The safety diagnostic inspection of large plate structures, such as nuclear power plant containment liner plates and aircraft wings, is an important issue directly related to the safety of life. This research intends to present a more quantitative defect imaging in the structural health monitoring (SHM) technique by using a wide range of diagnostic techniques using guided ultrasound. A noncontact detection system was applied to compensate for such difficulties because direct access inspection is not possible for high-temperature and massive areas such as nuclear power plants and aircraft. Noncontact systems use unstable pulse laser and air-coupled transducers. Automatic detection systems were built to increase inspection speed and precision and the signal was measured. In addition, a new Difference Hilbert Back Projection (DHB) algorithm that can replace the reconstruction algorithm for the probabilistic inspection of damage (RAPID) algorithm used for imaging defects has been successfully applied to quantitative imaging of plate structure defects. Using an automatic detection system, the precision and detection efficiency of data collection has been greatly improved, and the same results can be obtained by reducing errors in experimental conditions that can occur in repeated experiments. Defects were made in two specimens, and comparative analysis was performed to see if each algorithm can quantitatively represent defects in multiple defects. The new DHB algorithm presented the possibility of observing and predicting the growth direction of defects through the continuous monitoring system.

Silicone rubber (SiR) has been an important material widely used in the cable accessories in cross-linked polyethylene (XLPE) cables. The electrical tree is a serious threat to SiR insulation and it will cause breakdown when reaches the ground. The high carrying capacity of superconducting cable makes the magnetic flux density up to hundreds of mT around the conductor. However, the effect of high magnetic flux density on electrical tree in SiR has not been researched. In this paper, the magnetic flux density ranged from 0 to 400 mT. The electrodes were typical needleplate electrodes. The frequency of the applied AC voltage was 50 Hz. The growth process of electrical tree was recorded by a microscope system and the pictures were taken. The experiment result indicated that the high magnetic flux density changes the tree structure and affects the growth of tree length and width.