Prediction of Side-Drilled Hole Signals Captured by a Dual Crystal Contact Probe

The dual crystal transducer plays an important role in many practical ultrasonic inspections due to its outstanding near surface resolution and signal-to-noise ratio. In order to get a deeper understanding on the characteristics of this kind inspection system, it is essential to develop an ultrasonic measurement model for dual crystal probes. To address such a need, by combining a multi-Gaussian beam model and a scattering model with the separation of variables method, we provide an efficient ultrasonic measurement model for the dual element transducer. This measurement model can be used to determine the system efficiency factor and predict the responses of a side-drilled hole. Furthermore, the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided model.     

New design and analysis for point-focusing of surface waves in contact testing

A method was presented for the intensive focusing of surface ultrasonic waves in contact testing, and an ultrasonic contact transducer was fabricated and characterized. The acoustic contact lens of the transducer was in a shape which was obtained by rotating a right-angled triangle having a critical angle for the generation of surface waves. PVDF film was employed as an ultrasonic transmitter and receiver. The fabricated transducer showed the focusing feature of a narrow lateral half width and high sound intensity at a focal point. Also, a simple model was presented to estimate theoretically the stress pattern on a symmetry axis of the transducer. The stress pattern predicted using the model showed good agreement with the experimental result. This concept can also be used in acoustic microscopy.     

Electrostatic airborne ultrasonic transducers: modeling and characterization

An a priori theoretical model for electrostatic airborne ultrasonic transducers has been developed. The historical development of transducer modeling is briefly reviewed. This paper applies the plate-on-air-spring model to establish a mathematical formulation for the transducer behavior in terms of the characterized impedance parameters. It is clarified that such an electrostatic transducer is a capacitive-type device and obeys the reciprocity principle in the same way as a piezoelectric device. The accurate prediction of multiple resonant frequencies and transmitting responses for a typical V-grooved backplate transducer serve to substantiate the theoretical model.     

超声换能器声场的激光可视化研究

为了提高超声检测的灵敏度和检测精度,优化检测工艺参数,充分了解超声换能器形成的声场至关重要。搭建了超声换能器声场的激光可视化实验平台,利用超声换能器在试样中激发出超声波,利用激光散斑接收试样表面某点在一段时间内的位移,再通过扫查获得一定区域内质点的位移,进而形成多时刻的质点位移场,以此实现超声场的动态显示。利用该系统对超声换能器声场的扩散情况进行了探测,探测结果与理论计算结果基本一致。     

超声波换能器性能指标测试方法的研究

介绍了一种新的超声波换能器灵敏度的测试方法，排除了常规测试方法中仪器对它的影响。对超声波换能器的频率特性测试，采用了一种简便，经济，实用的方法，并给出了测试结果。     

Design of advanced ultrasonic transducers for welding devices

A new high frequency ultrasonic transducer has been conceived, designed, prototyped, and tested. In the design phase, an advanced approach was used and established. The method is based on an initial design estimate obtained with finite element method (FEM) simulations. The simulated ultrasonic transducers and resonators are then built and characterized experimentally through laser interferometry and electrical resonance spectra. The comparison of simulation results with experimental data allows the parameters of the FEM models to be adjusted and optimized. The achieved FEM simulations exhibit a remarkably high predictive potential and allow full control of the vibration behavior of the transducer. The new transducer is mounted on a wire bonder with a flange whose special geometry was calculated by means of FEM simulations. This flange allows the transducer to be attached on the wire bonder, not only in longitudinal nodes, but also in radial nodes of the ultrasonic field excited in the horn. This leads to a total decoupling of the transducer to the wire bonder, which has not been achieved so far. The new approach to mount ultrasonic transducers on a welding device is of major importance, not only for wire bonding, but also for all high power ultrasound applications and has been patented     

Polyurea thin film ultrasonic transducers for nondestructive testing and medical imaging

Ultrasonic transducers using polyurea piezoelectric thin film are studied in this paper. Aromatic polyurea thin films, prepared by vapor deposition polymerization, have useful characteristics for use as an ultrasonic transducer. This paper presents the fabrication and experimental evaluation of ultrasonic transducers formed using polyurea films. First, the vapor deposition polymerization process using two monomers is briefly reviewed, and the temperature conditions for higher piezoelectric constants are explored. Second, in order to test the fundamental characteristics of this material as a high-frequency, ultrasonic transducer, a polyurea film of 2.5 microm thickness was deposited on a silicon substrate. In the pulse/echo experiment results, a resonant frequency of about 100 MHz was observed. Third, we fabricated a concave point focus transducer and a cylindrical line focus transducer. To examine the performances of the focus transducers, two-dimensional images of a coin and V(z) curve measurements for an aluminum surface were demonstrated.     

夹心式压电陶瓷超声换能器的非线性研究进展

夹心式压电陶瓷超声换能器是目前大功率超声设备中应用最广的一种换能器,其在大功率工作状态下会呈现出明显的非线性特征。综述了夹心式压电陶瓷超声换能器非线性方面的研究进展。首先介绍了国内外在压电陶瓷非线性方面的重要理论及实验研究成果,着重阐述了大功率领域常用的硬压电陶瓷的非线性研究工作,其次对夹心式压电陶瓷超声换能器的结构及工艺所引起的非线性进行了简要分析和论述,最后介绍了夹心式压电陶瓷超声换能器非线性建模方面的研究进展。     

A flexible piezoelectric transducer design for efficient generation and reception of ultrasonic Lamb waves

This paper describes the development of a flexible piezoelectric transducer for the generation and detection of ultrasonic symmetrical Lamb waves in plate-like structures. This piezoplatelet transducer structure comprises an array of miniature piezoceramic plates embedded within a soft setting polymer filler material, combining the efficiency of the active piezoceramic phase with a degree of flexibility, which is a function of the platelet/polymer dimensions. For many condition-monitoring applications, the generation of ultrasonic Lamb waves is often appropriate, and this was achieved by incorporating interdigital design techniques via the transducer electrode pattern. The performance of the piezoplatelet transducer structure was evaluated using a combination of linear systems and finite-element modeling, substantiated by experimental results. Importantly, the transducer is shown to operate as an ensemble of platelets, each operating in the thickness mode and well decoupled from neighboring piezoelectric elements. Using this transducer configuration, an unimodal s1 Lamb wave, at 1.45 MHz, has been generated and detected in a 3-mm thick steel plate. Furthermore, a propagation distance of almost 1 m was recorded for s0 Lamb wave generation/detection in a fiber-reinforced composite plate.     

一种大功率超声换能器的设计

基于超声换能器设计理论,提出一种大功率超声换能器的设计及工程计算方法。该换能器由纵向振动夹心式换能器、半波长圆锥形变幅杆和盘棒式工具头组成,根据设计参数及特点,实际制作换能器,通过测试该换能器频率f=20.24kHz,标称功率可达1500W,符合设计初衷。进而验证了这种计算方法的可行性。该换能器可用于污水处理、油田开采及生物柴油等领域的技术开发中,具有推广价值。     

An analytical model of multilayer ultrasonic transducers with an inversion layer

Inversion layer ultrasonic transducers have been investigated recently as an interesting approach in wideband transducer design. In this paper we present an analytical model of multilayer ultrasonic transducers with an inversion layer. Our analysis of the wave propagation problem of an inversion layer transducer includes a functional decomposition of the electrical input impedance. It becomes clear from this decomposition that an inversion layer transducer can be modeled as three elements in series connection, i.e., a clamped capacitance, a classical motional impedance, and a coupled motional impedance. The first two elements make up the classical model of a single element transducer. The coupled motional impedance describes the coupled interaction between the regular and the inverted piezoelectric sublayers, and thus reflects the effect of an inversion layer. We present examples which show that inversion layer transducers are advantageous in achieving such useful features as dual-frequency operation mode as used in harmonic imaging or broadband performance desired in most ultrasonic applications.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System I: Modeling Foundations

A comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system is developed that combines models for the electrical components (pulser/receiver, cabling), electromechanical components [transducer(s)], and the acoustic/elastic processes present in the materials being inspected, including the scattering of ultrasonic waves from a flaw. This model is called the electroacoustic measurement (EAM) model . Here, in Part I, the underlying modeling foundations of the EAM model are described in detail and the use of the EAM model is demonstrated in a transducer design study. This EAM model provides a new, powerful tool for analyzing virtually any element in the measurement process. In Part II it will be shown that this power can be extended to characterizing typical commercial measurement systems through the use of models and purely electrical measurements of the system components.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System I: Modeling Foundations

Abstract

A comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system is developed that combines models for the electrical components (pulser/receiver, cabling), electromechanical components [transducer(s)], and the acoustic/elastic processes present in the materials being inspected, including the scattering of ultrasonic waves from a flaw. This model is called the electroacoustic measurement (EAM) model. Here, in Part I, the underlying modeling foundations of the EAM model are described in detail and the use of the EAM model is demonstrated in a transducer design study. This EAM model provides a new, powerful tool for analyzing virtually any element in the measurement process. In Part II it will be shown that this power can be extended to characterizing typical commercial measurement systems through the use of models and purely electrical measurements of the system components.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System I: Modeling Foundations

A comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system is developed that combines models for the electrical components (pulser/receiver, cabling), electromechanical components [transducer(s)], and the acoustic/elastic processes present in the materials being inspected, including the scattering of ultrasonic waves from a flaw. This model is called the electroacoustic measurement (EAM) model . Here, in Part I, the underlying modeling foundations of the EAM model are described in detail and the use of the EAM model is demonstrated in a transducer design study. This EAM model provides a new, powerful tool for analyzing virtually any element in the measurement process. In Part II it will be shown that this power can be extended to characterizing typical commercial measurement systems through the use of models and purely electrical measurements of the system components.     

Determination of an ultrasonic transducer's sensitivity and impedance in a pulse-echo setup

The role that an ultrasonic piezoelectric transducer plays in an ultrasonic measurement system can be described in terms of the transducer's input electrical impedance and its sensitivity. Here, a new model-based approach is proposed to determine both the transducer impedance and sensitivity in a pulse-echo setup. This new method is much simpler to apply than previous "self-reciprocity" calibration methods for determining sensitivity and generalizes those methods. It is demonstrated that sensitivities obtained with this new method agree well with the sensitivities obtained by a three-transducer method commonly used in calibration studies. It is demonstrated that at the megahertz frequencies at which ultrasonic transducers operate it is important to compensate for cabling effects in these measurements. The influence of the pulser/receiver settings on the results obtained also will be discussed.     

基于扫描数据可视化的超声换能器参数测量

超声探头是超声无损检测中的关键部件,其参数直接影响到对超声检测系统性能的评价与校准。在自主建立的水浸超声声场自动扫查系统基础上,以标准ASTM E1065-99为依据,利用水听器法对聚焦超声换能器声场进行扫描,并将数据可视化。在数据可视化的基础上,对声场中若干重要参数进行了测量。实验结果表明,测量结果与理论计算结果吻合程度良好,所实现的声场自动扫查系统能够真实反应出换能器空间的声场分布,能够为超声换能器应用特性的准确评价提供可信的数据。     

A frequency domain ultrasonic model for the pulse-echo transducer response of an arbitrary scatterer in a fluid

A very general model formulation is presented in the frequency domain for the pulse-echo ultrasonic response of an arbitrary scatterer in a fluid. The transducer is modeled as a piston source and the scatterer can be located anywhere in the transducer wavefield. The model is computationally efficient and is shown to agree well with initial experiments.     

超声键合换能器的研究——回顾与展望

回顾了超声键合用换能器的发展状况,特别是在我国的研究状况。对超声键合用换能器的研究方法进行了总结,例如等效网络法、直接解振动与波动方程法、有限元法。不少单位已经编制了等效网络法的计算程序,可以迅速准确地得到细长和简单换能器结构的频率特性和导纳曲线;利用有限元软件可以计算复杂结构的换能器特性,是当今设计仿真的有效工具。论文结合当前微电子、集成芯片对超声键合的大量需求,展望了超声键合换能器的发展前景。除高频换能器和小体积的换能器需要进一步研究外,性能更加稳定和优良的换能器依然是研究的热点。     

A piece-wise spatial invariant model of ultrasonic image formation

A model of ultrasonic image formation has been developed for an electronically focused linear-array transducer. An analytical expression for the point-spread function of the image degradation process is obtained. It consists of two terms: one accounts for the electromechanical properties of the transducer; the other describes the diffraction phenomena associated with the wave propagation. To reduce the computational complexity in image restoration, a piecewise-invariant form for the point-spread function has been suggested. Experimental results prove the validity of the model and the feasibility of the reconstruction process with a few shift-invariant filters.     

一种超声手术刀推挽激励换能器的研究

设计了一种超声手术刀用的新型推挽激励换能器。它是在夹心式单晶堆压电超声换能器的经典构造基础上,把原先激励一组压电陶瓷晶片堆的方式,改为同时施加反相激励的前后两组晶堆。利用有限元方法,对该推挽激励换能器进行模态分析和频率响应分析。在相同大小的电压激励下,相对单晶堆换能器,推挽激励换能器可以获得更高的工作带宽和机电耦合系数,提高了换能器的电声转换效率。按照仿真结果加工推挽激励换能器,实现良好的动力学和电学特性,满足设计要求。