A general quantitative identification algorithm of subsurface defect for infrared thermography

A numerical method for determining thermal conductivity distribution of the interlayer of a sandwich plate based on thermographic temperature measurement

“…In recent years, inverse methods for heat conduction problems have become widely used in theory and practice. These inverse heat conduction problems (IHCPs) are involved with finding the unknowns such as the boundary conditions [1,2], thermophysical properties [3][4][5][6][7][8][9], boundary configurations [10,11] and subsurface inclusions [12][13][14] from interior or surface temperature measurement. In this paper, the thermal conductivity distribution of the interlayer of a sandwich plate is estimated with an inverse method based on the surface temperature measurement.…”

A new computational scheme on quantitative inner pipe boundary identification based on the estimation of effective thermal conductivity

“…The identification of the geometry of the irregularly shaped inner pipe boundary based on temperature measurement at the outer surface belongs to the inverse geometry problem, a kind of inverse heat conduction problem (IHCP). Two branches of the inverse geometry problem have been of major concern recently to researchers: one is the detection of the possible damage in the finite body which has been studied by using the steepest descent method [5], the Levenberg-Marquardt method [6,7], the conjugate gradient method [8,9] and other specific methods [10,11]; the other is the identification of the unknown boundary shape which is the problem considered in this paper. Many algorithms have also been developed by now to solve this boundary identification problem.…”

An algorithm study on the identification of a pipeline's irregular inner boundary based on thermographic temperature measurement

“…The past three decades have been most active in the advancement of solution techniques for the IHTP, such as Tikhonov's regularization procedure [8,9], Alifanov's iterative regularization techniques [10][11][12], Beck's function estimation approach [13,14] and their succeeding developments for which one can refer to [15]. Among these techniques, the Levenberg-Marquardt method and conjugate gradient method stand out in solving IHTP for their stable, powerful and straightforward characteristics, which have been applied by many authors to shape identification [16][17][18], boundary condition estimation [19][20][21], heat source strength determination [22], subsurface defect detection [23,25], and so on. By comparison of the two methods in boundary identification of one direction, Huang [16] concluded that the conjugate gradient method is more powerful in dealing with problems with more parameters.…”

“…Based on Huang's [16] work and our previous studies [2,[23][24][25][26] on quantitative thermographic inspection, this paper will (1) numerically study the thermal character and detectability of defects on a pipeline's inner boundary when a steady-state or a transient inspection method is employed, including their effecting factors; (2) apply the conjugate gradient method along with the finite element method to the identification of a pipeline's inner boundary for both steadystate and transient inspection techniques; and (3) investigate the effect of the initial guess, measurement error, etc on the algorithm's precision level.…”