Linear Buckling analysis

Buckling analysis is a technique used to determine buckling loads and buckled mode shapes. A buckling load is the critical load at which a structure becomes unstable, and a buckled mode shape is the characteristic shape associated with a structure's buckled response.

A linear buckling analysis identifies the loading conditions that make a structure unstable and result in various buckled mode shapes, as determined by the eigenvalue extraction method and the number of modes for which the analysis is solved.

In a linear statics analysis, a structural model is normally considered to be in a state of stable equilibrium. As you remove the load previously applied, the structure goes back to its original position. However, under certain loading combinations, the structure becomes unstable. When this loading is reached, the structure continues to deflect without an increase in the loading magnitude and "buckles" or becomes unstable.

To build the model for a linear buckling analysis, choose the Linear Buckling analysis. Before performing the Solve operation, enter a number for the required buckled shape modes and, if desired, the upper and lower eigenvalue range. A default value (usually the lowest number of modes) is given if these values are not defined.

How loads are treated in Linear Buckling analysis

If the analyzed model only contains a buckling load (that is, a load, which when large enough, would cause the system to become unstable), the critical buckling load is the load multiplied by the eigenvalue.

The model can contain one or more buckling loads and also other loads that would not cause buckling on their own, but instead act on the part by making it more (or less) likely to become unstable. The figure below illustrates one such case.

P1 is the buckling load and P2 is a load that makes the part more likely to become unstable. The part in the example will become unstable for a lower value of P1 than the same part without P2.

P2 may be a known load acting on the part. You may want to find out the value of P1 at which the part becomes unstable.

With a linear buckling solution, you cannot keep P2 constant and analyze the part only for buckling caused by P1. The linear buckling solution considers all loads as a system. The relation between the loads is not considered to change. For example, if the part is analyzed with P1=1 and P2=0.5 and the lowest eigenvalue turns out to be 500, the system is calculated to be unstable for the load combination: P1=500 and P2=250.

Supported environments

Pre/Post supports the following linear buckling environments:

• Nastran - SOL 105 Linear Buckling

• ANSYS - Buckling

• Abaqus - Buckling Perturbation Substep

• Simcenter Samcef - Buckling AnalysisSimcenter Samcef - Standalone Buckling Analysis

Learn more

Linear static analysis

Modal analysis

Thermal and Thermal-Structural analysis

Nonlinear analysis

Aeroelastic analysis

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Linear Buckling analysis, Simcenter 3D 2021.1 Series

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