A novel approach to surface defect detection

Abstract

Defects or flaws in highly loaded structures have a significant impact on the structural integrity. Early inspection of faults can reduce the likelihood of occurrence of potential disasters and limit the damaging effects of destructions. According to our previous work, a novel approach called as Quantitative Detection of Fourier Transform (QDFT) using guided ultrasonic waves is developed in this paper for efficiently detecting defects in pipeline structures. Details of this fast method consist of three steps: First, an in-house finite element code has been developed to calculate reflection coefficients of guided waves travelling in the pipe. Then, based on boundary integral equations and Fourier transform of space-wavenumber domain, theoretical formulations of the quantitative detection are derived as a function of wavenumber using Born approximation. This lays a solid foundation for QDFT method, in which a reference model in a problem with a known defect is utilized to effectively evaluate the unknown defects. Finally, the location and shape of the unknown defect are reconstructed using signal processing for noise removal. Several examples are presented to demonstrate the correctness and efficiency of the proposed methodology. It is concluded that the general two-dimensional surface defects can be detected with high level of accuracy by this fast approach.

Circumferential defect detection using ultrasonic guided waves

“…Based on authors' previous work [21], the hybrid FEM [22] is implemented to numerically determine the scattered fields of annulus structures with circumferential defects as follows:…”

“…where and represent circumferential coordinates along the axis at the truncated left and boundaries of the defect. More details about the calculation of scattered fields using hybrid FEM can be found in [21].…”

“…Two important stages in this procedure include the calculation of reflection coefficients introduced in section 3 and the correction of integral coefficients below. More detailed information about QDFT can be found in [21]. Selecting a reference model with the surface defect function 0 ( 1 ) and calculating the corresponding reflection coefficients 0 ( 01 ) by the hybrid FEM Converting the spatial surface defect function into the…”

“…The obtained results have been validated by other published data. To calculate scattered fields, the in-house hybrid finite element method (FEM) (Da et al , 2018; Stoyko et al , 2014) has been developed to numerically determine the scattered fields and its correctness has been verified by the theory of energy conversation. Finally, the developed quantitative detection of Fourier transform (QDFT) approach has been applied to reconstruct four types of surface defects in annulus structures with high levels of accuracy and efficiency.…”

Research on Pipeline Damage Imaging Technology Based on Ultrasonic Guided Waves

“…e phenomena of energy focusing can magnify the small defect, and the location of the defect is given simultaneously. Da et al [16] proposed the Quantitative Detection of Fourier Transform (QDFT), a novel approach capable of providing a high level of accuracy and efficiency for nondestructive detection of defects.…”