期刊
INTERNATIONAL JOURNAL OF PLASTICITY
卷 90, 期 -, 页码 116-145出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijplas.2016.12.008
关键词
NiTi shape memory alloy; Fatigue; Luders bands; Cyclic phase transformation; Microstructure degradation
One of the challenging issues in studying the fatigue behaviors of NiTi shape memory alloy is the interaction between the material damage and material's martensitic phase transformation which takes place in a macroscopic homogeneous mode or a heterogeneous mode (forming macro-domains like Luders bands). In this paper, we conducted systematic experiments on NiTi polycrystalline strips under stress-controlled cyclic tensile loadings with in-situ optical observation on the Luders-band evolution. It is found that the applied stress level and frequency influence the band formation changing the material's fatigue behaviors significantly. The band evolution divides a specimen into non-active zones (with the elastic deformation of Austenite or/and Martensite) and active zones (with the cyclic phase transformation) where fatigue failure occurs. Based on the local strain measurement by Digital Image Correlation, the local residual-strain (damage) accumulation rate is determined and found to have a good correlation with the material's fatigue life. Our results would be helpful for further understanding and modeling the material's stress- and frequency -dependent fatigue behaviors. (C) 2016 Elsevier Ltd. All rights reserved.
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