Development of Corrosion Estimation System With Scanning Vibrating Electrode Technique by usint Boundary Element Inverse Analysis

边界元反分析扫描振动电极腐蚀估算系统的开发

基本信息

批准号：
06555026
负责人：
AOKI Shigeru
金额：
$ 4.35万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

A new effective three-dimensional boundary element method of analyzing electric field produced by localized corrosions was developed to estimate the accuracy of SVET (Scanning Vibrating Electrode Technique). With decreasing height of the electrode probe from the surface of a sample in order to improve the resolution of SVET,the electrode probe disturbs the electric field and measuring errors of the current distribution increase. Although the boundary element method is suitable for estimating the error by a numerical method, the scale ratio of whole vessel of the instrument to measurement area is larger than a factor of 10^5, and the conventional BEM has a difficulty with huge number of elements. To overcome this difficulty, a new effective method classifing computation into a few steps was proposed.A method for estimating the galvanic corrosion rate from the potential values measured at some points far from the metal surfaces was developed. This inverse problem was formulated by employ … More ing the boundary element method. Since the system of linear equations obtained is ill-conditioned, direct application of conventional numerical procedures to the equation system results in an oscillatory solution. To cope with this difficulty, the polarization characteristics which represent the relationship between potential and current density was estimated first. In order to improve the accuracy, a new method using a priori information which was expressed as fuzzy membership functions was developed.The above method was generalized. The generalized method consists of the following procedures. 1.The singular value decomposition of the coefficient matrix is performed, and then the rank is appropriately reduced. 2.A set of solutions is represented by Moore Penrose's solution and null space. 3.The solution is obtained by fuzzy reasoning using the set of solutions and a priori information which is expressed as fuzzy membership functions. Since the solution is identified by taking into account a priori information, the iteration converges quickly and stably, and oscillatory solutions can be avoided.To improve the measuring accuracy of SVET,an inverse problem, in which the true current density distribution along the metal surface was estimated from the data having errors due to the probe disturbance, was solved by using the 3-D boundary element method. The data were, however, not the real experimental data, but the numerical simulation results. Further study is necessary to perform an inverse analysis using experimental data, because more complicate electro-chemical phenomena than the simulation must prevail near the surface of the metal. Less

开发了一种新的有效的三维边界元素方法，该方法通过局部腐蚀产生的分析电场，以估计SVET的准确性（扫描振动电极技术）。随着电极探针从样品表面的降低，以改善SVET的分辨率，电极探针会扰乱电场并测量电流分布的误差。尽管边界元素方法适用于通过数值方法估算误差，但仪器的整个容器与测量区域的比例大于10^5倍，并且常规BEM在大量元素上遇到困难。为了克服这一困难，提出了一种将计算分类为几个步骤的新有效方法。开发了一种从远离金属表面的某些点测得的电势值估算电流腐蚀速率的方法。这个反问题是由员工提出的……更多的边界元素方法。由于获得的线性方程系统是不适合条件的，因此将常规数值程序直接应用于方程式系统会导致振荡解决方案。为了应对这一难度，首先估算了代表电势和电流密度之间关系的极化特征。为了提高准确性，开发了一种使用先验信息的新方法，该方法被开发为模糊成员功能。上述方法已概括。广义方法包括以下程序。 1.执行核心矩阵的奇异值分解，然后将等级适当降低。 2.摩尔·彭罗斯（Moore Penrose）的解决方案和空空间代表了一组解决方案。 3.解决方案是通过使用一组解决方案和以模糊成员函数表示的先验信息来获得的。由于通过考虑先验信息来识别解决方案，因此可以避免迭代迅速而稳定，并且可以避免振荡溶液。为了提高SVET的测量精度，这是一个逆问题，在该问题中，通过使用3-D边界元素的方法来解决由于探针灾难而产生的误差的数据，沿着金属表面的真实电流密度分布估算出来。但是，数据不是实际的实验数据，而是数值模拟结果。进一步的研究对于使用实验数据进行反向分析是必要的，因为比模拟必须在金属表面附近盛行更紧凑的电化学现象。较少的