Finite Element Analysis
in Product Design - |
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When the word “standards” is mentioned
in an engineering context, plenty of acronyms come to mind such as ISO,
ANSI, ASTM, & SAE to name a few.
One acronym that rarely gets associated with standards is FEA
(Finite Element Analysis). Most
FEA users in traditional product development environments take for
granted that the results calculated by their FEA tool are accurate, or
at least the correct solution to the question posed, by means of their
choice of boundary conditions, properties, and geometry.
While in most cases, the latter is true, it is important to
remember that a successful FEA project requires that at least three
complex processes be carried out properly. First, the user must be capable of and qualified to pose a
‘question’ correctly to the software.
Second, the software must be mathematically robust and accurate
enough to provide a good solution.
Finally, the user must again be capable of and qualified to
understand the results and assess the performance of the system under
study based on these results. None
of these steps should be taken for granted. The second step in that process, the
numerical accuracy of the solver is perhaps the easiest to quantify.
In 1983, an organization called NAFEMS (www.nafems.org) began to
develop a set of standards, or benchmarks, with the specific intent of
validating FE solutions and technologies.
The solutions to these benchmarks provide vendors and users alike
to assess the quality of the FE solution.
Today, NAFEMS has developed benchmarks for statics, dynamics,
nonlinear, and contact. These
benchmarks serve a dual purpose, acting as an educational tool as well. While NAFEMS has provided a set of
standards against which FE vendors can prove to you, the user, that
their code is capable of correctly solving a properly formulated
‘question’, the discussion must turn to the other two steps in the
process. How can you or
your management be confident that you are capable of formulating that
question and qualified to interpret the results.
It is in these areas that most users, rookie or veteran, point to
their degree from an accredited engineering university and their
certificate of completion from the introductory FE vendor training as
evidence of qualification. Unfortunately,
as the proliferation of FE software and the enormous advances in
ease-of-use have outpaced FE education, users across the industry must
acknowledge that this is no longer good enough. At the 2001 NAFEMS World Congress in Lake
Como, Italy, I presented three brief case studies highlighting typical
mistakes in meshing, boundary conditions (loads and constraints), and
problem definition. These
mistakes completely invalidated any results calculated by the solver and
in each of these cases, the respective analysts would have characterized
themselves as experts. In
fact, their companies considered them to be experts! The important point in all this is that
while software vendors have gone to great lengths to make their codes
accurate and easy to use, most users aren’t holding up their end of
the bargain by learning the techniques, engineering, and discipline
required to successfully use these products.
If these ‘experts’ I described previously can’t properly
assess their own skill level, what chance do part-time design analysts
have to get it right? On-going support and education in FE basics as well as
engineering mechanics and failure theory will go a long way to address
this problem. Organizations
like NAFEMS and IMPACT Engineering Solutions have addressed these issues
thru the development of code-dependent and independent training classes,
seminars and quality control tools.
However, the old saying, “You can lead a horse to water…”
applies here too. As FEA becomes more mainstream in the
product design world, control systems and checks/balances are becoming
more the exception than the rule. Unfortunately,
putting analysis tools into the hands of rookies or part-timers without
some means for control and standardization is a recipe for disaster.
In a dedicated analysis group where the supervisor is a former
analyst of similar skill level to his team, all members of the team
speak the same "language" and the supervisor knows what to
look for and where to look for it when evaluating a project.
This is not the case in most of today's design environments.
Now more than ever, managers in a product development
organization that has embraced simulation need tools to quickly and
accurately assess the accuracy and effectiveness of their analysis
efforts. Standards and certification of skill level are important in all aspects of engineering, from fasteners to simulation. Engineering organizations that fail to embrace these standards face huge risks in revenue and product safety. Whether it is a bolt failing or a weldment buckling due to improper testing or analysis, all design engineers and managers must take responsibility and accept accountability for all the parts, tools and techniques used in their product development process. |