Metamaterials are materials having artificially tailored internal structure and unusual physical and mechanical properties. Due to their unique characteristics, metamaterials possess great potential ...in engineering applications. This study proposes a tunable metamaterial for the applications in vibration or acoustic isolation. For the state-of-the-art structural configurations in metamaterial, the geometry and mass distribution of the crafted internal structure is employed to induce the local resonance inside the material. Therefore, a stopband in the dispersion curve can be created because of the energy gap. For the conventional metamaterial, the stopband is fixed and unable to be adjusted in real-time once the design is completed. Although the metamaterial with distributed resonance characteristics has been proposed in the literature to extend its working stopband, the efficacy is usually compromised. In this study, the incorporation of tunable shape memory materials (SMM) via phase transformation into the metamaterial plate is proposed. Its theoretical finite element formulation for determining the dynamic characteristics is established. The effect of the configuration of the SMM cantilever absorbers on the metamaterial plate for the desired stopband in wave propagation is simulated by using finite element model and COMSOL Multiphysics software. The result demonstrates the tunable capability on the stopband of the metamaterial plate under different activation controls of the SMM absorbers, and shows the ability to trap the vibration at the designed frequency and prevent vibration wave from propagating downstream in different absorber arrangement and alloy phase. To conclusion, this study should be beneficial to precision machinery and defense industries which have desperate need in vibration and noise isolation.
Shape memory materials have been widely used as programmable soft matter for developing multifunctional hybrid actuators. Several challenges of fabrication and effective modelling of these soft ...actuating systems can be addressed by implementing novel 3D printing techniques and simulations to aid the designer. In this study, the temperature-dependent recovery of an embedded U-shaped Shape Memory Alloy (SMA) and the shape fixity of a 3D-printed Shape Memory Polymer (SMP) matrix were exploited to create a bi-state Shape Memory Composite (SMC) soft actuator. Electrical heating allowed the SMA to achieve the bi-state condition, undergoing phase transformation to a U shape in the rubbery phase and a flat shape in the glassy phase of the SMP. A COMSOL Multiphysics model was developed to predict the deformation and recovery of the SMC by leveraging the in-built SMA constitutive relations and user-defined material subroutine for the SMP. The bi-state actuation model was validated by capturing the mid-point displacement of the 80 mm length × 10 mm width × 2 mm-thick 3D-printed SMC. The viability of the SMC as a periodic actuator in terms of shape recovery was addressed through modelling and simulation. Results indicated that the proposed COMSOL model was in good agreement with the experiment. In addition, the effect of varying the volume ratio of the SMA wire in the SMC on the maximum and recovered deflection was also obtained. Our model can be used to design SMC actuators with various performance profiles to facilitate future designs in soft robotics and wearable technology applications.
In this paper, we describe a novel human interaction platform in a car, called buttons on demand, that will serve as buttons inside the interior of a car, which can be called upon and activated when ...required but remain concealed and inactive when not required. The mechanism to obtain such interaction is driven by a combination of smart materials and mechanical design. The elaboration of smart materials and mechanical design employed to achieve this mechanism is discussed. A demonstration of how the buttons on demand mechanism described in this paper can potentially substitute or minimize the use of bulkier physical buttons in cars and provide the user with haptic and tactile feedback with low power consumption and fast response time is also presented.
A continuum thermodynamics formulation for micromagnetics coupled with mechanics is devised to model the evolution of magnetic domain and martensite twin structures in ferromagnetic shape memory ...alloys. The theory falls into the class of phase-field or diffuse-interface modeling approaches. In addition to the standard mechanical and magnetic balance laws, two sets of micro-forces and their associated balance laws are postulated; one set for the magnetization order parameter and one set for the martensite order parameter. Next, the second law of thermodynamics is analyzed to identify the appropriate material constitutive relationships. The proposed formulation does not constrain the magnitude of the magnetization to be constant, allowing for spontaneous magnetization changes associated with strain and temperature. The equations governing the evolution of the magnetization are shown to reduce to the commonly accepted Landau–Lifshitz–Gilbert equations for the case where the magnetization magnitude is constant. Furthermore, the analysis demonstrates that under certain limiting conditions, the equations governing the evolution of the martensite-free strain are shown to be equivalent to a hyperelastic strain gradient theory. Finally, numerical solutions are presented to investigate the fundamental interactions between the magnetic domain wall and the martensite twin boundary in ferromagnetic shape memory alloys. These calculations determine under what conditions the magnetic domain wall and the martensite twin boundary can be dissociated, resulting in a limit to the actuating strength of the material.
Phenolic cross linked-epoxy resin based shape memory thermoset was realized through ‘click’ chemistry. Towards this, propargylated novolac and bisphenol A (bis azido hydroxy propyl) ether were ...synthesized and characterized by FTIR and proton NMR. The functionalized resins were co-cured by click reaction between alkyne and azide group under catalyzed and uncatalysed conditions to form triazole networks. The cure reaction centered around 130°C decreased to 74°C on catalysis by Cu2l2. The triazole coupled phenolic-epoxy thermoset displayed shape memory properties with high foldability, shape fixity of 99% and shape recovery of 90% at a low transition temperature of 73°C. The cross-linked matrix was thermally stable upto 250°C under nitrogen.
Shape memory polymers were derived from phenolic crosslinked epoxy resin via click chemistry. High shape fixity and 90% shape recovery were shown by the crosslinked network at a switching temperature of 73°C. Display omitted
► First time reporting the shape memory properties of azide/alkyne click chemistry cured epoxy resin. ► Novolac chemistry has never been introduced for shape memory features. ► Relatively lower temperature curable epoxy resin is achieved by this approach. ► Moreover, a facile approach for incorporating features of novolac resins to epoxy polymers is described.
In order to increase both the interfacial strength and interphase region strength between TiNi wires and shape memory epoxy, a novel interface structure including aminated CNTs was designed. The ...morphology shows that after electroplating and etching, continuous and homogeneous concave–convex layers form on the surface of as-treated TiNi wires, meanwhile aminated CNTs were planted on the surface which could react with shape memory epoxy at the interface region. The interfacial shear strength increases first with the CNT content rising but then a dramatic drop happens, and the maximum is obtained at CNT content of 0.6 g·L
−1
, which is about twice the result of acid etching TiNi wires.
In this work, we use the finite element method to investigate the free volume evolution, as well as the martensite transformation effect and its connection with the pretreatment strain, in a shape ...memory alloy-metallic glass composite. Our simulation results show that the martensite phase transformation can enhance the blocking effect while relieving the free volume localization. The synergistic effect among the martensite transformation effect, blocking effect, and shear band interaction in the composite is responsible for the tensile plasticity and work-hardening capability. In addition, we design a Sierpinski carpet-like fractal microstructure so that the composite exhibits improved tensile performance as a result of the enhanced synergistic effect. However, the tensile performance of the composite deteriorates with increasing pretreatment strain since the martensite transformation effect is weakened.
In an explicit sense of thermodynamical consistency, we propose a non-linear combined hardening elastoplastic J
2
flow model to display deformation recovery effects. With this model, we show that any ...axial strain of a uniaxially bar loaded well beyond initial yielding is recoverable upon removal of the applied load. As such, each process of application/removal of the axial load results in a deformation recovery loop. In a broad sense, we demonstrate that loops of any given shape may be generated by specifying suitable hardening functions. It follows that deformation recovery effects with various shapes of recovery loops may be derived from non-linear combined hardening elastoplastic J
2
flow models. In particular, we show that there exist hardening functions generating flag-like recovery loops. The latter are associated with the remarkable deformation recovery effects of shape memory alloys. This suggests that the finite recoverable deformation behaviour (superelasticity or pseudoelasticity) of shape memory alloys may be characterised straightforwardly by classical elastoplasticity models from a direct phenomenological standpoint.
We present a shape memory composite which is made of two types of shape memory materials, namely shape memory alloy (SMA) and shape memory hybrid. This composite has repeated instant self-healing ...function by means of not only shape recovery but also strength recovery (over 80%). The activation of the self-healing function is triggered by joule heating the embedded SMA.
Magnetic shape memory actuator performance Suorsa, Ilkka; Pagounis, Emmanouel; Ullakko, Kari
Journal of magnetism and magnetic materials,
05/2004, Volume:
272
Journal Article
Peer reviewed
Magnetic shape memory (MSM) is a newly developed actuator material. The MSM material changes its shape when exposed to an external magnetic field. Accordingly, motion generation applications such as ...actuators can be made. Coupling factor, temperature range, acceleration, speed, rise time, stroke and force of different MSM actuators are presented in this paper. Different types of dependencies of MSM actuators performance on their structure are also discussed.
PDF
