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

为了评价扫描振动电极技术（SVET）的精度，提出了一种分析局部腐蚀电场的三维边界元方法。为了提高SVET的分辨率，减小电极探头离样品表面的高度，电极探头对电场的干扰增大了电流分布的测量误差。虽然边界元法适合于通过数值方法估计误差，但是仪器的整个容器与测量区域的比例比大于10^5倍，并且传统的边界元法难以处理大量的单元。为了克服这一困难，提出了一种新的有效方法，将计算分为几个步骤，并发展了一种由远离金属表面的某些点的电位值估算电偶腐蚀速率的方法。这个反问题是由雇用 关于我们 边界元法。由于得到的线性方程组是病态的，直接应用传统的数值计算程序的方程系统的结果在一个振荡的解决方案。为了科普这一难题，首先估计了代表电位与电流密度之间关系的极化特性。为了提高预测精度，提出了一种利用先验信息的模糊隶属度函数进行预测的新方法，推广了该方法。广义方法包括以下步骤。1.对系数矩阵进行奇异值分解，然后适当降低秩。2.用摩尔彭罗斯解和零空间表示一组解。3.该方法利用解集和先验信息通过模糊推理得到解，先验信息表示为模糊隶属函数。为了提高SVET的测量精度，采用三维边界元法求解了由探头扰动引起的误差数据估计金属表面真实电流密度分布的反问题。然而，这些数据不是真实的实验数据，而是数值模拟结果。进一步的研究是必要的，以执行使用实验数据的逆分析，因为更复杂的电化学现象比模拟必须盛行附近的金属表面。少

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