Thermographic Control by New Methods of Multiscale Analysis of Nonstationary Thermal Fields

Abstract

In this paper, we present the results of the application of new methods of monitoring and diagnostics based on a computer analysis of multiscale dynamic thermographic patterns. Depending on the size of the inspected area, as well as the nature, location, orientation, and size of defects, various energy sources, such as an airflow, focused laser beam, and point contact, were used for probing dynamic heating of the product under control. The nonstationary thermal image of the monitored area was recorded by a high-resolution thermal camera and then analyzed by using original model approaches and developed specialized software. The development of defects was initiated by a calibrated local power load using the built-in force generator. This allowed identifying dynamic (prone-to-growth) defects and assessing the degree of their danger for further operation and the residual resource of the product. Using the proposed methods, defects of various types (cracks, delaminations, detachments, and degradation of coatings, defects in welding and adhesive joints, deposits of transported substances, etc.), sizes (from fractions to tens of millimeters), and location in the product (near both the outer and inner surfaces of vessels, pipelines, reactors, tanks, etc.) can be detected and quantitatively characterized. The developed techniques also allow determining the thermophysical characteristics of the material, in particular, the thermal diffusivity coefficient with an accuracy better than ±3%.