Nonlinear buckling load is greater than linear buckling load. why?

- October 21, 2019 at 1:40 pm
  
  venugopal4048
  Subscriber
  
  I am doing nonlinear buckling analysis using workbench. so that I have done a linear buckling analysis, added imperfection and save it as a .cbd file. Then I used external model tool to import the geometry and shared the data with structural analysis. switched the large deformation and used ARCLEN method to solve the nonlinear analysis. But the problem is the Nonlinear buckling load does not reduces significantly as expected. I have checked all the material properties and all possible parameters. I think the problem with external model. can anyone help me?
- November 12, 2019 at 1:51 am
  
  Sandeep Medikonda
  Ansys Employee
  
  Are you running into any specific errors? Have you observed the same behavior for varying mesh size?
  
  Please provide comparisons of your linear and non-linear bifurcation points?
  
  When you mention nonlinear buckling, how are you accounting for the nonlinearity? Geometric (large deflection), Materials or Contact? Be sure to look in the legend to see if Load Multiplier States Linear or Nonlinear? Post snapshots of your comparison.
- November 12, 2019 at 3:41 am
  
  venugopal4048
  Subscriber
  
  Thank you sandeep for your reply.
  
  In my model I am using large deflection alone when I was post here. After that i found that large deflection may create nonlinearity or may not be based on geometry. so in my model there is geometric nonlinearity. Then i added material nonlinearity(MISO), the buckling load is considerably reduced due to this. Now problem is on convergence.
  
  Could you tell me above stated words about large deflection is correct or not? also how to improve convergence.
  
  regards
  
  venugopal b
- November 12, 2019 at 4:57 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  Non-linear buckling is often smaller than the linear buckling.
  
  Improving convergence is a very generic and open-ended question.
  
  Some suggestions have been provided in this post.
- November 13, 2019 at 4:28 am
  
  venugopal4048
  Subscriber
  
  Thank you sandeep.
  
  Is the geometric nonlinearity(large deflection) has effect on buckling load for all geometries? because in my model simply large deflection alone does not make any impact, after adding material nonlinearity the buckling load got reduced.
- November 13, 2019 at 5:59 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  We can't generalize, but of course, large deflection will have an effect, maybe its not significant in the problem you have.