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<p>The shape memory alloy (nitinol) was studied under low-cycle fatigue at a&#xa0;frequency of 0.5 Hz under varying maximum stress levels (σ<sub>max</sub>), and stress ratios&#xa0;<i>R</i> (0.1&#xa0;and 0.5). The results demonstrated that, independent of σ<sub>max</sub>, the energy dissipated during deformation at <i>R</i> = 0.1 consistently exceeded that observed at <i>R</i> = 0.5 and exhibited a&#xa0;more pronounced decline with increasing fatigue cycles. This enhanced energy dissipation at the lower stress ratio was accompanied by more significant self-heating of the specimens, thereby promoting the stabilization of the alloy in the austenitic phase. Such stabilization is considered to impede the stress-induced austenite-to-martensite transformation under cyclic loading. Differences in the nitinol mechanism of fracture at different&#xa0;<i>R</i> were studied.</p>

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The influence of stress ratio on properties and mechanism of nitinol fracture

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • V. P. Iasnii,
  • H. V. Krechkovska,
  • N. Z. Bykiv,
  • O. Z. Student,
  • R. S. Lubianytskyi

摘要

The shape memory alloy (nitinol) was studied under low-cycle fatigue at a frequency of 0.5 Hz under varying maximum stress levels (σmax), and stress ratios R (0.1 and 0.5). The results demonstrated that, independent of σmax, the energy dissipated during deformation at R = 0.1 consistently exceeded that observed at R = 0.5 and exhibited a more pronounced decline with increasing fatigue cycles. This enhanced energy dissipation at the lower stress ratio was accompanied by more significant self-heating of the specimens, thereby promoting the stabilization of the alloy in the austenitic phase. Such stabilization is considered to impede the stress-induced austenite-to-martensite transformation under cyclic loading. Differences in the nitinol mechanism of fracture at different R were studied.