固体板背覆薄层特性的低频超声反演方法研究
文献类型：学位论文
| 作者 | 王杨 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-06-02 |
| 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 | 超声谱方法 谐振频率 幅度谱 薄层检测 |
| 其他题名 | Characterization of an Inaccessible Thin Film under a Plate by Low-Frequency Ultrasound |
| 学位专业 | 声学 |
| 中文摘要 | 薄层结构在微电子、自动化、航空航天等重要的工业领域中广泛存在，对薄层结构进行几何参数测量、声学参数定征以及组织结构和力学性能表征在无损检测行业日益受到重视。其中对固体板背覆薄层除厚度外的特性检测，尤其是多个特征参数的同时检测，还存在着很大的困难，而背覆薄层的特性检测对诸如石油化工压力容器、管道等产品的质量及使用安全评估具有重要意义。 本论文围绕固体板背覆薄层的低频超声检测问题展开研究，这里的低频指的是薄层厚度明显小于所用超声声波波长。从声传播理论入手，通过层状固体材料中超声波传播特性在频域的显式解，建立背覆薄层特征参数（包括厚度、声速、密度、衰减、特性阻抗、声时）与垂直入射声波反射回波频谱的谐振频率和幅度谱之间的关系，从灵敏度函数、目标函数及误差传递方程的角度讨论应用反射回波频谱的谐振频率和幅度谱反演模型系统（铝板/聚合物薄层）的单参数和双参数的方法。通过灵敏度函数选择反演所用谐振频率和幅度谱的区间；通过目标函数判定反演的收敛特征，包括是否收敛、收敛速度以及局部极值问题等；通过误差传递方程粗略估计已知参量的测量误差对反演精度的影响并指导设计实验。 在理论分析的基础上利用课题组搭建的实验平台对反演单层铝板下背覆薄层的各特征参数进行了实验研究。实验使用中心频率为7MHz的探头，检测样品为铝板(6.232mm)/聚合物薄层(0.054mm)，薄层厚度小于四分之一的声波波长。单参数的反演效果谐振频率法和幅度谱法相当，双参数的反演效果谐振频率法优于幅度谱法，前者薄层特性阻抗和声时同时反演的平均误差为3.4%和4.7%，而后者没有得到结果。两种方法都没有反演出薄层衰减和与之相关的参数组合。 本文的主要创新点包括采用两种方法：1．对薄层任一特征参数的检测，除厚度外，还包括纵波声速、密度、衰减、特性阻抗和等效声时的检测；2．对背覆薄层任意两个参数的同时反演，并从工程应用角度出发，将基体板材厚度作为待反演参数之一，和背覆薄层任一特征参数的组合进行双参数反演；3．通过分析误差传递方程，预判检测的精度，并根据对反演精度的要求设计实验，控制各直接测量量的精度。 论文所取得的结果对进一步应用固体板背覆薄层的检测技术提供了重要的参考依据。 |
| 英文摘要 | Thin films and coatings are widely used in manufacturing such as in the microelectronics, automotive and aerospace industries. The geometrical and acoustic properties determination has received considerable attention in NDE application. However, it is hard to evaluate a thin layer adhering beneath a substrate, especially to determine multi-properties simultaneously, which plays an important part in assessing the quality and security of petrochemical pressure vessels and pipelines. The objective of this paper is to research on characterization of a composite consisting of a soft thin film adhering beneath to a hard plate substrate of finite thickness by ultrasonic spectroscopy in low frequency region. Beginning with the wave propagation theory, the relationship between the properties of a film and the resonance frequencies or the amplitude spectra of the reflection spectrum at normal incidence is established. On this basis, an analysis of sensitivity function, objective function and error transfer function are presented for discussing the effect of the two methods for both one parameter and two-parameter inversion. The orders of the resonance frequencies and region of amplitude spectra used for the inversion are determined by the sensitivity function. The objective function is used to decide the convergence, including whether it converges, velocity of convergence and it converges to local minimum or global minimum. The error transfer function serves the purpose of roughly analysis of the influence of the given values’ error on the inversion accuracy and direction on design experimental conditions. The two techniques mentioned above are employed to characterize a composite consisting of a thin film(0.054mm) adhering beneath to an Al plate substrate of finite thickness(6.232mm) with a broadband 7MHz center frequency transducer. It is observed that the two methods’ results are similar for one parameter inversion and the method based on resonant frequencies gains better result for two-parameter inversion under the same experimental condition. The relative errors of the method based on resonant frequencies for inversing characteristic acoustic impedance and time-of-flight are 3.4% and 4.7% respectively, and the method based on amplitude spectra gains no result. Both the two methods cannot inverse the attenuation of the thin layer. The presented results of this thesis offer an important support to further application of evaluating the composite system consisting of a thin film adhering beneath to a plate substrate of finite thickness. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 91 |
| 源URL | [http://159.226.59.140/handle/311008/380]  |
| 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 | 王杨. 固体板背覆薄层特性的低频超声反演方法研究[D]. 声学研究所. 中国科学院声学研究所. 2008. |
入库方式： OAI收割
来源：声学研究所
浏览0
下载0
收藏0
其他版本
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。