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Courtroom FEA: Why Did It Fail?
Author : Steve Roensch
Submitted : 2010-11-19 14:57:43 Word Count : 630 Popularity: 11
Tags: stress, stress analysis, law, legal, attorney, court, courtroom, fea, finite element, expert witness, engineer, product liability, personal injury, forensic
The Courtroom FEA Newsletter discusses the use of Finite Element Analysis in the courtroom, and serves thousands of product liability and personal injury attorneys in 26 countries.
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Courtroom FEA: Why did it fail?
Do you have a case where a loss, injury or death was caused by something bending or breaking? Finite element analysis (FEA) can help explain why the product failed, which can often identify the responsible party.
Was the product design deficient? Was the subject part defectively manufactured? Or was the product abused by the end user? Being able to answer these questions with engineering certainty may be the difference between winning and losing your case.
The FEA results can be presented as color images and animations. As discussed in previous issues of Courtroom FEA, this makes the analysis conclusions more understandable for the jury. An accurate FEA can also be powerful leverage in reaching an advantageous settlement with your opposition.
FEA is a fairly recent discipline which allows the numerical solution of governing physical equations over complicated geometric domains. The method is regularly applied to the structural analysis of designs with complex geometries. The part being analyzed is divided into many small regions called "finite elements". The physical behavior within each element is understood in concise mathematical terms. Assemblage of all elements' behavior produces a large matrix equation, which is solved for the quantity of interest, e.g. the deformation due to a maximum loading condition. Additional quantities, such as stresses, are then computed. Commercial FEA packages are usually used, to insulate the user from the substantial programming required to perform even a simple analysis. Still, obtaining accurate results from any package requires an experienced analyst. FEA can, and will, deliver incorrect results to the inexperienced user, who will then make important design decisions based on this false information.
An experienced FEA expert can determine the stresses and displacements in the failed part. When compared to industry standards, earlier designs and competitive designs, this often identifies the cause of failure, and hence the responsible party. As in any field, your choice of an expert is important in making your case. It's not unusual for an inexperienced FEA analyst to generate incorrect results; this is both a warning to the wise and a strategy for dealing with the other side's expert. FEA results lend themselves to color plots and animations, making conveying the key concepts to the jury much easier.
Why does FEA usage continue to grow when all of these companies already have hand calculations? Because, when applied correctly, FEA works. It delivers accurate stress estimates for parts with geometry too complicated for hand calculations alone, which describes most of today's parts. Accuracy means that localized stress concentrations can be removed. Accuracy means one less uncertainty, meaning that a lower factor of safety can be considered--resulting in lower weight, lower cost parts that are still stronger and have longer life cycles. Accuracy means that an expert witness can pinpoint areas of concern, and can often nail down the why's and how's of a part failure. As discussed in previous issues of Courtroom FEA, this will often point the finger at the responsible party, be it designer, manufacturer or end user. Accuracy can mean reduced lab testing by concentrating the investigation on the suspect areas. Accuracy means credibility. FEA has internal checks that a good analyst needs to apply to verify the results.
Given the advantages of a carefully applied analysis, it is worth your time to consider how an experienced FEA expert can help you win your client's case.
Author's Resource Box
Steve Roensch is a mechanical engineer with more than 25 years experience. He has served as an expert witness across many industries. Learn more about mechanical engineer expert witness services at www.FiniteElement.com.
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