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Designing for failure prevention

November 6th, 2014 / By: / Industry News

As C.S. Lewis would have it, “Failures are finger posts on the road to achievement.” Haskell Beckham of the scientific and engineering consulting firm Exponent Inc. likely would agree.

Speaking on “Failure Analysis of Industrial Fabrics and Design for Failure Prevention” as part of the 2014 IFAI Advanced Textiles Expo, Beckham identified failure as “the inability to perform as intended,” and noted both physical and chemical “failure modes.” He then offered three examples of the kinds of failure that can frustrate efforts to perform for the customer: failure of design (including material selection), failure in manufacturing (processing and assembly) and failure during the end use (either due to unanticipated exposure conditions or misuse)—or some combination of these three.

One example Beckham offered was an “environmental failure” in the case of fabrics use by farmers to wrap large rolled hay bales that are then left in the field (or sometimes gathered for storage). Among the kinds of hazards affecting the bale wrap is environmental deterioration caused by exposure to extreme sunlight and severe weather as well as potential contact with corrosive elements such as pesticide degradation products used in the same fields. As with most product failures, these can cause economic loss for the farmer.

His second example was evaluation of a coated tent fabric, particularly in light of California’s Proposition 65, which requires the state to publish a list of chemicals known to cause cancer or birth defects or other reproductive harm. According to the California Office of Environmental Health Hazard Assessment, the list contains a range of naturally occurring and synthetic chemicals that are known to cause cancer or birth defects or other reproductive harm. These chemicals include additives or ingredients in pesticides, common household products, food, drugs, dyes, or solvents. Listed chemicals may also be used in manufacturing and construction, or they may be byproducts of chemical processes, such as motor vehicle exhaust.\

Beckham’s final example of significant and costly failure was straps, such as those used in safety harnesses by tree workers or window cleaners, among others. Failure of these products can have catastrophic, even fatal, consequences. He offered high-tech examples of determining the kinds of failure—tensile, fatigue, sabotage—such straps might experience.

The lessons to be learned from such analyses are:

  • “Simple” substitutions are not always simple
  • Diffusion can lead to progressive failures
  • Certification and standard testing should not be a substitute for end-use performance testing
  • Understand reasonable use and foreseeable misuse of product
  • Don’t let history blind your engineering judgment

Finally, Beckham offered a variety of things to be learned from failure, however it occurs, including the importance of material type, grade, composition; design; process effects; understanding end-use conditions; testing for certification and for end-use performance; understanding test method capabilities and limitations, and building on historical knowledge and field use.

www.exponent.com