Hi all,
I'm trying to run a nonlinear (elastic for now) buckling analysis in ANSYS. Basically I have a thin cylindrical shell (made up of SHELL181). fixed at one end (rigid) and applied force and/or displacement specified on the other end to make it buckle.
I have pretty much tried all options. These were:
i) Linear buckling (Eigenbuckling)
ii) Displacement controlled buckling with a lateral point force to provide eccentricity/imperfection.
iii)Force controlled buckling with, again, a lateral point force (arc-length method)
iv) same as (ii) and (iii) however instead of the lateral point force I superimposed the 1st mode of the linear buckling analysis to provide eccentricity/imperfection with UPGEOM command.
For the force-controlled analysis, the arc-length method doesn't converge. I have also tried the STABILIZE command to apply artificial damping but I got shooting nodes near the end of the analysis so that also blew up.
For displacement controlled cases, in none of these analysis have I seen reduction in load displacement curve that I can identify as bifurcation/buckling. The axial force vs. lateral deflection plot looks almost like bilinear with a steep linear region and almost a flat post-buckling region. (just like an elastic perfectly plastic stress-strain curve if you will).
If you would have this problem, which of the above methods would you use? What should I do to get load reduction I'm looking for. I attached the input file for the displacement controlled buckling attempt. I'd appreciate any help and guidance. Thanks in advance,
I'm trying to run a nonlinear (elastic for now) buckling analysis in ANSYS. Basically I have a thin cylindrical shell (made up of SHELL181). fixed at one end (rigid) and applied force and/or displacement specified on the other end to make it buckle.
I have pretty much tried all options. These were:
i) Linear buckling (Eigenbuckling)
ii) Displacement controlled buckling with a lateral point force to provide eccentricity/imperfection.
iii)Force controlled buckling with, again, a lateral point force (arc-length method)
iv) same as (ii) and (iii) however instead of the lateral point force I superimposed the 1st mode of the linear buckling analysis to provide eccentricity/imperfection with UPGEOM command.
For the force-controlled analysis, the arc-length method doesn't converge. I have also tried the STABILIZE command to apply artificial damping but I got shooting nodes near the end of the analysis so that also blew up.
For displacement controlled cases, in none of these analysis have I seen reduction in load displacement curve that I can identify as bifurcation/buckling. The axial force vs. lateral deflection plot looks almost like bilinear with a steep linear region and almost a flat post-buckling region. (just like an elastic perfectly plastic stress-strain curve if you will).
If you would have this problem, which of the above methods would you use? What should I do to get load reduction I'm looking for. I attached the input file for the displacement controlled buckling attempt. I'd appreciate any help and guidance. Thanks in advance,