Original Date: 10/14/1988
Revision Date: 01/18/2007
Information : Photoelastic Technique for Stress Analysis
Bell Helicopter Textron, Inc. (BHTI) uses photoelasticity to evaluate stress levels and locate stress concentrations in geometrically complex parts. This technique allows the designer to quickly assess the effects of design changes. Although the photoelastic technique is not new, BHTI has continued to enhance this procedure while most of the industry has abandoned it in favor of finite element analysis. BHTI has developed an epoxy resin from which they mold and machine the test specimen. The part is subjected to the appropriate loading conditions and a final curing process is performed. The curing process locks the stress patterns into the specimen. The stress patterns can be observed through a polarizing filter which reveals fringe patterns. The magnitude of the stress can be quantified by cutting the specimen and comparing the stress patterns to a reference standard.
Although BHTI uses finite element analysis extensively, they have demonstrated the photoelastic technique to be faster and less costly in many cases. This method was compared to a million element finite element model in an accuracy comparison.
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