压电式摆动圆柱形偶极发射换能器优化研究

为了实现偶极信号有效辐射,获得足够高的信噪比,全面分析弯曲波频散,本文提出了一种新型的频带范围为0.5–5 k Hz的压电式摆动圆柱形偶极声波测井换能器,并采用有限元方法对其进行了模拟和优化设计。此外,论文还对换能器进行了实验样机制作和实验测量,将实验测量与数值模拟结果进行了对比。研究表明,提出的新型偶极声波换能器比传统换能器具有更高的发射灵敏度,尤其是在低频响应范围。本文为新型偶极声波测井换能器的研发工作奠定了基础。     

随钻声波测井四极子发射换能器的设计*

提出一种基于金属基片结构的随钻四极子发射换能器,其一阶弯曲模式可用于随钻四极子声源。利用有限元法对该换能器进行了设计分析,结果表明在5kHz附近存在一阶弯曲振动模态,其径向位移分布及发射电压级响应均优于单纯的瓦片状压电阵子,非常适合随钻四极子工作频率及声场的测量需求。针对一阶弯曲振动模态,数值模拟了几何尺寸对换能器性能参数的影响。换能器谐振频率随着陶瓷片厚度、陶瓷片高度、陶瓷片张开角度、金属基片厚度的增大而升高。最大发射电压级幅值随着陶瓷片高度、陶瓷片张开角、金属片厚度的增大而升高;随着陶瓷片厚度的增大,最大发射电压级幅值先升高后逐渐降低。金属基片采用铝片可以使换能器有较大的发射功率。数值模拟结果可以对随钻声波测井仪四极子发射换能器的设计起到良好的指导作用。     

结构参数对偶极声波换能器谐振频率的影响

偶极横波远探测技术在我国复杂地质结的构油气勘探中具有十分广阔的应用前景。换能器的工作频率直接影响声波测井的探测深度。本文对正交偶极声波测井换能器弯曲模态的谐振频率进行了解析计算,并利用有限元方法研究了其结构参数对谐振频率的影响。计算结果表明:当压电陶瓷片的长度增加时,换能器一阶谐振频率先降低后升高,三阶谐振频率先升高再降低之后又上升;当金属基片厚度增加时,换能器一阶与三阶谐振频率均升高;当压电陶瓷片厚度增加时,换能器谐振频率的变化方向与幅度还与压电陶瓷片长度等其他参数相关,有可能升高或降低。     

四边型弯张换能器特性研究及宽带设计

四边型弯张换能器通常工作带宽较窄,为了提高带宽性能,对四边型弯张换能器振动及辐射特性进行了研究,重点分析壳体结构参数对换能器发送电压响应的影响。根据分析结果提出了拓宽换能器工作带宽的方法,利用有限元软件进行了仿真计算并制作了四边型弯张换能器样机。测量得到在2.4~5 kHz的频率范围内,换能器的最大发送电压响应值达到140 dB,带内起伏4 dB,有限元仿真结果与实验结果吻合较好。研究结果表明设计的四边型弯张换能器不仅能够低频工作,并且可以在小尺寸下实现大功率发射,同时还具备宽带发射特性。      

偶极声波换能器振动特性计算

利用ANSYS有限元软件计算了声波测井中使用的偶极子换能器在不同机械边界条件下的振动模态和频率响应。计算结果显示,偶极子换能器在一定的频率范围内有多个振动模态,不同的机械边界条件不仅影响振动模态的个数而且还影响同一振动模态的谐振频率;从频率响应曲线上还可以看出此结构的偶极子换能器在做弯曲振动时的频带较窄,这对在不同地层井眼中进行的偶极子声波测井非常不利。通过多个不同主频的偶极子换能器组合工作可以从根本上拓宽偶极声波换能器的频带宽度。     

折回型纵向振子低频拼合圆柱换能器

提出一种具有小尺寸、低频、水平无指向性的新结构换能器——折回型纵向振子拼合圆柱换能器,换能器由4组共享尾质量块的折回型压电纵向振子正交布置驱动环形辐射面拼合构成。采用有限元方法对换能器进行优化设计,并制作了换能器样品。实验结果表明:换能器直径为Φ180 mm,谐振频率为1.5 kHz,最大发射电压响应为131 dB,最大声源级不低于188 dB,水平全向。该换能器具有低频、小尺寸、水平无指向性的特点,具有良好的应用前景。      

横波远探测测井换能器研究

为提高偶极子横波远探测反射波的信噪比和增加其探测距离,根据偶极子井孔模式波的激发特性及反射波传播特征分析,研制了基于三叠片的低频大功率偶极子的横波远探测换能器,以降低模式波的相对能量和增加反射波的相对能量。为了得到满足要求的低频大功率偶极换能器,采用有限元方法对现有三叠片进行了优化改进,得到一种符合设计要求的换能器结构,最后制作了样机并对其进行了测试。样机测试结果跟仿真吻合得很好,低频性能得到了极大改善：换能器在谐振频率1.2 kHz附近具有极好的偶极子指向性,谐振频率处的响应比X-MAC同频率段大19 dB。该换能器的研发成功将为偶极子远探测测井仪器性能及成像质量的提高奠定了坚实的基础。     

自由端盖Ⅲ型宽带弯张换能器的设计

提出了一种利用多模耦合实现低频、宽带、大功率特性的新结构Ⅲ型弯张换能器。通过在压电陶瓷堆内部嵌入与凹型弯张壳体相连的弹性辅助弯曲梁结构,并用弯曲圆盘作为顶部自由端盖,增加有效工作模态。利用有限元方法对换能器进行了设计优化,分析结果显示换能器在低频段存在4个主要工作模态。根据优化结果,加工制作了换能器样机,水池实验的测试结果表明:在1.5～5.5 kHz范围内,换能器样机的发送电压响应均大于135 dB;1.5～4 kHz内的最大发送电压响应大于142 dB,响应起伏小于6 dB。研究结果表明自由端盖Ⅲ型弯张换能器不仅能够在小尺寸设计下实现大功率工作,还能获得低频宽带发射性能。      

低频宽带大功率“星型”柱面发射换能器

提出一种具有水平无指向性、低频、宽带、大功率特点的新结构换能器——“星型”柱面发射换能器,换能器由共享后质量块的6个复合棒换能器按“星型”方式组成柱面结构。采用有限元方法对换能器进行了分析设计并制作了换能器样机。在1—10 kHz内,换能器有3个主要工作模态,前两阶工作模态对换能器工作带宽的展宽有贡献,第三阶模态显示出较强的指向性,水池测试换能器具有1倍频程的工作带宽,最大声源级为199.1 dB。有限元模拟结果和实验结果符合较好。研究结果表明,新结构换能器在满足水平无指向性的前提下,利用复合棒的纵振及辐射面的弯曲振动实现了低频、宽带、大功率的要求,提供了一种设计该特性换能器的新思路。      

声子晶体结构在功率超声换能器中的应用*

该文提出了一种二维声子晶体结构模型,并将该模型应用于横向尺寸较大的功率超声换能器的前盖板中,避免了形成耦合振动对换能器的影响,从而优化了该类换能器的工作性能。首先设计了一种具有近周期性结构的圆柱形孔的前盖板,然后研究了声子晶体结构前盖板散射体的半径大小和高度对换能器共振频率以及前盖板带隙的影响。结果表明,随着散射体半径和高度的增大,换能器的共振频率会随之发生改变,带隙范围也在发生变化,可以通过调节使换能器的共振频率处于声子晶体的带隙范围内,可以有效抑制换能器的横向振动。     

Optimization Design for the Sandwich Piezoelectric Transmitters in Acoustic Logging

An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging,especially in acoustic logging while drilling,by taking account of drilling environments with high temperature and pressure,as well as strong collar drilling vibration during the drilling process.Aimed to improve the transmitting performance,numerical and experimental studies for the transducer optimization are conducted.The impact of location and length of the piezoelectric stack on resonance characteristics and effective electromechanical coupling coefficient is calculated and analyzed.Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments,and the results are compared with simulated ones.It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies.This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging,especially in acoustic logging while drilling.     

从换能器技术的变化看声波测井技术的发展

无论是在电缆测井还是在随钻测井方面,声波换能器结构和振动模式的变化导致了声波测井技术的进步和重大演化.文章以声波测井换能器技术的变化为主线,分析了声波测井技术的发展和进步以及我国在该技术领域取得的进步.单极子声波测井技术已经成为我国成熟的声波测井技术,包括非对称声源技术在内的多极子声波测井技术是我国刚刚攻克的先进声波测井技术并已经进入产业化进程,以井下声波的定向辐射和定向接收为最主要特征的相控声波测井技术是正在研发的新一代声波测井技术,我国在此领域也已经取得显著突破.     

Analysis of unidirectional broadband piezoelectric spherical shell transducers for underwater acoustics

This paper presents an analytical investigation and experimental verification of the properties of unidirectional broadband piezoelectric acoustic transducers utilizing axisymmetric vibrations of both complete and incomplete spherical piezoelectric shells and is a continuation of a previous paper that presented the electromechanical modal analysis part of the problem [J. Acoust. Soc. Am. 130(2), 753-763 (2011)]. The analysis covers the treatment of the acoustic radiation and reception problem by including analysis of the acoustic impedances and diffraction coefficients as a function of geometry and modal excitation as well as providing specific design examples including multimode spherical acoustic transducers with conformal baffles, and transducers made of incomplete shells (e.g., hemispheres and caps) with free circumferential boundary conditions. The energy method is used to obtain equivalent parameters for a multi-contour electromechanical circuit representation of the transducer and to calculate the transducer performance characteristic as sound projectors and as receivers. Experimental results are obtained on representative piezoceramic transducer prototypes and are in good agreement with the analytical results.     

Advantage analysis of PMN-PT material for free-flooded ring transducers

The acoustic radiation characteristics of free-flooded ring transducers made of PZT4 and PMN-PT materials are calculated and compared.First,the theoretical formulae for free-flooded ring transducers are studied.The resonant frequencies of a transducer made of PZT4 and PMN-PT materials are calculated.Then,the transmitting voltage responses of the free-flooded ring transducers are calculated using the finite element method.Finally,the acoustic radiation characteristics of the free-flooded ring transducers are calculated using the boundary element method.The calculated results show that the resonant frequencies of the free-flooded ring transducer made of PMN-PT are greatly reduced compared with those made of PZT4 with the same size.The transmitting voltage response of the transducer made of PMN-PT is much higher than that of the transducer made of PZT4.The calculated 3-dB beamwidth of the acoustic radiated far-field directivity of the free-flooded ring transducer made of PZT4 at the resonant frequency 1900 Hz is 63.6 and that of the transducer made of PMN-PT at the resonant frequency 1000 Hz is 64.6.The comparison results show that the free-flooded ring transducer made of PMN-PT material has many advantages over that made of PZT4.The PMN-PT is a promising material for improving the performance of free-flooded ring transducers.     

弯曲圆盘驱动的双Helmholtz共振腔换能器

使用双面同相振动的弯曲圆盘换能器驱动双Helmholtz共振腔,既放大了弯曲圆盘换能器弯曲共振频率以下频段的声输出,又利用两个Helmholtz共振腔的同相声源辐射模型实现了在Helmholtz共振频率处的"∞"字形垂直指向性,实现了低频指向性声发射。阐述了换能器实现"∞"字形低频指向性发射的机理,研究了腔体长度、金属圆片厚度及弯曲圆盘边缘简支厚度等关键结构参数对Helmholtz共振频率的影响,求解了换能器的发送电压响应、指向性等参数。依据仿真结果制作了实验样机,在消声水池中进行了电声性能测试。测试结果显示,指向性形状及液腔共振频率与仿真结果基本相符。这种由弯曲圆盘驱动的双Helmholtz共振腔水声换能器为实现水声换能器小尺寸、低频指向性发射提供了一种技术手段。      

充液圆槽中单极声波仪器响应数值模拟与分析

为了实现声波测井仪器工作状态的快速检测,工程人员通常将仪器水平放置在载液圆槽中进行发射和接收测试,然而对于这种非轴对称结构中的声波导传播规律尚缺乏数值模拟和理论分析,因此迄今仍难以形成有效的测试规范和标准。本文利用三维有限差分算法模拟了载液圆槽中的单极测井仪器声波响应,对比了不同的圆槽物理、几何参数以及液体性质条件下单极子声场首波的幅度和相慢度大小。分析结果表明,单极仪器激发的首波慢度仅由圆槽的物理特征所决定,与圆槽几何参数、声源频率及液体特性无关;而首波幅度大小则与圆槽几何尺寸、圆槽和液体弹性波速等诸因素具有明确的对应关系。本研究结果可为用于仪器测试或速度刻度的圆槽模型井优化设计提供理论依据。     

Structural acoustic control of plates with variable boundary conditions: design methodology

A method for optimizing a structural acoustic control system subject to variations in plate boundary conditions is provided. The assumed modes method is used to build a plate model with varying levels of rotational boundary stiffness to simulate the dynamics of a plate with uncertain edge conditions. A transducer placement scoring process, involving Hankel singular values, is combined with a genetic optimization routine to find spatial locations robust to boundary condition variation. Predicted frequency response characteristics are examined, and theoretically optimized results are discussed in relation to the range of boundary conditions investigated. Modeled results indicate that it is possible to minimize the impact of uncertain boundary conditions in active structural acoustic control by optimizing the placement of transducers with respect to those uncertainties.     

Fabrication and comparison of PMN-PT single crystal, PZT and PZT-based 1-3 composite ultrasonic transducers for NDE applications

This paper describes fabrication and comparison of PMN-PT single crystal, PZT, and PZT-based 1-3 composite ultrasonic transducers for NDE applications. As a front matching layer between test material (Austenite stainless steel, SUS316) and piezoelectric materials, alumina ceramics was selected. The appropriate acoustic impedance of the backing materials for each transducer was determined based on the results of KLM model simulation. Prototype ultrasonic transducers with the center frequencies of approximately 2.25 and 5 MHz for contact measurement were fabricated and compared to each other. The PMN-PT single crystal ultrasonic transducer shows considerably improved performance in sensitivity over the PZT and PZT-based 1-3 composite ultrasonic transducers.     

基于倒双谱的套管井声学评价系统特性辨识

将发射探头(T)、接收探头(R)和TR之间介质视为套管井声学评价系统的组成部分，由套管井声波测井响应，采用倒双谱技术辨识该声学系统的冲激响应，计算得到了该声学系统的特性曲线(冲激响应曲线)。当T、R同时位于自由套管区域时，声学系统特性曲线幅度最高，并且曲线的两端和中心点附近都有比较大的起伏；当T、R同时位于水泥完全胶结区域时，特性曲线幅度最低且比较平坦；随着T、R间窜槽面积的增大，特性曲线幅度逐渐增加并且中心点附近幅度的增加比较明显。通过对该声学系统特性的辨识，从冲激响应曲线瀑布图中可直观反映出套管井水泥胶结的质量。该方法对丰富、完善声波水泥胶结测井资料解释工作具有重要参考价值。     

任意阵形水声换能器阵辐射声场计算

本文用边界元的方法计算了阵形任意的水声发射换能器共形阵的辐射声场。在详细研究了边界元方法基本理论的基础上，采用Pro／ENGINEER软件与ANSYS软件相结合来建立换能器阵的边界元模型，再用SYSNOISE软件计算其辐射声场和辐射阻抗。这种声场计算方法可用于发射换能器阵设计阶段对设计结果进行预报。