变载荷作用下TiNi形状记忆合金弹簧的变形特性

研究了电流和预拉伸长度对形状记忆合金螺旋弹簧的承载能力,动态变形速度及刚度的影响关系。结果表明：在一定电流范围内,形状记忆合金弹簧的承载能力和刚度随着电流的增大而增大,当电流超出此范围后,它们几乎不再随电流变化。形状记忆合金弹簧在单次回复变形过程中的速度变化规律是先随着回复位移的增加而增加,在接近中间段时达到最大,然后随着位移的增加而减小。电流是对SMA弹簧动态变形速度影响最明显的参数,通过选择合适的电流可有效的控制SMA弹簧的回复变形速度。在预拉伸长度不大的情况下,SMA弹簧的承载能力、平均变形速度与拉伸长度成线性关系。     

变形约束时效NiTi形状记忆合金弹簧的双程记忆效应

利用变形约束时效的方法制作了双程记忆弹簧,采用DSC和温度-位移记录仪表征了弹簧的相变行为和双程记忆效应。DSC和双程记忆动力学曲线均表明弹簧在升温过程的形状变化由马氏体逆相变M/R→A控制,而冷却过程受A→R→M两阶段相变控制,并且R相变对双程记忆应变量的贡献比马氏体相变的贡献大。与马氏体相变相比,R相变诱发的双程记忆效应具有较窄的动作滞后温度以及很高的记忆稳定性,这与变形约束时效时所获得的一定取向的Ti3Ni4相共格内应力场有关。结果表明:变形约束时效是获得双程记忆弹簧的良好途径,制作方法相对简单,获得的双程记忆应变量大,且稳定性高,尺寸制作具有很强的可设计性以及动作温度的可控性。     

基于形状记忆合金的智能混凝土梁桥设计与试验研究

研究了埋置形状记忆合金(Shape Memory Alloy,SMA)束的智能预应力空心板及梁桥的变形性能,探索了SMA在实际工程中的应用。提出了一种SMA在实际工程应用的设计方法,测量了SMA通电加热时产生的回复力、SMA的温度以及空心板和梁桥的变形,并试验研究了激励电流强度对SMA回复力产生速度的影响。结果表明:可以通过控制埋置在空心板内的SMA束的温度控制其产生附加预应力的大小,调节混凝土梁和桥的变形,从而提高桥梁结构的承载能力。     

形状记忆合金(SMA)弹簧驱动器的变形研究

建立了可作为软体机器人中的形状记忆合金(SMA)弹簧驱动器的变形模型,获得了模型的待定参数A1、A2、A3、B1、B2、B3,并对该模型进行了实验验证。首先基于Clausius-Clapeyron方程和泰勒展开式,使用待定参数法建立了SMA弹簧的变形模型,描述了SMA弹簧的变形量、负载和温度之间的非线性关系;然后根据热平衡方程建立了电加热情况下的SMA弹簧温度变化模型,并获得了加热时间与弹簧温度的关系曲线;继而进行了零负载状态下的变形实验,根据实验结果计算出变形模型中的待定参数;最后通过定长通电驱动和定载荷通电驱动实验,验证了模型的正确性。所建模型能够为软体机器人中的SMA弹簧驱动器的控制方案建立提供参考。     

影响Fe-Mn-Si-Cr-Ni形状记忆合金相变点的因素

研究了变形量和回复退火温度对Fe-14Mn-5Si-8Cr-4Ni形状记忆合金相变点的影响。结果表明：当回复退火温度为673K时，Af点和Ms点都随变形量的增加而显著增加，As点增加较缓慢；303K加热前和加热后合金电阻率之差△ρ也随变形量的增加而增加，可回复变形量随变形量的变化与△ρ的变化是一致的。Fe-Mn-Si-Cr-Ni形状记忆合金的形状回复来源于应力诱发γ→ε马氏体转变及其逆转变；当变形量为10%时，Ms点随回复退火温度的增加而显著下降。     

FeMnSiCrNiCo合金记忆性能的研究

针对具有良好耐蚀性的FeMnSiCrNiCo系合金 ,确定了合理的热加工及固溶处理温度 ,研究了预变形量、退火温度及记忆训练对合金记忆性能的影响 ,并分析了微观组织。结果表明 ,随着预变形量增加 ,记忆回复率 (ηm)下降 ,但记忆回复应变量 (εm)有一个最佳值。合金的记忆性能和微观组织随训练退火温度变化而不同 ,训练退火温度对训练效果起十分关键的作用 ,母相亚结构是决定合金记忆性能的根本因素     

新型SMA隔震支座动载性能试验研究

以提高SMA利用率为目的，设计了几种不同形式的SMA橡胶支座并进行了耗能试验。研究了水平位移幅值、水平加载频率以及竖向荷载等因素对SMA橡胶支座水平刚度、耗能量以及阻尼等基本力学性能的影响，结果表明，新型的SMA橡胶支座均可有效提高橡胶支座的耗能性能和回复能力，并为SMA橡胶支座优化设计提供了依据。     

Fe-Mn-Si-Cr-Ni系形状记忆合金管接头形状记忆效应和耐腐蚀性能的研究

研究了Fe-Mn-Si-Cr-Ni系形状记忆合金管接头形状记忆效应和耐腐蚀性能。结果表明,随着预变形量的增加,管接头的形状记忆效应下降,而恢复应变呈上升趋势,当预变形超过5.3%左右时,上升幅度不大;连接状态的管接头在模拟油田介质中的耐腐蚀性能比3.5%的NaCl溶液中的抗蚀性差;在模拟油田介质中,连接状态和未连接的管接头相比,由于回复应力使表面产生拉应力以及应力诱发ε马氏体的存在,使连接状态的管接头耐腐蚀性能下降;随着预变形的增大,由于回复应力、管接头裂纹以及晶体缺陷密度增加的共同作用,使连接状态的管接头耐腐蚀性能降低。     

新型形状记忆合金驱动器与三指灵巧手设计

针对现有形状记忆合金（shape memory alloy,SMA）温度反馈控制难以实现及SMA应变量小导致实际应用中存在驱动位移小的问题,提出了一种基于电阻反馈控制的新型SMA驱动器,并采用这种驱动器研发了一种绳索传动的三指灵巧手。新型SMA驱动器由滑轮、空心螺柱、SMA丝和弹簧拉伸装置等组成,通过采用滑轮绕线的方式增长SMA丝的使用长度以提高驱动位移输出量;利用SMA自身的电阻特性得到SMA电阻变化与相变的关系,设计了基于电阻反馈的开关控制系统;采用模块化思想设计了三指灵巧手,3根手指共有8个自由度,并通过实验验证三指灵巧手对物品的抓取能力。结果表明：新型SMA驱动器不需要通过测温来判断SMA丝相变进程,省去了外部温度传感器;SMA驱动器输出的驱动量可达驱动器总长的8%以上;通过监测SMA丝的电阻变化可实现驱动器通电加热的控制,防止SMA丝过热烧毁。研究结果为提高SMA驱动器驱动位移和降低SMA驱动器控制难度提供了一种思路。     

超弹性TiNi记忆合金螺旋弹簧的滞回性能实验研究

通过滞回性能实验研究了大尺寸Ti Ni形状记忆合金(Ti Ni SMA)螺旋弹簧用于结构振动控制的可行性。利用两种Ti Ni合金制作了大尺寸超弹性螺旋弹簧试件。对Ti Ni弹簧试件进行了单轴反复荷载作用下的力学实验,获得了其在不同加载条件下的恢复力-位移曲线。分析了不同循环加卸载次数、加载频率、位移幅值对两种Ti Ni弹簧的滞回环及等效刚度、单位循环耗能、等效阻尼比和残余位移4个力学参数的影响。研究结果表明,超弹性Ti Ni弹簧可提供较大的恢复力、位移以及稳定的复位性能,并具有一定的耗能能力,在工程结构自复位振动控制中具有较好的应用潜力较好。     

Finite element simulation of low velocity impact on shape memory alloy composite plates

Delamination of composite materials due to low velocity impacts is one of the major failure types of aerospace composite structures. The low velocity impact may not immediately induce any visible damage on the surface of structures whilst the stiffness and compressive strength of the structures can decrease dramatically.

Shape memory alloy (SMA) materials possess unique mechanical and thermal properties compared with conventional materials. Many studies have shown that shape memory alloy wires can absorb a lot of the energy during the impact due to their superelastic and hysteretic behaviour. The superelastic effect is due to reversible stress induced transformation from austenite to martensite. If a stress is applied to the alloy in the austenitic state, large deformation strains can be obtained and stress induced martensite is formed. Upon removal of the stress, the martensite reverts to its austenitic parent phase and the SMA undergoes a large hysteresis loop and a large recoverable strain is obtained. This large strain energy absorption capability can be used to improve the impact tolerance of composites. By embedding superelastic shape memory alloys into a composite structure, impact damage can be reduced quite significantly.

This article investigates the impact damage behaviour of carbon fiber/epoxy composite plates embedded with superelastic shape memory alloys wires. The results show that for low velocity impact, embedding SMA wires into composites increase the damage resistance of the composites when compared to conventional composites structures.     

A nonlinear plate finite element formulation for shape memory alloy applications

The aim of the present work is to develop a new finite element model for the finite strain analysis of plate structures constituted of shape memory alloy (SMA) material. A three‐dimensional constitutive model for shape memory alloys able to reproduce the special thermomechanical behavior of SMA characterized by pseudoelasticity and shape memory effects is adopted. The finite strain constitutive model is thermodynamically consistent and is completely formulated in the reference configuration. A two‐dimensional plate theory is proposed based on a tensor element shape function formulation. The displacement field is expressed in terms of increasing powers of the transverse coordinate. The equilibrium statement is formulated on the basis of the virtual displacement principle in a total Lagrangian format. The proposed displacement formulation is particularly suitable for the simple derivation of high‐order finite elements. Numerical applications are performed to assess the efficiency and locking performance of the proposed plate finite element. Some additional numerical examples are carried out to study the accuracy and robustness of the proposed computational technique and its capability of describing the structural response of SMA devices. Copyright © 2011 John Wiley & Sons, Ltd.     

Ti-Ni形状记忆合金环超弹阻尼器的阻尼特性研究

应用Ti-Ni形状记忆合金环作耗能元件设计了一种新型的阻尼器,介绍了Ti-Ni合金环的制备及热处理工艺,并测试了其力学性能.分析了加载卸载过程中力-位移曲线与环内应力的关系.当无档板对Ti-Ni合金环进行横向约束时,由于环内的应力没达到应力诱发马氏体相变的临界应力,表现为线弹性,并且回复力非常小.当档板对环施加水平约束,出现滞迟耗能.随着位移的增加,回复力和滞迟环的面积都大幅度增加,滞迟环形状发生变化.小位移时,滞迟环为透镜状,当位移达到一定值时,滞迟环为倒三角形.倒三角形的滞迟环与双折线形滞迟环相比,在振动控制过程中具有更好的阻尼效果.     

Repeatable temperature memory effect of TiNi shape memory alloys

An incomplete transformation cycle induces a kinetic stop in the following complete transformation cycle in TiNi shape memory alloys. The kinetic stop can be regarded as a memory of the previous interruption temperature. This memory was generally believed to be a one-time phenomenon. Herein, we show that the temperature memory effect is actually a long-lasting phenomenon. Experimental results show that a repeatable temperature memory effect can be introduced into a TiNi alloy by a deformation lager than 12%. Deformation induced dislocations are considered a main factor to the persistence of the memory. The memory becomes more distinct with increasing numbers of the incomplete thermal cycle, but the memory becomes less distinct with increasing numbers of subsequent complete transformation cycling.     

具有形状记忆合金弹簧支承的转子系统的动力稳定性研究

提出一个具有形状记忆合金（SMA）弹簧支承的旋转轴转子系统的自由振动分析模型。基于Euler-Bernoulli梁理论建立旋转轴的连续分布弹性振动方程, 并且考虑旋转轴材料内阻的影响。采用Brinson模型分析SMA螺旋弹簧的受限回复刚度特性。在振型假设的基础上利用虚功原理得到转子系统的特征方程。通过数值计算分析了SMA弹簧的激励温度和初始应变对转子系统的临界转速和失稳阈的影响规律。研究表明, 利用SMA弹簧的受限回复特性调节支承刚度可以提高转子系统的临界转速和失稳阈,从而增强转子系统的动力学稳定性。     

A simulation study on the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires

In this paper, numerical simulation analyses of the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires were performed to investigate the effect of embedded SMA wires on the characteristics of thermal buckling. In order to simulate the thermomechanical behavior of SMA wires, the constitutive equation of the SMA wires was formulated in the form of an ABAQUS user subroutine. The computational program was verified by showing the response of the pseudoelasticity and shape memory effect (SME) at various temperatures and stress levels. Modeling of the laminated composite shells with embedded SMA wires and thermal buckling analyses were performed with the use of the ABAQUS code linked with the subroutine of the formulated SMA constitutive equations. The thermal buckling analyses of the composite shells with embedded SMA wires show that the critical buckling temperature can be increased and the thermal buckling deformation can be decreased by using the activation force of embedded SMA wire actuators.     

功能梯度形状记忆合金复合梁的力学行为

功能梯度形状记忆合金（Functionally graded shape memory alloy,FGSMA）兼具功能梯度材料和形状记忆合金材料的双重特性,广泛应用于微机电、航空航天等工程领域。为研究FGSMA复合梁的弯曲行为,本文对形状记忆合金（SMA）力学本构方程进行简化处理,并根据复合材料层合板理论建立了FGSMA复合梁的力学模型,据此研究了SMA体积分数沿厚度方向呈线性变化的FGSMA悬臂梁内SMA纤维铺设角度对悬臂梁横截面应变、中面轴向位移、中性面高度和相变层高度的影响以及悬臂梁中面应变、曲率、SMA马氏体相变临界层高度和中性面高度随弯矩载荷的变化规律。研究结果表明:在弯矩载荷作用下,悬臂梁中性面位置与中面位置不重合,且悬臂梁上下层SMA马氏体相变临界层位置不对称;截面轴向应变绝对值随铺设角度增大而增大,截面纵向应变绝对值随铺设角度增大先增大后减小,中面轴向位移随铺设角度增大先增大后减小;随着铺设角度增大,悬臂梁中性面高度逐渐增大,拉伸状态下相变结束临界层高度先减小后增大,压缩状态的趋势相反;随着弯矩载荷绝对值逐渐增大,中性面位置高度表现出先稳定后减小然后逐渐增大的趋势,相变临界层逐渐向中性面位置靠拢;中面正应变和挠曲率随着弯矩载荷绝对值逐渐增大而发生变化,且变化率先增大后减缓。      

Cylindrical film deposition system for three-dimensional titanium-nickel shape memory alloy microstructure

We have designed and developed a sputtering deposition apparatus to fabricate a cylindrical spring-like microstructure for a titanium-nickel (Ti-Ni) shape memory alloy (SMA) film-actuated micro-catheter. The developed apparatus that mainly consists of gearboxes to transform rotation of a stage into rotation of a shaft specimen is mounted on a ternary-source sputtering system. By using this system, a Ti-Ni SMA film with the controlled composition has been successfully deposited around a copper (Cu) shaft surface and the annealed film has possessed the shape memory characteristics evaluated by X-ray diffraction (XRD). A spring shape of the film has been capably patterned by photolithography and wet etching, so the developed deposition apparatus with a specimen rotation unit would be useful for fabricating a three-dimensional (3D) microstructure towards the active micro-catheter.     

Vibration characteristics of laminated composite plates with embedded shape memory alloys

Shape memory alloy (SMA) is commercially available for a variety of actuator and damping materials. Recently, SMA wires have also become commercially available for the design of smart composite structures because SMA wires with a small diameter can be easily produced. In this work, two types of SMA-based composites are presented for investigating the vibration characteristics. First, laminated composite plates containing unidirectional fine SMA wires are fabricated. By measuring the vibration mode of a clamped cantilever, the influence of both SMA arrangement and temperature on the vibration characteristics is made clear. Next, laminated composite plates with embedded woven SMA layer are fabricated. The stiffness tuning capability is evaluated by impact vibration tests with different temperatures. It is found that the stiffness tuning capability may be improved by increasing the volume fraction of SMAs and by controlling accurately the internal stress according to the phase transformation temperature of SMAs from martensite to austenite. The theoretical prediction on the natural frequency considering the SMAs behavior and laminated structures is proposed and their results agree reasonably with experimental ones.