Page 25 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

12 • Using ansys for finite element analysis
from, and all are nonlinear. Frictional response can be chaotic, making
solution convergence difficult.
In addition to these two difficulties, many contact problems must also
address multi-field effects, such as the conductance of heat and electrical
currents in the areas of contact.

1.1.6.9 fracture Mechanics

Cracks and flaws occur in many structures and components, sometimes
leading to disastrous results. The engineering field of fracture mechanics
was established to develop a basic understanding of such crack propaga-
tion problems.
Fracture mechanics deals with the study of how a crack or flaw in a
structure propagates under applied loads. It involves correlating analytical
predictions of crack propagation and failure with experimental results.
The analytical predictions are made by calculating fracture parame-
ters such as stress intensity factors in the crack region, which you can
use to estimate crack growth rate. Typically, the crack length increases
with each application of some cyclic load, such as cabin pressurization-
depressurization in an airplane. Further, environmental conditions such
as temperature or extensive exposure to irradiation can affect the fracture
propensity of a given material.

1.1.6.10 composites

Composite materials have been used in structures for a long time. In recent
times, composite parts have been used extensively in aircraft structures,
automobiles, sporting goods, and many consumer products.
Composite materials are those containing more than one bonded
material, each with different structural properties. The main advantage of
composite materials is the potential for a high ratio of stiffness to weight.
Composites used for typical engineering applications are advanced fiber
or laminated composites, such as fiberglass, glass epoxy, graphite epoxy,
and boron epoxy.
FEA allows you to model composite materials with specialized ele-
ments called layered elements. Once you build your model using these
elements, you can do any structural analysis (including nonlinearities such
as large deflection and stress stiffening).