Bi-Directional Origami-Inspired SMA Folding Microactuator

Lena Seigner; Georgino Kaleng Tshikwand; Frank Wendler; Manfred Kohl

doi:10.3390/act10080181

Bi-Directional Origami-Inspired SMA Folding Microactuator

Actuators ◽

10.3390/act10080181 ◽

2021 ◽

Vol 10 (8) ◽

pp. 181

Author(s):

Lena Seigner ◽

Georgino Kaleng Tshikwand ◽

Frank Wendler ◽

Manfred Kohl

Keyword(s):

Finite Element ◽

Phase Transformation ◽

Angular Dependence ◽

Martensite Phase ◽

Fem Simulations ◽

Folding Angle ◽

Double Beam ◽

Fabrication And Characterization ◽

With Memory

We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of 20 µm thickness with memory shapes set to a 180° folding angle. Bi-directional self-folding is achieved by combining two counteracting SMA microactuators. We present a macromodel to describe the engineering stress–strain characteristics of the SMA foil and to perform FEM simulations on the characteristics of self-folding and the corresponding local evolution of phase transformation. Experiments on single-SMA microactuators demonstrate the uni-directional self-folding and tunability of bending angles up to 180°. The finite element simulations qualitatively describe the main features of the observed torque-folding angle characteristics and provide further insights into the angular dependence of the local profiles of the stress and martensite phase fraction. The first antagonistic SMA microactuators reveal bi-directional self-folding in the range of −44° to +40°, which remains well below the predicted limit of ±100°.

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Influence of material parameters on 2D-martensitic transformation based on the phase-field finite-element method

Metallurgical Research & Technology ◽

10.1051/metal/2019036 ◽

2019 ◽

Vol 116 (6) ◽

pp. 614

Author(s):

Li Chang ◽

Gao Jingxiang ◽

Zhang Dacheng ◽

Chen Zhengwei ◽

Han Xing

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Phase Transformation ◽

Martensitic Transformation ◽

Phase Field ◽

Martensite Transformation ◽

Transformation Process ◽

Martensite Phase ◽

Phase Field Method ◽

Element Method

Obtaining an accurate microscopic representation of the martensitic transformation process is key to realizing the best performance of materials and is of great significance in the field of material design. Due to the martensite phase transformation is rapidly, the current experimental is hard to capture all the information in the Martensite phase transformation process. Combining the phase-field method with the finite-element method, a model of martensitic transformation from a metastable state to a steady state is established. The law of a single martensite nucleus during martensitic transformation is accurately described. By changing the key materials that affect martensite transformation and the phase-field parameters, the effects of the parameters on the single martensitic nucleation process are obtained. This study provides an important theoretical basis for effectively revealing the essence of martensite transformation and can determine effective ways to influence martensite transformation, obtain the optimal parameters and improve the mechanical properties of such materials.

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Finite element analysis of the phase transformation effect in residual stresses generated by quenching in notched steel cylinders

The Journal of Strain Analysis for Engineering Design ◽

10.1243/030932405x7755 ◽

2005 ◽

Vol 40 (2) ◽

pp. 151-160 ◽

Cited By ~ 11

Author(s):

E P Silva ◽

P M C L Pacheco ◽

M. A Savi

Keyword(s):

Finite Element ◽

Phase Transformation ◽

Residual Stresses ◽

Induction Hardening ◽

Martensite Phase ◽

The Finite Element Method ◽

Element Analysis ◽

Thermomechanical Behaviour ◽

Quenching Process

The determination of residual stresses is an important task in the analysis of the quenching process. Nevertheless, because of the complexity of the phenomenon, many simplifications are usually adopted in the prediction of these stresses for engineering purposes. One of these simplifications is the effect of phase transformation. Many studies analyse residual stresses generated by the quenching process considering a thermoelastoplastic approach, neglecting phase transformation. The present study analyses the effect of austenite-martensite phase transformation during quenching in the determination of residual stresses, comparing two different models: complete (thermoelastoplastic model with austenite-martensite phase transformation) and without phase transformation (thermoelastoplastic model without phase transformation). The finite element method is employed for spatial discretization together with a constitutive model that represents the thermomechanical behaviour of the quenching process. Progressive induction hardening of steel cylinders with semicircular notches is of concern. Numerical simulations show situations where great discrepancies are introduced in the predicted residual stresses if phase transformation is neglected.

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Influences of W Content on the Phase Transformation Properties and the Associated Stress Change in Thin Film Substrate Combinations Studied by Fabrication and Characterization of Thin Film V1–xWxO2 Materials Libraries

ACS Combinatorial Science ◽

10.1021/acscombsci.7b00192 ◽

2018 ◽

Vol 20 (4) ◽

pp. 229-236 ◽

Cited By ~ 6

Author(s):

Xiao Wang ◽

Detlef Rogalla ◽

Alfred Ludwig

Keyword(s):

Thin Film ◽

Phase Transformation ◽

Stress Change ◽

Fabrication And Characterization ◽

Film Substrate

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Nonlinear two-dimensional finite element model for transient and damping analysis of cylindrical sandwich panels with pseudoelastic shape memory alloy composite face sheets

Journal of Sandwich Structures & Materials ◽

10.1177/1099636216685916 ◽

2017 ◽

Vol 21 (1) ◽

pp. 19-76 ◽

Cited By ~ 1

Author(s):

Maryam Khanjani ◽

Mahmoud Shakeri ◽

Mojtaba Sadighi

Keyword(s):

Finite Element ◽

Phase Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

Volume Fraction ◽

Element Model ◽

Martensite Phase ◽

Governing Equations ◽

Time Step ◽

Composite Face

A new nonlinear finite element model is proposed for the dynamic analysis of cylindrical sandwich panels with shape memory alloy hybrid composite face sheets and flexible core. In order to present a realistic transient vibration analysis, all the material complexities arising from the instantaneous and spatial martensite phase transformation of the shape memory alloy wires are taken into consideration. The one-dimensional constitutive equation proposed by Boyd and Lagoudas is used for modeling the pseudoelastic behavior of the shape memory alloy wires. Since the martensite volume fraction at each point depends on the stress at that point, the phase transformation kinetic equations and the governing equations are coupled together. Therefore, at each time step, an iterative method should be used to solve the highly nonlinear equations. Moreover, considering that the stress resultants generated by the martensite phase transformation in the wires are path-dependent values, an incremental method is used to estimate the increment of the stress resultants at each time step. The governing equations are derived based on the energy method and Newmark time integration method is used to solve the discretized finite element equations. Finally, several numerical examples are presented to examine the effect of various parameters such as intensity of applied pressure load, operating temperature, location of shape memory alloy wires, volume fraction of the shape memory alloy wires, and also boundary conditions upon the loss factor for panels with different aspect ratios.

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Phase field-elasticity analysis of austenite–martensite phase transformation at the nanoscale: Finite element modeling

Computational Materials Science ◽

10.1016/j.commatsci.2018.07.034 ◽

2018 ◽

Vol 154 ◽

pp. 41-52 ◽

Cited By ~ 16

Author(s):

Sam Mirzakhani ◽

Mahdi Javanbakht

Keyword(s):

Finite Element ◽

Phase Transformation ◽

Finite Element Modeling ◽

Phase Field ◽

Martensite Phase ◽

Elasticity Analysis ◽

Element Modeling

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Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089123 ◽

1991 ◽

Vol 49 ◽

pp. 962-963

Author(s):

J. Cooper ◽

O. Popoola ◽

W. M. Kriven

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Glass Matrix ◽

Nickel Sulfide ◽

Plate Glass ◽

Thermal Expansion Mismatch ◽

Volume Increase ◽

Β Phase ◽

Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

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