Effect of shape memory alloy actuator geometric non-linearity and thermomechanical coupling on the response of morphing structures

Abstract

The response of adaptive structures entailing shape memory alloy actuators is investigated both numerically and experimentally in this work. Emphasis is placed on the inclusion of large displacements and rotations, as well as thermomechanical coupling in the simulation of the shape memory alloy actuators. Reduced multi-field beam finite element models for shape memory alloy actuators, encompassing a co-rotational formulation for large displacements and capability to provide the thermomechanically coupled transient response, are briefly overviewed. Prototypes of two adaptive structure configurations are developed, experimentally characterized, and numerically modeled. The measured response of the two prototypes is correlated with respective numerical results that consider both the geometric non-linearity and the thermomechanical coupling of the shape memory alloy actuators. Hence, the influence of these two effects on the predicted response of both the actuator and the adaptive structure is demonstrated. The results quantify also the interactions between geometric non-linearity and thermomechanical coupling terms. As it is shown, better agreement with experimental data is obtained when considering both effects.

Multi-objective optimization of a morphing structure incorporating shape memory alloy actuators

“…The SMA material properties were extracted in our lab (Machairas et al, 2019) and are summarized in Table 1 for an equi-atomic NiTi wire with 1.0 mm diameter.…”

“…with P 1 = 67,926 and P 2 = 19.0 (Machairas et al, 2019) while DT denotes the difference between the current and the initial temperature of the SMA actuators which is considered equal to the ambient one (21.3 o C).…”

“…Moreover in many reported works the prediction of the SMA actuator response was mainly based on simple models or equivalent point loads implying the action of SMA actuators. Hence the non-linear interactions between the actuators and the passive components, which have been found to be significant (Machairas et al, 2019) were not adequately represented.…”

Cosserat modeling for deformation configuration of shape memory alloy unimorph actuators

“…Bending mechanics coupled with heat transfer and phase kinetic models have been used to model the quasi-static transient response of a SMA-actuated catheter (Veeramani et al, 2008). Finite element techniques and numerical approaches have also been used to model and optimize the deformation profile of SMA bending actuators (Crews and Buckner, 2012; Machairas et al, 2019; Simone et al, 2019; Wang and Shahinpoor, 1997). Additionally, the Galerkin method has been applied to novel piezoelectric composite actuators to characterize their performance (Ma et al, 2019, 2022; Zhou et al, 2020a, 2020b).…”

Analysis, optimization and testing of morphing structures employing shape memory alloy actuators

“…Due to the high deformations that a morphing structure is foreseen to undergo, the consideration of the geometric non-linearity was included in the numerical analysis. Additionally as it has been proved, the thermomechanical coupling of the SMA behavior can substantially affect the response of a morphing structure (Machairas et al, 2019). Hence the specialty beam finite element developed by Solomou et al, (2017) and overviewed in section 3.2.3, was used to account for the coupled thermomechanical behavior of the SMA actuators and to predict their geometrically non-linear response during the simulation of the morphing chevron.…”