Papers by Keyword: SMA

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Authors: S.A. Rizvi, T.I. Khan
Abstract: Nitinol (NiTi) shape memory alloys are widely used in a variety of biomedical applications, such as dental implants, cervical and lumbar vertebral replacements, joint replacements and stents. In this study, commercially pure Ti and Ni foils ~100 um thick were diffusion bonded in vacuum. The experimental conditions were optimized to achieve a near equiatomic composition to produce NiTi SMA thin foil of approx. 5-8 micron thick. The cross-sectional surfaces of joint were subjected to metallographic investigation using optical microscope after grinding, polishing and etching. Scanning electron microscope equipped with EDX system was utilized to characterize the bonded layer and compositional analysis. Differential scanning calorimetry (DSC) technique was employed to determine the shape memory effect. The samples were subjected to X-ray diffraction analysis in order to establish phase structures formed during the diffusion bonding stage. An ultra fast femto-second laser facility was utilized to ensure the production of complex shapes or patterns within micron scale.
Authors: Yi Zhou, Jian Zuo Ma, Dong Zuo
Abstract: This paper presents a self-adaptive fan clutch for automotive application using MR fluid and SMA. Based on Bingham model, the equation of transmission torque developed by the MR fluid for fan clutch is derived. A SMA spring actuator is designed to control the angular velocity of the fan clutch. The characteristic of output angular velocity is studied in detail. The results indicate that, the change of temperatures has a tremendous influence on the output angular velocity characteristic of the fan clutch, and output angular velocity of the fan clutch can meets the demand of engine cooling fan satisfactorily.
Authors: Salvatore Ameduri
Abstract: This paper analyses a morphing leading edge device, activated by a Shape Memory Alloy (SMA) actuator. The objective is to achieve the Droop Nose effect for particular phases of the flight (e.g. take-off, landing), both obtaining an increased lift and preserving the laminar flow. The device is constituted of: a kinematic chain at the level of the wing section, transmitting motion to the skin, this way fitting the Droop Nose target shape; a span-wise architecture integrated with a SMA actuator, ensuring both a reduction of the actuation forces and the balancing of the aerodynamic external load. A dedicated logical framework was adopted for the design, taking into account the SMA material features and the device intrinsic non-linearity. The framework was integrated within an optimization genetic algorithm, to fit the target shape with an appropriate architecture topology. The optimized system proved to produce the desired morphing, also under the most severe aerodynamic loads.
Authors: Tian Qi Liu, Shu Ping Chen, Jiang Long Guo, Zhi Long Dou, Chun Liu, Qing Chun Zhang
Abstract: According to the characteristics of jumping locomotion, a solution of Tetra-state Hopping Robot (for short: THR) actuated by Shape Memory Alloy Spring (for short: SMAS) is presented in this paper. This article establishes a mechanical model of the jumping robot and analyzes the kinematics and the dynamics of the mechanical model. Lagrange method is applied to analyze the dynamics the mechanical model. Meanwhile, a preliminary explanation of the THR flipping phenomenon during the take-off and flight process is conducted from the perspective of momentum moment.
Authors: Jian Min He, Jin Huang, Yu Xi Liu
Abstract: This paper presents a cylindrical Shape memory alloy (SMA) fan clutch for automobile cooling system application. The resilience of pre-strain 2% SMA alloy wire is analyzed in the processes of heating and cooling. The Design method of SMA helical spring is described. The expression of transmission torque provided by SMA spring is established. The relationship between transmission torque and temperature is analyzed in detail. The results indicate that the transmission torque increases gradually with the increasing of airflow temperature and decreases with the decreasing of airflow temperature, respectively. The cylindrical SMA fan clutch has the property that its transmission torque changes rapidly according to the temperature of airflow from radiator.
Authors: Paola Bassani
Abstract: This overview highlights very recent application of electron backscatter diffraction (EBSD) to shape memory alloys, as main investigation technique but also as ancillary technique for other characterization methods. Over the last two decades EBSD in the scanning electron microscope has become a powerful tool for the characterization of many materials and transformation. In the mean time, shape memory alloys (SMA) are continuously studied: from a theoretical point of view, in order to clarify unsolved fundamentals of their phase transformations and characterize or develop new SMA systems, and from an engineering point of view, to solve design and processing problems related to the continuously growing examples of applications. Application of EBSD to SMA, even if hindered by limitations generally found also in other metallic system when phase transformation and martensitic phases are involved, provided useful information for both research areas.
Authors: Wei Pan, Jing Wu
Abstract: At present, SMA mixture generally to the use of SBS modified asphalt, especially in the area of expressway construction in our country, but in recent years, the use of SBS modified asphalt has some problems, for example: SBS of storage stability of modified asphalt is a difficult problem, because SBS and asphalt compatibility between components of the difference, the modified agent and asphalt separation, reduces the performance of SBS modified asphalt; SBS modified asphalt in the stored procedure, the performance will decay, even if not stop stirring, decay cannot avoid, also influence the effect of the use of SBS modified asphalt.
Authors: Rong Liu, Ping He, Chang Shui Feng
Abstract: Shape memory alloy (SMA) wire actuators have broad application prospects in many fields. But due to the nonlinearity of inherent hysteresis of SMA, the precise position control system is difficult to be obtained to these kinds of actuators. Therefore, it is significant to research the control technology of SMA wire actuators to extend the application of SMA wire actuators. In the current paper, a shape memory alloy wire actuator is designed to control the displacement of an adaptive beam. The dynamic model of SMA wire actuator is derived based on Brinson’s model and two types of inputs are used to produce different displacements. Then, PID control strategy for the SMA actuators is established and implemented to active control the position. Also, real-time control (RTC) is applied to the SMA wire actuators, which can concurrently generate real-time codes and accelerate the process of simulation. Through the comparison of different amplitudes and frequencies of current inputs, the different control abilities and characteristics to acquire the maximal displacement can be approximately achieved. Significantly, the position can basically remain stable. The results demonstrate the SMA wire actuators can be used to stably control the displacement of the adaptive beam.
Authors: Chao Wang, Ying Chun Li, Zhen Xing Yao
Abstract: The alloy of Nylon6/Acrylonitrile-Butadiene-Styrene (ABS) with styrene-maleic anhydride (SMA) was prepared by melt blending as the compatilizer. Mechanical characteristics, dynamic mechanical analysis (DMA) and fracture appearances were determined. It was found that the impact and tensile strength firstly increased and then decreased along with the increase of the SMA content. The properties reached maximum values when the content of SMA was 2%. The results of DMA and scanning electron microscope (SEM) indicated that the addition of SMA can effectively enhance the compatibility of Nylon6 and ABS.
Authors: Chun Ying Wu, Ai Fang Li, Zhe Zhao
Abstract: The objective of this study was to investigate the performance of SMA mixtures with AMBS (Activated Mineral Binder Stabilizer), a new type of bitumen stabilizer, comparing with SMA with fibers. In the paper, after a short introduction about the modification mechanism, general performances of these mixtures were researched through a series of laboratory tests. The results show that the performance of SMA with AMBS meets the requirement of criterion. It shows better results than SMA with fibers in Immersed Marshall test, Rutting test, Low temperature bending test and etc. Besides, with less consume of energy and less CO2 emission, the comparison of the environmental indicators shows a quantitative decline in the negative environmental economic cost per ton SMA mix, when using the activated-mineral binder-stabilizer as compared to the cellulose fibers. In a word, there are tremendous promotion value and good engineering application prospect in AMBS
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