What does transient condition mean?

• A. Temperature remains constant
• B. Temperature changes over time
• C. Temperature is always higher than ambient
• D. Temperature is undefined

Answer: (B)

Transient condition means the temperature is changing over time, not staying constant. In infrared thermography, this happens when heat is applied or removed and the surface (and subsurface) temperatures rise or fall as the material responds. This time-dependent behavior—the way temperature evolves with time—is what we analyze to reveal differences in material properties, thickness, or possible defects. The other options describe steady-state (constant temperature), a condition not required for transient, or an undefined state, which aren’t what transient means.