摘要
Datong Yungang Grottoes is called "Treasure house of Chinese grotto art", which dating back over 1500 years of history, due to long-term suffering from human factors, natural conditions, climate and environmental change, the existing state is deteriorating. Therefore, it is urgent to carry on systematic and comprehensive exploration, restoration and protection. The ultrasonic method as a quick and effective nondestructive technology plays an important effect in disease detection and protection of stone relics. Application of couplant is a necessary precondition to obtain satisfactory results, and inappropriate choice of couplant will directly affect the test accuracy. In this paper, the detection methods of TO and test block were used indoor for testing kinds of common and self-made couplants, though analyzing the first wave of sound and the root mean square error, combining with the characteristics of the actual target of detection, analyzing and evaluating material, complexity of operation, advantages and disadvantages of each couplant, to propose alternative couplant and also provide technical basis for the stone relics of Yungang Grottoes on-site inspectton.