Slender models tend to buckle under axial loading. Buckling is defined
as the sudden
deformation
that
occurs when the stored membrane (axial) energy is converted into bending energy with
no change in the externally applied loads. Mathematically, when buckling occurs, the
stiffness becomes singular. The Linearized buckling approach, used here, solves an
eigenvalue problem to estimate the critical buckling factors and the associated
buckling mode shapes.
A model can buckle in different shapes under different levels of
loading. The shape the model takes while buckling is called the buckling mode shape
and the loading is called the critical or buckling load. Buckling analysis
calculates a number of modes as requested in the Buckling dialog. Designers are
usually interested in the lowest mode (mode 1) because it is associated with the
lowest critical load. When buckling is the critical design factor, calculating
multiple buckling modes helps in locating the weak areas of the model. The mode
shapes can help you modify the model or the support system to prevent buckling in a
certain mode.
SOLIDWORKS Simulation does not consider the effect of offset axial
loads (that is, remote loads or loads that are not applied at the centroid of a
geometric cross section) in the linearized buckling analysis. In theory, the
application of offset loads can further reduce the buckling load factors calculated
by the software.
To account for the effect of offset loads for models that are
susceptible to buckling, you can create a nonlinear study. Nonlinear studies can
recalculate the stiffness matrix
incrementally,
and
so
take into account the bending and compressive effects that eccentric loads induce in
the geometry.
In a nonlinear study, you can also apply plasticity material models
to more accurately predict if failure might occur by material yielding or by the
onset of buckling.
When to Use Buckling Analysis
Slender parts and assemblies with slender components that are loaded in the
axial direction buckle under relatively small axial loads. Such structures can fail
because
of buckling while the stresses are far below critical levels. For
such structures, the buckling load becomes a critical design factor. Buckling
analysis is usually not required for bulky structures as failure
usually
occurs
because of high stresses.