PVDF压电薄膜在应力波测量中的应用

综合介绍了PVDF压力传感器的测试原理、动态标定实验，并采用定制的PVDF压力传感器测量了不同类型分层介质在冲击载荷作用下的压力衰减，说明了PVDF压力传感器在压力测量中有着很好的前景．     

PVDF压力传感器的冲击压电特性研究

PVDF薄膜是一种新型的聚合物压电材料.为了研究PVDF薄膜在低压和一维应变下的压电特性,利用立式Hopkinson压杆和一级轻气炮标定了自研制PVDF压力传感器的压电曲线,实验表明该应力传感器频响高,波形稳定,线性度良好,拟合灵敏度系数K值在0～20MPa和100～450MPa压力范围分别为14.96pC/N和11.9pC/N,可以基本满足动态冲击应力测试的要求.但由于PVDF薄膜的系数K受多方面的影响,定量分析有相当难度,建议使用跟实际工作状况相近的标定K值.     

基于PVDF复合压电效应的低强度冲击波柔性测量

为探索低强度冲击波的柔性测量技术,对PVDF(polyvinylidene fluoride)压力传感器开展冲击波加载和灵敏度标定实验,评估其低强度冲击波压力测量的可靠性。基于微结构设计改进薄膜传感器,获得适用于低强度冲击波压力测量的高灵敏柔性传感器,结果表明:单一压电工作模式的薄膜传感器测量低强度冲击波时有效输出电荷量和信噪比较低,测量结果容易受压电膜力电响应非线性、结构表面变形振动以及封装因素的影响,灵敏度系数不稳定、个体差异性大。采用周向固支的微结构设计能够将作用于薄膜传感器表面幅值较低的冲击波转换为幅值较高的面内拉应力,产生的复合压电效应可大幅提高传感器名义灵敏度系数、降低个体差异性。研制的柔性传感器在0.2～0.7 MPa压力范围内名义灵敏度约900～1 350 pC/N,相对测量误差不大于±13%。     

混凝土结构内冲击波应力传感器设计及其行为

为测量混凝土结构内的冲击波应力,研制了PVDF压力传感器;介绍了传感器的原理和设计思想,通过传感器的标定试验,得出传感器与混凝土介质匹配性能稳定,通过修正传感器灵敏度或采用将传感器打入包体标定的方法可减小应力测量误差;最后介绍了传感器在混凝土结构内药包爆炸应力波测试中的应用。     

硅集成式压力传感器设计和使用中的几个主要技术问题

本文根据测量爆炸冲击波中对测压传感器的要求,提出高频动态硅集成式压力传感器结构及封装方式。在对动态试验的记录波形进行分析比较中,发现高频硅集成式压力传感器桥臂电阻阻值对记录波形响应的影响。进而对桥臂电阻阻值参数的选择提出见解。文中还叙述了传感器安装条件和为消除在化爆中观测到的干扰波形而对传感器结构做的改进。     

石英压力传感器

最近,我们研制了一种压电式的石英压力传感器.由于在结构上作了较大改进,传感器的线性好、自振频率高、灵敏度稳定.本传感器可以用来进行气体和液体介质中600个大气压以下的各种动态和准静态压力测量,也可以用 ...     

关于压力传感器动态测试和标定中的两个疑点澄清

在动态压力测量技术中,总是首先关心传感器的波形质量和它的灵敏度。这是有关测量真实性和保证测量精度的两个重要问题。 目前存在两种不全面的看法:一是测得的压力波形不合理想,统归咎于传感器质量不佳;二是由于激波管标定所得灵敏     

PVDF应力测试技术及其在多孔材料爆炸冲击实验中的应用

通过精确测量Hopkinson杆子弹速度,实现了对PVDF压力传感器的动态标定,测试数据线性度良好,误差不超过1.9%,得到动态灵敏度系数K=32.83 pC/N,采用500 g TNT对“钢板-泡沫铝-钢板”复合结构进行爆炸冲击加载,测量结构间应力波的传播情况。研究结果表明:电压测试信号可以较为准确地反映弹性波与塑性波的加载时间和传播速度,PVDF对弹性应力波段高频信号的动态响应灵敏准确,与理论数据的相对误差为3.5%。测得泡沫铝材料中塑性波的传播速度为590 m/s,A₁-B₁界面塑性波透射系数达到了0.53,远高于弹性波透射系数。从机理上对应力时程曲线中出现的特殊现象进行了阐述,为相关爆炸测试提供参考。     

静态法测定金属材料杨氏模量的探讨

用机械式仪器测量E和θ_(0.2)的传统静态法,技术要求高,费时且精度不够理想。要提高静态法的精度,关键在于改进测量变形的方法。我校研制的电阻式弓形变形传感器,自1975年以来反复使用证明,灵敏度和精确度高,稳定性好、使用方便。我们用这种传感器和载荷传感器,通过一般万能试验机、动态应变仪和函数记录仪,对十     

PVDF在动态应变测量中的应用

研究了用PVDF压电薄膜进行动态应变测量的原理和方法,在单向应变块上对两种PVDF应变片的应变电荷常数进行了标定,并对一维应力杆中的应变波形进行了测量。实验给出了较好的测量精度。研究结果表明,PVDF应变片在动态应变测量中具有很好的应用潜力。     

Development of a PVDF sensor array for measurement of the impulsive pressure generated by cavitation bubble collapse

To study the impulsive pressure generated by cavitation bubble collapse, a PVDF piezoelectric array of pressure sensors is developed. The sensor array is fabricated directly on a 25 μm thick aluminum-metalized polarized PVDF film using a laser micro-machining technique. Dynamic calibration of the sensor array is accomplished in a gas shock tube. The average response time of the PVDF sensors to the fast-rising gas dynamic shock is found as fast as 31 ns. The array sensor is then attached on the solid boundary attacked by the collapse of the bubble. The features and the possible mechanisms of the impulsive pressure are discussed. The high sensitivity, low crosstalk, and low cost of the PVDF sensor array indicates its applicability in high amplitude impulsive field measurements.     

Development of an array of pressure sensors with PVDF film

 A new type of an array of pressure sensors, composed of PVDF (polyvinylidenefluoride), was devised and evaluated. In order to obtain the system transfer function of the PVDF system, a dynamic calibration was performed utilizing the signal from a 1/8 inch B&K microphone as input. The time history of the unsteady pressure was then reconstructed from the output of the sensor by using this transfer function. The reconstructed pressure signals showed good agreement with the reference signal in both temporal and spectral sense. This sensor was then used to measure the wall pressure fluctuations in a two-dimensional turbulent channel flow. Various statistical moments were obtained from the measurement data set. Comparison of these quantities with the existing studies demonstrated satisfactory agreement. These tests give credence to the relevance and reliability of this sensor for applications in more complicated turbulent flows. Received: 13 August 1996 / Accepted: 26 January 1998     

介质与静压对激波管校准压阻式绝压传感器动态特性的影响

激波管通常用于动态压力传感器的校准，压阻式绝压传感器在激波管校准过程当中，会出现谐振频率等动态性能指标随着激波管静态压力环境、气体介质变化而改变的情况，影响传感器动态特性的校准。基于压阻式传感器的工作原理，对传感器的敏感膜片结构进行了机理分析，建立了膜片结构与校准环境中介质和静压关系的动态模型；通过ANSYS与SIMULINK软件开展了数值模拟验证工作，模拟结果与理论推导一致。通过激波管校准实验验证了气体介质与静压的影响关系，结果表明:传感器的谐振频率与静压间存在非线性关系，并且随着敏感膜片径厚比的增大而显著增大；系统阻尼比大小与气体介质有关，随着气体密度的降低而升高；传感器的灵敏度与气体介质和静压无太大直接关系。在使用激波管校准压阻式绝压传感器时，应当考虑介质与静压参数对校准结果的影响。     

Design and modeling of an endoscopic piezoelectric tactile sensor

The paper presents a proof-of-concept design of a tactile sensor capable of measuring compliance of a contact tissue/sensed object. The main objective of this study is to design and model a piezoelectric sensor capable of measuring the total applied force on the sensed object as well as its compliance. The sensor consists of a rigid and compliant cylindrical element. Determination of the compliance of sensed objects is based on the ratio of force experienced by the rigid cylinder to the total force applied to the sensor. To obtain this force ratio, a circular PVDF film is sandwiched between rigid cylinder and plate to measure the force applied on the rigid element and a rectangular PVDF film is sandwiched between the two base plates to measure the total force applied on the sensor. The detailed design of the senor was performed using finite element analysis. A prototype was fabricated and tested and it has been shown that good agreement exists between the finite element results and experimental values. The proposed sensor exhibits high force sensitivity and good linearity and offers the potential for future miniaturization in order to be integrated with the commercial endoscope graspers used in minimally invasive surgery.     

Characteristics of impact-driven high-speed liquid jets in water

This paper describes a preliminary investigation of the characteristics of high-speed water jets injected into water from an orifice. The high-speed jets were generated by the impact of a projectile launched by a horizontal single-stage powder gun and submerged in a water test chamber. The ensuing impact-driven high-speed water jets in the water were visualized by the shadowgraph technique, and the images were recorded by a high-speed digital video camera. The processes following such jet injection into water, the jet-induced shock waves, shock wave propagation, the bubble behavior, bubble collapse-induced rebound shock waves and bubble cloud re-generation were observed. Peak over-pressures of about 24 and 35 GPa measured by a Polyvinylidence difluoride (PVDF) piezoelectric film pressure sensor were generated by the jet impingement and the bubble impingement, respectively. The peak over-pressure was found to decrease exponentially as the stand-off distance between the PVDF pressure sensor and the nozzle exit increases.