Abstract: This paper discusses research and development efforts directed at producing a passive, smart bolt for infrastructure applications. The smart bolts are fabricated from high-strength TRIP (Transformation Induced Plasticity) Steels. TRIP steels gradually transform from a non-magnetic, austenitic parent phase to a ferromagnetic, martensitic product phase. The stress-assisted (elastic range) and strain-induced (plastic range) phase transitions that inherently occur in the material provide a magnetic signature by which the damage state of the bolt can be determined. The irreversible nature of the phase transformations means that the bolt can passively retain peak strain (i.e., peak damage information) for later interrogation. Several different smart bolt design concepts were considered and evaluated. Design modeling and smart bolt optimization were achieved with the aid of a series of Pro/Engineer solid model renderings and a Pro/Mechanica finite element model analysis. The smart bolt was developed for high-tension fastener applications in the USAF C-130 Hercules cargo aircraft. Alloy design efforts, testing, and evaluation data are presented and discussed. Full-scale, smart aircraft bolt manufacturing is discussed and field application scheduling/evaluation plans are outlined. Extension of the smart bolt technology for construction industry applications is discussed.!16
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