SMA短纤维增强复合材料在热载下的相交特性

在形状记忆合金（ＳＭＡ）复合材料研究中,相变特性的研究是一个主要的工作．基于Ｅｓｈｅｌｂｙ的等效夹杂模型和Ｍｏｒｉ和Ｔａｎａｋａ的场平均法,考虑到ＳＭＡ材料的强物理非线性,发展了增量型的等效夹杂模型（ＩｎｃｒｅｍｅｎｔａｌＥｑｕｉｖａｌｅｎｔＩｎｃｌｕｓｉｏｎＭｏｄｅｌ）．考虑在某一温度循环条件下讨论形状记忆合金短纤维增强的铝基复合材料在热载下的相变行为．特别研究了ＳＭＡ短纤维复合材料在变温过程中纤维几何尺寸、体积分数等参数对ＳＭＡ复合材料的相变行为和ＳＭＡ内残余应力等的影响．这些工作对于指导材料设计和了解ＳＭＡ复合材料热机械特性是颇有意义的．     

SMA短纤维增强复合材料在热载下的相变特性

在形状记忆合金（ＳＭＡ）复合材料研究中,相变特性的研究是一个主要的工作。基于Ｅｓｈｅｌｂｙ的等效要模型和Ｍｏｒｉ和Ｔａｎａｋａ的场平均法,考虑到ＳＭＡ材料的强物理非线性,发展了增量型的等效夹杂模型（ＩｎｃｒｅｍｅｎｔａＩＥｑｕｉｖａｌｅｎｔＩｎｃｌｕｓｉｏｎ Ｍｏｄｅｌ）。考虑在某一温度循环条件下讨论开关记忆合金短纤维增强的铝基复合材料在热载下的相变行为。特别研究了ＳＭＡ短纤维复合材料在变温过程     

SMA复合材料在热载条件下的残余应力分析

本文基于三相复合圆柱模型发展了增量型的分析方法,讨论在ＳＭＡ复合材料中由于ＳＭＡ材料相变以及各相材料热特性随温度变化引起的残余应力。研究基体与过渡恸介面和纤维与过渡界面间的残余应力,同时讨论由于基体相的变化对残余应力的影响。特别研究了涂层和复合材料基体间界面处的残余应力受纤维体积比、涂层厚度、纤维最大相变应以及基体中纤维取向等影响,而且讨论了计及应力对相就运动方程的影响时对ＳＭＡ复合材料相变温度和     

损伤自诊断自适应智能材料结构的研究

本文介绍了一种强度型损伤自诊断自适应智能复合材料结构的研究情况。这种智能材料结构基于电阻应变丝为传感元件，形状记忆合金为动作元件。为使结构具有高的灵敏度及诊断精度，文中研究了传感元件的布置方案，提出了四点布置传感元件的方法。同时采用形状记忆合金为动作元件。在自诊断出损伤后，对相应的ＳＭＡ激励，以减小损伤或防止其扩展。     

形状记忆合金作动器的设计及优化

采用Ｂｒｉｓｉｏｎ［１］等提出的ＳＭＡ材料的本构关系，分析了形状记忆合金作动器在三种热交换方式（自然冷却、强制冷却和采用半导体热泵技术）下的动力特性，同时研究了ＳＭＡ丝在恒载和载荷变化时对完成正逆相变所用时间的影响，并简单讨论了影响作动器响应的几个因素和改进方法     

Al2O3SiO2/ZL109 金属基复合材料的强度性能研究

介绍了硅酸铝短纤维增强ＺＬ１０９铸铝合金（Ａｌ２Ｏ３ＳｉＯ２／ＺＬ１０９ＭＭＣ）的静态实验和冲击实验结果。给出了这种复合材料的静态强度、动态屈服强度和层裂强度并对实验结果进行了分析讨论。     

往复摩擦下热压镍－二硫化钼复合材料的自润滑性能及其耐磨机理研究

对于含ＭｏＳ２的复合材料在单向滑动摩擦条件下的实用性能，人们已经进行了比较多的研究，然而好多摩擦部件在工程实际中经受的却都是往复摩擦。为了探明热压Ｎｉ－ＭｏＳ２复合材料的自润滑性能及其耐磨机理，在往复摩擦条件下研究了这种材料盘表面和偶件ＧＣｒ１５钢球表面之ＭｏＳ２膜的形成过程与形貌特征，并且利用扫描电子显微镜等观察分析了ＭＯＳ２膜的磨损表面形貌及其微区成分。结果表明，在给定的往复摩擦条件下，对偶双方表面都形成了具有层状结构的ＭｏＳ２润滑膜，这种膜是通过疲劳剥落、转移、粘附与叠压等方式所形成；ＭｏＳ２含量对Ｎｉ－ＭｏＳ２复合材料自润滑性能的影响，主要取决于它是否能够在对偶双方表面形成分布均匀而稳定的润滑膜，含６０％（ｗｔ）ＭｏＳ２的复合材料的自润滑性能最好；Ｎｉ－ＭｏＳ２复合材料的自润滑性是通过其表面ＭｏＳ２膜的连续生成与疲劳剥落，并在偶件表面形成转移膜，使复合材料与金属间的摩擦变成复合材料表面ＭｏＳ２膜与偶件表面ＭｏＳ２膜之间的摩擦所实现。由此可见，Ｎｉ－ＭＯＳ２复合材料是适合在往复摩擦运动场合应用的一种性能良好的自润滑复合材料。     

用形状记忆合金的强度自适应智能复合材料初探

将具有特殊力学性能和物理性能的形状记忆合金埋入或粘贴在复合材料结构上将使结构的力学行为发生改变。本文介绍了ＳＭＡ在增强复合材料基本力学试件的承载能力，复合材料穿孔损伤后有效止裂并提高疲劳寿命等方面的应用。     

热残余应变对金属基复合材料塑性规律的影响

热残余应变是影响晶须增强金属基复合材料的重要因素。本文利用作者改进的等效夹杂理论定量研究了热残余应变对金属基复合材料塑性强化规律的影响，并对２０％ＳｉＣｗ／Ａｌ材料的拉、压断口做了ＳＥＭ观察，通过其拉、压性能实验验证了本文理论的合理性，说明了考虑热残余应变的必要性。     

主动探测裂纹和控制裂纹扩展的智能材料结构

将具有特殊力学和物理性能的形状记忆合金──ＮｉＴｉ合金复合于主体材料内部,利用ＮｉＴｉ合金的主要特性,可以实现对构件中裂纹的自行探测和控制．本文对这种材料结构的定义、ＮｉＴｉ形状记忆合金的主要特性、含ＮｉＴｉ合金的杂交复合材料的智能效果、国内外发展动态、自动探测裂纹和控制裂纹扩展的基本原理以及发展的方向和应重点研究的问题等进行了论述．我们通过试验研究证明,该材料结构用于裂纹的探测和裂纹扩展控制,其效果是明显的．      

超弹性NiTi合金丝动力特性试验及本构模型研究

形状记忆合金(SMA)是一种兼具感知和驱动功能的功能材料,因其独特的形状记忆效应、超弹性和高阻尼等特性,成为土木工程结构振动控制的理想材料.论文研究了超弹性NiTi丝的动力特性和应变率相关的本构模型.试验测试了NiTi丝在不同应变率下的力学性能,建立了应力增量与应变率的关系方程.在试验的基础上,提出了改进的SMA本构模...     

SMA扭力驱动器的响应速度分析及实验研究

介绍了马氏体逆相变的驱动力的形成原因以及和相变阻力的关系。研究了通电加热时形状记忆合金(SMA)丝的热平衡方程以及相变时间与丝直径的关系,并进行了实验验证。将SMA丝按与筒母线方向成某夹角缠绕并粘贴在外表面可以构成SMA扭力驱动器。利用SMA丝的本构关系和圆筒的扭转应力-应变关系给出了空载情况下最大驱动扭转角对应的缠绕方向;研究了模拟飞机尾气通过扭力管进行加热时的响应速度,并与实验结果进行了比较。     

Local displacements and load transfer in shape memory alloy composites

Although there has been a significant amount of research dedicated to characterizing and modeling the response of shape memory alloys (SMAs) alone, little experimental work has been done to understand the behavior of SMAs embedded in a host material. The interaction between SMA wires and a host polymer matrix was investigated by correlating local displacements and stress fields induced by the embedded wires with SMA/polymer adhesion. Most SMA composite applications require transfer of strain from the wire to the matrix. In these applications, maximum interfacial adhesion between the SMA wire and the polymer matrix is most desirable. The adhesion was varied by considering four different surface treatments: untreated, acid etched, hand sanded and sandblasted. The average interfacial bond strength of the SMA wires embedded in an epoxy matrix was measured by standard pull out tests. Sandblasting significantly increased the bond strength, whereas hand sanding and acid cleaning actually reduced interface strength. In situ displacements of embedded, surface-treated SMA wires were measured using heterodyne interferometry, whereas the resulting stresses induced in the polymer matrix were investigated using photoelasticity. Increased wire adhesion resulted in lower axial wire displacement and higher interfacial stresses due to the restraining effect of the matrix on the actuated wire. A simplified theoretical analysis was carried out to estimate the shear stress induced in the matrix due to wire actuation. The maximum shear stress predicted for the case of a perfect interfacial bond was about 7 percent larger than the value measured experimentally for the sand-blasted wire.     

Micro-mechanical behaviors of SMA composite materials under hygro-thermo-elastic strain fields

An analytical procedure to evaluate the behavior of shape memory alloy (SMA) composite under hygrothermal environment is presented. The SMA wires are considered as inclusions embedded in a homogeneous matrix medium of the composite. The inhomogeneity associated with the phase transformation and thermal strains in the SMA wire as well as the hygrothermal strain in the matrix is homogenized using Eshelby’s equivalent inclusion method. In the present work, a similar approach adopted for SMA composites by Marfia and Sacco [Marfia, S., Sacco, E., 2005. Micromechanics and homogenisation of SMA-wire-reinforced materials. J. Appl. Mech. 72 (2), 259–268.] is considered in order to validate the response of SMA composite subjected to thermo-elastic strain field. However, in the present approach, certain modifications and new derivations for the inelastic strain tensors is carried out. First, the constitutive laws for the SMA wire and matrix are expressed in terms of the average strain in the composite. The evolutionary equations used to characterize the pseudoelastic (PE) behavior of the SMA wire are redefined in terms of the eigen strains (phase transformation and thermal strains) occurring in the SMA wire, which are then expressed in terms of the average strain in the composite. Further, the SMA composite constitutive law under coupled hygro-thermo-elastic strain fields is proposed. The generic homogenized hygric and thermal inelastic composite tensors required for the proposed hygro-thermo-elastic constitutive law are derived. Finally, the SMA composite lamina is characterized using Eshelby’s equivalent inclusion method. Using the proposed modifications and derivations, the analytical results are validated for the case of thermo-elastic strain fields and the procedure is then extended to evaluate the SMA composite behavior under hygro-thermo-elastic strain fields. The results include the effect of thermo-elastic and hygro-thermo-elastic strains on the transformation stresses and the nature of hysteresis due to hygric and thermo-elastic strains.     

VIBRATION ANALYSIS OF A BEAM WITH EMBEDDED SHAPE MEMORY ALLOY WIRES

In this study, analytical relations for evaluating the exact solution of natural fre- quency and mode shape of beams with embedded shape memory alloy （SMA） wires are presented. Beams are modeled according to Euler-Bernoulli, Timoshenko and third order beam （Reddy） the- ories. A relation is obtained for determining the effect of axial load generated by the recovery action of pre-strained SMA wires. By defining some dimensionless quantities~ the effect of different me- chanical properties on the frequencies and mode shapes of the system are carefully examined. The effect of axial load generated by SMA wires with buckling load and frequency jump is accurately studied.     

Shape memory elastic foundation and supports for passive vibration control of composite plates

The paper presents an approach to passive vibration control of shear deformable and thin plates. The first of two methods of vibration control employs prestressed shape memory alloy (SMA) wires embedded in sleeves attached to the surface of the plate. The spacing between the wires can be arbitrary and variable enabling the development of a SMA support system for maximum control with minimum additional weight. The other method considered in the paper utilizes SMA wires supporting the plate at strategically selected points. The mechanism of passive control includes two components: (1) SMA wires prestressed as a result of constrained phase transformation act as an elastic foundation with a variable stiffness and (2) energy dissipation occurs as a result of hysteresis in superelastic wires vibrating together with the structure. As follows from examples, it is possible to achieve a significant reduction of the vibration amplitude over a broad spectrum of driving frequencies using any of two methods considered in the paper.     

Effects of matrix inelasticity on the overall hysteretic behavior of TiNi-SMA fiber composites

The effects of the inelastic deformation of the matrix on the overall hysteretic behavior of a unidirectional titanium–nickel shape-memory alloy (TiNi-SMA) fiber composite and on the local pseudoelastic response of the embedded SMA fibers are studied under the isothermal loading and unloading condition. The multiaxial phase transformation of the SMA fibers is predicted using the phenomenological constitutive equations which can describe the two-step deformation due to the rhombohedral and martensitic transformations, and the inelastic behavior of the matrix material using the standard nonlinear viscoplastic model. The average behavior of the SMA composite is evaluated with the micromechanical method of cells. It is observed that the inelastic deformation of the matrix due to prior tension results in a compressive stress in the matrix after unloading of the SMA composite and this residual stress impedes the complete recovery of the pseudoelastic strain of the SMA fibers. This explains that a closed hysteresis behavior of the SMA composite is no longer observed in contrast with the case that an elastic behavior of matrix is assumed. The predicted local stress–strain behavior indicates that the cyclic response of matrix is crucial to the design of the hysteretic performance of the SMA composite under the repeated loading conditions.     

Study on energy absorbing composite structure made of concentric NiTi spring and porous NiTi

An energy absorbing composite structure made of a concentric NiTi spring and a porous NiTi rod is investigated in this paper. Both NiTi spring and porous NiTi rod are of superelastic grade. Ductile porous NiTi cylindrical specimens are fabricated by spark plasma sintering. The composite structure exhibits not only high reversible force–displacement relation for small to intermediate loading but also high energy absorbing property when subjected to large compressive load. A model for the compressive force–displacement curve of the composite structure is presented. The predicted curve is compared to the experimental data, resulting in a reasonably good agreement.     

Large amplitude free vibration analysis of thermally post-buckled composite doubly curved panel embedded with SMA fibers

Thermal post-buckled vibration of laminated composite doubly curved panel embedded with shape memory alloy (SMA) fiber is investigated and presented in this article. The geometry matrix and the nonlinear stiffness matrices are derived using Green–Lagrange type nonlinear kinematics in the framework of higher order shear deformation theory. In addition to that, material nonlinearity in shape memory alloy due to thermal load is incorporated by the marching technique. The developed mathematical model is discretized using a nonlinear finite element model and the sets of nonlinear governing equations are obtained using Hamilton’s principle. The equations are solved using the direct iterative method. The effect of nonlinearity both in geometric and material have been studied using the developed model and compared with those published literature. Effect of various geometric parameters such as thickness ratio, amplitude ratio, lamination scheme, support condition, prestrains of SMA, and volume fractions of SMA on the nonlinear free vibration behavior of thermally post-buckled composite flat/curved panel been studied in detail and reported.     

应力引起的镍钛单晶形状记忆合金相变的实验研究

在单晶形状记忆合金试样中，由于没有晶粒之间的约束，它的马氏体相界面移动比多晶容易，用实验方法研究其相变的特点，对建立新的理论模型有意义，因而对它的实验分析显得重要。本文利用高分辨率的CCD系统监测到NiTi单晶形状记忆合金在拉伸时的相变伪弹性的过程；利用X射线衍射法得到了NiTi单晶试样在拉伸方向的晶向；运用高分辨率的云纹干涉技术，获得了应力引起的NiTi单晶形状记忆合金相变时的变形场；利用高分辨率、高灵敏度的红外相机记录了NiTi单晶在拉伸状态下的温度变化规律；对低温下NiTi单晶的拉伸性能做了初步的研究，得到一些有意义的现象。