Optimum Discrete Location of Shape Memory Alloy Wire for Enhanced Actuation of a Compliant Link

For discrete actuation with shape memory alloy (SMA) wires, the actuation moment can be controlled by changing the amount of wire offset. Increasing offset not only enhances the actuating moment, but also demands larger displacement capability of the actuator. In this paper, large deflection of a cantilever beam actuated by a SMA wire has been investigated. Both the theoretical and experimental results reveal the existence of an optimum offset maximizing the end deflection. The optimum offset depends on the flexural stiffness of the beam, SMA wire properties, and the input actuation level.

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Optimum Discrete Location of Shape Memory Alloy Wire for Enhanced Actuation of Slender Fixed-Free Beam

Smart Materials, Adaptive Structures and Intelligent Systems, Volume 1 ◽

10.1115/smasis2008-471 ◽

2008 ◽

Cited By ~ 1

Author(s):

A. Banerjee ◽

J. Badothiya ◽

B. Bhattacharya ◽

A. K. Mallik

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Large Deflection ◽

Flexural Stiffness ◽

Discrete Location ◽

Recoverable Strain ◽

Alloy Wire ◽

Nonlinear Force ◽

Force Displacement ◽

Free Beam

Shape memory alloy (SMA) wires are capable of exerting large force and undergoing large recoverable strain. These capabilities render them suitable for being used as actuators. SMA wires are either embedded within the structure, as in a composite Choi et.al. [1], or can be placed discretely Chaudhry et.al. [2]. The advantage of discrete actuation is that, depending upon the offset provided between the structure and the wire, the actuating moment can be controlled. More the offset, higher is the actuating moment. But simultaneously the displacement requirement of the SMA wire increases with increasing offset. Depending on the nonlinear force-displacement characteristics of SMA and the flexural stiffness of the structure, there is an optimum value of the offset for which the maximum actuation of the structure can be achieved for a given input. In this paper large deflection of a cantilever beam actuated through SMA wire with varying offset has been analyzed. The results reveal the existence of an optimum offset yielding more than 100% increment in the end deflection in comparison to the minimum offset position. The value of the optimum offset depends on the flexural stiffness of the beam, SMA wire properties and the input actuation level. Experimental results obtained from beams of different stiffness actuated with a particular SMA wire validate the theoretical prediction.

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Optimum placement of shape memory alloy wire actuator

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406216665134 ◽

2016 ◽

Vol 231 (7) ◽

pp. 1272-1291 ◽

Cited By ~ 1

Author(s):

Saptarshi Karmakar ◽

Nripen Kalita ◽

Atanu Banerjee

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Large Deflection ◽

Flexural Rigidity ◽

Characteristic Curve ◽

Beam Model ◽

Shape Memory Alloy Wire ◽

Alloy Wire ◽

Offset Distance ◽

Optimum Placement

Shape memory alloy wire actuators can be used in combination with compliant structures to attain desired force and displacement capabilities. The wires can be placed inside a matrix, as in composite, or outside the material connected at different points on the structure. In the latter case, the offset of the wire and the location of the points decides the overall deformation of the structure. In this article we study the effects of offset distance, and the number of points, called attachments, where the shape memory alloy wire is connected to a host beam. First the characteristic curve of the shape memory alloy wire actuator is derived from a constrained recovery model. Then the response of a beam model, undergoing large deflection due to follower forces, is superposed with the characteristic curve to obtain the maximum beam deformation. It is found that there exists a particular offset, called optimum offset, for which the deformation of the host is maximum. Moreover, the ratio of stress and change in strain in the shape memory alloy corresponding to the optimum offset, attains a particular value, irrespective of the flexural rigidities of the beam. Furthermore, it has been observed that for a set of beams that have flexural rigidity less than a particular value, the deformation increases with number of attachments. However, for the beams that have flexural rigidity more than that particular value, the deformation remains almost unaltered with number of attachments. These numerical results are also supported qualitatively by the experimental observations.

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