压电陶瓷需求日益增长

全球压电陶瓷销售额近 1 1 0亿美元 ,美国压电陶瓷销售额约 1 5亿美元。近年来压电陶瓷产品向小型化发展和性能更加稳定 ,促使市场对压电陶瓷的需求量迅猛增长。目前 ,新型的压电陶瓷传感器至少有 1 8～ 30种 ,可用于坐位控制的压力传感器。以汽车工业需求压电电陶瓷的数量最多 ,汽车工业越来越需要小型、廉价、灵敏度高和性能稳定的传感器 ,每辆新型小汽车压电陶瓷的用量就达 30片。加工工业、医疗卫生业、消费品制造业和发射、接收声波上都广泛使用压电陶瓷。例如 :石油、化学、食品和制药厂里用于非接触流量和水平监测和传感器、医学上图…     

声表面波传感器温度频率特性的数值分析

利用ANSYS软件对声表面波传感器进行温度频率特性的数值模拟研究。分析了在一定压力情况下,基于氮化铝压电薄膜铝叉指换能器的延迟型传感器结构内部的温度有限元分布情况。结果表明外界自然对流对传感器内部的温度场及应力场分布影响很小。并模拟计算出温度与输出串联谐振频率变化的关系,通过数据拟合得出,SAW传感器的输出谐振频率与环境温度变化呈良好的线性关系,因此可应用于温度的精确测试。     

声表面波传感器温度频率特性的数值分析

利用ANSYS软件对声表面波传感器进行温度频率特性的数值模拟研究。分析了在一定压力情况下,基于氮化铝压电薄膜铝叉指换能器的延迟型传感器结构内部的温度有限元分布情况。结果表明外界自然对流对传感器内部的温度场及应力场分布影响很小。并模拟计算出温度与输出串联谐振频率变化的关系,通过数据拟合得出,SAW传感器的输出谐振频率与环境温度变化呈良好的线性关系,因此可应用于温度的精确测试。     

锆钛酸铅陶瓷材料及压电振子的研究

本文讨论了锆钛酸铅(PZT)材料用作高频陶瓷滤波器压电振子的技术要求,论述了配方选择依据,着重讨论了某些氧化物:MnO_2,CeO_2及SrO等对性能的影响,确定了陶瓷体制备的适宜条件,研究了高频压电陶瓷滤波器振子制作工艺及影响振子特性的因素.实验结果表明,采用全电极极化,真空蒸发Cr-Ag点电极,选择点电极面积约为厚度值3～5倍时易获得具有较好频率特性的振子。点电极面积愈大,两侧点电极对称性愈好将有利于获得电压比高,输出功率大的振子.通过基波及谐波频率特性的比较,观察到一次谐波反谐振频率与基波反谐振频率的比值小于3,而它们的正谐振频率的比值大于3。这对利用谐波制作高频压电陶瓷滤波器具有特别重要的意义,因为上述结果为合理挑选振子,抑制基波,制作性能良好的高频谐波压电陶瓷滤波器提供了选择依据。     

具有检测功能的注射成型机

一种具有检测功能的注射成型机，包括一对模板及控制注射成型机工作的注射控制电器。两模板闭合时其间形成模穴供融化的塑胶注入，在模穴的底壁正中央位置设有一贯通的光纤收容孔；一光纤嵌设于光纤收容孔中，光纤的端面与光纤收容孔的开口平齐；一颜色识别传感器通过所述光纤发射检测光及接收检测光的反射光；一继电器与所述颜色识别传感器的控制信号发射端串联，     

环向偏角状态下超声内检测探头阵列声场模拟分析

压电超声内检测器检测含缺陷管道时，压电晶片加工、探头装配、管道几何结构不标准会导致探头与被检测管道处于环向偏转状态，对检测精度有显著干扰。基于超声内检测实验条件，采用COMSOL软件在0°～5°范围内建立环向偏角状态下的探头阵列声场有限元分析模型，研究环向偏角对声场特性的影响规律。结果表明：探头表面处声功率的模拟与实验数据最大偏差为1.54%，精度满足研究需求；随环向偏角增大，缺陷表面回波的声功率在0°～1°范围内锐减、在1°～5°范围内呈指数式递减；探头有效检测的临界环向偏角值为5.66°，大于工程上可能出现的最大偏角3.97°，该型检测器在工程应用时环向偏角不会导致检测盲区。     

压电陶瓷传感器监测混凝土内部缺陷的可行性研究

为监测在役混凝土结构在使用过程中的内部缺陷程度变化并定位缺陷位置,本文探索一种基于应力波的探测方法并进行试验研究,将压电传感器(PZT)以阵列形式安装在混凝土表面,将混凝土划分为不同区域,阵列中的一个传感器发射波,另一个传感器接收波,采用扫频模式和五峰值脉冲模式对混凝土不同区域进行监测。试验结果表明,当应力波通过待监测区域时,由于混凝土内部存在缺陷,应力波幅值衰减,波能降低。为了量化混凝土结构内部缺陷程度,构造基于接收信号的能量指数和损伤指数,并分别建立其与缺陷程度的函数关系,依据不同区域能量指数和损伤指数差异,确定混凝土内部缺陷存在的区域。试验结果与试件实际情况相吻合,验证了本文采用压电传感器监测混凝土内部缺陷的可行性。     

波导杆辅助声发射检测承压管道泄漏实验研究

在实验室将3根波导杆焊在实验用承压管道上,建立了声发射检测系统。通过对承压管道泄漏过程的声发射在线监测,分析了在不同压力、不同泄漏孔径情况下,波导杆上传感器所接收的信号幅度的规律,得出了波导杆可以应用于特殊工况下管道气体泄漏声发射检测的结论。     

基于1-3型压电单晶复合材料的高频宽带发射换能器

1-3型压电单晶复合材料结合弛豫铁电单晶与复合材料的优势,具有压电常数高、机电耦合系数极大、声阻抗低等特点,是理想的高频发射换能器压电元件.基于1-3型压电单晶复合材料设计并研制了高频宽带发射换能器,根据理论计算分析了压电单晶复合材料的性能特点,利用有限元建模仿真优化了换能器结构,研制的1-3型压电单晶复合材料发射换能...     

压电纤维复合材料能量采集仿真

采用多物理场仿真软件建立悬臂梁结构压电纤维复合材料仿真模型,研究了复合材料结构与性能参数对能量采集特性的影响及规律。研究表明:在相同宏观几何条件下,跟压电陶瓷相比,压电纤维复合材料能量采集装置的输出电压更高,且悬臂梁振动时的谐振频率更低,通过调节压电纤维尺寸和纤维含量可以调节输出电压和谐振频率。在固定复合材料尺寸情况下和恒定振动加速度条件下,压电纤维高度越小,压电纤维含量越低,聚合物基体弹性模量越小,则能量采集装置的输出电压越高,谐振频率越低,压电纤维体积分数为20%～30%可以获得较大输出电荷与输出电压。     

In situ measurement of elastic properties of cement by an ultrasonic resonant sensor

The ultrasonic sensor is composed of a resonator excited by a piezoelectric element. It is in the shape of a solid metallic cylinder with a fine cylindrical tip. The tip is dived into the cement to be tested, where it generates propagating and standing waves. The frequency of resonance of the system gives us information on the elastic properties of the paste. The sensor is mostly sensitive to the shear modulus G′ of the medium. With the described sensor, the range 10⁶<G′<10⁷ Pa is tested. Other ranges can be selected by changing the size of the cylinder or the tip.     

Giant Magnetoelectric Effect in Thin‐Film Composites

Highly sensitive AC magnetic field sensors are presented using magnetoelectric composites consisting of magnetostrictive and piezoelectric phases. They are offering passive nature, high sensitivity, large effect enhancement at mechanical resonance, and large linear dynamic range. Thin‐film magnetoelectric 2‐2 composites benefit from perfect coupling between the piezoelectric and magnetostrictive phases and from the reduction in size which is essential for high spatial resolution. Their design uses AlN and a plate capacitor or PZT with interdigital electrodes and magnetostrictive amorphous FeCoSiB single layers or exchanged biased multilayers. At mechanical resonance and depending on the geometry, extremely high ME coefficients of up to 9.7 kV/cm Oe in air and up to 19 kV/cm Oe under vacuum were obtained. To avoid external DC magnetic bias fields, composites consisting of exchanged biased multilayers serving as the magnetostrictive component with a maximum magnetoelectric coefficient at zero magnetic bias field are employed. Furthermore, the anisotropic response of these exchanged biased composites can be utilized for three‐dimensional vector field sensing. Sensitivity and noise of the sensors revealed limits of detection as good as to 2.3 pT/Hz^1/2 at mechanical resonance. Sensitivity between 0.1 and 1000 Hz outside resonance can be enhanced through frequency conversion using AC magnetic bias fields.     

Use of Autocorrelation Analysis in the Evaluation of Piezoelectric Coupling of Modified PLZT Ceramics Subjected to High Electric Fields

Two piezoelectric materials were investigated in electric fields, up to 3 kV/cm to determine whether single-sample testing can be used to evaluate piezoelectric coupling. Autocorrelation analysis of the data showed that the minimal increment of electric field necessary for successive independent measurements on single specimens is 1.3 kV /cm. This value coincides with the breakage field of the sample at resonance. Electrumechanical performance can still be evaluated with a sampling interval slightly lower than 1.3 kV/cm .     

Analysis of the Effect of Piezoelectric Patches on the Behavior of Adhesively Bonded Scarf Joints — An Analytical Study

In order to reduce the maximum peel and shear stress concentrations in the adhesive layer, a smart adhesively bonded scarf joint system was developed by surface bonding of piezoelectric patches onto a typical scarf joint. The forces and bending moments at the edges of the developed smart joint system can be adaptively controlled by adjusting the applied electric field on the piezoelectric patches, thus reducing the peel and shear stresses concentration in the adhesive layer. In order to verify the effect of surface bonding of piezoelectric patches in smart scarf adhesive joints, an analytical model was developed to evaluate the shear stress distribution and to predict the peel stress. It was established that the piezoelectric patched joint could reduce the stress concentrations at the scarf joint edges. The influence of the electric field and the effects of the scarf angle and the adherend Young's modulus on the peel and shear stresses were investigated. It was found that the effect of scarf angle is more significant at higher angles to raise the stresses. The effect of the electric field on the shear stress is more significant than on the peel stress.     

一种超声波传感器广角检测设备的研制

为了实现扩展超声波传感器检测角度的目的,通过对超声波传输过程以及超声波斜入射影响的分析,提出了基于传感器半功率角的传感器阵列及相关电路的设计方法,并对此设计进行了大量试验,证明此设计在不影响超声波波形的前提下,能够扩展超声波传感器的检测角度,并且易于实施.     

Piezoelectric properties of (Na1−xKx)NbO3‐based lead‐free piezoelectric ceramics and their application in knocking sensor

Piezoelectric knocking sensors with a dense microstructure were fabricated at 960°C for 2 hours using various CuO‐added (Na_0.5K_0.5)NbO₃ (NKN)‐based piezoelectric ceramics. The practical sensitivity (S_P) of the knocking sensor, which is the ability to detect the knocking of a car engine, was influenced by the g₃₃ × k_p value of the piezoelectric ceramics, indicating that the g₃₃ × k_p can be considered a figure of merit of the piezoelectric ceramics used in the knocking sensor. The knocking sensor synthesized using the CuO‐added 0.95(Na_0.5K_0.5)(Nb_0.95Sb_0.05)O₃–0.05CaTiO₃ (CNKNS–CT) ceramic, which showed a g₃₃ of 25.7 Vm/N and k_p of 0.46, exhibited a high S_P of 119 mV/g at the resonance frequency. The S_P of the commercial knocking sensor, which was synthesized using the Pb(Zr,Ti)O₃ (PZT)‐based ceramic, was 112 mV/g at the resonance frequency. Hence, the knocking sensor fabricated using the CNKNS–CT piezoelectric ceramic can be used to replace the commercial PZT‐based knocking sensor.     

Development of piezoelectric thick-film sensors to be embedded into adhesively bonded joints

Techniques have been developed for making a unique type of piezoelectric thick-film strain sensor in the form of a ‘piezoelectric adhesive’ to be embedded into a bonded joint. Lead zirconate titanate (PZT) powder is used as the active ingredient of the piezoelectric composite and epoxy resin as the matrix. The sensors have been fully characterised (i.e. type of piezoelectric powder, the surface area of the sensor, its thickness, weight fraction and the poling field) through an extensive testing programme in order to determine the optimum formulation for enhancing the sensitivity of the sensor. One of the main challenges was to effectively incorporate those sensors into the adhesive layer of a lap joint without greatly affecting the joint's mechanical properties. This application would allow the direct measurement of the stress field in a joint along the bond area, aiming at the optimisation of the adhesively bonded joint design as well as serving as an in-service structural health monitoring device. In the present work, the sensors were tested using the dynamic four-point bending test and preliminary results demonstrate the feasibility of this approach, achieving a satisfactory performance of the piezoelectric sensors applied on a metal substrate.     

Investigation of Silicon Carbide Based Optical Fiber Coupled Surface Plasmon Resonance Sensor

The performance parameter of a surface plasmon resonance sensor having silicon carbide as an additional layer is theoretically investigated. Using the transfer matrix method, the reflectivity and performance parameter in terms of sensitivity, detection accuracy and quality parameter have been calculated. To understand the dependency of sensitivity and detection accuracy in the proposed sensor, the model electric field, propagation length and penetration depth in aqueous media as well as the metal layer are calculated. It is observed that the sensitivity and detection accuracy of the proposed waveguide based sensor depend on the thickness of the silicon carbide layer. Therefore, by choosing a suitable value of thickness of the silicon carbide layer the overall performance of the proposed waveguide can be increased.     

Transparent lead lanthanum zirconate titanate (PLZT) ceramic fibers for high-frequency ultrasonic transducer applications

This paper presents fabrication of transparent lanthanum zirconate titanate (PLZT) fibers using extrusion technique. The diameter of the sintered PLZT fiber is about 400-μm, and the fibers exhibit very good transparency. Measured dielectric constant, remnant polarization and coercive field of PLZT fiber were found to be 2340, 22.5-μC/cm², and 9.8-kV/cm, respectively. The transparent piezoelectric materials may exhibit great potential for Photoacoustic (PA) imaging and hybrid intravascular imaging combining OCT and ultrasound imaging by using the transparent fiber as the path of light propagation and ultrasonic transducer material. In our study, these transparent PLZT fibers were designed to fabricate two types of high-frequency ultrasonic transducers: small aperture single PLZT fiber/epoxy composite and large aperture 1–3 PLZT fiber/epoxy composite ultrasonic transducers. Besides, a 20-μm tungsten wire phantom and the cornea of the porcine eye were also imaged with the 1–3 PLZT fiber/epoxy composite ultrasonic transducer to demonstrate its imaging capability.     

Ultrasonic in‐line monitoring of polymer extrusion

In‐line ultrasonic monitoring of polymer co‐extrusion and twin‐screw extrusion are presented. Co‐extrusion of high density polyethylene (HDPE) and a thermoplastic elastomer based on polypropylene‐EPDM (ethylene‐propylene‐diene monomer) has been investigated by ultrasonic sensors consisting of piezoelectric transducers and clad buffer rods. One extremity of the rod (probing end) was installed flush with the die surface so as not to disturb the material flow. The other end was air cooled in order to protect the transducer from excessive heating. This approach has been demonstrated to be quite convenient for monitoring and controlling industrial material processes: first, it can work at temperatures up to 1000°C; second, the clad buffer rod probing end can be machined to the same shape as those of commercial temperature and pressure sensors commonly used in the extrusion process. Therefore, no modifications are required for the installation in the original equipment. The information obtained includes the position of the interface between polymers and the stability of the process. The same ultrasonic probe has also been installed on a barrel of a twin‐screw extruder. This study was performed using polyethylene and polystyrene. It has been verified that the ultrasonic sensor can be successfully operated along the extruder screw and that the ultrasound can give access to the material properties while the polymer is being processed. This means that the technique can be exploited to monitor and control in situ the characteristics of the polymer being transformed in operations typically performed on twinscrew extruders, such as compounding, visbreaking or reactive extrusion.