Vibrothermography for NDT : dynamic control of thermal sources by acoustic fields

Among the plethora of Non-Destructive Evaluation (NDE) techniques, the coupling of acoustic/vibration and thermography has emerged as a powerful method, more particularly denoted as sonothermography, utilizing the principle of energy conversion from acoustic waves to thermal heat sources to reveal structural abnormalities or create tunable volumic sources in materials. The calculation of the displacement field induced by acousto-vibrational excitations, using the analytical expression of energy conversion, has led to the generation and modeling of localized thermal sources in space over time within a material. By manipulating the input parameters of acoustic signals (frequency, phase, amplitude), we have demonstrated that it is possible to strategically position these sources in space and optimize the dissipation of thermal energy. The variation of parameters (creating a phase shift, a beat, a reversal law, etc.) makes it possible to control and move these internal heat sources to scan the material (in numerical approach and in the near future experimentally). The analysis of the resulting fields (acoustic-vibration and thermal), using inverse methods, opens up new possibilities for measuring the physical properties (mechanical, thermal) or characterizing defects in a material.