Am trying to test out a new theory for filled-shell local shell buckling.
At present I have the theoretical values of the buckling loads and have already done modal analysis in Abaqus on several geometries using the "buckle" step in Abaqus.
However, I'm trying to now do post-buckling analysis to get the stress and strain fields inside the geometry at the point of buckling.
The way that I've done it right now is to use a script to introduce an imperfection into the shell by changing the part's geometry in Sketch mode.
The problem with this, though, is that the Abaqus solvers cannot seem to get past the buckling load (which is correctly found) and fails after too many increments at some given time step.
Is there a more correct way to introduce my own imperfections into the model? For doing what I'm trying to do here?
What I understood is that you're trying to do a non linear static analysis whith forces as your imposed boundary conditions which doesn't converge any more when you reach the buckling point. To get the full force-displacement curve and see the post buckling behavior you either need to use displacements as an imposed boundary condition or an arch-length solver (this last one is called Ricks in Abaqus).
If you perform a static analysis for a post buckling analysis your assumptions are not valid any more. If you want to perform a post buckling analysis you have to do that as a transient analysis. In that case you model the real dynamics of your problem. The work around to stabilize the solution is to use a velocity dependend damping factor. In that case you have to run multiple simulations to be sure, that the damping does not effect the result. If you want to know more details you can ask a colleage of mine. She nearly finished her PhD about this topic
https://www.researchgate.net/profile/Regina_Khakimova?_sg=RArmCpbjj-jYUOyh6z-KSBJzAn3SGfq1DkYdmiZdZn0pGa2bZigAONxxB-UAB8QyDNxNpHb6rQzuq8wsWe5y-Q.cI0wJ34g7VMoYKs4eH-1-mIFkLN2Uja7TPNyAKxHD1y1TnhIj9zN3axeBnQGa9KP
Hi all,
Thanks for your answers.
Mr. Decelle: yes I am trying to get the post-buckling behaviour but my boundary conditions are actually specified in displacements, as you had suggested. I'm not specifying a force as a load at all. I'll check out Ricks in Abaqus.
Mr. Willberg: would Abaqus Explicit be needed in this case? Since it is intended for dynamics analysis?
Hi,
I experienced the same problem, I believed that the problem is not the imperfection. Moreover, I realized that applying the imperfection on the geometry lead to more accurate results than the model with defined imperfection as displacement boundary condition. I think the problem is the time increments and the applied force, try with the smaller load and smaller time increment. Plus, try to apply a displacement boundary condition instead of load.
"would Abaqus Explicit be needed in this case?"
You can run it explict or implicit.
The advice of Zohreh Asaee won't help you in any case. The displacement boundary conditions reduce the size of the stiffness materix. Therefore, the system of equations are better solvable and the convergence problems may be stabilzed.
Also it depends what you want to model. A displacement boundary condition defines the movement of a point or multiple points. A load apllied somewhere influences localle the stress path, but the deformation in this area has to be solved.
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