Study on a health monitoring and defect imaging technology of special equipment that is based on optical fiber ultrasonic sensing

Abstract

Special equipment is prone to crack damage due to long-term pressure bearing during service. If the cracks in the structure are not detected in time and maintenance work is conducted, severe safety risks will be incurred. To overcome these problems, it is necessary to conduct full-time and full-domain structural on-line monitoring for special equipment to effectively prevent cracking of the special equipment and other safety accidents. Due to the satisfactory detection performance of optical fiber ultrasonic sensor technology, this paper conducted a finite-element simulation calculation and a detection experiment using a cracked plate and a special equipment model. Based on theoretical, simulation and experimental results, a distributed layout scheme of optical fiber ultrasonic sensor units for special equipment was proposed. The crack length, depth and external load conditions were discussed. The influence law of ultrasonic testing signals is employed for the identification and expansion analysis of the internal defects of special equipment with the optical fiber ultrasonic online monitoring technology that is investigated in this paper. A two-dimensional image of the internal defects of the structure is inverted via the time-of-flight method to realize the accurate positioning and quantification of defects, which endows the optical fiber ultrasonic nondestructive testing technology with a visualization functionality.