A Thermal Conduction Switch Based on Low Hysteresis Nitife Shape Memory Alloy Helical Springs

Krishnan, V.; Bewerse, C.; Notardonato, William; Vaidyanathan, R.

doi:10.1063/1.2900374

Cited by 13 publications

(8 citation statements)

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“…Shape memory alloys (SMAs) have the ability to recover their shape against external loads as a result of a thermally induced solid-state phase transformation. This ability to do work while transforming from one phase to another enables their use as high-force actuators with both sensory and actuation functions [1][2][3][4][5]. To date, the commercial use of SMAs has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the −100 to 100 °C range.…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

Nicholson

Padula

Noebe

et al. 2014

Smart Mater. Struct.

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Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance.

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Section: Introductionmentioning

confidence: 99%

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

Nicholson

Padula

Noebe

et al. 2014

Smart Mater. Struct.

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“…Previously, low-temperature shape memory alloy thermal switches were developed and tested based on conductive heat transfer [19,20]. These SMA-based conduction switches were designed for use in space applications for zero boil-off control, heat transfer between two cryogenic storage tanks and parasitic heat load reduction from secondary redundant cryocoolers.…”

Section: Introductionmentioning

confidence: 99%

Design and development of a shape memory alloy activated heat pipe-based thermal switch

Benafan

Notardonato

Meneghelli³

et al. 2013

Smart Mater. Struct.

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This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states were actuated by shape memory alloy (SMA) elements while heat was transferred by a two-phase heat pipe. The motivation for such a switch comes from NASA’s need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. As the temperature can approximately vary between −233 and 127 ° C during lunar day/night cycles, the switch was designed to reject heat from a cryogen tank into space during the night cycle while providing thermal isolation during the day cycle. A Ni47.1Ti49.6Fe3.3 (at.%) alloy that exhibited a reversible phase transformation between a trigonal R-phase and a cubic austenite phase was used as the sensing and actuating elements. Thermomechanical actuation, accomplished through an antagonistic spring system, resulted in strokes up to 7 mm against bias forces of up to 45 N. The actuation system was tested for more than thirty cycles, equivalent to one year of operation. The thermal performance, accomplished via a variable length, closed two-phase heat pipe, was evaluated, resulting in heat transfer rates of 13 W using pentane and 10 W using R-134a as working fluids. Experimental data were also compared to theoretical predictions where possible. Direct comparisons between different design approaches of SMA helical actuators, highlighting the effects of the helix angle, were carried out to give a layout of more accurate design methodologies.

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“…Despite SMAs typically operating under multiaxial stress states in applications, most previous in situ neutron diffraction based investigations on SMAs have been limited to homogenous stress states as a result of uniaxial loading. [ 10,11,15–23 ] Multiaxial loading and the accompanying heterogeneous stress state during neutron diffraction has the added benefit of offering hitherto unexplored mechanistic insight in these alloys especially given that shear is expected to significantly affect deformation in the various phases and the phase transformation itself. [ 1 ] The selection of the various mechanisms (elasticity, plasticity, twinning, and stress‐induced transformation) to accommodate the mismatch in a heterogeneous stress state is also of interest.…”

Section: Figurementioning

confidence: 99%

Mapping of Texture and Phase Fractions in Heterogeneous Stress States during Multiaxial Loading of Biomedical Superelastic NiTi

et al. 2020

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Thermoelastic deformation mechanisms in polycrystalline biomedical‐grade superelastic NiTi are spatially mapped using in situ neutron diffraction during multiaxial loading and heating. The trigonal R‐phase is formed from the cubic phase during cooling to room temperature and subsequently deforms in compression, tension, and torsion. The resulting R‐phase variant microstructure from the variant reorientation and detwinning processes are equivalent for the corresponding strain in tension and compression, and the variant microstructure is reversible by isothermal loading. The R‐phase variant microstructure is consistent between uniaxial and torsional loading when the principal stress directions of the stress state are considered (for the crystallographic directions observed here). The variant microstructure evolution is tracked and the similarity in general behavior between uniaxial and torsional loading, in spite of the implicit heterogeneous stress state associated with torsional loading, pointed to the ability of the reversible thermoelastic transformation in NiTi to accommodate stress and strain mismatch with deformation. This ability of the R‐phase, despite its limited variants, to accommodate stress and strain and satisfy strain incompatibility in addition to the existing internal stresses has significance for reducing irrecoverable deformation mechanisms during loading and cycling through the phase transformation.

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A Thermal Conduction Switch Based on Low Hysteresis Nitife Shape Memory Alloy Helical Springs

Cited by 13 publications

References 0 publications

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

Design and development of a shape memory alloy activated heat pipe-based thermal switch

Mapping of Texture and Phase Fractions in Heterogeneous Stress States during Multiaxial Loading of Biomedical Superelastic NiTi

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