PVDF压电计的动态响应特性及其在橡胶材料SHPB实验中的应用

通过夹心式PVDF(Polyvinylide Fluoride)压电计的动态分离式Hopkinson压杆(SHPB)标定实验,系统地讨论了传感器的动态响应特性,其中包括测量电路、PVDF表面应力集中、压电计的材料及结构特性和同一压电计受多次撞击对测试信号的影响,为PVDF压电计的制作工艺研究提供参考。利用标定好的压电计测试了橡胶材料在SHPB实验中的动态应力均匀过程。结果表明:调节并联电阻值可以提高压电计的传感精度;增大压电计的敏感面积可以减小因应力集中所造成的信号失真;材料的热粘塑性性质、摩擦效应等将使信号振荡幅度偏小;多次撞击对信号的加载与卸载段都将产生影响,但当传感器表面未发生明显损伤时,测试的应力平台平均值与真实信号近似相同。     

基于PVDF的膝关节控制肌群运动信息采集传感器研究

针对膝关节运动过程中控制肌群的运动信息的采集问题,文章设计了多种PVDF压电传感器的悬臂悬臂梁结构,利用传感器采集到的压电信息获取控制肌群的运动信息,并通过软件建模仿真和实验对比测试找到了最优悬臂梁结构设计为圆形简支悬臂梁结构,同时测试了传感器的性能;测试结果显示设计的PVDF压电传感器表现优越,可用于实际的信息采集。     

加速度传感器动态校准系统不确定度评估方法的研究

针对加速度传感器动态校准获取其工作频带的过程中,因校准系统存在测试不确定度导致传感器校准不准确的问题,设计了某型号加速度传感器的动态校准试验,以试验数据为依据提出了系统不确定度评估方法。通过对冲击试验台为冲击激励源构成的动态校准系统测试过程中几个主要误差源的分析,结合文中提出的系统不确定度评估方法计算出校准系统的测试标准不确定为1.77%,扩展不确定度为3.54%。对比测量仪器特性评定相关指标可知该校准系统符合工程校准需要,而该评估方法的提出对校准系统的不确定度评估有一定的现实指导意义。     

利用PVDF传感器检测激光超声的实验研究

简要介绍了激光超声技术以及声表面波的基本特点、激光超声产生和接收的基本原理及激光超声技术的应用。概述了聚偏二氟乙烯（PVDF）压电薄膜材料的结构、性质和应用，以及薄膜压电性产生的机理。对PVDF换能器的设计思路和实验方法进行了简单讨论。具体实验采用脉冲激光器激发声表面波，利用PVDF传感器接收实验信号，调试实验信号，得出波形，并对实验现象作出初步分析。证实了该实验装置应用于激光超声无损检测的可行性与可靠性。     

基于微结构光纤和游标效应的高灵敏度压力传感器

结构健康监测、医疗诊断分析、气压检测以及军事工程应用等领域对压力的高灵敏度探测要求越来越高。光纤传感器由于其体积小、灵敏度高及抗电磁干扰等优点被广泛应用于压力测量。针对石英材料的杨氏模量较高,传统实芯光纤压力传感器的受压变形量较小,导致测量灵敏度很难提高。文章提出了一种基于游标效应的双Sagnac干涉环式光纤压力传感器。传感器由保偏光子晶体光纤(Polarization Maintaining Fiber, PM-PCF)作为敏感单元实现Sagnac干涉并通过不同PCF长度实现针对压力增敏特性的游标效应。传感器分别采用在单模光纤中嵌入PM-PCF形成传感器的参考单元和压力敏感单元,并对Sagnac环的感压部分进行封装,通过实验对并联型Sagnac环压力传感器的压力特性进行研究。实验结果表明在压力范围为0～2.4MPa内,压力传感器最大灵敏度为-54.491nm/MPa,分辨率为0.367kPa。相比无游标效应的Sagnac环压力传感器,其压力灵敏度放大了16.7倍。此外,传感器具有制造简单、结构坚固、运行稳定的优点,为高灵敏度压力传感器提供了一种替代设计方案。     

耦合型光纤振动传感器实验研究

根据单模光纤耦合器的耦合比对耦合区长度变化敏感的特点,提出了一种耦合型光纤振动传感器,并设计了相应的解调系统对传感器的响应进行光电转换和信号处理.进行了静态和动态测试并给出了传感器在振动和冲击激励下的响应曲线,实验结果和压电传感器的测量结果相吻合.结果表明,耦合型光纤振动传感器不仅满足振动测量的要求,而且具有测量准确度高,制作简单,成本较低等优点.     

Hugoniot实验的粒子速度测量不确定度分析

 不确定度评定是Hugoniot实验的一项重要工作,针对飞片撞击法和对比法两类主要Hugoniot实验进行了粒子速度的测量不确定度分析。根据直接测量量和间接输入量及其不确定度,用不确定度传递律表述了粒子速度的不确定度,并给出了冲击压强（p）、压缩密度（ρ）和压缩比容（v）的评定方法。对于样品和基板为不同材料的非对称碰撞及对比法实验,不确定度评定除A类评定外还应包括B类评定,应考虑用Hugoniot镜像线近似二次冲击绝热线或卸载线而导入的不确定度。在Hugoniot实验中应尽量避免涉及B类评定的其它因素,如同种材料初始密度的显著差异、飞片击靶前的温升等情况。     

基于分布式体积速度传感的结构声辐射有源控制实验研究

以简支矩形薄板为研究对象,首先在波数域内对结构振动体积速度与辐射声功率的关系进行分析,推导出反映结构模态对体积速度贡献规律的数学表达式。在此基础上,结合PVDF (Polyvinylidene Fluoride)压电薄膜的电荷输出方程,利用三角函数的正交性,给出一种方法来设计体积速度传感器,并针对具体模型进行了结构体积速度测量实验。结果表明,所设计的分布式体积速度传感器具有较好的传感精度。在此基础上,利用所设计的传感器进行了结构声辐射有源控制实验研究,分别针对单频和带宽信号激励情况下的有源控制实验取得了满意的控制效果,从而验证了本文PVDF体积速度传感器设计方法的正确性以及通过PVDF膜传感结构声辐射并作为误差传感器进行有源控制的有效性。      

不确定度表示的进展和在测量中的应用

本介绍了不确定的有关概念、名词术语，给出了不确定度A类分量、B类分量和展伸不确定度的表达式。说明了不确定度在高校实验教学中的应用，列举了不确定度在实验中应用实例。     

PB-1型窄脉冲压电薄膜可逆式换能器

本文著者研制成PB-1型PVDF可逆式压电换能器。它的通频带较宽,中心频率500—900KHz,通带Q值1.5,发送电压响应[级]148.9dB(re:1μPa/V),灵敏度-210dB(re:1V/μPa)。在水中声脉冲持续时间7—10μs,并有足够的声功率输出,电声效率约10％。 本文介绍了该换能器的结构、理论分析、测量结果及应用效果。证明了理论与实验的一致性。可供电声、水声、超声等其它PVDF传感器设计时参考。     

Membranes of Poly (Vinyl Butyral) (PVB) or Cationic PVB (CPVB) Blended with Poly (Vinylidene Fluoride) (PVDF) Prepared by a Nonsolvent Induced Phase Separation Method: Miscibility and Hydrophilicity

The synthesized hydrophilic polymers [poly (vinyl butyral) (PVB) and cationic PVB (CPVB)] blended with poly (vinylidene fluoride) (PVDF) were used to fabricate hydrophilic ultrafiltration membranes. A visual inspection method and a glass transition temperature method were applied to study the miscibility of PVDF/PVB and PVDF/CPVB blend systems. The results showed that the PVDF/PVB was an immiscible blend and the PVDF/CPVB was a partially miscible blend. Dynamic contact angle experiments showed that the hydrophilicity of the blend membranes was significantly improved with the addition of PVB and CPVB. The pure water permeation (PWP) of blend membranes increased with the content of PVB and CPVB.     

冲击波压缩PVDF膜的电响应研究

 应用冲击加载技术,研究了PVDF膜在与其极化矢量方向平行的冲击波压缩下的冲击电响应。通过实验和数值模拟得到了PVDF释放电荷q(t)与冲击波压力p(t),给出了峰值电荷q_max与峰值压力p_max的关系,建立了PVDF膜的冲击电响应的理论模型及数值模拟方法。     

基于PVDF传感器的单脉冲激光推力加载过程研究

 利用高频响应材料PVDF作为敏感元件，建立了一套单脉冲瞬态推力测试系统，并用37 mm分离式Hopkinson压杆装置对该测试系统进行动态标定。标定结果显示，在0~150 MPa范围内，PVDF传感器（5 mm×5 mm）的压电特性呈线性，动态压电系数经线性拟合后为20 pC/N。用所建推力测试系统获得了单脉冲激光作用下，旋转抛物形激光推力器的推力加载曲线，并对该曲线形成多个峰值的原因进行了分析。实验结果表明，该系统可以捕获激光推力器脉冲推力加载特征。     

Effect of TiO2 nanoparticle size on the performance of PVDF membrane

The comparison of the performance and morphology was carried out between neat PVDF membrane and PVDF composite membranes with nanosized TiO₂ particles of different size. The results of permeability and instrumental analysis illustrated that nanometer size obviously affected the performance and structure of the PVDF membranes. The smaller nanoparticles could improve the antifouling property of the PVDF membrane more remarkably. The surface and cross-section of the membranes were observed with an atomic force microscopy (AFM), a scanning electron microscope (SEM). The TiO₂/PVDF membrane with smaller nanoparticles had smaller mean pore size on its surface and more apertures inside the membrane. X-ray diffraction (XRD) experiments also suggested that smaller TiO₂ nanoparticles had stronger effect on the crystallization of PVDF molecules.     

Giant permittivity of three phase polymer nanocomposites obtained by modifying hybrid nanofillers with polyvinylpyrrolidone

In this work, the combination of graphene decorated with graphene quantum dots (G-D-GQDs) and barium titanate (BaTiO₃) nanoparticles filled poly (vinyledene fluoride) (PVDF) nanocomposites are prepared using solvent casting method. The modification of G-D-GQDs and BaTiO₃ nanoparticles with polyvinyl pyrrolidone (PVP) show finer dispersion in PVDF matrix as compared to unmodified G-D-GQDs and BaTiO₃ nanoparticles in PVDF matrix. XRD of PVDF nanocomposites shows the formation of α and β form of PVDF crystals. The incorporation of the combination of PVP modified BaTiO₃ nanoparticles and G-D-GQDs in PVDF matrix show a decrease in crystallization temperature (T_c), percent crystallinity (X_c) and increase in thermal stability as compared to unmodified PVDF/BaTiO₃/G-D-GQDs nanocomposites, due to interaction of PVP modified nanoparticles with PVDF. Further, the incorporation of the combination of 20 wt.% BaTiO₃ nanoparticles and 3 wt.% G-D-GQDs in PVDF matrix show a giant dielectric constant. The giant dielectric constant is achieved due to accumulation of more charges across conductor-insulator interface, more numbers of microcapacitor formed and enhanced interfacial compatibility between BaTiO₃/G-D-GQDs with PVDF through PVP. The loss tangent (tan δ) of PVP modified G-D-GQDs and BaTiO₃ nanoparticles and its PVDF nanocomposites is low due to lower leakage current, which make the material suitable for various applications.     

中频小型矢量水听器设计研究

中频小型同振式矢量水听器采用低密度复合材料作为矢量通道外壳、压电加速度计作为内部振动传感器，以拾取水下声场中的矢量信息。与以往同振式矢量水听器设计不同的是每个矢量通道中只放置一只压电加速度计，这样，不仅减小了矢量水听器的体积，降低了水听器的整体平均密度，而且消除了以往同振式矢量水听器设计中矢量通道采用两只配对传感器而引起的相位不一致给矢量水听器定向带来的影响。而声压通道采用PVDF压电薄膜作为敏感元件，以拾取水下声场中的标量信息。     

Preparation of Symmetric Network PVDF Membranes for Protein Adsorption via Vapor-Induced Phase Separation

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor-induced phase separation from a PVDF/N,N-dimethylacetamide (DMAc)/water system. The effects of evaporation atmosphere, temperature, and humidity during the preparation of the membranes on their morphologies were investigated by scanning electron microscope (SEM). With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane formation process, and the casting solution formed membranes with symmetric morphologies in the vapor phase containing 0.79% DMAc. The effect of additives on the membrane structure and performance was also investigated. The results of adsorption experiments showed that the binding capacity of bovine serum albumin (BSA) increased with the appearance of a circular network morphology and the decrease of mean pore size of the membrane. With the addition of LiCl to the casting solution, the obtained membrane can adsorb BSA up to 150 μg/cm². Proteins on sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis gels were successfully electro-blotted onto these PVDF membranes. Compared with commercial membranes, the PVDF membranes prepared in this work were more suitable for protein blotting.     

An Atomic Force Microscopy Observation of Poly(Vinylidene Fluoride) Banded Spherulites

We examined the free surface of a banded spherulite of poly (vinylidene fluoride) (PVDF) by atomic force microscopy. The directions of the slope of multilayer terraces of lamellar crystals are retained in each half of a banded spherulite; this evidence confirms the macroscopic selection of one-handedness in the formation of spiral terraces in each growth direction of the sheaf at the center of banded spherulite of PVDF. In a previous paper, it was confirmed that the three-dimensional morphology of all single crystals of PVDF grown from the melt is of chair-type, and hence, it is most probable that the stress in the chair crystal is responsible for the formation of spiral dislocations and terraces keeping the same handedness in each growth direction. The chair-type morphology is created because of the chain tilting to the fold surface, which can introduce symmetry breaking and, consequently, the selection of handedness in nonchiral polymers such as PVDF.