Ceramics and defects

Abstract

The feasibility of square-pulsed thermography nondestructive testing for the detection of defects in one ceramic material sample has been carried out by finite element (FE) analysis. In particular, a ceramic plate containing defects of different diameters, depths, locations, nature, and shapes has been numerically investigated by means of Comsol Ò Multiphysics computer program, taking into account the results coming from both a MATLAB TM script and the infrared thermography (IRT) technique. Indeed, the FE method simulates through a 3D model the heat transfer process induced into the ceramic material by two halogen lamps that have been applied in order to provoke an optimum thermal stress. Moreover, further defects like cracks arose beneath the surface of the plate due to the shrinkage process, have been discovered, and contrasted using a non-usual segmentation algorithm that when correlated in the time to IRT data simulates the thermo-elastic effect. Following the non-direct procedure proposed, both the depth of each defect and its main dimensions have been retrieved into a satisfactory accuracy.

Thermal studies of fly ashes expansion

“…Part of the emitted gases (CO 2 ) is the result of oxidation of unburned carbonaceous materials and thermal decomposition of carbonates. Others are the effect of redox reactions (reduction of iron oxides, but also sulfates and sulfides), and some are the result of reactions between clay components and admixtures [17][18][19][20]. The gases formed during the reaction cannot escape from the sintered material, which causes bubble creation; however, sufficiently slow heating of the material allows to complete these reactions before sintering and closing the pores [21].…”

Combination of FEM simulations and shearography for defect detection on artwork

“…Although these works were focused on metallic samples, recently, composite structures like carbon fibre‐reinforced polymer were investigated by Pagliarulo et al . Furthermore, thermographic simulations were done by different groups on cultural heritage like frescos, mural paintings, and mosaics . The interpretation of holographic fringe patterns on artwork though was done only experimentally by Tornari et al .…”

“…Although these works were focused on metallic samples, recently, composite structures like carbon fibre-reinforced polymer were investigated by Pagliarulo et al [34] Furthermore, thermographic simulations were done by different groups on cultural heritage like frescos, mural paintings, and mosaics. [35][36][37][38][39] The interpretation of holographic fringe patterns on artwork though was done only experimentally by Tornari et al [40] Especially the dependence of the size and depth on the fringe density could be shown on manufactured samples. Unfortunately, the fringe density depends also on other parameters like the structure of the object or the loading.…”

Comparative study of microlaser excitation thermography and microultrasonic excitation thermography on submillimeter porosity in carbon fiber reinforced polymer composites

“…IRT was already used for diagnostics and monitoring in several fields such as thermal comfort, 7 buildings, 8,9 cultural heritage, 10 artworks, [11][12][13][14][15] composite materials, 16,17 and so on. [18][19][20][21] The most often used IRT techniques are pulsed thermography and lock-in thermography, which use high-energy lamps to produce a uniform heating source on the specimen surface. The heat transmits through the specimen to the subsurface anomalies such as defects or damages and then returns to the specimen surface.…”