I'm trying to simulate nonlinear compressive buckling of a material. However, it's not buckling as I would (theoretically) expect for lengths crossing the buckling threshold. It would just compress and fail at the failure strength/strain as specified in MAT024 - Piecewise Linear Plasticity. For further reference, I am using solid elements and it's a pin-pin configuration.
Theoretically, I'm thinking that a small lateral load/perturbation is needed to trigger the buckling and/or build the meshing with an out-of-straightness. I'm not an expert in FEA/LSDYNA, so any help with choosing the right keywords to get my specimen to buckle is appreciated.
I've already got the specimen to buckle elastically (eigenvalue), but struggling with nonlinear buckling.
It is possible that your simulation is not experiencing buckling because the material is behaving plastically before reaching the buckling threshold. In order to achieve buckling, you may need to increase the stiffness of the material or decrease the load applied to the specimen.
If you want to introduce a lateral load or perturbation to trigger buckling, you can do so by applying an initial geometric imperfection to the specimen. This can be done in LSDYNA by using the *INITIAL_IMPERFECTION keyword and specifying the magnitude and distribution of the imperfection.
You may also want to consider using an element type that is more suitable for simulating buckling behavior, such as a shell element or a reduced integration element.
Hi Faisal Qayyum
Appreciate your answer :)
1. Increasing the stiffness is not an option as I want to determine the buckling stress with varying slenderness of a particular material (stiffness is not a variable).
2. I'm applying a *BOUNDARY_PRESCRIBED_MOOTION_NODE to the upper surface with displacement control. So I'm not using a load, as the goal is to find the load. Would you advise another way?
3. I couldn't find the *INITIAL_IMPERFECTION keyword. I'm using V4.6.12. However, I did find *PERTURBATION. Would you happen to know how to get an imperfection through this keyword?
4. I will try different element types as suggested
Appreciate all your help.
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