Post-buckling analysis (SOL 401)

You can perform a post-buckling analysis in Pre/Post using the Simcenter Nastran SOL 401 Multi-Step Nonlinear solution.

At buckling, the stiffness of a structural model is singular. To enable the software to solve past the singularity and predict the post-buckling response of the structure, you must:

• Enable large displacements for the solution.The parameter you use to specify large displacements applies to all solution steps. Thus, you cannot create a linear static solution step in a solution that contains a post-buckling solution step.

• Create a solution step that uses an arc-length method as the time-stepping algorithm. This solution step is referred to as the post-buckling solution step.You cannot include a post-buckling solution step in a coupled multiphysics solution because the arc-length methods are not supported in coupled multiphysics solutions.Note: In Simcenter Nastran, solution steps are referred to as subcases.

Arc-length methods apply the loads that you define in the post-buckling solution step incrementally. You can specify the fraction of these loads (called the load factor) that the software uses to initiate the post-buckling solve. During the post-buckling solve, the software automatically adjusts the load factor for each iteration.

If the solution contains multiple solution steps, how the software applies the loads in the post-buckling solution step depends on whether the post-buckling solution step is sequentially dependent.

• If the post-buckling solution step is non-sequentially dependent, the initial loading is the product of the loads in the post-buckling solution step and the initial load factor regardless of where the post-buckling solution step is placed.For example, if the post-buckling solution step contains a single load of 1000 N and the initial load factor is 0.1, the software begins the post-buckling analysis by applying a load of 0.1 x 1000 N = 100N.

• If the post-buckling solution step is sequentially dependent, how the software applies the loads in the post-buckling solution step is also dependent on where the post-buckling solution step is placed.If the post-buckling solution step is the first solution step, the initial loading is the product of the loads in the post-buckling solution step and the initial load factor, which is the same as when the post-buckling solution step is non-sequentially dependent.If the post-buckling solution step is an intermediate solution step or the last solution step, the initial loading is the sum of the prevailing loads at the end of the previous nonlinear static solution step, and the product of the initial load factor and the difference between the loads in the post-buckling solution step and the prevailing loads at the end of the previous nonlinear static solution step.For example, if the post-buckling solution step contains a single load of 1000 N, the initial load factor is 0.1, and the value of the load at the end of the previous nonlinear static solution step is 500 N, the software begins the post-buckling analysis by applying a load of 500 N + 0.1 x (1000 N - 500 N) = 550 N.Note: If the post-buckling solution step is sequentially dependent and the post-buckling solution step is an intermediate solution step, only a modal solution step can follow it. If the modal solution step is sequentially dependent, the stress state at the end of the post-buckling solution step is treated as a preload in the modal solution step.

In the post-buckling solution step, in addition to large displacements, you can optionally include for any combination of the following types of nonlinearities:

• Buckling

• Plasticity

• Contact

You cannot include creep in a post-buckling solution step because creep is time-dependent and the post-buckling solution step occurs instantaneously. That is, the post-buckling solution step occurs at a single value of time. However, a creep solution step can precede the post-buckling solution step.

A bolt preload solution step can precede a post-buckling solution step. If the post-buckling solution step is sequentially dependent, the stress state that results from the bolt preload is treated as a preload in the post-buckling solution step and is applied fully throughout the post-buckling solve. This behavior is different than when you specify loads in the post-buckling solution step, where they are applied incrementally.

For additional information on post-buckling analysis using Simcenter Nastran SOL 401, see Nonlinear buckling in the Simcenter Nastran Multi-Step Nonlinear User's Guide.

How do I

Model an initial imperfection

Graph load factor vs. displacement

Learn more

Post-buckling analysis workflow (SOL 401)

Modeling initial imperfections

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Post-buckling analysis (SOL 401), Simcenter 3D 2021.1 Series

© 2020 Siemens

window.mainLanguage="en_US"

window.delivId=""

window.projectId=""

MathJax.Hub.Config({ TeX: { extensions: ["autoload-all.js"] }, tex2jax: { displayMath: [ ] }, "SVG": { scale: 125 } });