Page 21 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

8 • Using ansys for finite element analysis
isotropic: identical throughout, orthotropic: identical at 90 degrees, general
anisotropic: different throughout.
The basic ingredients of any FEA of structural problems are:

• Geometry
• Material model (constitutive model)
• Loading
• Support or boundary conditions

1.1.6 tyPes of structural analysis

Structural analysis is probably the most common application of the FEM.
Structure is defined as something that is designed to bear load. There-
fore, the term structural (or structure) implies not only civil engineer-
ing structures such as bridges and buildings, but also naval, aeronautical,
and mechanical structures such as ship hulls, aircraft bodies, and machine
housings, as well as mechanical components such as pistons, machine
parts, and tools.
FEA has become a solution to the task of predicting failure due to
unknown stresses by showing problem areas in a material and allowing
designers to see all of the theoretical stresses within. This method of prod-
uct design and testing is far superior to the manufacturing costs, which
would accrue if each sample was actually built and tested. FEA consists
of a computer model of a material or design that is stressed and analyzed
for specific results. It is used in new product design and existing product
refinement. A company is able to verify whether a proposed design will be
able to perform to the client’s specifications prior to manufacturing or con-
struction. Modifying an existing product or structure is utilized to qualify
the product or structure for a new service condition. In case of structural
failure, FEA may be used to help determine the design modifications to
meet the new condition. There are generally two types of analysis that
are used in industry: 2D modeling and 3D modeling. While 2D modeling
conserves simplicity and allows the analysis to be run on a relatively nor-
mal computer, it tends to yield less accurate results. 3D modeling, how-
ever, produces more accurate results while sacrificing the ability to run on
all, but the fastest computers effectively. Within each of these modeling
schemes, the programmer can insert numerous algorithms (functions),
which may make the system behave linearly or nonlinearly. Linear sys-
tems are far less complex and generally do not take into account plastic
deformation. Nonlinear systems do account for plastic deformation, and
many also are capable of testing a material all the way to fracture.