Abstract
The assembling process of Ni47Ti44Nb9 alloy pipe joints considering the phase transformation and plasticity was numerically simulated for the first time with a developed constitutive model. The simulated process was based on the experimental material parameters, which were determined with the experimental tensile results of Ni47Ti44Nb9 shape memory alloy (SMA) and steel bars. The results showed that, after assembly, the Mises stress distributed uniformly along the longitudinal direction of the NiTiNb joint, but nonuniformly along the radial direction. The maximum σeq does not appear at the inner wall of the joints due to the coupling effect of the plastic deformation and the recoverable transformation. The contact pressure distributed uniformly along the circumferential direction, but nonuniformly along the longitudinal direction. The sizes of the SMA joint and the pipe should be properly matched to ensure contact during the stage of the rapid reverse phase transformation to obtain stable connection performance. The pull-out force was also computed, and the results were in good agreement with the experimental results. The results obtained can provide available information for the optimization of the design parameters of the high-performance SMA pipe-joint, such as inner diameter and assembly clearance.
Highlights
Due to their two unique properties, the shape memory effect (SME), and pseudoelasticity (PE), the shape memory alloy (SMA) has drawn significant attention in a broad range of commercial applications, such as automotive, aerospace, robotics, and biomedical domains [1, 2]. e pipe-joint is manufactured with SMA even widely used as the oil pipe connection in aircraft [3]
While the NiTi SMA pipe-joint should be stored and transported in liquid nitrogen to avoid the unexpected recovery of the predeformation, in contrast, NiTiNb SMA exhibits a much larger transformation temperature hysteresis (∼150°C) compared with conventional NiTi binary alloy (∼30°C) [4], and the pipe joints made of NiTiNb alloys can be stored and transported at room temperature, which is greatly convenient for engineering applications
Model Checking. e uniaxial tension at −60°C and subsequent constrained heating recovery are simulated firstly to verify the correctness of the constitutive model. e results of the calculation are compared with experimental results, as shown in Figures 6 and 7. e tensile stress-strain (σ33 − ε33) curve calculated with the constitutive model agrees reasonably with the experimental results
Summary
Due to their two unique properties, the shape memory effect (SME), and pseudoelasticity (PE), the shape memory alloy (SMA) has drawn significant attention in a broad range of commercial applications, such as automotive, aerospace, robotics, and biomedical domains [1, 2]. e pipe-joint is manufactured with SMA even widely used as the oil pipe connection in aircraft [3]. It is reported that the largest strain for the NiTiNb SMA joints appears on the inner wall, and there exists a larger strain gradient along the axis [17] Piotrowski and his coworker did excellent studies on the constitutive model of NiTiNb SMA and the application to tightening rings [18, 19]. The constitutive models adopted in the above excellent work did not consider the plasticity of SMA and its effects, while during predeformation, plastic deformation involved in the NiTi matrix can obviously increase the transformation hysteresis temperature [20]. The assembling process of Ni47Ti44Nb9 alloy pipe joints is simulated with the threedimensional SMA model developed by Chen et al [24]. The distribution of Mises stress, contact pressure, and other thermal-mechanical quantities in the pipe-joint systems is analyzed and discussed
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