NASA "Smart Bolts" Likely To Revolutionize Some Industries

The world's first high-temperature resistant "intelligent" fastener is on the market, thanks to a partnership between NASA's Marshall Space Flight Center in Huntsville, Ala., and Ultrafast, Inc., of Malvern, PA.

Developed by Ultrafast under a NASA small business innovation research contract managed by the Marshall Center, the improved fastening technology was needed for the critical-fastening appraisal and validation of spacecraft segments that are coupled together in space. On-orbit assembly requires both lightweight wrenches for enhanced robot arm mobility as well as remote fastener-load inspection capability.

Finding a solution to NASA's out-of-this-world needs yielded an innovation that is likely to have lots of down-to-earth applications.

Ultrafast's "intelligent bolt" uses a piezoelectric thin-film deposited directly on one end of the fastener. When electrically excited by an Ultrafast tool, tensile loads can be accurately controlled during the bolt-tightening process. Insufficient bolt preload is usually at the root of joint failures resulting from joint separation, bolt loosening or fatigue.

In effect, a bolt topped by the thin-film technology - at a cost of just pennies per fastener - functions as a transducer for measurement and recording of the bolt's tensile load. The coating itself is less than 0.001 inch thick and is durable. It is deposited on the fastener by sputtering, a vacuum process that has a history of applications ranging from integrated circuits to reflective coatings on glass to decorative coatings on plastic. The coating can be applied to all types of existing fasteners without changing the basic design or metallurgy.

Ultrasonic measurements of a fastener are possible by using piezoelectric thin films, in both longitudinal and transverse directions, heretofore impractical in typical fasteners. Ultrafast technology uses the relationship between the speed of ultrasonic waves in a material and the stress applied to the material as its basis for computing load measurements. The idea is that the "time-of-flight" of an ultrasonic signal traveling in a fastener will increase as the load on the fastener is increased.

Ultrafast's intelligent bolt technology eliminates the self-defeating procedure of having to untighten the fastener, and thus upset the joint, during inspection and maintenance. Even the smallest fasteners can be turned into latent sources of information in numerous applications.

Ultrafast fasteners can be used in the auto industry for safety-critical components such as the power train, steering systems and brakes - achieving higher reliability while reducing the amount of service and maintenance required. Use of high-speed impact or impulse wrenches to improve joint integrity and inspection can lower costs by reducing assembly time.

Practical use of ultrasonic thin-film fasteners go beyond the realm of automotive, aviation and space applications. In nuclear engineering, they can be used from small flanges to large pressure vessels. For chemical processing, critical-fastening applications include offshore platforms and pipes. In construction, they can be used when erecting buildings and bridges.

Ultrafast expects sales of its product to exceed $100 million in a few years. Joint ventures between the firm and two European power tool companies have been formed, including an agreement to handle all European automotive fasteners.