Application of Terahertz Nondestructive Testing Technology in the Detection of Polyethylene Pipe Defects

At present, polyethylene pipeline is widely used in urban gas projects, but a relatively mature and reliable nondestructive testing technology has not been formed. Therefore, it is urgent to develop a new nondestructive testing technology to meet the increasing demand for inspection of non-metallic pipes. The terahertz testing technology and related equipment have played an increasingly important role in the nondestructive testing of many nonmetallic structures, but they have not been applied to polyethylene (PE) pipes. In this work, terahertz time-domain spectroscopy was used to detect prefabricated defects inside the PE pipe specimens. The results show that the terahertz nondestructive testing technology can be used to detect common defects in nonblack PE pipes with a detection error of less than 10%. Higher-power terahertz devices can detect defects in black PE pipe, while lower-power terahertz devices cannot. Because the black PE pipe contains carbon and has a strong absorption of terahertz waves. The penetration of lower-power terahertz devices to the black PE pipe is not enough, resulting in a low resolution of the imaging. The results of this work may promote the progress of the nondestructive testing technology of nonmetallic pipelines.