Structural vibration control using high strength and damping capacity shape memory alloys

Designing structures to withstand dynamic environmental hazards such as earthquakes, strong winds, and hurricanes is of primary concern for civil engineers. In addition, recent advances in architectural forms, structural systems, and high performance materials have enabled the design of very slender and lightweight structures. These flexible structures are susceptible to be exposed to high levels of vibrations under strong winds and earthquakes, which may lead to structural damage and potential failure. Over the past two decades, shape memory alloys (SMAs) have emerged as a smart material that can be used in passive vibration control devices for energy dissipating and re-centering purposes. However, the quantity of equivalent viscous damping provided by superelastic NiTi SMA wires or bars is not sufficient to render the use of SMAs as the sole damping device implemented in a tall structure subjected to severe dynamic loadings. This study explores the performance of recently developed NiTiHfPd alloys that have very high strength, high dissipation/damping capacity, good cyclic stability and large operating temperature for vibration control applications. In particular, superelastic response of single crystal and polycrystalline NiTiHfPd alloys were investigated systematically to reveal the effects of composition alteration and heat treatments. The design of a novel passive vibration control device by utilizing the superelastic effect of NiTiHfPd SMAs under compression was illustrated.