Frankevych L. Development of the speckle correlation method for evalution of surface damage degree during local corrosion

The object of study is the process of controlling and monitoring the extent of damage the surface of localized corrosion by treating the speckle images of the surface. The purpose of research is to develop a speckle correlation method and means for controlling the surface damage degree by the local corrosion damages. The next methods were applied: metod of mathematical statistics, theory of information-measuring systems, optical systems theory, theory of measurement and measurement systems, methods of non-destructive testing methods of digital image speckle correlation, test methods for resistance to localized corrosion. On the basis of theoretical and experimental studies in the thesis: proposed to consider the time dependence of the surface damage degree by the local corrosion damages as multivariable stochastic process, which is determined by the parameters of probabilistic estimates of the speckle signals from the surface under study, which makes it possible to monitor the development of local surface corrosion damage; proposed and validated method to control the surface damage degree by the local corrosion damages by the use of local estimates of the normalized correlation coefficient speckle image information as a parameter; proposed and verified method for correcting the effect of noise on the normalized correlation coefficient, thus improving the accuracy of monitoring the extent of damage the surface of localized corrosion; the restrictions for the correlation method for various metals in controlling the extent of damage the surface of localized corrosion on the basis of probability characteristics of speckle signals. Also developed an experimental model of speckle correlation device to control the surface damage degree of metal surfaces; tests of experimental sample means for controlling the extent of damage the surface of the local corrosion damage with the use of three materials: 17G1S, 08H18N10, 12H18N9TL, which have very different corrosion resistance; developed and implemented a portable device to control the degree of local lesion surface. The results of the work are used in Kamianka-Buzka management operation of gas facilities to monitor the surface damage degree by the local corrosion damages aboveground parts of steel pipe and Company "112 Ukraine" during the development of the definition of corrosion damage of steel parts.