Influence of limiting the actuation strain on the functional fatigue behavior of Ni(50.3)Ti(29.7)Hf(20)high temperature shape memory alloy

Tugrul H. O., Saygili H. H., Kockar B.

JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES, vol.32, no.2, pp.219-227, 2021 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 32 Issue: 2
  • Publication Date: 2021
  • Doi Number: 10.1177/1045389x20953610
  • Journal Name: JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, PASCAL, Aerospace Database, Applied Science & Technology Source, Business Source Elite, Business Source Premier, Communication Abstracts, Compendex, Computer & Applied Sciences, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.219-227
  • Keywords: Shape memory, alloys, functional fatigue, high temperature shape memory alloy, NITI, MICROSTRUCTURE
  • Hacettepe University Affiliated: Yes

Abstract

The cyclic stability and the fatigue life of NiTiHf alloys are very important for their functionality at high temperatures. The previous studies have shown that the increase in Upper Cycle Temperature (UCT) and the magnitude of applied stress decreased the cyclic stability and fatigue life of NiTiHf high temperature shape memory alloys due to plasticity with dislocation formation at high temperature. On the other hand, this study was dedicated to the effect of limited actuation strain against the applied constant stress to the functional fatigue life and the possible damage mechanism such as dislocation and crack formation. Strain limitation led to observe insignificant amount of accumulated irrecoverable strain but significant amount of crack formation such that the reason of the failure of Ni50.3Ti29.7Hf20(at%) alloy was found to be the crack formation instead of dislocation accumulation.