Pulsed thermography and active thermography are both non-destructive testing techniques used for detecting defects or anomalies in materials or structures. While they share similarities, there are some differences between the two methods.
Pulsed thermography is a technique where a specimen or structure is heated using a short burst or pulse of energy, typically through an intense flash of light or a high-power heat source. The energy input causes a rapid temperature rise on the surface of the material, and as the heat diffuses into the material, any subsurface defects or irregularities affect the thermal response. A thermal camera or an infrared imaging system is used to capture the surface temperature variations over time. By analyzing the cooling patterns, thermal contrasts, or temperature gradients, defects such as delaminations, voids, cracks, or inclusions can be detected.
On the other hand, active thermography encompasses a broader category of techniques that involve applying an external energy source to the material under inspection. This energy source can be in the form of heat, light, ultrasound, or electromagnetic radiation. Active thermography techniques include pulsed thermography as one of its variants. Other variants of active thermography include step-heating thermography, lock-in thermography, frequency modulated thermography, and vibrothermography.
The primary difference between pulsed thermography and active thermography lies in the nature of the energy source and the temporal profile of energy application. Pulsed thermography specifically refers to the use of a short, intense energy pulse to heat the material. In contrast, active thermography encompasses a wider range of techniques that employ different energy sources and application methods, such as continuous heating, modulated heating, or vibrational excitation.
To summarize, pulsed thermography is a specific type of active thermography technique where a short, intense energy pulse is used to heat the material for defect detection. Active thermography, on the other hand, is a broader term encompassing various techniques that utilize external energy sources to induce thermal responses in materials for defect detection.