Research Article Open Access

Cyclic Instability of Shape-Memory Alloys in Seismic Isolation Systems

Filipe Amarante dos Santos1, Corneliu Cismasiu2 and Francisco Braz Fernandes1
  • 1 Ciê ncias e Tecnologia da Universidade NOVA de Lisboa, Portugal
  • 2 Ciências e Tecnologia da Universidade NOVA de Lisboa, Portugal

Abstract

Shape-memory alloys are being progressively introduced as kernel components in seismic retrofitting devices for civil engineering structures. In order to control the instability associated with the first mechanical cycles, a training procedure is usually implemented, which stabilizes the superelastic behavior of the alloy. This paper addresses the characterization of the cyclic behavior of an austenitic NiTi alloy with emphasis on the definition of the instability functions associated with the cumulative residual strain and the variation of the critical stress needed to induce martensite. A wide set of experimental tensile tests are performed to study the influence of strain-rate and ambient temperature on the material coefficients controlling the described functions. A numerical model for shape-memory alloys is presented, which is able to simulate the instability phenomena associated with superelastic cycling in NiTi wires. It is shown that prior stabilization by initial training may not be advantageous, since it is during the first cycles that the alloy shows greater energy dissipation capabilities.

International Journal of Structural Glass and Advanced Materials Research
Volume 2 No. 1, 2018, 82-95

DOI: https://doi.org/10.3844/sgamrsp.2018.82.95

Submitted On: 28 September 2017 Published On: 7 January 2018

How to Cite: dos Santos, F. A., Cismasiu, C. & Braz Fernandes, F. (2018). Cyclic Instability of Shape-Memory Alloys in Seismic Isolation Systems. International Journal of Structural Glass and Advanced Materials Research, 2(1), 82-95. https://doi.org/10.3844/sgamrsp.2018.82.95

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Keywords

  • Shape-Memory Alloy
  • Superelasticity
  • Instability
  • Mechanical Cycling