QQ客服 官方微博 反馈留言

题名	三叠片型偶极声波测井换能器的有限元设计
作者	郑林
学位类别	博士
答辩日期	2008-05-29
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	换能器设计 有限元法 偶极声波换能器
其他题名	The Design of Sandwich Dipole Transducer Based on Finite Element Method
学位专业	声学
中文摘要	声波测井方法通过测量井孔中的声场参数来估计井外地层的性质。井孔声场中的弯曲振动模式包含了地层的横波信息，在油储勘探和储量评估中有着广泛的应用。目前，在声波测井中广泛使用三叠片型偶极声波测井换能器，确定地层介质的横波声速以及地层的各向异性。 作为横波测井仪器的核心部件，偶极声波换能器的研制设计涉及材料、声学、力学、电学等多学科领域，并需要结合井下高温高压的特殊工作环境限制。同时，三叠片型偶极声波测井换能器结构比较复杂，难以直接通过解析求解的方法进行描述，只能采用数值模拟方法进行优化设计，以达到进一步降低工作频率和提高发射效率的目的。 本文基于有限元方法，分析了三叠片型偶极声波测井换能器的振动模式、谐振频率、声发射效率、声场压强等声学性能，并系统讨论了换能器的结构参数对其声学性能的影响。数值计算的结果表明，当压电陶瓷片的厚度增加、金属基片的厚度增加，或者压电陶瓷片的长度增加时，换能器的谐振频率升高，当金属基片的长度增加时，换能器的谐振频率降低。换能器的声辐射效率随压电陶瓷片或者金属基片长度的增加而增加，随它们厚度的增加而降低。 本文还首次提出了一种开槽型偶极声波测井换能器的设计方案，以改善原换能器结构在高温环境下的工作性能。由于压电陶瓷片和金属基片的热膨胀系数存在明显差异，传统的三叠片型偶极声波测井换能器结构在高温固化过程中和井下高温工作环境下常常出现粘接胶层稳固性变差，压电陶瓷片从金属基片上脱落的现象。为了解决这一难题，本文提出了一种沿压电陶瓷片的中线进行刻槽的设计思路，通过减小单块压电陶瓷片尺寸来有效降低热膨胀时对胶层产生的剪切力。有限元分析表明，这样的结构改进并不影响换能器的振动模式，但换能器谐振频率略有下降。在我们的算例中，开槽宽度每增加1mm，谐振频率下降大约12Hz。开槽后，换能器发射效率略有下降，但下降的幅度不超过10%。有限元分析结果说明开槽型偶极声波换能器设计有希望替代原有的换能器结构，用于横波测井的生产实践。
英文摘要	Acoustic well logging measures formation properties through borehole acoustic wave propagation. Borehole flexural mode waves, which include formation shear wave events, are very valuable in petroleum exploration and reservoir evaluation. Presently, sandwich dipole transducers are widely used in acoustic well logging to measure shear wave velocity and anisotropy of formation. Base on finite element method, we analyze the acoustic attributions of sandwich dipole transducer, such as vibrate mode, natural frequency, transmitting efficiency, sound pressure, etc. We also discuss the relationship between the structural parameters of transducers and the acoustic attributions. Our analysis demonstrates that, the natural frequency will increase as the ceramic slices thickness, metal slice thickness or ceramic slice length increases, while the natural frequency will decrease as the length of metal slices increases. Numeral simulation also shows either the increase of the length or width of ceramic and metal slices, or the decrease of their thickness, will cause an increase of the transmitting efficiency of dipole transducer. We also present a modified design for dipole transducer to improve its stability in high temperature environment. Due to the apparent difference between the thermal expansion coefficients of piezoelectric ceramic and that of metal, the traditional dipole transducer always encounters a technical difficulty that its adhesive layer becomes very weak in the high-temperature environment and piezoelectric ceramic slices might detach from the support slice. Aim at this difficulty; we present a novel scheme by cutting notches at the midline of the piezoelectric ceramic slices. As the piezoelectric ceramic slices are cut into small pieces, shear stress caused by thermal expansion releases drastically at the adhesive layer and the piezoelectric ceramic slices would be stuck on the support slice tightly. Numerical simulations based on finite element method are conducted for evaluating the efficiency of the modified dipole transducer. The numerical results demonstrate that this structural improvement does not change the vibration modes of the dipole transducer, and the natural frequency will decrease as the notch width increases. In our numerical simulations, natural frequency decreases approximately by 12Hz as the notch width increases in every 1mm. As the transducer vibrates under certain electric stimulation, the average amplitude of displacement at its surface decreases less than 10%. Finite element analysis demonstrates that the notched dipole transducer could be an alternative to the traditional dipole transducers for acoustic well logging.
语种	中文
公开日期	2011-05-07
页码	69
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/374]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	郑林. 三叠片型偶极声波测井换能器的有限元设计[D]. 声学研究所. 中国科学院声学研究所. 2008.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。