Large Deformation of Nitinol Under Shear Dominant Loading

Abstract

Full-field quantitative strain maps of phase transformation and plasticity in Nitinol under large sheardominated deformation are presented. To achieve a sheardominated deformation mode with relatively uniform stresses and strains, a shear compression specimen (SCS) geometry was utilized. Shear deformation appears to impede the development of the strain localization during phase transformation that is seen in uniaxial testing. The shear-dominant deformation of Nitinol in the plastic regime exhibits low hardening and results in the development of significant strain inhomogeneity.

Strain rate effects on the localization of the stress-induced martensitic transformation in pseudoelastic NiTi under uniaxial tension, compression and compression–shear

“…7b and c; strain rates of 10 2 s À 1 and 10 3 s À 1 , respectively) loading conditions, the material does not exhibit localized deformation. During loading (images 1-4) and subsequent unloading (5)(6)(7)(8), the axial strain fields are nearly homogeneous aside from minor axial strain fluctuations, which is in good agreement with previous studies [6,36]. This homogeneous mode of deformation differs strongly from what is observed under tension.…”

“…Previous research on the localization behavior of these alloys has mainly concentrated on quasistatic loading conditions and on different transformation behavior under tension (where distinct bands are formed) and compression (where the macroscopic deformation appears to be homogeneous). Furthermore, apart from two notable exceptions [6,7], no experimental studies on the deformation behavior of pseudoelastic NiTi under combined compression-shear loading, where the superimposed shear-stresses may trigger the formation of distinct martensite bands, have been reported so far. Numerous experimental studies on the effect of strain rate on the SIMT in NiTi SMAs under tension [8][9][10] and compression [11][12][13] have been performed.…”

The Evolution of the Field of Biomechanics Through the Lens of Experimental Mechanics

“…Due to its unique mechanical properties, 55NiTi has potential as a bioimplant [116]. A study on nitinol, another alloy of nickel and titanium, presented strain maps of the material under shear deformation [117]. An additional study investigated the strain behavior of an aluminum magnesium alloy with nanocrystalline microstructures [74].…”

Study of Phase Transformation Intermittency in S.M.A. Using the Grid Method

“…The idea is to track speckles which are randomly deposited on the surface under investigation, and to deduce the displacement field by image processing [5]. DIC was for instance used to study intermartensitic transformations in a Ni-Fe-Ga single crystal [6], to compare experimental strain fields with their numerical counterparts in a Cu-Al-Be SMA multicrystal [7], to study the development of martensite in Nitinol [8,9] or to investigate local transformations in precipitated Ni-Ti single crystals [6]. A comparison between DIC and digital speckle pattern correlation to measure displacement fields in a Cu-AlBe SMA was presented in Reference [10].…”