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Experimental and Theoretical Behavior of Self-healing Bolted Joints

Department of Mechanical Engineering, American University of Beirut, Riad el Soleh, Beirut, Lebanon

Daniel J. Inman

Center for Intelligent Material Systems and Structures, Virginia Polytechnic Institute and State University, VA, USA, dinman{at}vt.edu

Ahmad Smaili

Department of Mechanical Engineering, American University of Beirut, Riad el Soleh, Beirut, Lebanon

This article focuses on improving the experimental behavior of a self-healing bolted joint using shape memory alloys (SMAs). Self-healing bolted joints are used to reduce the likelihood of failure of structures due to loosening of bolted joints. The clamping force (CF) in a bolted joint assembly plays an important role in maintaining the integrity of the structure. Controlling the preload in a bolted joint assembly by external heating activates the heat-to-recover (HTR) SMA washer. The SMA washer is initially in the martensitic state. When the bolt is loosened to a certain amount of preload, a heater enveloping the ring is activated allowing an axial constrained recovery of the SMA and a control of the preload in the bolt. Several experiments are conducted to ascertain the effect of heating rate, cooling rate, relaxation of assembly, and initial preload, on the preload-temperature relationship. Experimental results indicate that the use of SMA rings is promising for retightening and controlling preload in bolted joint assemblies. Two analytical models are established; one is based on the Liang-Rogers model (Liang, C. and Rogers, C.A. 1990. "One-dimensional Thermo-mechanical Constitutive Relations for Shape Memory Materials," Journal of Intelligent Materials Systems and Structures, 1:207-234) and the other draws on the analogy between the cyclic stress-strain curves.

Key Words: self-healing structures • bolted joints • shape memory alloy in compression

Journal of Intelligent Material Systems and Structures, Vol. 17, No. 6, 499-509 (2006)
DOI: 10.1177/1045389X06058872


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