Table 2.
Summary of active IRT methods used for aerospace applications.
| Physical Principle | Thermal Source | Active IRT Terminology | Abbreviation | |
|---|---|---|---|---|
| Optical Radiation | Optical flash, lamp and electrical heaters | Optically Stimulated Thermography (OST) | Pulsed Thermography [20] (or Flash Thermography) | PT |
| Lock-in Thermography [21] (or Amplitude Modulated Thermography) | LIT | |||
| Step-Heating Thermography [22] and Long Pulse Thermography [23] | SHT and LPT | |||
| Frequency Modulated Thermography [24] | FMT | |||
| Optical laser | Laser-spot Thermography [25] and Laser-line Thermography [26] | LST and LLT | ||
| Acoustic/Ultrasonic Wave Propagation | Acoustic/Ultrasonic horn, piezo-ceramic sensors, air-coupled transducers | Ultrasonic Stimulated Thermography [27] (or Thermosonics, Vibro-thermography and Sonic IR Thermography) | UST | |
| Nonlinear Ultrasonic Stimulated Thermography [28] | NUST | |||
| Electromagnetic Radiation for dielectric materials | Induced eddy currents | Eddy Current Stimulated Thermography [29] | ECST | |
| Microwaves | Microwave Thermography [30] | MWT | ||
| Material enabled thermo-resistive radiation for composite materials | Electrical current applied to carbon fibres | Direct Material-based Thermography (DMT) | Electrical Resistance Change Method (ERCM) coupled to thermography [3] | |
| Electrical current applied to embedded steel wires | Indirect Material-based Thermography (IMT) | Metal-based Thermography [32] | MT | |
| Electrical current applied to embedded carbon nanotubes | Carbon Nanotubes-based Thermography [33] | CNTT | ||
| Electrical current applied to embedded shape memory alloys wires | Shape Memory Alloys-based Thermography [34] | SMArT | ||