Phenomenological modeling of induced transformation anisotropy in shape memory alloy actuators

Hartl, Darren J.; Σολωμού, Αλέξανδρος; Lagoudas, Dimitris C.; Saravanos, Dimitris A.

doi:10.1117/12.915972

Cited by 15 publications

(22 citation statements)

References 10 publications

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“…Implementing various constitutive models [7][8][9][10][11], fracture of SMAs has been studied numerically in the presence of stationary cracks [12][13][14][15][16][17][18][19]. It is shown that stress concentration at the crack tip causes forward transformation (i.e.…”

Section: Introductionmentioning

confidence: 99%

Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State

Haghgouyan

Караман

Jape

et al. 2018

Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; En

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Fracture behavior in nickel-titanium (NiTi) shape memory alloys (SMAs) subjected to mode-I, isothermal loading is studied using finite element analysis (FEA). Compact tension (CT) SMA specimen is modeled in Abaqus finite element suite and crack growth under displacement boundary condition is investigated for plane strain and plane stress conditions. Parameters for the SMA material constitutive law implemented in the finite element setup are acquired from characterization tests conducted on near-equiatomic NiTi SMA. Virtual crack closure technique (VCCT) is implemented where crack is assumed to extend when the energy release rate at the crack-tip becomes equal to the experimentally obtained material-specific critical value. Loaddisplacement curves and mechanical fields near the crack-tip in plane strain and plane stress cases are examined. Moreover, a discussion with respect to the crack resistance R-curves calculated using the load-displacement response for plane strain and plane stress conditions is presented.

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Section: Introductionmentioning

confidence: 99%

Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State

Haghgouyan

Караман

Jape

et al. 2018

Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; En

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“…The prediction of the coupled thermomechanical behaviour of the SMA wire actuators was performed based on the 1‐D form of the phenomenological constitutive model developed by Lagoudas et al as extended by Hartl et al The coupled thermomechanical constitutive equations were implemented through a User MATerial subroutine (UMAT) in commercial finite element analysis (FEA) package ABAQUS . The SMA wire actuators were modeled as 2‐node, 3‐D, thermally coupled truss elements (T3D2T) with linear approximation of the displacements, because they are subjected mainly to tension loads.…”

Section: Methodsmentioning

confidence: 99%

Active load alleviation potential of adaptive wind turbine blades using shape memory alloy actuators

et al. 2019

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Upscaling of wind turbine blades calls for implementation of innovative active load control concepts that will facilitate the flawless operation of the machine and reduce the fatigue and ultimate loads that hinder its service life. Based on aeroelastic simulations that prove the enhanced capabilities of combined individual pitch and individual flap control at global wind turbine scale level, a shape adaptive concept that encompasses an articulated mechanism consisting of two subparts is presented. Shape memory alloy (SMA) actuators are investigated and assessed as means to control the shape adaptive mechanism at airfoil section level in order to alleviate the developed structural loads. The concept is embedded in the trailing edge region of the blade of a 10‐MW horizontal axis wind turbine and acts as a flap mechanism. Numerical simulations are performed considering various wind velocities and morphing target shapes and trajectories for both normal and extreme turbulence conditions. The results prove the potential of the concept, since the SMA controlled actuators can accurately follow the target trajectories. Power requirements are estimated at 0.22% of the AEP of the machine, while fatigue and ultimate load reduction of the flap‐wise bending moment at the blade root is 27.6% and 7.4%, respectively.

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“…The authors have recently extended the SMA constitutive material model of Lagoudas et al (2012) as extended by Hartl et al (2012), to adopt PT capabilities through a modified hardening function expression (Karakalas et al, 2019a). The modified constitutive model does not require any additional calibration parameters, as well as sophisticated memory tracking, thus showing significant computational advantages and has been experimentally validated for thermo-mechanical behavior of thin SMA wires (diameter of 1.00 mm) under constant mechanical load.…”

Section: Adopted Constitutive Equationsmentioning

confidence: 99%

“…To model the nonlinear, thermo-mechanically coupled behavior of shape memory alloys (SMAs), the authors have adopted the model of Lagoudas et al (2012) as extended by Hartl et al (2012). The constitutive equations were derived following a procedure based on the evolution of the Gibbs free energy potential as the means to characterize the thermodynamic state of the material.…”

Section: Full Transformation Constitutive Modelmentioning

confidence: 99%

Effect of shape memory alloys partial transformation on the response of morphing structures encompassing shape memory alloy wire actuators

Karakalas

Machairas

Saravanos

2019

Journal of Intelligent Material Systems and Structures

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The present article investigates and explores the effect of partial phase transformation on the response of shape adaptive/morphing structures controlled by shape memory alloy wire actuators subject to variable trajectory and high actuation speed requirements, where the effect of partial transformation becomes more dominant. A modified constitutive model is adopted for the prediction of the thermo-mechanically coupled response on a trailing edge shape adaptive rib prototype intended for active load alleviation in large wind turbine blades, and the simulated behavior is subsequently correlated with experimental results. The experimentally validated model is further used to predict the response of the full-scale camber-line adaptive structure with shape memory alloy Ni51Ti49 wt% actuators in antagonistic configurations, under demanding operational time target trajectories at extreme turbulence conditions. Comparison of the results, with a case that omits partial transformation behavior, reveals substantial improvements in the predicted target trajectories, actuation speed, actuator stresses, and required operational temperature variation. The latter discloses the enhanced potential of shape memory alloy actuators to provide higher transformation rate and possibly higher fatigue life combined with lower energy demands toward the design and realization of efficient morphing structures.

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Phenomenological modeling of induced transformation anisotropy in shape memory alloy actuators

Cited by 15 publications

References 10 publications

Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State

Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State

Active load alleviation potential of adaptive wind turbine blades using shape memory alloy actuators

Effect of shape memory alloys partial transformation on the response of morphing structures encompassing shape memory alloy wire actuators

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