A baseline-free damage localization method for multisource excited crosstalk using mixed copula function

Abstract Nondestructive testing (NDT) systems are critical for structural lifecycle management, yet existing algorithms struggle to address the challenges of distributed multisource systems, particularly crosstalk interference during large-area inspections. This study introduces an innovative damage detection and localization method tailored for fiber-based distributed ultrasonic excitation that uniquely enables lightweight, large-area coverage through multipoint excitation via a single optical fiber. To overcome the limitations of conventional approaches in handling distributed signal correlations, we propose a hybrid binary copula framework that optimizes copula hybridization to minimize fitting errors and precisely characterize signal dependencies. This method quantifies damage effects through correlation coefficient analysis and a novel correlation index, synergistically integrated with an energy index to form a baseline-free damage index that amplifies damage-induced signal variations. By eliminating the reliance on baseline data, this approach addresses a major bottleneck in scalable NDT applications. Experimental validation on a 2000 mm × 1000 mm × 0.5 mm aluminum plate demonstrated the system’s high-precision capability, successfully locating three coexisting damages with an average absolute error of 3.83 mm (0.31% relative error). The fusion of hybrid copula modeling and baseline-independent quantification establishes a paradigm shift for distributed NDT systems, balancing expansive coverage with sub-centimeter accuracy, which is a critical advancement in next-generation infrastructure maintenance.