【作者】 付远；

【导师】 朱正吼；

【作者基本信息】 南昌大学 ， 材料学， 2014， 博士

【摘要】 应力传感器是目前工程及机械领域应用非常广泛的一类探测工程及机械结构在实际工作状态下受力安全性的重要器件，特别是在大型建筑，桥梁，隧道，运输管道等实际应用领域有着非常重要的作用。而探测结构的微应力指标又是我们评估材料的疲劳、寿命以及材料起始失效的一个非常重要的信息。本文基于柔性橡胶基体与非晶态合金应力敏感材料开发一种柔性应力敏感薄膜。本文首先分别以丁基橡胶和硅橡胶为复合力敏薄膜基体材料，以Fe73.5Cu1Nb3Si13.5B9纳米晶粉体和Fe73Si18B9非晶粉体作为应力敏感材料，通过机械共混以及精密铸压热成型分别制备了复合薄膜。然后较系统地研究了其内部的组织结构、理化特点、力敏特性、环境适应性、宏观及微观的应力分布及变形特性、薄膜的应力应变非线性本构关系以及应力敏感机理等。并通过薄膜的应力阻抗变化关系来表征其应力敏感特性。（1）研究了不同粉体含量的Fe73Si18B9非晶粉体/SiR柔性薄膜在压应力连续加载/卸载速度条件下的力敏特性。薄膜厚度200μm，Fe73Si18B9粉体粒度为300目，测试频率为1kHz。研究表明，薄膜在连续加载/卸载速度不大于0.1mm/min，测试频率1kHz、压应力0.03~1.0MPa时，具有良好的力敏稳定性和灵敏性。薄膜对于小于0.2MPa应力更加灵敏，在此应力范围内，薄膜中粉体含量增加，薄膜的力敏特性变化趋势相同，但薄膜的力敏敏感度增大。当薄膜中粉体含量为83.3wt%，压应力由0.03增大到0.2MPa时，在加载过程中薄膜的SI%由36.51%增大到82.48%，k值由42.91减小到1.889；当应力为0.2~0.7MPa时，粉体含量为83.3wt%薄膜的k值在1.889~0.6之间，应力继续增大至1MPa时，k值逐渐接近0。（2）研究了Fe73.5Cu1Nb3Si13.5B9纳米晶粉体/橡胶柔性薄膜的在连续加载/卸载条件下的力敏特性。对于Fe73.5Cu1Nb3Si13.5B9纳米晶粉体/SiR柔性薄膜，研究表明，薄膜粉体含量为35volwt%、厚度200μm的薄膜在测试频率1kHz下具有优异的力敏性能。复合薄膜在连续加载/卸载速度不大于0.5mm/min和保压加载/卸载条件下、测试频率1kHz、压应力0.2~1.0MPa时，复合薄膜具有良好的力敏稳定性和灵敏性。随着应力σ增大，阻抗Z呈非线性下降，SI%值6%~23%，灵敏精度k值2~0.2，测试标准偏差稳定在0.02~0.05，薄膜对于小于0.2Mpa应力更加灵敏；对于Fe73.5Cu1Nb3Si13.5B9纳米晶粉体/丁基橡胶柔性薄膜，研究表明，复合薄膜在v=0.1mm/min时，其稳定性最好，在加载过程中，应力灵敏精度|k|值随着应力的增大呈现先增大后减小的变化趋势，卸载过程中，k值随着应力的逐渐减小而增大。在1kHz测试频率下复合薄膜的力敏特性优于50kHz。相同测试条件下，厚度为200μm的复合薄膜的力敏特性略优于150μm。在39.5℃-80℃温度范围内，随着温度的升高复合薄膜的力敏特性越好。（3）本文通过有限元分析了薄膜在拉伸和压缩应力作用下相关的宏观和细观力学特征。研究表明，橡胶内部的应力分布在整个受力状态下都是均匀分布的，而刚性非晶纳米晶粉体内部的受力状态则是非均布的，存在局部应力集中的情况，这和粉体颗粒的形状、大小及所处的位置有关。对于薄膜的拉伸应力的变形情况，总体来说，在薄膜的受力端变形量最大，约束端位移最小，且呈现梯度减小的状态。（4）通过采用拉伸和压缩试验机对柔性薄膜的应力应变关系测量表明，薄膜可以等效为一个塑性元和一个粘性元的并联结构再与一个弹性元的串联而成的粘弹塑性体。在缓慢的低应力作用下，薄膜可以看成是一个纯弹性材料，当外应力达到屈服点时，开始发生塑性变形。同时在低速载荷下，材料的粘性可以忽略。本文采用米塞斯屈服对该类型薄膜进行了应力应变关系的探讨，提出了相应的本构关系。（5）在力敏机理研究方面，针对柔性薄膜的阻抗值Z及其分量L、C、和R以及不同时段的各分量的相位角θ频率特点分析，对前期关于铁基纳米晶粉体/橡胶柔性薄膜的等效电路模型进行了修正，得出了更为精确的理论计算结果。本文研究认为，柔性薄膜的应力阻抗效应的主导因素是由应力容抗效应起主导作用，而交流电阻、感抗等因素对应力阻抗效应的影响是次要的。本文将该电路模型中外在和次要的影响等效为一个交流电阻，而内在主要的影响因素等效为多电容元，两者组成一个串并联电路模型。铁基非晶粉体或纳米晶粉体/橡胶柔性薄膜具有耐候性好、力敏稳定性高，以及材料的形状、大小及厚度可控等优势，在接触应力测量传感器中具有很大的优越性，具有良好的应用前景。更多还原

【Abstract】 Stress sensor is an important kind of device which have wildly been used indetecting the safety of engineering and mechanical structure. Especially, stress sensorplays a significant role in some huge buildings, bridges, tunnels and pipeline transportetc. Moreover, tiny stress characteristic in structures is an important informationwhich helps us to appraise fatigue, life and initial failure of materials. In this paper, itis worked on developing a tiny stress sensitive composite film which is made ofIron-based amorphous powder and rubber.In this article, the matrix material of these composite stress sensitive films arebutyl rubber (IIR) and silicon rubber (SIR). Meanwhile, the reinforcing materials areamorphous Fe73.5Cu1Nb3Si13.5B9and Fe73Si18B9powders (Hereinafter referred to asFeCuNbSiB and FeSiB powder). Fe73Si18B9/SIR, Fe73.5Cu1Nb3Si13.5B9/SIR andFe73.5Cu1Nb3Si13.5B9/IIR (Hereinafter referred to as FeSiB/SIR, FeCuNbSiB/SIR andFeCuNbSiB/IIR composite films) composite films have been made by means ofmechanical blending and precision casting pressure heat molding. And wesystematically researched the organization structure, physicochemical properties,stress sensitive, environment applicability, macroscopic and microcosmic distributionstress sensitive of these films. And the stress sensitive property is represented bystress impedance effect.On the basis of preliminary study and the study of this article,it is summarized several conclusions:(1) The preporties of different powder content with Fe73Si18B9soft film havebeen researched, which is applied stress at continuous upload and offload. When thefilm thickness of200μm, the particle size of Fe73Si18B9powder is300mesh number,and testing frequency is1kHz. Research shows that, with the speed of continuousupload or offload below0.1mm/min, testing frequency at1kHz and pressue at0.03~1MPa, the film is of a nice stability and sensitivity. The film is more sensitivewith pressure below0.2MPa. In this pressure range, with the powder contentincreased, the tendency of stress sensitive is indential. But the sensitive is increased.When the content of powder increased to83.3wt%, and pressure increased from0.03 to0.2MPa, the SI%value is from36.51%increase to82.48%. And the value of k isreduced from42.91to1.889. When pressure from0.2~0.7MPa, and the content ofpowder is83.3wt%, the value of k is from1.889~0.6. When pressure increased to1MPa, the value of k reduced approach to0.(2) The properties of Fe73.5Cu1Nb3Si13.5B9nanocrystalline powder/rubber softfilm. For the Fe73.5Cu1Nb3Si13.5B9/SIR soft film also have been researched, resultshows that, when the content of powder is35volwt%the thickness of film is200μm,and testing frequency is1kHz the film is of nice stress sensitive property. With thespeed of continuous upload or offload below0.5mm/min, testing frequency at1kHzand pressue at0.2~1MPa, the film is of a nice stability and sensitivity. With theincrease of pressure σ, the value of impedance Z reduced nonlinear, and the value ofSI%is from6%to23%,the sensitive value k is2~0.2, The standard deviation isbetween0.02~0.05. Film is more sensitive with stress below0.2MPa. But forFe73.5Cu1Nb3Si13.5B9/IIR soft film, the result shows that stability is better with stressloaded speed at v=0.1mm/min. When the process of upload, the sensitive value of kincreased in the beginning and reduced in the end. When offload, the value of kincreased with stress reduced. The sensitive property is better with frequency at1kHzthan50kHz. In the same testing conidion, the thickness of composite is better at200μm than150μm. The temperature between39.5℃and80℃, stress sensitiveproperty is increased with temperature increased.(3) Numerical simulation about this film have been done by means of ANSYSsoftware. It is mainly worked on the stress and deformation process of micro andmacro aspects. By the analysis, it is drawn two conclusions: Firstly, the contact ofamorphous powder and rubber can regard as soft contact. The stress distribution inflexible rubber is uniformly distributed and in rigid powder is not so. Stressconcentration phenomenon have appeared in rigid powder, which may be induced bythe dimensions, shapes and positions of amorphous powder. Secondly, Aboutdeformation of stretching process, general speaking, the mechanical side is muchbigger than constraint side, and deformation is gradient decreases between these twosides.(4) Stress-strain relationship of this film is measures by means of tensile testing machine and compression testing machine. The stress-strain behavior of thiscomposite film is a typical viscoelastoplastic material. We regard it as a plasticelement, a cohesive unit and an elastic element which combined together. It can beseen as a pure elastic material with slowly and tiny stress. While the stress up to itsyield point, plastic deformation appears. The property of cohesive can be ignoredwith low velocity loading. In this paper, we also discussed about the stress-strainrelationship of this composite film by Mises yield theory, and get its constitutiverelation.(5)In aspects of stress sensitive mechanism: In the base of preliminary study, theindependence value Z and its components L, C, R and phase angle θ have been tested.These kind of film appears stress-capacitive reactance and stress-impedanceproperties with high frequency alternating current testing. We also have modified theequivalent circuit model, and attached a more accurate calculated results. This articlesuggests that, the leading function of stress-impedance effect about the compositefilm is stress-capacitive reactance effect. The other aspects such as ICR, inductivereactance, and magnetoelectriceffects lead a secondary role. The equivalent circuitmodel renewed can equivalent as an ICR and multi-capacitance series connection.Since, Iron-based amorphous powder enhanced and rubber matrix compositefilms have some unique superiority, which include good weathering resistance, highlystability, excellent repeatability, and advantages on good controls of shapes, thicknessand size of material. It will hopefully to be widely used in tiny stress sensor area.更多还原