Section: New Results

Non Destructive Testing using Infrared Thermography

Optimal designs of experience for thermal NDT

Participants : Antoine Crinière, Jean Dumoulin.

During previous works, square pulsed thermography was used to carry out non destructive testing of bonding quality of CFRP glued on civil engineering structures during reinforcement operations. The use of such wave form excitation was motivated by “on-site” requirements, but also by measurements duration, number of composite layers to test, depth of possible faulting areas versus temperature elevation allowed at composite level according to inner heat diffusion. Nevertheless, square pulsed excitation implies to choose an adapted heat duration. This duration is directly linked to the reliability of the parameter estimator. According to these observations, an indicator able to predict the sufficient heating time when the reliability of the parameter estimator reached an asymptotic evolution behaviour was studied. Based on the absolute thermal contrast, the proposed indicator Iph is defined with the maximum thermal contrast and the time delay between the heating time and the appearance of the maximum contrast. This indicator allows to take into account the detectability as well as the induced flaw temporal effect on the thermal contrast shape evolution. This paper will present the establishment of this indicator for optimal square heating time and present an analysis of results obtained with numerical simulations and laboratory experiments. [28]

Thermal NDT and signal processing

Participant : Jean Dumoulin.

This work deals with the detection of non-emergent small structures like mosaic, hidden under a plaster layer, with various spatial layout and nature. Three post processing approach by PPT, SVD and Polynomial analysis were conducted on this experimental and simulated data set. Results obtained are analysed and discussed. Finally, influence of IR camera used will be also addressed and discussed in the dissertation. [35]