Complex of optical-television and acoustic-emission diagnostics of the mechanical state of loaded materials and structural elements

To construct a field of displacement vectors, two images of the research/control object, taken after a period of time (deformation increment), are required. The field of displacement vectors is a vector field consisting of a finite number of vectors, each of which corresponds to the displacement of one area in the second image relative to the first. The resolution of the displacement estimation algorithms implemented in the program is no lower than 0.125 pixels, which, for example, corresponds to 0.5 microns with an image resolution of 768x576 pixels and the real dimensions of the shooting object (object area) of 1600x1200 microns. The vector field is converted into distributions of deformation components, from which the localization of deformations can be determined.
The fractal analysis method has been used in materials science for a number of years. The basis for the application of the method was the change in the relief of the metal surface under loading. As a result of the destruction of metal under tension or from an impact load, a fracture surface is formed that will be uneven and heterogeneous. One of the algorithms for calculating the fractal dimension implemented in the software is the pyramid method.
The main disadvantage of the method for calculating the fractal dimension is the inability to accurately identify and visualize the characteristic elements of the image that determine a particular value of the fractal dimension. This drawback is partially removed by analyzing the dependence of the Fourier energy of the power spectrum of two-dimensional images on the spatial frequency. The data obtained in our work indicate that analysis of the distribution of the Fourier power spectrum of optical images of a surface in the low-frequency region makes it possible to determine the leading scale of development of plastic deformation, and the use of information about the magnification of the optical system can serve as a source of information about the characteristic size of its carriers.
Wavelet spectra are characterized by their ability to accurately characterize signals in both the time and frequency domains. This circumstance was the basis for a new method for describing the deformation relief on a surface, which is carried out through the analysis of a graphical representation of the energy of the wavelet spectrum.
The mathematical apparatus of the OTIS software makes it possible to build on its basis high-level automation systems that can be optimized for use in specific software and hardware systems for materials research. By developing and implementing such systems, it is possible to automate a significant part of the work associated with processing experimental results. The mathematical apparatus of the software allows you to process not only optical flow data, but also data obtained using an atomic force/scanning tunneling microscope, data on the surface reliefs of real physical objects that change over time, obtained by other methods.
The acoustic emission testing device implements an acoustic non-destructive testing method based on recording mechanical (elastic) waves emitted by the material, caused by dynamic, local restructuring of the internal structure of a solid body when it is loaded. Their nature depends on the size of the object, material, internal structure, and degree of defectiveness. This allows non-destructive testing of various objects (including those with one-way access, for example, parts of compressor equipment in working condition or pipeline sections hidden in the ground) for the presence of corrosion and erosion damage, discontinuities in the base material and weld material. In this case, the criteria for diagnosing the pre-fracture state of a loaded material are the features of the accumulation of acoustic emission signals, as well as the amplitude-frequency characteristics of each of the generated signals.
At different stages of material loading, a correlation was established between the stages of change in mesoscopic deformation parameters and the accumulation of acoustic emission signals. A comprehensive study based on optical-television and acoustic-emission methods allows, during subsequent inspection of industrial facilities, to carry out reliable diagnostics of the stages of damage accumulation and the pre-fracture state (limit state) based only on acoustic-emission control data. The tools being developed are promising for use both as part of automated stationary continuous systems and as periodic monitoring tools.

Technical characteristics of the complex