934
Mechanical Engineering Design
Mechanical components in the form of simple bars, beams, etc., can be analyzed quite
easily by basic methods of mechanics that provide closed-form solutions. Actual com-
ponents, however, are rarely so simple, and the designer is forced to less effective
approximations of closed-form solutions, experimentation, or numerical methods.
There are a great many numerical techniques used in engineering applications for which
the digital computer is very useful. In mechanical design, where computer-aided design
(CAD) software is heavily employed, the analysis method that integrates well with
CAD is
fnite-element analysis
(FEA). The mathematical theory and applications of the
method are vast. There is also a number of commercial FEA software packages that are
available, such as ANSYS, NASTRAN, Algor, etc.
The purpose of this chapter is only to expose the reader to some of the fundamen-
tal aspects of FEA, and therefore the coverage is extremely introductory in nature. For
further detail, the reader is urged to consult the many references cited at the end of this
chapter. Figure 19–1 shows a ±nite-element model of a crankshaft that was developed
to study the effects of dynamic elastohydrodynamic lubrication on bearing and struc-
tural performance.
1
There are a multitude of FEA applications such as static and dynamic, linear and
nonlinear, stress and de²ection analysis; free and forced vibrations; heat transfer (which
can be combined with stress and de²ection analysis to provide thermally induced
stresses and de²ections); elastic instability (buckling); acoustics; electrostatics and
1
S. Boedo, “Elastohydrodynamic Lubrication of Conformal Bearing Systems,”
Proceedings oF 2002 ANSYS
Users ConFerence,
Pittsburgh, PA, April 22
–
24, 2002.
(
a
)
X
Z
Y
(
b
)
X
Z
Y
Figure 19–1
Model of a crankshaft using
ANSYS Fnite-element
software. (
a
) Meshed model
(
b
); stress contours.
Courtesy
of S. Boedo (see footnote 1).