Load–Displacement Behavior of Helical Shape Memory Alloy Spring Actuators with Small Spring Diameter to Wire Diameter Ratios

Puchaty, Ryan; Vita, Giovanni De; Vaidyanathan, R.

doi:10.1007/s40830-020-00295-x

Cited by 1 publication

(1 citation statement)

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“…Several works have studied and produced helical springs from circular cross-sections using binary NiTi [20], NiTiPdPt [21,22], NiTiFe [23,24], NiTiCu [25], among others. Design methodologies of these circular cross-section springs have also been reported by several researchers using linear approximations [26] and other more expanded approaches [27][28][29]. These springs are conventionally formed using a shape setting procedure, in which a circular cross-section wire is wound onto mandrels, constrained and heat treated to form the spring.…”

Section: Introductionmentioning

confidence: 99%

Machined helical springs from NiTiHf shape memory alloy

Benafan

Gaydosh²

2020

Smart Mater. Struct.

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Machined helical springs were fabricated from rod stock using a Ni-rich Ni50.3Ti29.7Hf20 (at. %) high-temperature shape memory alloy. Springs with three different spring rates of 35, 87.5, and 175.1 N mm−1 were designed, and the rectangular cross-section spring formulas were used to approximate the deflection and shear stresses. Springs were then subjected to isothermal testing at room temperature and constant-force thermal cycling experiments at varying loads. Actuation displacements on the order of 19 mm were obtained for starting flexures of 20 mm in length, resulting in nearly 95% total actuation extension. Thermal cycling under loads ranging from 0 to ∼500 N (stresses of 0 to ∼500 MPa) showed higher actuation displacements for springs with the lowest spring rates compared to the stiffer, higher spring rate counterpart. With increasing applied load, actuation displacements were still increasing even at stresses near 500 MPa (no maxima reached), indicating more actuation potential at higher loads. Two-way shape memory effect was assessed at 0 load and found to be very minimal (less than 3 mm) due to lack of training.

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