共查询到20条相似文献,搜索用时 15 毫秒
1.
The two-dimensional automatic alignment system with an optical aperture is developed. The optical aperture with four integrated photodiode cells for feedback control signal is fabricated by MEMS techniques. The translation stage of the system is driven by four shape-memory-alloy positioning actuators to realize two-dimensional (XY-plane) movement. 相似文献
2.
The use of shape memory alloys in actuators allows the development of robust, simple and lightweight elements for application
in a multitude of different industries. Over the years, the intermetallic compound Nickel-Titanium (NiTi or Nitinol) together
with its ternary and quaternary derivates has gained general acceptance as a standard alloy. Even though as many as 99% of
all shape memory actuator applications make use of Nitinol there are certain properties of this alloy system which require
further research in order to find improvements and new markets:
• Lack of higher transformation temperatures in the available alloys in order to open the field of automotive applications
(Mf temperature > 80 °C)
• Non-linearity in the electrical resistivity in order to improve the
controllability of the actuator,
• Wide hysteresis in the temperature-vs.-strain behaviour, which has a signi-ficant effect on both, the dynamics of the actuator
and its controllability.
Hence, there is a constant strive in the field towards an improvement of the related properties. However, these improvements
are not always just alloy composition related. There is also a tremendous potential in the thermomechanical treatment of the
material and in the design of the actuator. Significant improvement steps are already possible if the usage of the existent
materials is optimized for the projected application and if the actuator system is designed in the most efficient way. This
paper provides an overview about existent designs, applications and alloys for use in actuators, as well as examples of new
shape memory actuator application with improved performance. It also gives an overview about general design rules and reflects
about the strengths of the material and the related opportunities for its application. 相似文献
3.
E. Choi Y.-S. Chung B.-S. Cho T.-H. Nam 《The European physical journal. Special topics》2008,158(1):255-259
This study proposed a new method to confine concrete
cylinders or reinforced concrete columns using martensitic, Ti-49.7Ni (at
%), or austenitic, Ti-50.3Ni (at %), shape-memory-alloy wires.
Prestrained martensitic SMA wire was used to wrap a concrete cylinder and,
then, was heated by a heating jacket. In the process, confining stress was
developed around the cylinder by the SMA wire due to shape memory effect,
which can increase the strength and ductility of the cylinder under axial
compressive load. For austenitic shape memory wires, some prestraining was
introduced in the wires during wrapping concrete cylinders on which
post-tensioning stress was generated. In this study, 1.0 mm diameter of
martensitic and austenitic SMA wire was used for confinement. Recovery tests
were conducted for the martensitic and the austenitic shape memory wires to
determine the recovery stress and superelastic behavior, respectively. The
confinement by martensitic shape memory wires had increased the strength
slightly and the ductility substantially. However, the austenitic shape
memory wires only increased the ductility because the imposed prestress was
too small. This study showed the potential of the proposed method to
retrofit reinforced concrete columns using shape memory wires to protect
themselves from earthquakes. 相似文献
4.
Ratchatee TechapiesancharoenkijSamuel M. Allen Robert C. O'Handley 《Journal of magnetism and magnetic materials》2011,323(23):3109-3116
The prospect of using ferromagnetic shape memory alloys (FSMAs) is promising for a resonant actuator that requires large strain output and a drive frequency below 1 kHz. In this investigation, three FSMA actuators, equipped with tetragonal off-stoichiometric Ni2MnGa single crystals, were developed to study their frequency response and resonant characteristics. The first actuator, labeled as A1, was constructed with low-k bias springs and one Ni-Mn-Ga single crystal. The second actuator, labeled as A2, was constructed with high-k bias springs and one Ni-Mn-Ga crystal. The third actuator, labeled as A3, was constructed with high-k bias springs and two Ni-Mn-Ga crystals connected in parallel. The three actuators were magnetically driven over the frequency range of 10 Hz-1 kHz under 2 and 3.5 kOe magnetic-field amplitudes. The field amplitude of 2 kOe is insufficient to generate significant strain output from all three actuators; the maximum magnetic-field-induced strain (MFIS) at resonance is 2%. The resonant MFIS output improves to 5% under 3.5-kOe amplitude. The frequency responses of all three actuators show a strong effect of the spring k constant and the Ni-Mn-Ga modulus stiffness on the resonant frequencies. The resonant frequency of the Ni-Mn-Ga actuator was raised from 450 to 650 Hz by increasing bias spring k constant and/or the number of Ni-Mn-Ga crystals. The higher number of the Ni-Mn-Ga crystals not only increases the magnetic force output but also raises the total stiffness of the actuator resulting in a higher resonant frequency. The effective modulus of the Ni-Mn-Ga is calculated from the measured resonant frequencies using the mass-spring equation; the calculated modulus values for the three actuators fall in the range of 50-60 MPa. The calculated effective modulus appears to be close to the average modulus value between the low twinning modulus and high elastic modulus of the untwined Ni-Mn-Ga crystal. 相似文献
5.
《Infrared Physics & Technology》2002,43(3-5):151-155
Temperature changes during tensile test and simple shear test of TiNi shape memory alloys loaded at various strain rates and at different temperatures have been presented. The temperature changes were measured by recording infrared radiation emitted by the surface of the specimen. It was found that the martensite transformation was accompanied by an increase in temperature while the reversible transformation––temperature decrease. 相似文献
6.
Z.H. LiuX.Q. Ma Z.Y. ZhuH.Z. Luo G.D. LiuJ.L. Chen G.H. Wu Xiaokai ZhangJohn Q. Xiao 《Journal of magnetism and magnetic materials》2011,323(16):2192-2195
The magnetoresistance (MR){=[R(H)−R(0)]/R(0)} properties in ferromagnetic shape memory alloy of NiMnFeGa ribbons and single crystals, and NiFeGa ribbons have been investigated. It is found that the NiMnFeGa melt-spun ribbon exhibited GMR effect, arising from the spin-dependent scattering from magnetic inhomogeneities consisting of antiferromagnetically coupled Mn atoms in B2 structure. In the absence of these magnetic inhomogeneities, Heusler alloys seem to show a common linear MR behavior at around 0.8TC, regardless of sample structures. This may be explained by the s-d model. At low temperatures, conventional AMR behaviors due to the spin-orbital coupling are observed. This is most likely due to the diminished MR from s-d model because of much less spin fluctuation, and is not associated with martensite phase. MR anomaly at intermediate field (ρ⊥>ρ||) is also observed in single crystal samples, which may be related to unique features of Heusler alloys. 相似文献
7.
8.
S. P. Belyaev R. F. Konopleva I. V. Nazarkin A. I. Razov V. L. Soloveĭ V. A. Chekanov 《Physics of the Solid State》2007,49(10):1969-1972
The recovery of inelastic strains in Ti-Ni alloy samples irradiated in a nuclear reactor under isothermal conditions was studied. Before irradiation, the cylindrical samples were compressed to a residual strain of 3–6% in the martenstici state at room temperature. The samples were irradiated at a temperature of 45°C, which does not exceed the temperature of the onset of the reverse martensitic transformation A S . Irradiation with a fastneutron fluence of 5 × 1020 cm?2 is established to result in the recovery of the residual strain. The value of the recoverable strain is comparable to that observed under the conditions of the shape memory effect on heating of the deformed alloy and even somewhat exceeds it. The obtained data show that neutron irradiation can induce the shape-memory effect in the TiNi alloy. This is due to a decrease in the temperatures of the martensitic transformations under irradiation. 相似文献
9.
J. M. Dutkiewicz W. Maziarz T. Czeppe L. Lityńska W. K. Nowacki S. P. Gadaj J. Luckner E. A. Pieczyska 《The European physical journal. Special topics》2008,158(1):59-65
Powder metallurgy technology was elaborated for
consolidation of shape memory NiTi powders. The shape memory alloy was
compacted from the prealloyed powder delivered by Memry SA. The powder shows
Ms = 10°C and As = -34°C as results from DSC
measurements. The samples were hot pressed in the as delivered spherical
particle's state. The hot compaction was performed in a specially
constructed vacuum press, at temperature of 680°C and pressure of 400 MPa. The alloy powder was encapsulated in copper capsules
prior to hot
pressing to avoid oxidation or carbides formation. The alloy after hot
vacuum compaction at 680°C (i.e. within the B2 NiTi stability range)
has shown similar transformation range as the powder. The porosity of
samples compacted in the as delivered state was only 1%. The samples
tested in compression up to ε = 0.06 have shown partial
superelastic effect due to martensitic reversible transform- ation which
started at the stress above 300 MPa and returned back to ε = 0.015 after unloading. They have shown also a high ultimate compression
strength of 1600 MPa. Measurements of the samples temperature changes during
the process allowed to detect the temperature increase above 12°C for
the strain rate 10-2 s-1 accompanied the exothermic martensite
transformation during loading and the temperature decrease related to the
reverse endothermic transformation during unloading. 相似文献
10.
NiTi形状记忆合金的高应变动态响应特性在军事、航空等领域具有重要应用.为研究NiTi合金在动态力学诱导下的相变行为,在不同温区不同冲击速率下,通过轻气炮装置对NiTi合金进行了动态加载实验.利用差示扫描量热仪(DSC),综合物性测量系统分析了冲击波残余效应对NiTi合金相变行为的影响.研究发现:受冲击的样品在第一次DSC热循环中观察到了三个马氏体吸热峰,表现为三步逆马氏体相变,而在第二次热循环中其中两个应力诱发马氏体吸热峰因变形恢复消失.形成两个应力诱发马氏体吸热峰的原因可能是晶粒内部与晶界处的相变过程不同步.受冲击后样品DSC放热峰上出现了一小肩峰,表明可能因中间相(R相)的出现而发生了两步相变,结合电阻测量曲线进一步确认R相的存在,且发现奥氏体相向R相转变以及R相向马氏体相转变这两种相变过程在某一温度范围内可同时进行.同时,文中也具体讨论了不同的冲击加载条件对相变过程的影响. 相似文献
11.
Manufacturing technology for the fabrication a discrete actuator
using a magnetic shape memory alloy
B. Spasova M. C. Wurz H. H. Gatzen 《The European physical journal. Special topics》2008,158(1):243-247
To demonstrate the feasibility of combining thin-film fabrication techniques and discrete MSM stripes, a hybrid actuator system
was designed. The actuator system consists of four thin-film stators and two discrete MSM stripes mounted in a row. For creating
an actuator motion, one of the MSM stripes has to be excited by a pair of stators to cause variant switching. This results
in an elongation plus a compression of the second stripe and vice versa. The technologies required for fabricating the thin-film
stator are sputter deposition, PECVD, electroplating, etching, and photolithography. This paper describes the fabrication
process for a thin-film stator used for the MSM micro actuator system. It also presents technology study results indicating
the feasibility of the planned fabrication sequence. 相似文献
12.
K. V. Sapozhnikov S. N. Golyandin S. Kustov E. Cesari 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(10):1423-1426
Elastic, anelastic, and magnetoelastic properties of polycrystalline Ni-Fe-Ga-Co ferromagnetic shape memory alloy have been
studied by means of mechanomagnetic spectroscopy under thermal cycling in the temperature range from 80 to 300 K. The data
obtained point to the presence of reversible thermally induced modifications of martensitic and magnetic domain structures
in the alloy studied. 相似文献
13.
结合双温模型的分子动力学模拟方法,研究了飞秒激光脉冲辐照B2结构镍钛合金时烧蚀阈值附近的靶材蚀除机制,数值模拟了中心波长为800 nm,脉宽为100 fs,能量密度为25~50 mJ/cm2的激光与90 nm厚B2结构镍钛合金薄膜相互作用过程。确定了脉宽为100 fs的脉冲激光与镍钛形状记忆合金相互作用的烧蚀阈值,发现烧蚀阈值条件下,靶材的蚀除机制是单纯基于应力作用的机械破碎;烧蚀阈值附近,未蚀除靶材受热影响发生无序化相变的区域较小,且随激光能量密度的降低而减小。 提高激光功率密度,烧蚀同时呈现热机械蚀除和机械破碎机制。 相似文献
14.
结合双温模型的分子动力学模拟方法,研究了飞秒激光脉冲辐照B2结构镍钛合金时烧蚀阈值附近的靶材蚀除机制,数值模拟了中心波长为800nm,脉宽为100fs,能量密度为25~50mJ/cm2的激光与90nm厚B2结构镍钛合金薄膜相互作用过程。确定了脉宽为100fs的脉冲激光与镍钛形状记忆合金相互作用的烧蚀阈值,发现烧蚀阈值条件下,靶材的蚀除机制是单纯基于应力作用的机械破碎;烧蚀阈值附近,未蚀除靶材受热影响发生无序化相变的区域较小,且随激光能量密度的降低而减小。提高激光功率密度,烧蚀同时呈现热机械蚀除和机械破碎机制。 相似文献
15.
The damping characteristics of an Ni–Ti shape memory alloy (SMA) beam are theoretically and experimentally studied with interest in identifying an appropriate damping model for the material. The SMA beam is manufactured by a spray deposition method followed by heat treatment and found to have nanocrystalline structure in which damping capacity is high. The beam is then tested to obtain an impulse response and the frequency response function (FRF). By using the Hilbert transform technique it is shown that damping of the beam is almost amplitude independent in the tested range of displacement. It is also shown from the FRF that the damping of the spray-deposited shape memory alloy beam is well represented by a model including both linear viscous and hysteretic dampings. 相似文献
16.
C.W. ChanH.C. Man 《Optics and Lasers in Engineering》2011,49(1):121-126
In this study, two L27 Taguchi experiments were carried out to study the effect of fibre laser welding parameters and their interactions upon the weld bead aspect ratio of nickel-titanium thin foil. The optimum parameters to produce full penetrated weld with the largest aspect ratio and desirable microstructure were successfully obtained by the Taguchi experimental design. The corrosion property of the optimized NiTi weld in Hank’s solution at 37.5 °C was studied and compared with the as-received NiTi. To improve the corrosion properties of the weld, the effect of post-weld-heat-treatments ranging from 573 to 1173 K was investigated. The corrosion properties, surface morphology, microstructure and Ti/Ni ratio of the heat-treated NiTi weld were analysed. It was found that a post-weld heat treatment at 573 K for 1 h provided the best pitting corrosion resistance at the weld zone. 相似文献
17.
Yigui Li Shuhai Jia Hongkun Wang Di Chen Kazuhiro Hane 《Optics & Laser Technology》2002,34(8):649-653
This paper describes a novel pitch-variable transmission-type bulk grating fabricated by silicon micromachining technology driven by a shape memory alloy (SMA) actuator. The grating is specially designed to change the pitch easily with a small force and assured moderate stress by finite element method. Using deep reactive ion etching (deep-RIE) technology, the grating has a high aspect ratio more than 10. In the diffraction experiment, more than 10% extension ratio has been obtained. The SMA actuator has been installed to the grating. Due to the two-way shape memory effect, the translation mechanism is simple and is easily controlled. 相似文献
18.
This contribution deals with the analysis of a rotordynamic nonsmooth shape memory alloy (SMA) system. The rotor–bearing system is modeled as a Jeffcott rotor with two-degrees of freedom and discontinuous supports. Two different situations are investigated: linear elastic support and shape memory alloy support. Numerical simulations are carried out establishing a comparison between elastic and SMA systems, showing situations where nonlinear effects of SMAs are interesting in dynamical responses avoiding undesirable behaviors. Temperature dependence of SMA response is investigated showing adaptive aspects of this kind of system. 相似文献
19.
AbstractThe shock behaviour of NiTi shape memory alloy is investigated by using molecular dynamics simulation. The nano-pillar samples of the alloy are subjected to the impact of a piston with a velocity of 350 m/s at initial environment temperatures of 325 and 500 K. At 325 K, we observe two different pathways of the formation of BCO phase, the gradient twins, and the detwinning phenomena, strongly depending on the local stress and the deformation state. As the initial temperature increases to 500 K, the plasticity is dominated by the dislocation movements rather than the twinning at 325 K. The phase transformation and plasticity result in stress attenuation when the stress wave propagates through the nano-pillar. Furthermore, it is interesting to note that multiple stress peaks occur due to the formation of local complex atomic structures with various wave speeds, leading to the catch up and overlap of the stress waves. 相似文献
20.
A nonlinear finite element model is provided to predict the static aero-thermal deflection and the vibration behavior of geometrically imperfect shape memory alloy hybrid composite panels under the combined effect of thermal and aerodynamic loads. The nonlinear governing equations are obtained using Marguerre curved plate theory and the principle of virtual work taking into account the temperature-dependence of material properties. The effect of large deflection is included in the formulation through the von Karman nonlinear strain-displacement relations. The thermal load is assumed to be a steady-state constant-temperature distribution, whereas the aerodynamic pressure is modeled using the quasi-steady first-order piston theory. The Newton-Raphson iteration method is employed to obtain the nonlinear aero-thermal deflections, while an eigenvalue problem is solved at each temperature step and static aerodynamic load to predict the free vibration frequencies about the deflected equilibrium position. Finally, the nonlinear deflection and free vibration characteristics of a composite panel are presented, illustrating the effects of geometric imperfection, temperature rise, aerodynamic pressure, boundary conditions and shape memory alloy fiber embeddings on the panel response. 相似文献