Abstract
The experiments involved infrared thermography analysis and inspection technique for electrical apparatus are common in US, Europe, and Japan. Infrared thermography is also adopted for researches of buildings for many years, such as noncontacting, nondestructive testing for structures of energy conservation purposes. Recently, infrared thermography is also used to detect defects of buildings, such as water leakage, air conditioner system leakage of building exterior walls and peeling of tiles from exterior walls.
Since peeling of tiles from exterior walls involves public safety concerns, it is paid highly attention both in Taiwan and worldwide. Many researchers have already devoted to relevant detection methods. In Japan, the detection of peeling exterior wall tile using infrared thermography became an industry and a system was build for the industry.
The nondestructive testing method of infrared thermography applied to exterior tile wall was mainly used to detect delamination between tile surface, adhesive layer and base concrete layer. The air layer caused by delamination produced temperature difference between the normal and defect area after exposed to the sun. The difference can be shown immediately by the infrared thermography images.
This research applied design of experiments method as using different adhesive materials for tiles of exterior walls. The nondestructive testing technique of infrared thermography was used to discuss the characters for detecting delaminated tile adhesive system with different adhesive durations and locations. Infrared thermography method has the advantages as remote, noncontact and one-time inspection
A simulated exterior tile wall system was established using the existing infrared camera in our institute with active heater design and a heavy, adjustable experimental frame. Therefore, the infrared thermography inspection can be conducted under the same heating condition.
The research results showed that after heating the exterior tile wall system using an infrared lamp in the laboratory for 2 minutes, locations of buried delamination defects can be observed in infrared thermography images. The infrared thermography images that heated between 37~69 minutes showed the location of buried delamination defect with most color contrast (i.e. with the most temperature difference with the perfect bonding location). The locations of defects cannot be observed when the temperature near the peak and at the following cooling stage.
The historical temperature distribution for each temperature picked at cooling stage was fitted into an equation of 3 sections with 3 characteristic value m, which was treated as the response value of experimental design. The results of analysis of regression and variance showed and most representative characteristic value m for the exterior tile wall system was the m value of the fitted equation during the initial 5 minutes at the cooling stage, which can identify adhensive material, adhensive duration and specimen location most.
The discussion above showed the best time to conduct non-destructive testing on exterior tile wall system of real buildings for delaimnation defects is in the morning when the building is heated by the sun. As to identify surface temperature characters of the exterior tile wall system, such as adhensive material and adhensive duration, the characteristic value m of fitted equation for initial 5 minutes at cooling stage can be used for comparison.