Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems.

摘要

Conclusions from this research activity are summarized as: (1) Cavity like mechanical defects and heat induced damages in porous foam tiles can be detected by electromagnetic THz radiation; (2) Required frequency of the THz beam for sensing mechanical defects depends on the orientation of the defects. THz beam propagating parallel to a cylindrical cavity can detect the cavity at much lower frequency compared to a THz beam propagating perpendicular to the cavity axis; (3) Electromagnetic properties of the foam material are altered significantly, well before its melting point. Therefore, heat induced damage can be easily detected by THz beam, well before the material is melted; (4) Distributed point Source Method (DPSM) has been extended to model both electromagnetic and elastic wave interaction with defects. DPSM is found to be more efficient than FEM, especially for three-dimensional modeling; (5) Some modifications on the DPSM technique have been suggested to improve the technique's accuracy and efficiency for solving both steady state and transient problems; and (6) Some experimental observations have been justified through model predictions.