SMA纤维复合材料变截面板簧的固有频率特性研究

摘 要:研究了形状记忆合金（SMA）纤维混杂复合材料变截面板簧的固有频率特性。基于Brinson本构模型,讨论了SMA的受限回复特性。在建立具有SMA纤维的各向异性层合梁本构方程的基础上,利用瑞利-里兹能量法求板簧的固有频率,并给出板簧固有频率的表达式。应用MATLAB进行数值计算,得到板簧固有频率与温度、铺层角、SMA含量的关系曲线,揭示了形状记忆合金纤维复合材料变截面板簧的固有频率可调节机理。     

形状记忆合金纤维正交各向异性层合矩形板的非线性弯曲振动

研究了形状记忆合金(SMA)纤维混杂复合材料大挠度层合板的非线性自由与受迫振动特性。基于描述SMA力学行为的Brinson理论以及层合板材料性能预测的混合率, 建立了SMA纤维混杂复合材料大挠度层合板的本构方程, 基于对称层合各向异性弹性板的非线性理论, 建立了以横向挠度和应力函数表示的板的横向振动方程和相容方程。采用Galerkin近似解法将振动方程化为时间变量的含有三次非线性项的Duffing型常微分方程, 采用谐波平衡法(HBM)获得系统的固有频率方程和强迫振动稳态频率响应方程。数值计算表明: 非线性板自由振动频率比与激励温度的关系具有与线性板相同的特征, 马氏体相向奥氏体相转变阶段温度对板的振动频响特性曲线的影响最显著, 同时也讨论了SMA纤维含量、 板的纵横比以及自由振动幅值对板的非线性频率比的影响。      

SMA纤维复合材料变截面板簧固有频率特性研究

研究了形状记忆合金(SMA)纤维混杂复合材料变截面板簧的固有频率特性.基于Brinson本构模型,讨论了SMA的受限回复特性.在建立具有SMA纤维的各向异性层合梁本构方程的基础上,利用瑞利-里兹能量法求板簧的固有频率,并给出板簧固有频率的表达式.应用MATLAB进行数值计算,得到板簧固有频率与温度、铺层角、SMA含量的关系曲线,揭示了形状记忆合金纤维复合材料变截面板簧的固有频率可调节机理.     

SMA混杂复合材料单层的被动阻尼

由形状记忆合金纤维、普通纤维、基体构成的混杂复合材料是一类用途广泛的智能材料结构系统。阻尼性能研究是结构被动振动控制的一项重要研究内容。本文采用混杂复合材料阻尼预测的细观力学理论计算SMA纤维混杂复合材料单层的阻尼特性。首先计算包含普通纤维和基体材料的复合材料介质的阻尼性能,其次计算由横观各向同性介质和SMA纤维构成的混杂材料的阻尼性能。通过计算实例分析SMA纤维混杂复合材料单层的正轴阻尼特性及其偏轴阻尼的特性随SMA纤维体积含量、纤维铺设角等参数改变的规律。     

埋入形状记忆合金丝的复合材料圆柱壳壁板的热振动特性分析

采用有限元软件ABAQUS实现了埋入形状记忆合金（SMA）丝的复合材料圆柱壳壁板结构热振动特性分析．基于“ang-Rogers本构模型编写用户子程序（UMAT）模拟形状记忆合金材料的超弹性行为和形状记忆效应，并在不同温度和应力状态下验证了程序的正确性．基于此程序，计算了埋入SMA丝的复合材料圆柱壳壁板在温度和机械载荷作用下的一阶固有频率，分析了其热振动特性和屈曲特性．模拟结果表明：加热驱动SMA丝一般会提高结构的固有频率和屈曲临界，SMA丝的数量对结构的热振动和屈曲特性有显著影响。这些结论将对智能复合材料结构设计、抗热设计有一定的指导作用。     

利用SMA的SME特性改善复合材料板低速冲击响应性能的研究

本文将具有一定塑性应变的形状记忆合金(SMA)纤维埋设在复合材料板中，利用其形状记忆功能(SME)改善复合材料板的低速冲击响应性能。研究中，应用有限元法对SMA杂交复合材料板的低速冲击响应进行了分析，其中，SMA中产生的恢复应力通过实验得出的应力-温度关系确定，冲击接触力通过修正的Hertzian接触定律求得；研究结果表明具有形状记忆功能的SMA能有效地改善复合材料的低速冲击响应性能。     

SMA纤维混杂层合梁的振动分析

提出一类形状记忆合金(SMA)纤维混杂层合梁的数学模型。采用多胞模型、形状记忆合金一维本构关系分析方法,同时考虑铁木辛柯剪切和马氏体相变的影响。目的是为了更进一步了解层合梁的振动控制。SMA纤维用来作为驱动器,它能够改变弹性模量和回复力,以此改变梁的频率。分析了SMA纤维含量、铺设角度和横向剪切变形的影响。结果表明,通过激活形状记忆合金纤维及改变初始变形,对层合梁的自振频率有很强的控制和调节能力。     

热载荷作用下嵌入SMA丝复合材料梁的横向自由振动

基于形状记忆合金Brinson一维热力学本构方程,采用复合材料细观力学分析方法,建立了热载荷作用下嵌入SMA丝复合材料梁的一维热弹性本构关系。其次利用Euler-Bernoulli梁的轴线可伸长几何非线性理论和自由振动理论,建立了嵌入SMA丝复合材料梁在均匀升温场内自由振动的动力学控制方程,导出了热过屈曲构形附近嵌入SMA丝复合材料梁微幅横向自由振动的模型。最后通过打靶法求解了两端固定约束条件下嵌入形状记忆合金丝复合材料梁在加热过程中的振动响应,获得了梁的前四阶固有频率在不同SMA相对体积含量时随温度变化的特征关系曲线。数值结果表明,SMA丝相变过程中的回复应力和弹性模量变化对梁在过屈曲前后的各阶固有频率均有影响,是实现梁自振频率主动控制的一种有效方法。     

埋入SMA丝的复合材料层合板在热激励下的自由振动分析

采用Liang-Rogers的形状记忆合金(SMA)本构模型和相变动力学关系,编写了ABAQUS中的相应UMAT用户材料子程序,模拟了形状记忆合金材料的超弹性行为和形状记忆效应,并在不同温度和应力状态下验证了程序的正确性.基于此程序,建立了埋入SMA丝的复合材料层合板结构计算模型,仿真计算了两端固支边界条件下,热驱动SMA时的结构的固有振动特性,分析了SMA丝的热驱动温度,埋丝数量及埋设方式等对结构热振动特性的影响规律.模拟结果表明:加热驱动SMA丝一般会提高结构的固有频率,增加SMA丝的数量可以实现增大结构频率的目的;不同的埋设角度对结构的振动特性影响显著.这些结论将对智能复合材料结构设计、抗热设计有一定的指导作用.     

形状记忆合金梁的建模及混沌阈值计算

从形状记忆合金（SMA）的等应变拉压实验数据出发,利用van-der-pol环模型模拟了形状记忆合金在加载和卸载过程中的应力应变迟滞环特性。并根据弹性理论和Galerkin方法建立了形状记忆合金简支梁在受轴向激励时的振动模型。随后得出了自由振动系统的分岔特性。在利用待定固有频率法研究了模型的非线性参数对系统固有频率的影响后,根据待定固有频率法的计算结果和时间尺度变化提出了系统Melnikov函数的改进表达式,提高了计算形状记忆合金梁模型在参数激励下发生混沌的阈值的精度。数值模拟的结果证明了该途径的有效性。     

An approach to optimization of shape memory alloy hybrid composite plates subjected to low-velocity impact

The paper presents an approach to the problem of optimum design of composite plates subjected to low velocity impact. The deflections and stresses are reduced by employing prestrained shape memory alloy (SMA) fibers which are in the martensitic phase when embedded within the plate. At an elevated temperature, the SMA fibers transform into the austenitic phase and tend to contract. However, due to a constraint, the contraction is either completely prevented or reduced resulting in significant tensile recovery stresses. This tension reduces deformations and stresses in the plate subjected to low-velocity impact.The solution in the paper addresses an impact of cross-ply plates with SMA fibers embedded within the layers oriented in both directions. An approach to optimization considered in the paper involves variations of the volume fractions of SMA fibers in each direction subject to a constraint on the total volume of the shape memory alloy. It is shown that an application of SMA fibers can significantly reduce deflections and stresses. A further benefit can be achieved by an optimization of a distribution of volume fractions of SMA fibers between the layers.     

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.     

Free vibration of buckled SMA reinforced composite laminates

The effect of shape memory alloys (SMA) on the free vibration behavior of buckled cross-ply and angle-ply laminates by varying the SMA fiber spacing was investigated using the finite element method. The formulation of the location-dependent linear, nonlinear stiffness and mass matrices due to non-homogeneous material properties and the temperature-dependent recovery stress stiffness matrix were derived. Numerical results show that the increase of SMA fiber volume fraction and prestrain may generate more recovery stress, and increase the stiffness of SMA reinforced composite laminates. Therefore, the postbuckling deflections of the plate will be decreased considerably and the natural frequencies of the plate may be modified significantly. The buckling mode and fundamental natural mode are dependent on the graphite fiber orientation of the SMA reinforced angle-ply laminates. The relationship between the buckling mode and fundamental natural mode is clearly displayed and studied in detail.     

Thermal post-buckling and flutter characteristics of composite plates embedded with shape memory alloy fibers

It is investigated that the composite plate embedded with shape memory alloy (SMA) fibers is subject to the aerodynamic and thermal loading in the supersonic region. The nonlinear finite element equations based on the first-order shear deformation plate theory (FSDT) are formulated for the laminated composite plate embedded with SMA fibers (SMA composite plate). The von Karman strain–displacement relation is used to account for the large deflection. The incremental method considering the influence of the initial deflections and initial stresses is adopted for the temperature-dependent material properties of SMA fibers and composite matrix. The first-order piston theory is used for modeling aerodynamic loads. This study shows the effect of the SMA on the critical temperature, thermal post-buckling deflection, natural frequency and critical dynamic pressure of the SMA composite plate.     

Vibration characteristics of SMA composite beams with different boundary conditions

Recently, the development of shape memory alloy (SMA) actuators, in the forms of wire, thin film and stent have been found increasingly in the fields of materials science and smart structures and engineering. The increase in attraction for using these materials is due to their many unique materials, mechanical, thermal and thermal-mechanical properties, which in turn, evolve their subsequent shape memory, pseudo-elasticity and super-elasticity properties. In this paper, a common type of SMA actuator, Nitinol wires, were embedded into advanced composite structures to modulate the structural dynamic responses, in terms of natural frequency and damping ratio by using its shape memory and pseudo-elastic properties. A simple theoretical model is introduced to estimate the natural frequency of the structures before and after actuating the embedded SMA wires. The damping ratios of different SMA composite beams were measured through experimental approaches. The natural frequencies changed slightly at a temperature above the austenite finish temperature of composite beams with embedded non-prestrained SMA wires. However, the increase of the natural frequencies of the beams with embedded prestrained SMA wires were found in both the theoretical prediction and experimental measurements. The damping ratios of SMA composite beams increased with increasing the temperature of the embedded wires with and without being pre-strained. Compressive and local failures of the beams with high wire content are a possible explanation.     

Modulated interaction in double-layer shape memory-based micro-designed actuators

The effect of superposed transitions in actuators with layered shape memory alloy (SMA) films undergoing martensitic phase transformation is analyzed in terms of a model developed for two layers of different composition, deposited at the same temperature on a substrate. A significant difference is observed in the actuation versus temperature relationship, depending on the thermal and elastic properties of the SMA layers and their martensitic transformation temperature. The prediction of the actuation is exemplified using a multilayer model and is verified for a cantilever actuator with NiTi and NiMnGa layers deposited on a Si substrate. The model sets the ground for a smart selection of SMAs in order to achieve a modulated actuation.     

Modulated interaction in double-layer shape memory-based micro-designed actuators

Abstract

The effect of superposed transitions in actuators with layered shape memory alloy (SMA) films undergoing martensitic phase transformation is analyzed in terms of a model developed for two layers of different composition, deposited at the same temperature on a substrate. A significant difference is observed in the actuation versus temperature relationship, depending on the thermal and elastic properties of the SMA layers and their martensitic transformation temperature. The prediction of the actuation is exemplified using a multilayer model and is verified for a cantilever actuator with NiTi and NiMnGa layers deposited on a Si substrate. The model sets the ground for a smart selection of SMAs in order to achieve a modulated actuation.