Shape memory alloy actuators in smart structures: Modeling and simulation

Constitutive model for shape memory alloys including phase transformation, martensitic reorientation and twins accommodation

Shape-Memory Alloys Handbook

https://hal.archives-ouvertes.fr/docs/00/44/91/31/PDF/A_3D_super-elastic_model_for_shape_memory_alloys_taking_into_account_progressive_strain_under_cyclic_loadings_-_Luc_Saint-Sulpice.pdf

A 3D super-elastic model for shape memory alloys taking into account progressive strain under cyclic loadings

Triple yielding and deformation mechanisms in metastable Cu47.5Zr47.5Al5 composites

Magnetic Shape Memory Alloys (MSMs) are attractive smart materials because they exhibit, at the same time, a large strain (10 %) and a short time response (100 microns s). In this paper, we propose a novel MSM based actuator exploiting the characteristics of MSMs. This device is a push-pull actuator where two pieces of MSM act in an opposite way. The magnetic fields are created by two magnetic coils supplied by current pulses. The hysteretic behaviour of the MSM permits to keep a stable position when no current is applied and so limits heat losses in the coils. A model of this actuator is proposed and validated by experiments. A precise position feedback control of the actuator is then achieved using a displacement laser sensor.

https://hal.archives-ouvertes.fr/hal-00263954/document

Multistable actuator based on magnetic shape memory alloy..

In the field of micromechatronics, microrobotics and specially microfactories, active materials are used in most cases. They permit high resolution and distributed actuation. In this area, Magnetic Shape Memory Alloys (MSMA) are possible candidates. If a lot of studies deal with MSMA, only few applications use them until now. MSMA are attractive active materials because they have large strain (about 10%) as the classical shape memory alloys (SMA), but can provide a 100 times shorter time response. The main disadvantages of MSMA based actuators are the brittleness of the single-crystal material, the difficulty to apply the strong magnetic field required to obtain sufficient strain and the nonlinear behaviour. We propose in this paper a novel MSMA based actuator changing the disadvantage of the hysteretic behaviour into an advantage. This device is a push-pull actuator: two pieces of MSMA material act in an opposite way. The magnetic fields are created by coils and concentrated by ferromagnetic circuits. In order to move the central part of the actuator, a current pulse in the first coil is generated. The hysteretic behaviour of the material permits to keep a stable position when no current is applied. A current pulse in the second coil permits to displace the central part in the opposite direction. The stable position depends on the magnitude and the time duration of the current pulses and an infinity of stable positions can be reached. The use of current pulses permits also a reduction of the coil heating (Joule effect losses) and a reduction of the magnetic circuit size. The performances and characteristics of MSMA are between these of classical SMA and these of piezo-electric materials. A thermo-magneto-mechanical model of our actuator is currently in development in order to design an efficient control law welladapted to the specific MSMA properties.

https://hal.archives-ouvertes.fr/hal-00260670/document

Magnetic shape memory alloy and actuator design.

We study the yield conditions of phase transformation initiation for shape memory alloys exhibiting asymmetry between tension and compression. An extension of the choice of the classical invariant parameters such as those of Lode is proposed. A necessary and sufficient condition of convexity of these surfaces representing the elastic domain of austenite in the stress space, is established. Moreover the transport of these surfaces in the space of effective transformations strains of martensite is done. Hence, the duality between these two spaces is built. Some applications involving Cu—Al—Be and NiTi shape memory alloys end the purpose.

/pdf/yield-criteria-for-shape-memory-materials-convexity-3ah57zi8hv.pdf

Yield Criteria for Shape Memory Materials: Convexity Conditions and Surface Transport:

Shape memory alloys (SMAs) are good candidates for being used as passive dampers, strain sensors, stiffness or shape drivers In order to develop the use of these alloys in structural vibration control, we present in this paper an implementation of a phenomenological model based on the Rl model (Raniecki et al 1992 Arch Meh 44 261–84) in a finite element code called COMSOL© which allows one to build automatically many loading cases in force or displacement This implementation is used to simulate internal loops in order to characterize the stiffness and the damping effect by an equivalent complex Young's modulus approach under static strain offsets The results clearly show the influence of the initial static strain offset and the amplitude of vibration on the damping and stiffness properties

http://iopscience.iop.org/article/10.1088/0964-1726/16/4/001/pdf

Implementation of a multi-axial pseudoelastic model to predict the dynamic behavior of shape memory alloys

Microtechnologies and microsystems engineering use new active materials. These materials are interesting to realize microactuators and microsensors. In this category of materials, Shape Memory Alloys (SMA) are good candidates for microactuation. SMA wires, or thin plates, can be used as active material in microfingers. These microstructures are able to provide very important forces, but have low dynamic response, especially for cooling, in confined environment. The control of the SMA phase transformations, and then the mechanical power generation, is made by the temperature. The Joule effect is an easy and efficiency way to heat the SMA wires, but cooling is not so easy. The dynamic response of the actuator depends on cooling capabilities. The thermal convection and conduction are the traditional ways to cool the SMA, but have limitations for microsystems. We are looking for a reversible way of heating and cooling SMA microactuators, based on the thermoelectric effects. Using Peltier effect, a positive or a negative electrical courant is able to pump or produce heat, in the SMA actuator. A physical model based on thermal exchanges between a Nickel/Titanium (NiTi) SMA, and Bismuth/Telluride (Te3Bi2) thermoelectric material has been developed. For simulation, we use a numerical resolution of our model, with finite elements, which takes into account the Peltier effect, the Joule effect, the convection, the conduction and the phase transformation of the SMA. We have also developed the corresponding experimental system, with two thermoelectric junctions, where the SMA actuator is one of the element of each junction. In this paper, the physical model and its numerical resolution are given, the experimental system used to validate the model is described, and experimental results are shown.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Christian Lexcellent

Papers

Multistable actuator based on magnetic shape memory alloy..

Magnetic shape memory alloy and actuator design.

Yield Criteria for Shape Memory Materials: Convexity Conditions and Surface Transport:

Implementation of a multi-axial pseudoelastic model to predict the dynamic behavior of shape memory alloys

Thermoelectric control of shape memory alloy microactuators: a thermal model