Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics

Abstract

This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths.

Non-Destructive Evaluation of Concrete Structures by Non-Stationary Thermal Wave Imaging

“…Pulse compression technique prevalent in RADAR allows the transmission of a medium peak power, long duration modulated wave to improve the target detection range and resolution comparable to that achieved with a short duration high peak power pulsed based techniques [11,12,14]. This can be achieved with a correlation based pulse compression technique by cross correlation of the temporal temperature distribution over the chosen reference pixel s (t) over the sample, with the time delayed attenuated version of the pixel h (t) for an imposed linear frequency modulated incident heat flux over the sample.…”

“…Insight of the above mentioned advantages and limitations of the widely used conventional methods, this paper focuses on an experimental investigation for detection of corrosion of rebar in reinforced concrete structures by frequency modulated non-stationary thermal wave imaging [7][8][9][10][11][12][13][14][15][16][17][18].…”

“…This requires an external thermal stimulus to the inspected specimen in order to obtain significant temperature differences witnessing the presence of subsurface anomalies. The present work is mainly focused on the active approach [8][9][10][11][12][13][14][15][16][17][18].…”

“…In active approach [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], external heat stimulus is provided to the test sample of whose thermal response is to be observed. Known characteristics of the external thermal stimulation applied onto the specimen (i.e., nature of excitation, its time duration and its band width etc), facilitates the qualitative and quantitative characterization of sub-surface defects.…”

Application of IRNDT method for materials in wide range of thermal diffusivity

“…The necessary conditions for IRNDT testing method are homogeneous thermal excitation of whole inspected surface, limited inspection depth combined with defects size and elimination of reflections from surrounding and/or thermal excitation source directly to the detector of IR camera. According to the application, a suitable combination of excitation method, analysis method and evaluation method including their parameters has to be found [4][5][6][7].…”