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方法来分析局部腐蚀产生的电场，以估计 SVET（扫描振动电极技术）的精度，随着电极探针距样品表面的高度降低，以提高精度。虽然边界元法适合用数值方法估计误差，但仪器的整个容器与测量区域的比例较大。大于10^5的因子，而传统的边界元法存在单元数量庞大的困难，为了克服这一困难，提出了一种将计算分为几个步骤的新有效方法。一种从电位估计电偶腐蚀速率的方法。由于获得的线性方程组是病态的，因此可以直接将传统的数值程序应用于该反演问题。方程组的结果是为了解决这个困难，首先估计代表电势和电流密度之间关系的极化特性，为了提高精度，开发了一种使用先验信息表示为模糊隶属函数的新方法。对上述方法进行了推广。推广方法由以下步骤组成：1.对系数矩阵进行奇异值分解，然后适当降低秩。2.将一组解表示为Moore Penrose解。零空间。 3.利用解集和先验信息进行模糊推理获得解，先验信息表示为模糊隶属函数，由于解是通过考虑先验信息来识别的，因此迭代收敛快速且稳定，并且可以得到振荡解。为了提高SVET的测量精度,利用三维边界元法解决了根据因探头扰动而产生误差的数据来估计沿金属表面的真实电流密度分布的逆问题。。然而，这些数据并不是真实的实验数据，而是需要进一步研究数值模拟结果，以利用实验数据进行反演分析，因为在金属表面附近必然存在比模拟更复杂的电化学现象。较少的