Internal loops in superelastic shape memory alloy wires under torsion - Experiments and simulations/predictions

Ashwin Rao, Annie Ruimi, Arun R. Srinivasa

Research output: Contribution to journalArticle

14 Citations (Scopus)


Understanding torsional responses of shape memory alloy (SMA) specimens under partial or fully transformed cases with internal loops is of particular importance as the entire response might not be always utilized and only a portion of the entire response (internal loop) might be of significance to designers. In this work, we present experimental results of large complex loading and unloading torsional cycles which were conducted on superelastic SMA wires, under isothermal conditions with the purpose of elucidating the torsional internal loop response during loading and unloading. Such data hereto has not been available in open literature. Utilizing this data, we model the torsional response of superelastic SMA wires subjected to various loading and unloading situations that can result in different extents of transformation. A thermodynamically consistent Preisach model (Rao and Srinivasa, 2013) captures such complex internal loops with a high degree of precision by modeling driving force for phase transformation vs. volume fraction of martensite relationships. This approach is different from capturing purely phenomenological stress-strain or stress-temperature Preisach models. The thermodynamic approach utilized here has broader predictive capability. The model predictions indicate good agreement with the internal loop structures even though only the outer loop information was used for model calibration. The addition of a single inner loop information for model calibration greatly improves the predictions.

Original languageEnglish
Pages (from-to)4554-4571
Number of pages18
JournalInternational Journal of Solids and Structures
Issue number25-26
Publication statusPublished - 1 Dec 2014



  • Design
  • Hysteresis
  • Internal loops
  • Preisach
  • Return point memory (RPM)
  • Shape memory alloy (SMA)
  • Superelastic effect
  • Thermomechanical
  • Torsion

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Science(all)
  • Condensed Matter Physics
  • Applied Mathematics
  • Modelling and Simulation

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