Effect of tension/compression asymmetry and anisotropy on the response of pseudoelastic NiTi tubes under equibiaxial stress. (May 2022)

• Record Type: Journal Article
• Authors: Kazinakis, Karlos; Kyriakides, Stelios; Landis, Chad M.
• Is Part Of: Extreme mechanics letters. Volume 53(2022)
• Publication Date: 2022-05
• Subjects: Equibiaxial stress -- NiTi tubes -- Pseudoelasticity -- Tension/compression asymmetry -- Anisotropy -- Inhomogeneous deformation -- Analysis; Mechanics -- Periodicals; Mechanics, Applied -- Periodicals; Mechanics; Electronic journals; Periodicals; 531.05
• DOI: 10.1016/j.eml.2022.101689
• Languages: English
• ISSNs: 2352-4316

Abstract

Abstract: The stress–strain response and inhomogeneous deformation of pseudoelastic NiTi tubes loaded under combined axial force and internal pressure are governed not only by the well-known tension/compression asymmetry but also anisotropy (Bechle and Kyriakides, 2016). This behavior was simulated successfully in Kazinakis et al. (2022) using a finite element analysis coupled to a recently developed constitutive model that incorporates these key material characteristics. Interestingly, equibiaxial tension induces monotonic stress–strain hystereses and nearly homogeneous deformations, but with the hoop transformation strain being approximately double the axial one. This letter uses analysis to highlight how the tension/compression asymmetry and anisotropy individually influence the predictions of this experiment. When both asymmetry and anisotropy are included, the analysis captures the level of transformations stresses and the extent of axial strain, overpredicting the hoop strain by a small amount. The hardening is somewhat reduced compared to the experiment allowing weak and diffuse inhomogeneous deformation to develop. In the absence of anisotropy, the hoop and axial hystereses coincide with much higher stresses, and strains that lie between the experimental values, while the tube deforms uniformly. If the model is assumed symmetric with the properties of the hardening uniaxial compression, the behavior is the same as that of the previous case. When the model is calibrated instead to the partially unstable uniaxial tensile response, the analysis predicts again coincident stress–average strain hystereses with lower stress plateaus than measured and strongly inhomogeneous deformation. Highlights: Shape Memory Alloy under equibiaxial tensile stress. Constitutive modeling of pseudoelastic phase transformation. Analysis of NiTi tubes loaded under combined axial tension and internal pressure. Comparison of effects of tension/compression asymmetry and anisotropy.