Recently we proposed a modification of the classical flash thermography method for diffusivity measurement: by putting a mask having a periodic pattern of apertures between the flash lamp and the orthotropic material to be tested, one can obtain simultaneously the out-of-plane diffusivity and the in-plane diffusivity of the material. Here we present two examples where the measurement of the thermal properties is made at a local level: the experiment is performed with a large grid mask, however the parameter identification is made on a sliding window whose width corresponds to one-period of the mask. By this way, one can get a profile for each diffusivity. By applying this procedure, one can expect detecting localised variations of the thermal properties, as well as cracks.
We controlled by this way a series of C/C-SiC dog-bone samples during a tensile test. We systematically observed a rather uniform and linear decrease of about 0.1%/MPa for the in-plane diffusivity. This behaviour is related with the fact that a stress increase induces a gradual increase of the microcracks density. The second example deals with carbon disk brakes control. By using a circular mask, one can get in about two minutes the circumferential profile of both in-plane and out of plane diffusivities of the composite piece.
The aim of this work is to demonstrate the possibility to develop and test a specific control procedure based on the use of thermography, for hot forging of glass components. A methodology for the analysis and the control of the process, in terms of amount of wastes, has been implemented, through the control of some easily measureable features, such as the temperature of the forge or of the component itself.
Among the non destructive methods used for the control of composite material, the infrared thermography is being given more and more attention since it enables to analyze the effects induced by the anomalies on the thermal behavior of the material. In particular the Lock-in and the Pulse techniques can provide information about the dimension and the depth of the defects. The present work aims at exploit the results given by the thermographic analysis, after a continuous heating by means of a microbolometric thermocamera, by defining a hybrid procedure, numerical and experimental. The main purposes of the hybrid procedure are: Determining the characteristics (in terms of dimensions and depth) necessary in order to make a certain type of defect detectable inside a laminate of composite material; Discovering the minimum prerequisites which a thermographic detection system should have.