Finite_Element_Analysis__Introduction by seragsamy

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									Title:
Finite Element Analysis: Introduction

Word Count:
648

Summary:
The following four-article series was published in a newsletter of the
American Society of Mechanical Engineers (ASME). It serves as an
introduction to the recent analysis discipline known as the finite
element method. The author is an engineering consultant and expert
witness specializing in finite element analysis.


Keywords:
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injury,forensic


Article Body:
The following four-article series was published in a newsletter of the
<I>American Society of Mechanical Engineers (ASME)</I>. It serves as an
introduction to the recent analysis discipline known as the <B><I>finite
element method</I></B>. The author is an engineering consultant and
expert witness specializing in finite element analysis.


<b><i>FINITE ELEMENT ANALYSIS: Introduction</i></b>
by Steve Roensch, President, Roensch & Associates

<i>First in a four-part series</i>


Finite element analysis (FEA) is a fairly recent discipline crossing the
boundaries of mathematics, physics, engineering and computer science. The
method has wide application and enjoys extensive utilization in the
structural, thermal and fluid analysis areas. The finite element method
is comprised of three major phases: (1) <B><I>pre-processing</I></B>, in
which the analyst develops a finite element mesh to divide the subject
geometry into subdomains for mathematical analysis, and applies material
properties and boundary conditions, (2) <B><I>solution</I></B>, during
which the program derives the governing matrix equations from the model
and solves for the primary quantities, and (3) <B><I>post -
processing</I></B>, in which the analyst checks the validity of the
solution, examines the values of primary quantities (such as
displacements and stresses), and derives and examines additional
quantities (such as specialized stresses and error indicators).

The advantages of FEA are numerous and important. A new design concept
may be modeled to determine its real world behavior under various load
environments, and may therefore be refined prior to the creation of
drawings, when few dollars have been committed and changes are
inexpensive. Once a detailed CAD model has been developed, FEA can
analyze the design in detail, saving time and money by reducing the
number of prototypes required. An existing product which is experiencing
a field problem, or is simply being improved, can be analyzed to speed an
engineering change and reduce its cost. In addition, FEA can be performed
on increasingly affordable computer workstations and personal computers,
and professional assistance is available.

It is also important to recognize the limitations of FEA. Commercial
software packages and the required hardware, which have seen substantial
price reductions, still require a significant investment. The method can
reduce product testing, but cannot totally replace it. Probably most
important, an inexperienced user can deliver incorrect answers, upon
which expensive decisions will be based. FEA is a demanding tool, in that
the analyst must be proficient not only in elasticity or fluids, but also
in mathematics, computer science, and especially the finite element
method itself.

Which FEA package to use is a subject that cannot possibly be covered in
this short discussion, and the choice involves personal preferences as
well as package functionality. Where to run the package depends on the
type of analyses being performed. A typical finite element solution
requires a fast, modern disk subsystem for acceptable performance. Memory
requirements are of course dependent on the code, but in the interest of
performance, the more the better, with 512 Mbyte s to 8 Gbytes per user a
representative range. Processing power is the final link in the
performance chain, with clock speed, cache, pipelining and multi-
processing all contributing to the bottom line. These analyses can run
for hours on the fastest systems, so computing power is of the essence.

One aspect often overlooked when entering the finite element area is
education. Without adequate training on the finite element method and the
specific FEA package, a new user will not be productive in a reasonabl e
amount of time, and may in fact fail miserably. Expect to dedicate one to
two weeks up front, and another one to two weeks over the first year, to
either classroom or self-help education. It is also important that the
user have a basic understanding of the computer's operating system.

Next month's article will go into detail on the pre-processing phase of
the finite element method.

copyright 2005 Roensch & Associates. All rights reserved.

								
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