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1.
In this work, tensile tests and one-dimensional constitutive modeling are performed on a high recovery force polyurethane shape memory polymer that is being considered for biomedical applications. The tensile tests investigate the free recovery (zero load) response as well as the constrained displacement recovery (stress recovery) response at extension values up to 25%, and two consecutive cycles are performed during each test. The material is observed to recover 100% of the applied deformation when heated at zero load in the second thermomechanical cycle, and a stress recovery of 1.5 MPa to 4.2 MPa is observed for the constrained displacement recovery experiments.After performing the experiments, the Chen and Lagoudas model is used to simulate and predict the experimental results. The material properties used in the constitutive model - namely the coefficients of thermal expansion, shear moduli, and frozen volume fraction - are calibrated from a single 10% extension free recovery experiment. The model is then used to predict the material response for the remaining free recovery and constrained displacement recovery experiments. The model predictions match well with the experimental data. 相似文献
2.
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
3.
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
4.
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
5.
E. Asua A. García-Arribas V. Etxebarria 《The European physical journal. Special topics》2008,158(1):231-236
Shape memory alloys (SMA) can be used to generate motion or force in electromechanical
devices and micro-machines, although their accuracy is severely limited by their highly nonlinear
and hysteretical stimulus-response characteristics. In this work we present some results regarding
a nonlinear control method suitable for SMA-based positioning applications. In particular, we show how the hysteresis effects
can be compensated using an inverse hysteresis model generated by a neural network, trained using experimental data. The control
strategy, experimented on a laboratory SMA actuator, uses the inverse model inserted in a proportional-integral with antiwindup
control loop. It is found that neural networks successfully improve the closed-loop response, leading to position accuracies
close to a micrometer. 相似文献
6.
利用磁控溅射的方法在氧化后的单晶Si基片上制备了TiNi形状记忆合金薄膜,利用示差扫描量热法和原位X射线衍射研究了薄膜的马氏体相变特征。通过60keV质子注入(辐照)薄膜样品研究了H+离子对合金薄膜马氏体相变特征的影响,结果表明氢离子注入后引起了马氏体相变开始Ms和结束点Mf以及逆马氏体相变开始As和结束温度Af的下降,而对R相变开始Rs和结束温度Rf影响不大。掠入射X射线衍射表明H+离子注入后有氢化物形成。H+离子注入形成的氢化物是引起相变点的变化的主要因素。 相似文献
7.
Unstable form changing (click) of an arched TiNi strip annealed at 773 K is investigated. After the annealing, the strip is
placed into the grips of a deforming machine and is transferred to the martensitic state by bending in the direction opposite
to its initial bend. Subsequent heating of the strip, which carries it to the austenitic state, is accompanied by a click
under the conditions of constrained form changing. Analysis of the martensitic deformation in terms of the theory of diffuse
martensitic transformations makes it possible to establish the conditions under which the form changing process becomes unstable. 相似文献
8.
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
9.
10.
《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
11.
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
12.
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
13.
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
14.
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
15.
Finite element simulation of the magneto-mechanical response of a magnetic shape memory alloy sample
Abstract In this paper, the stress- and magnetic field-induced variant reorientation in a magnetic shape memory alloy (MSMA) sample is simulated by using the finite element method. This model is set up based on a three-dimensional setting with the whole sample and the surrounding space taken into account. A typical loading pattern is proposed on the sample. The unknowns of the model governing system include the spatial displacement vector, the scalar magnetic potential and some internal variables related to the effective magnetization vector. By considering the different properties of the unknowns, an iterative computational scheme is proposed to derive the numerical solutions. With the obtained solutions, the magneto-mechanical response of the MSMA sample under different field and stress levels can be predicted. The distributions of the variant state and the effective magnetization in the sample can also be determined. By comparing with the experimental results, it is found that the numerical solutions obtained in this model can predict the response of the MSMA sample at a quantitative level. 相似文献
16.
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
17.
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
18.
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
19.
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
20.
采用第二近邻修正型嵌入原子势的分子动力学方法,建立了共格沉淀相与半共格沉淀相块状/柱状模型,模拟了温度诱发相变和应力诱发相变,分析了Ni4Ti3沉淀相对Ni Ti形状记忆合金相变行为的影响.结果表明,Ni4Ti3沉淀相本征应变诱发的弹性应力场对相变中马氏体变体类型、形核位置、分布等有重要影响.在温度诱发相变时,共格沉淀相促进部分马氏体变体的形核生长,能显著提高Ni Ti超弹性形状记忆合金的马氏体相变开始温度;在应力诱发相变时,Ni4Ti3沉淀相使马氏体早于无沉淀相区域形核,导致了相变应力降低、抑制了马氏体解孪,减小了应力-应变曲线的滞回环. 相似文献