Page 22 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

IntroductIon to FInIte element AnAlysIs • 9

F Linear

Nonlinear

Δ

Figure 1.7. Linear and nonlinear behavior of the structure.

Structural analysis consists of linear and nonlinear behavior of the
structural material, as shown in Figure 1.7. Linear behavior assumes that
the material is not plastically deformed. Nonlinear behavior consists of
stressing the material past its elastic capabilities (into the plastic range).
The stresses in the material then vary with the amount of deformation.
Vibrational analysis is used to test a material against random vibrations,
shock, and impact. Each of these incidences may act on the natural vibra-
tional frequency of the material, which, in turn, may cause resonance and
subsequent failure. Fatigue analysis helps designers to predict the life of a
material or structure by showing the effects of cyclic loading on the spec-
imen. Such analysis can show the areas where crack propagation is most
likely to occur. Failure due to fatigue may also show the damage tolerance
of the material. Heat transfer analysis models the conductivity or thermal
fluid dynamics of the material or structure. This may consist of a steady-
state or transient transfer. Steady-state transfer refers to constant thermal
properties in the material that yield linear heat diffusion.
Thus, some of the common types of structural analysis performed
using FEA are as follows.

1.1.6.1 static analysis (linear and nonlinear)

A static analysis calculates the effects of steady loading conditions on a
structure, while ignoring inertia and damping effects, such as those caused
by time-varying loads. A static analysis can, however, include steady
inertia loads (such as gravity and rotational velocity) and time-varying
loads that can be approximated as static equivalent loads (such as the
static equivalent wind and seismic loads commonly defined in many
building codes).
Static analysis is used to determine the displacements, stresses,
strains, and forces in structures or components caused by loads that do