Page 24 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

IntroductIon to FInIte element AnAlysIs • 11
1.1.6.5 spectrum analysis

Spectrum analysis is one in which the results of a modal analysis are used
with a known spectrum to calculate displacements and stresses in the
model. It is mainly used in place of a time history analysis to determine
the response of structures to random or time-dependent loading condi-
tions such as earthquakes, wind loads, ocean wave loads, jet engine thrust,
rocket motor vibrations, and so on.

1.1.6.6 Buckling analysis

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

1.1.6.7 nonlinear analysis

If a structure experiences large deformations, its changing geometric
configuration can cause the structure to respond nonlinearly.
Nonlinear stress–strain relationships are a common cause of non-
linear structural behavior.
Many factors can influence a material’s stress–strain properties,
including load history (as in elastoplastic response), environmental condi-
tions (such as temperature), and the amount of time that a load is applied
(as in creep response).

1.1.6.8 contact Problems

Contact problems are highly nonlinear and require significant computer
resources to solve. It is important that you understand the physics of
the problem and take the time to set up your model to run as efficiently
as possible.
Contact problems present two significant difficulties. First, you gen-
erally do not know the regions of contact until you have run the problem.
Depending on the loads, material, boundary conditions, and other factors,
surfaces can come into and go out of contact with each other in a largely
unpredictable and abrupt manner. Second, most contact problems need to
account for friction. There are several friction laws and models to choose