On the effect of detwinning-induced plasticity in compressive cyclic loading of NiTi shape memory alloys

Abstract

A new inelastic mechanism, detwinning-induced plasticity (DIP), is proposed to model the response of NiTi SMAs to cyclic loading, based on thermodynamic considerations. DIP is incorporated into a constitutive framework for NiTi SMA. The constitutive framework also includes well-established inelastic mechanisms of phase transformation, transformation-induced plasticity, residual martensite, and detwinning. The model is constructed at the single crystal scale using the framework of thermodynamics and a crystal plasticity formulation. An explicit scale-transition rule is adopted for the simulation of polycrystalline materials, allowing direct comparison of the model predictions with published experimental test data. Thermodynamic considerations result in a strong contribution of DIP for cyclic loading regimes where compressive stress occurs during part of the loading cycle. However, the contribution of DIP is negligible for cyclic loading regimes that result exclusively in tensile stress. This predicted dependence of DIP on compression, but not on tension, is strongly supported by experimental cyclic loading results. Inclusion of DIP results in improved prediction of experimentally observed NiTi SMAs behavior, including strain-controlled cyclic compression-unloading and cyclic tension-unloading tests and stress-controlled cyclic tension-compression and tension-unloading tests. During the first loading cycle the contribution of DIP is not significant in any loading regimes. However, in cases where compressive stress occurs during part of the loading cycle, DIP contributes strongly to the material response from the second cycle onwards. In strain-controlled cyclic compression-unloading tests DIP leads to a less negative peak stress and a more negative residual strain following several loading cycles. In stress-controlled tension-compression cyclic loading DIP leads to a reduction of peak and residual strains.

Microstructure-based finite deformation modelling of super-elastic NiTi shape memory alloy considering various inelastic mechanisms

“…The velocity gradient tensor, L , can also be divided into elastic, e L , and inelastic, p L , parts (Dhala et al, 2019;Erdle and Böhlke, 2017;Fohrmeister et al, 2019): Due to experimentally observed accumulation of residual martensite (Kang et al, 2009), the volume fraction of each martensite variant can be divided into the reversible, rev   , and the irreversible, ire   , volume fractions. The total volume fraction of martensite is considered as the sum of eversible and irreversible parts (Ebrahimi et al, 2020).…”

“…Consequently, some habit plane variants (HPVs) will be formed. Each HPV is composed of two lattice correspondent variants (LCVs) or sub-variants (Ebrahimi et al, 2020;Yu et al, 2014). The stress-induced movement of interfaces between sub-variants is called detwinning (Thamburaja, 2005).…”

“…In addition, the experimental results of Liu et al (Liu et al, 1998) show a high density of dislocations at the interfaces of lattice correspondent variants during compressive loading, but no significant plastic deformation is detected in such areas under tension. Detwinning-induced plasticity is referred to that part of plastic deformation which is induced to relax the local stress field at the interfaces of lattice correspondent variants (Ebrahimi et al, 2020). As demonstrated by Ebrahimi et al (Ebrahimi et al, 2020), DIP has considerable effect on compressive cyclic loading of NiTi SMAs.…”

“…Detwinning-induced plasticity is referred to that part of plastic deformation which is induced to relax the local stress field at the interfaces of lattice correspondent variants (Ebrahimi et al, 2020). As demonstrated by Ebrahimi et al (Ebrahimi et al, 2020), DIP has considerable effect on compressive cyclic loading of NiTi SMAs. It should be noted that the cyclic behavior of NiTi SMA under large deformations, considering the crucial mechanisms of TRIP and DIP, has not been investigated in previous studies.…”

Surface Nanostructuring of a CuAlBe Shape Memory Alloy Produces a 10.3 ± 0.6 GPa Nanohardness Martensite Microstructure

“…In practice, the cyclic loading-unloading of SMAs introduces a small amount of plastic strain which accumulates during the process. This process affects the SDC of the alloy, increases the peak stress during strain-controlled cycling [ 29 , 30 , 31 ] and influences the fatigue [ 32 ] and low cycle fatigue [ 33 ] of SMAs. This effect on fatigue confirms the role of dislocation storage as a damage accumulation effect.…”