| Abstrakt: |
A new type of surface eddy current probes of double differential type, which are characterized by increased sensitivity to surface and subsurface defects of various types, is presented. A family of double differential eddy current probes of different diameters with different spatial resolutions has been developed. The paper analyzes the main features of double differential eddy current probes and presents new innovative inspection techniques which allow solving the most complex problems of non-destructive testing. In particular, the developed eddy current probes have been researched and tested as an effective tool of inspection of multilayered aircraft structures, in which it is necessary to detect internal defects. they provide, in particular, the detection of cracks in the second layer of stratified aircraft structures or cracks on the back surface of the aircraft structures skin; detection of subsurface defects in the weld zone with a rough surface; detection of cracks through repair patches made of aluminium alloy or carbon composite; detection of subsurface cracks near rivet holes, etc. these techniques create unique opportunities for timely detection of dangerous damage without disassembling the inspected object or removing the protective coating. The developed eddy current probes are effective for detecting cracks in ferromagnetic steel products such as forgings, gas turbine blades and shafts, rails, wheels or axles of railway rolling stock, rough-surfaced castings, etc. In addition, high sensitivity to defects can be achieved even during the inspection through an air gap or dielectric coating. this allows them to be successfully used in many automated inspection systems. [ABSTRACT FROM AUTHOR] |
