New methods of thermographic control using multi-scale analysis of non-stationary thermal fields

Abstract

A set of new approaches and techniques of non-destructive testing is described and implemented within a unified computer analysis of the patterns of multi-scale dynamic thermography. Depending on the size of the inspected area, nature, location, orientation and size of the defects, various energy sources were used for probe dynamic heating of the controlled article: air flow, focused laser beam, and point contact. The non-stationary thermal picture of the monitored area was recorded with a high resolution thermal imaging device and then analyzed using original model approaches and developed software. A set of discussed approaches allows detecting and quantitative characterizing of the defects of various types, size (from fractions to tens of millimeters) and orientation, including cracks, coating delamination or degradation, welding and glue seams defects, deposits, etc., both at the outer and inner surfaces of tubes, tanks, and reactors, etc. The developed methods provides determination of the thermophysical characteristics of the material, i.e., the thermal diffusivity coefficient with an accuracy better than ±3%.