The R-Phase Transformation in the Ti-Ni Shape Memory Alloy and its Application

ABSTRACTWe discuss a comprehensive design approach of Ti-Ni alloy coil springs and introduce a new application of the R-phase transformation. In order to attain high cyclic performance, one must understand the two relationships between design parameters and material characteristics and between material characteristics and cyclic performance. Metallurgical parameters and coil spring dimensions play an important role as design parameters in the former relationship. High cyclic performance of an actuator is closely related to the suppression of the monoclinic martensite. Transformation temperatures and their stress dependence is of primary importance as material characteristics in the latter relationship. A thermostatic mixing valve, which is the latest application of the R-phase transformation in Japan is then discussed as a new type of a shape memory alloy actuator. The R-phase transformation is employed to achieve not only a long cycle life but a linear operation with the set temperature to continuously control the mixing ratio of hot and cold water. This is achieved by changing the total length of the two-way actuator in a linear manner with the set temperature. The linear characteristic is satisfied between 35–50°C by optimizing thermomechanical treatment and the dimensions of Ti-Ni and biasing coil springs.

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Control of Wave Propagation in Periodic Composite Rods Using Shape Memory Inserts

10.1115/imece1999-0563 ◽

1999 ◽

Author(s):

M. Ruzzene ◽

A. Baz

Keyword(s):

Wave Propagation ◽

Phase Transformation ◽

Elastic Modulus ◽

Shape Memory Alloy ◽

Shape Memory ◽

Longitudinal Wave ◽

Design Parameters ◽

Impedance Mismatch ◽

Periodic Composite ◽

Longitudinal Wave Propagation

Abstract Longitudinal wave propagation is controlled using shape memory inserts placed periodically along rods. The inserts act as sources of impedance mismatch with tunable characteristics. Such characteristics are attributed to the unique behavior of the shape memory alloy whereby the elastic modulus of the inserts can be varied up to three times as the alloy undergoes a phase transformation from martensite to austenite. With such controllable capability, the inserts can introduce the proper impedance mismatch necessary to impede the wave propagation along the rods. An analytical model is presented to study the attenuation capabilities of the composite rods and to determine the influence of the various design parameters of the inserts that can control the width of the pass and stop-bands. The numerical results demonstrate the potential of shape memory alloys in controlling the dynamics of wave propagation in rods. Furthermore, the obtained results provide a guideline for designing inserts that are capable of filtering out selected excitation frequencies through proper adjustment of the geometry of the inserts as well as their activation strategies.

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Finite Element Simulation of NiTiNb Shape Memory Alloy Pipe-Joint Subjected to Coupled Transformation and Plastic Deformation

Advances in Materials Science and Engineering ◽

10.1155/2020/6895850 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Xiang Chen ◽

Bin Chen ◽

Xianghe Peng ◽

Xiaoqing Jin ◽

Ying Ma ◽

...

Keyword(s):

Plastic Deformation ◽

Phase Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

High Performance ◽

Coupling Effect ◽

Longitudinal Direction ◽

Design Parameters ◽

Pull Out ◽

Pipe Joint

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.

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Thermo-Mechanical Behavior of the Shape Memory Alloy Strip

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.750.127 ◽

2015 ◽

Vol 750 ◽

pp. 127-132

Author(s):

Peng Tao Zhao ◽

Jin Hao Qiu ◽

Hui Chen Yu

Keyword(s):

Numerical Simulation ◽

Phase Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

Room Temperature ◽

Alloy Strip ◽

Biological Compatibility ◽

Mechanical And Physical Properties ◽

New Type ◽

Initial Transformation

As a new type of smart material, shape memory alloy (SMA) is widely used in the aerospace, biomedicine, civil engineering and so on due to its unique mechanical and physical properties such like the shape memory effect, pseudoelasticity and good biological compatibility. This paper investigates the numerical simulation and application of the SMA component: A SMA strip, which has been pre-curved in the room temperature and is expected to extend upon heating and shorten on cooling along the curve. According to the investigation of the thermal respond of the SMA strip component, it can be seen that the temperature of the phase transformation can increase with the initial transformation strains and the process of the phase transformation in the boundary is more complex due to the complicated stress state.

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Control of Wave Propagation in Periodic Composite Rods Using Shape Memory Inserts

Journal of Vibration and Acoustics ◽

10.1115/1.568452 ◽

1999 ◽

Vol 122 (2) ◽

pp. 151-159 ◽

Cited By ~ 91

Author(s):

M. Ruzzene ◽

A. Baz

Keyword(s):

Wave Propagation ◽

Phase Transformation ◽

Elastic Modulus ◽

Shape Memory Alloy ◽

Shape Memory ◽

Longitudinal Wave ◽

Design Parameters ◽

Impedance Mismatch ◽

Periodic Composite ◽

Longitudinal Wave Propagation

Longitudinal wave propagation is controlled using shape memory inserts placed periodically along rods. The inserts act as sources of impedance mismatch with tunable characteristics. Such characteristics are attributed to the unique behavior of the shape memory alloy whereby the elastic modulus of the inserts can be varied up to three times as the alloy undergoes a phase transformation from martensite to austenite. With such controllable capability, the inserts can introduce the proper impedance mismatch necessary to impede the wave propagation along the rods. An analytical model is presented to study the attenuation capabilities of the composite rods and to determine the influence of the various design parameters of the inserts that can control the width of the pass and stop-bands. The numerical results demonstrate the potential of shape memory alloys in controlling the dynamics of wave propagation in rods. Furthermore, the obtained results provide a guideline for designing inserts that are capable of filtering out selected excitation frequencies through proper adjustment of the geometry of the inserts as well as their activation strategies. [S0739-3717(00)00102-1]

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