Non-linear analysis of a buckling cylinder
Non-linear analysis of a buckling cylinder
(OP)
I am currently trying to solve a localised buckling problem in a cylindrical piece of equipment modelled using plate elements. The buckling comes about due to a combination of thermal effects and eccentric loading on the cylinder.
When I run a linear static and a linear buckling analysis I get some nice answers out that reasonably replicate what is observed out on site.
When I try to run the non-linear geometry analysis I cannot get it to converge.
Does anyone have some tips, tricks or techniques to get around this problem? I have simplified the geometry and the mesh, fiddled endlessly with load increments... as the cylinder is buckling does this mean the non-linear analysis is unstable and won't converge?
When I run a linear static and a linear buckling analysis I get some nice answers out that reasonably replicate what is observed out on site.
When I try to run the non-linear geometry analysis I cannot get it to converge.
Does anyone have some tips, tricks or techniques to get around this problem? I have simplified the geometry and the mesh, fiddled endlessly with load increments... as the cylinder is buckling does this mean the non-linear analysis is unstable and won't converge?





RE: Non-linear analysis of a buckling cylinder
Tara
http://tinyurl.com/4ydjg7m
RE: Non-linear analysis of a buckling cylinder
if the latter, then apply less load for your non-linear run. maybe apply the load without the temp (just to see what happens).
RE: Non-linear analysis of a buckling cylinder
RE: Non-linear analysis of a buckling cylinder
I am using Strand7 to run the analysis, which I don't believe allows me to perform an explicit analysis. Nor does it do anything fancy to force convergence.
I am planning to proceed as follows;
1. Modify the geometry slightly so the buckling mode I am interested in is the 1st mode in the linear buckling analysis (stiffeners in areas I am not concerned with buckle at lower load factors)
2. Run the non-linear geometry analysis and find the fraction of the load which brings about the onset of buckling (point at which the stiffness matrix becomes singular)
Then it is a case of determining how to prevent buckling occurring via some sort of stiffening arrangement.
My concern now is that the thing out on site has already buckled so in devising a solution to prevent further buckling, should I really be modelling the permanent deformation in the cylinder and applying some sort of stiffening solution to that?
RE: Non-linear analysis of a buckling cylinder
Tara
http://tinyurl.com/4ydjg7m
RE: Non-linear analysis of a buckling cylinder
have you asked Strand7 helpdesk ?
from your linear run, what's the highest stress ? this'll tell you the %age of load that the structure should be able to carry to yield.