碳纳米管应变传感器的性能分析：实验偏振模式的影响机制

碳纳米管作为一种拉曼力学传感介质具有优异的力学性质及共振、偏振拉曼特性。将碳纳米管散布在基体材料中,即可实现局部应力/应变的测量。受到光学衍射极限的限制,常规的远场拉曼光谱得到的是一定区域内众多碳管的平均散射信息。本文综合考虑了采样点内各方向碳管的影响,并对碳管散射的共振状态、碳管的分布状态、拉曼系统的偏振构型及偏振方向等实验因素对碳纳米管应变传感器性能的影响进行了深入分析,采用分峰和重构的方法定量地给出了不同实验模式下采样点内的拉曼信息组成以及各种实验模式的测量精度。分析和对比表明,采用双偏振构型且偏振方向沿荷载施加方向时的测量精度最高,即最优的实验模式。     

微纳米尺度效应作用下充流微通道系统波动特性研究

结合非局部弹性应力/应变梯度耦合本构关系和流体非局部应力关系式,基于Euler梁理论,建立了充流微通道流固耦合波传导模型;根据耦合固体非局部应力/应变梯度弹性效应以及流体非局部效应,分别模拟了微通道和管腔内流体的尺度效应,推导得出了充流微通道在微纳米尺度的波动控制方程和边界条件。通过对控制方程的求解,分析了不同类型尺度效应对微通道的波动和振动特性的影响。结果显示,各类尺度效应对系统的动力学特性影响不同。微通道非局部弹性效应对波动产生阻尼,特别是对波长较短的波传导;而应变梯度弹性效应对波传导有促进作用,且该效应对波动的影响与波长无关;非局部效应和应变梯度效应对微通道刚度产生不同影响,非局部效应降低刚度,应变梯度效应增加刚度。     

碳纳米管纤维及其传感器力电性能实验研究

基于UTM T150微纳米力学测试系统搭建了纤维力电耦合测试平台,并对碳纳米管纤维进行了多组力电耦合作用下的拉伸性能实验研究。通过观察分析碳纳米管纤维的电阻-应变曲线,发现其电阻变化与应变大小密切相关,随着应变的不断变大,碳纳米管纤维的电阻也在逐渐增加。基于此,设计制作了碳纳米管纤维柔性应变传感器,并将其贴在标准试件上分别进行了弯曲变形测试、单次/循环加载性能测试以及标定实验。结果表明:当对试件进行加载时,碳纳米管纤维柔性应变传感器的电阻会随着载荷的增大而增大;当载荷逐渐消失时,其电阻会逐渐减小直至回归初始电阻值附近。这表明碳纳米管纤维具备优异的电学与力学特性,并且利用它所制作的柔性应变传感器也有着较好的灵敏度与稳定性。     

用于光谱力学分析的显微拉曼外光路子系统

显微拉曼光谱法是一种无损非接触的微尺度实验力学技术。本文设计研制了可用于空间任意几何和偏振构型下力学测量的显微拉曼外光路子系统,用以开展复杂载荷环境下应力/应变的原位、在线测量。该外光路子系统采用观察光路与信号光路同轴设计,并基于笼式光机组件搭建光路。为标定、验证系统的性能与可靠性,本文采用所研制的外光路系统开展了Kevlar 29纤维的拉伸实验和单晶硅的围压实验。实验结果表明,将外光路子系统用于光谱力学测量能够给出与商用系统性能一致的测量结果、精度及可靠性,并能够用于获取商用系统无法给出的几何与偏振构型下的光谱信息,从而实现复杂环境、载荷、应力状态下的光谱力学精细测量。     

基于光纤光栅传感器的玻璃纤维复合材料层间应变测试的实验分析

通过对内埋未封装光纤光栅传感器(Fiber Bragg Grating,FBG)的玻璃纤维增强复合材料进行力学实验分析,得到不同试件层间的应变曲线与试件断面的微观截面图.探讨了玻璃纤维复合材料固化过程中温度和压力对FBG传感器的传感性能的影响,深入分析了FBG传感器与玻璃纤维复合材料的融合度以及弯曲实验中FBG传感器检测精度.在试件三点弯曲实验中,与传统电测方法不同,应用新型未封装FBG传感器进行复合材料的层间应变测量,得到的层间应变与载荷数据,拟合直线的线性相关系数均在0.99以上,并且传感器在监测不同试件同一层的层间应变的相对误差不超过5％.为应用FBG传感器检测实际的复合材料构件内部应变以及形成FBG传感网络损伤监测系统提供了实验基础.     

实验力学最新进展——————2008国际实验力学会议概况

介绍了2008国际实验力学会议的基本情况.大会报告内容涉及数字图像相关测量、激光干涉测量、光栅应变传感技术、非制冷型红外探测技术等当今实验力学的热点研究领域,以及其它科学领域的发展对实验力学带来的挑战和机遇,尤其是微纳米和多尺度力学问题的研究给实验力学提出的诸多具有挑战性的研究课题.分会场邀请报告和交流论文也充分展示了实验力学各个研究领域的最新研究成果和发展动向.      

1-3型OPCM应变传感元件的传感机理研究

本构造了正交异性压电复合材料（OPCM）应变传感元件。从理论上推导了OPCM传感元件检测平面应变场中任意方向应变的力-电耦合方程,用实验手段对OPCM元件的压电正交异性效应进行了验证。实验证明仅当压电相的极化方向与元件的受力面平行时,OPCM元件具备压电正交异性之特性。     

微尺度散斑制备方法研究及应用进展评价

数字图像相关法(DIC)由于具有非接触、全场、精度高、易操作等特点,已被广泛应用于宏微观尺度的变形测量。在微观尺度,DIC可以方便地与显微镜结合,实现变形测量;散斑作为变形的载体,其质量的好坏直接影响到DIC在微尺度变形测量的精度。本文重点介绍了离心甩胶法制备微尺度散斑的方法,并对其应用进展进行评价。具体包括:优化制备工艺参数,获得最优的散斑图;提出散斑膜转移方法,扩大其使用范围;研究散斑膜增韧方法,用于大变形的测量;基于超景深光学显微镜,设计双向加载测试系统;将散斑膜应用于微尺度界面、裂纹尖端等。获得了局部变形场信息,表明该微尺度散斑制备方法具有较好的可行性和应用前景。     

锗硅缓冲双轴应变硅材料ε-Si/Ge_(0.3)Si_(0.7)/Ge_xSi_(1-x)/C-Si内部残余应力的显微拉曼实验分析

应变硅技术是一种被称为延续摩尔定律的技术,是集成微电子技术的热点之一。本文以锗硅缓冲双轴应变硅材料(ε-Si/Ge_(0.3)Si_(0.7)/Ge_xSi_(1-x)/C-Si)为研究对象,采用显微拉曼光谱技术,开展了该多层半导体异质结构内部残余应力的实验力学分析。这是面向多层结构残余应力与表/界面力学行为的多尺度实验力学分析,本文首先简述了该应变硅的制造工艺和超低粗糙度横截面样品的加工方法,并推导了针对锗硅合金拉曼-力学测量修正关系,进而对应变硅样品的表面和横截面进行了显微拉曼力学测量实验,给出了多层异质结构内部的残余应力分布,并以此为基础讨论了多层界面的力学行为。     

一种基于压电扫描的新型微梁阵列免疫传感器

微梁免疫传感技术是在原子力显微镜和微机电系统基础上发展起来的一项新兴传感技术,具有检测灵敏度高、无需标记、能实时原位再现生化反应过程等优点。本文针对单梁传感系统中存在的环境扰动和不能多通道检测等问题进行改进,设计制作了一种基于压电扫描的新型微梁阵列免疫传感器。利用商品化微梁阵列对传感器进行了温度测试实验,所得信号曲线稳定一致,且检测灵敏度达到2nm,实验结果验证了该微梁阵列传感系统在多通道信号检测中的可行性,为微梁阵列生化传感技术的实现提供了一种新的方案。     

基于神经网络与光纤传感阵列的结构状态监测方法

以探测机敏复合材料与结构内应变、应力及损伤等物理状态的位置信息为目的．提出了一种新颖的可内埋于材料与结构内作为结构状态监测用的强度调制型光纤传感阵列网络，并采用人工神经网络来处理传感阵列输出的并行分布式传感信号，阐述了适用的Ｋｏｈｏｎｅｎ网模型及其变化形式，给出了仿真实验结果     

导电混凝土传感器的热变形与机敏性研究

摘要 本文设计了具有不同灵敏度的水泥基传感器。测试了传感器的热变形特征与机敏性规律。验证了传感器埋入混凝土进行结构变形检测的可行性。热膨胀系数测定实验发现：与传统认为的受热膨胀不同,添加了碳纳米管的传感器具有热胀-热缩特性。通过对比传感器单独加载与埋入混凝土中加载,发现了大掺量的碳纳米管传感器的压阻效应更易受到混凝土干缩应力的影响。在荷载作用下,传感器的压阻效应会发生变化：压缩应变导致导电填料间距减小致使传感器电阻率减小;微损伤的产生导致导电填料间距增大而致使传感器电阻率增大。两者的竞争机制形成了水泥基传感器压阻效应的非线性特征。本文根据实验结果和电子跃迁的隧道效应理论,建立了水泥基传感器的压阻模型。     

一种动光弹模型材料的制作方法及其应用

基于#618环氧树脂、甲基六氢苯酐、促进剂DMP-30、环氧树脂消泡剂四种原料,提出制作光弹性模型的新配方和新方法,并利用单轴压缩实验、电测法和动态光弹法分别测定了制作的光弹模型的动态力学参数。新方法工艺简单,制作周期短,对人体无害。制作的光弹模型初始应力小,表面光洁,质地均匀,透光性好,光学灵敏度高,具有良好的机械加工和切削性能。通过三点弯曲梁冲击实验,得到了清晰的光弹等差条纹图像,验证了该配方和方法制作的模型可以应用于动态光弹性实验。     

A statistical mechanics model of carbon nanotube macro-films

Carbon nanotube macro-films are two-dimensional films with micrometer thickness and centimeter by centimeter in-plane dimension. These carbon nanotube macroscopic assemblies have attracted significant attention from the material and mechanics communities recently because they can be easily handled and tailored to meet specific engineering needs. This paper reports the experimental methods on the preparation and characterization of single-walled carbon nanotube macro-films, and a statistical mechanics model on the deformation behavior of this material. This model provides a capability to optimize the synthesis process by comparing with the experiments.     

Multi-Scale Experiments and Interfacial Mechanical Modeling of Carbon Nanotube Fiber

The multi-scale deformation and interfacial mechanical behavior of carbon nanotube fibers with multi-level structures are investigated by experimental and theoretical methods. Multi-scale experiments including uniaxial tensile testing, in situ Raman spectroscopy, and scanning electron microscopy are conducted to measure the mechanical response of multi-level structures within the fiber under tension. A two-level interfacial mechanical model is then presented to analyze the interfacial bonding strength of mesoscopic bundles and microscopic nanotubes. The evolution characteristics of multi-scale deformation of the fiber are described based on experimental characterization and interfacial strength analysis. The strengthening mechanism of the fiber is further studied. Comprehensive analysis shows that the property of multi-level interfaces is a critical factor for the fiber strength and toughness. Finally, the method of improving the mechanical properties of fiber-based materials is discussed. The result can be used to guide multi-level interface engineering of carbon nanotube fibers and fiber-based composites to produce high performance materials.     

A DAMAGE MECHANICS MODEL FOR TWISTED CARBON NANOTUBE FIBERS

Carbon nanotube fibers can be fabricated by the chemical vapor deposition spinning process. They are promising for a wide range of applications such as the building blocks of high-performance composite materials and micro-electrochemical sensors. Mechanical twisting is an effective means of enhancing the mechanical properties of carbon nanotube fibers during fabrication or by post processing. However, the effects of twisting on the mechanical properties remain an unsolved issue. In this paper, we present a two-scale damage mechanics model to quantitatively investigate the effects of twisting on the mechanical properties of carbon nanotube fibers. The numerical results demonstrate that the developed damage mechanics model can effectively describe the elastic and the plastic-like behaviors of carbon nanotube fibers during the tension process. A definite range of twisting which can effectively enhance the mechanical properties of carbon nanotube fiber is given. The results can be used to guide the mechanical twisting of carbon nanotube fibers to improve their properties and help optimize the mechanical performance of carbon nanotube-based materials.     

On a “deterministic” explanation of the stochastic resonance phenomenon

The cantilevered carbon nanotube is a traditional model in the design of some precise nano-oscillators. The sensitivity that is denoted by the quality factor defined as the ratio of the energy stored to the energy dissipated by losses in the oscillator is an important index for the nano-oscillators. In this paper, the small mass impacting on the single-walled carbon nanotube is simplified as an impact load and the governing equation of the transverse oscillation for the nanotube is established firstly. Based on the structure-preserving idea, the generalized multi-symplectic formulations of the governing equation are constructed. The oscillation of the damping nanotube under the transverse impact load with different amplitudes is simulated after the small numerical dissipation and the good convergence of the scheme constructed is verified. From the numerical results, the effects of the induced tension and the energy dissipation are investigated. More importantly, the high precision and the feasibility of the numerical approach proposed in this paper for reproducing the energy dissipation in the carbon nanotube oscillator are illustrated, which gives a new way to investigate the properties of the carbon nanotube oscillators.     

Method for identifying elastoplastic properties of ground media by penetration of impactors

We combine physical and mathematical simulation of the processes of impact and penetration of cylindrical rods to develop a computational-experimental method for identifying strain and strength characteristics of ground media in a wide range of pressure. As a result, we determine the parameters of the equation of state under which it is guaranteed that the discrepancy between the experimental and theoretical results does not exceed the experiment error. The efficiency of this method is demonstrated by solving the problem of identifying the parameters of the sandy ground resistance to compression and shear under penetration speeds up to 1 km/s.