to numbers of half-waves n,m of the tube buckling. Assume the beam length equal to 1 m, and the crosssection dimensions R = 0.056 m, h = 0.006 m.

Buckling Analysis of a Compressed Straight Beam

Material characteristics assume default values: Young's modulus E = 2.1E+011 , Poisson's ratio ν = 0.28.

Let's define the boundary conditions as follows. The up and bottom faces are restrained in XY-axes, the bottom face is additionally fully restrained at a point; outer surface is subjected to the pressure load in the amount of 1 Pa.

Analytical solution:

Solution is sought for n,m = (2,1); (2,2).

Buckling Analysis of a Compressed Straight Beam, the finite element model with applied loads and restraints

The finite element model with applied loads and restraints

After carrying out calculation with the help of AutoFEM, the following results are obtained:

Table 1. Parameters of finite element mesh

Finite Element Type

Number of nodes

Number of finite elements

linear triangle

3636

7200

Table 2. Result "Critical load"*

Numerical solution
Critical load P*critical, Pa

Analytical solution
Critical load Pcritical, Pa

Error δ = 100% *|P*critical-Pcritical| / |Pcritical|

9.5702E+007

9.5204E+007

0.52

1.0796E+008

1.0436E+008

3.45

Buckling Analysis of a Compressed Straight Beam, first buckling mode of the beam

 

 

*The results of numerical tests depend on the finite element mesh and may differ slightly from those given in the table.

 

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