Study of the phase transition of a medium using reverberated signals

Abstract

Abstract Non-destructive testing (NDT) methods nowadays are essential in materials and structures control due to their capability to not affect the integrity of material. These methods are particularly efficient for the monitoring of resin or composites formation. In particular, ultrasonic technics can be used to evaluate mechanical properties of materials by measuring acoustic waves characteristics. In general classical characterization techniques, based on linear measurements, give local information’s of medium. Reverberation methods, classically used in room acoustics, allow global characterization. This approach is not so common in NDT or structure monitoring. The reverberation signals which contain global information about propagation media properties, are highly dependent on the boundary conditions. Sabine’s formula gives the relationship between reverberation time RT and wall attenuation coefficient can be adapted in many acoustic applications. Previous studies established a relation between RT and solid interfaces absorption. In the case of a sol-gel material, the reverberation time measured in a metallic block can be linked to the material properties such as density or viscosity. The RT will vary during the phase transition of our material from liquid to solid state. Hence, our motivation is to derive the equation of the acoustic intensity for solid interface absorption considering the shear and the longitudinal waves. Furthermore, to estimate the reverberation time from the determined acoustic intensity (simulation part) and to compare the results with the experimental part. For this reason, experiments were performed to validate the simulation part. Measurements are preformed in an aluminium mold using five piezoelectric (PZT) patches, one being used as emitter and the others as receivers has been studied and it’s evolution is shown to lead to a good estimation of the phase transition time.