Reconstruction and analysis of pulsed thermographic sequences for nondestructive testing of layered materials

Abstract

We develop a heat transfer model to reconstruct pulsed thermographic data of layered objects. One of its salient features is its incorporation of normalized variables for a generalized approach to such problems. Additionally, we establish a methodology to determine the spatial and temporal limits of the data reconstruction process. Moreover, we describe an effective nondestructive technique for detecting and characterizing internal defects in multilayer objects. This inspection technique is verified on the construction of physical models and their examination. The depth, transverse dimensions, and front-surface shape of the detected defects are straightforwardly obtained from 3D depthgrams.

Detection of Differentiated Tissue with Pulse Thermography

“…This concept is illustrated schematically in Figure 2. [5] The obvious advantage of the detection of abnormal tissue in-vivo with IR radiation is its human-friendliness. Additionally, the living tissue is may be probed within the so-called therapeutic spectral interval, encompassing red to near IR [6], permitting transmission of illuminating radiation up to the point where a boundary between two optically/ physically different materials is encountered.…”

“…We may model a differentiated tissue as a three-layer setup to perform the pulse thermography. [5] object, with the thickness of the third layer very large.…”

Pulse Thermography for Detection of Differentiated Tissue

“…This concept is illustrated schematically in Figure 2. [5] The obvious advantage of the detection of abnormal tissue in-vivo with IR radiation is its human-friendliness. Additionally, the living tissue is may be probed within the so-called therapeutic spectral interval, encompassing red to near IR [6], permitting transmission of illuminating radiation up to the point where a boundary between two optically/ physically different materials is encountered.…”

“…Thus, optimum pulse duration must be adjusted to the anticipated depth of the defect. Figure 3 [5] illustrates normalized pixel temperature increase vs normalized observation of the temperature increase. This diagram may also be interpreted as showing two representative pixels in successive series of the frames: one encountering buried obstruction, and one freely propagating through the infinitely thick object.…”

Three-dimensional reconstruction of subsurface defects using finite-difference modeling on pulsed thermography

“…In the proposed technique, we use synthetic PT data with low noise to significantly simplify their processing. Synthetic data may be obtained from experimental data by using one of the procedures previously reported [28][29][30][31][32][33]. Then, we build a nodal network of a defect-free sample with the same geometry, structure, and physical properties as the inspected object.…”