Strain Gages and the Black Swan

In his book, The Black Swan: The Impact of the Highly Improbable, Nassim Nicholas Taleb extended the concept of black swan events beyond his original limit of financial circles.  Black swan is the metaphor used to describe events which are unexpected and have a major effect on the circle of influence.  In other words, black swan events are meaningful and surprising, at least to those involved.  Extending this concept further, one can look at unexpected structural failures as black swan events.  More importantly, and more relevant to strain gage work, it is far more desirable to be proactive and look ahead for ways of monitoring structures and materials to preclude the occurrence of black swan events in the first place.

Recent examples for structural black swan events includes cracks found in different airplane designs, PCB failures caused by harsh environments, including the stress placed on consumer electronics gadgets, transportation industry  failures and Li-ion battery failures .  All of these events have serious consequences for those involved, and just maybe could have been avoided by using strain gage monitoring, or at the least, increased strain gage testing prior to product release. The typical battery-enclosure expansion indicative of impending battery failure can be easily detected well in advance of catastrophic failure.

Strain gages are not magic, but they can produce seemingly magical results.  Sensitive enough to resolve the weight of a fly landing on a plate glass window, robust enough to survive the trip to Mars, these simple looking sensors are used in all forms of electro-mechanical transducers.  Fundamentally, strain gages convert the imperceptible stretch of a surface to which they are bonded into a measureable electrical signal (change in resistance).  Highly sensitive electrical circuits like the Wheatstone bridge circuit are required to detect the micro-ohm changes in strain gage resistance with applied stretch.

Whether the requirement is to measure strains caused by loads which can lead to fatigue failures, or is to resolve fractions of a gram in force or weight to determine the load applied to a part, strain gages have proved themselves capable allies in preventing component, equipment or system failures.  Used as an integral part of the design process and/or as sensors in long term structural health monitoring, strain gages can serve with distinction as defenders against black swan events.