Inverse Contrast in Non-Destructive Materials Research by Using Active Thermography

Area of Science:

• Building Science
• Materials Science
• Non-Destructive Testing

Background:

• Defects in building partitions and units are undesirable.
• Advanced non-destructive techniques are needed for defect localization, particularly active thermography.
• Research aims to improve active thermography for testing large, high heat capacity building units.

Purpose of the Study:

• To explore the application of active thermography for detecting material inclusions in large building units.
• To assess the effectiveness of active thermography in identifying defects within gypsum board and oriented strand board partitions.

Main Methods:

• Construction of gypsum board (GB) and oriented strand board (OSB) partition models with embedded inclusions (styrofoam, granite, steel).
• Thermal excitation using a 7.2 kW infrared radiator for 30 minutes.
• Monitoring temperature field distribution on both sides of the partitions over several hours.

Main Results:

• Defects detectable under at least 22 mm of cladding.
• Observation of inverse temperature contrasts during the cooling phase (warm areas become cool, and vice versa).
• Defects appear as warmer areas in transmission mode; quantitative depth analysis achieved with 10% accuracy using Echo Defect Shape method.

Conclusions:

• Active thermography is a viable non-destructive testing method for construction applications.
• Appropriate recording duration allows for the observation of inverse contrasts on the same surface.