Abstract: [Objective] A method for rapid and effective detection of internal cavity damages of wooden columns was explored to precisely determine the position and size of the internal cavity inside the columns.[Method] Pinus massoniana which are commonly used wood species in wooden members of ancient timber buildings were studied, and cavities with different shapes, sizes and positions were artificially made at the end of the wood columns to simulate the internal damages. Radar nondestructive testing technology was adopted to detect the cavities. By analysis of the specific patterns of the radar waves, rapid identification and characterization of the internal cavity damages of the wood columns can be realized.[Result] The result indicate that the radar nondestructive testing technology can be used to detect the internal damages of the wood columns rapidly. Once cavities inside the columns are detected, strong reflection will appear on the boundary presenting a reflection waveform of valley-peak-valley and meanwhile, the black-white-black especial patterns will appear on the radar image. The internal damage area inside the wood columns can be assessed roughly based on the radar image, though there is a discrepancy between the detected damage area by the radar and the actual damage area. It should be noted that the radar wave based method is difficult in retrieving the specific shape of the internal damages inside the columns. Without further data processing and analysis, it is difficult to identify various shapes of cavity damages such as triangle, quadrangle and circle. The radar image of the cavity damage at the edge of the wood columns differs remarkably from that in the center. The former is featured with a high fluctuation while the latter with a mild fluctuation. Thus, the cavity damages at the edge can be distinguished from those in the center based on this radar wave method.[Conclusion] Radar nondestructive testing technology is based on radar echo for target detection. This technology can be used to detect the internal cavity damages of timbers rapidly and estimate the position and size of the damages inside the timber.

Key words: Pinus massoniana, wooden column, cavity damage, nondestructive testing, radar, ancient timber building