iMechanica - Buckling of thin walled cylindrical shell - Comments

Buckling of thin walled cylindrical shell

Himayat Ullah — Fri, 26 Sep 2008 03:34:09 -0400

Xiao-Yan Gong,

May I have some examples of such structure designed beyond elastic buckling limit. As the elastic critical load, determined by theory and linear FEM is usually lesser than design (actual) load because of imperfections.

Himayat

Its post buckling!

Xiao-Yan Gong — Thu, 25 Sep 2008 13:51:14 -0400

Elastic buckling may trigger the failure. You can do a post buckling analysis to find out. Keep in mind there are structures in use today that beyond elastic buckling limit.

Happy analyzing.

Xiao-Yan Gong, PhD

Re: Buckling of thin walled cylindrical shell

Alejandro A. Ortiz — Thu, 25 Sep 2008 12:38:28 -0400

Apart from the aesthetic thing there is a more powerful reason. If the load is larger than the critical load for the elastic buckling and because of the material is elasto-plastic, the following would be the picture:

elastic buckling --> extremely large deformation --> plastic buckling --> catastrophic collapse

So, in conclusion the most safest is to consider the elastic buckling as a failure.

Alejandro A. Ortiz

Yes, I agree that it is

Alejandro A. Ortiz — Thu, 25 Sep 2008 04:28:39 -0400

Yes, I agree that it is considered as a failure and should be avoided. Just think what the final user of the structure would think if the structure is evidently backled even in the elastic range. Certainly, he or she would not be confident about the safety of the structure.

Alejandro A. Ortiz

Buckling of thin walled cylindrical shell

Himayat Ullah — Thu, 25 Sep 2008 03:32:05 -0400

Thanks all for your replies.

It means that we can design structures for buckling. Where as in buckling,a structure changes its equilibrium configuration and undergoes large deformation, even if it is elastic. Load-Deflection curve is linear upto bifurcation point and becomes nonlinear in the post buckled region. To bring the structure to its original configuration, an external energy is required. It will not recover its pre buckled shape by itself.

Further ,buckling is usually considered as a failure and i avoided in the design of structures.

Himayat

Re: Buckling of thin walled cylindrical shell

Alejandro A. Ortiz — Wed, 24 Sep 2008 18:44:12 -0400

I assume an elasto-plastic material like mild steel and that you have calculated the ciritical load for the actual ratio Do/t and the critical load was lower than the load obtained for the yield stress. Under such circumstances of elastic buckling the shell will remain backled while the load is applied and will recover its original configuration as soon as the load is removed. Because of the material is elasto-plastic the latter is independent of whether buckling has occurred or not.

Alejandro A. Ortiz

Elastic buckling?

Ying Li — Wed, 24 Sep 2008 02:38:37 -0400

I am not sure. If the shell only undergoes the elastic buckling, it will recover to its original shape.

Ying Li Department of Engineering Mechanics Tsinghua University Beijing, 100084, P. R. CHINA

Buckling of thin walled cylindrical shell

Himayat Ullah — Wed, 24 Sep 2008 00:28:24 -0400

I am analyzing a steel thin walled cylidrical shell subjected to axial compression against buckling.I performed both eigen value linear and nonlinear buckling analyses using ANSYS.The buckling load is less than the material yield limit and is therefore elastic buckling.

One of my colleague argues that the shell will regain its original shape after the buckling load is removed,as its is elastic buckling.My plea is that the shell has passed the limit point (buckling load) and it is global buckling and no shape recovery will occur after the load removal.

Your advice is requested in the design of this structure.

Thanks in advance