A non-iterative reconstruction technique for wave velocity field of damaged structures based on acoustic emission finite response

Aiming at the issue of low iterative efficiency and accuracy of reconstruction methods in wave velocity field such as algebraic reconstruction technique (ART) and simultaneous iterative reconstruction technique(SIRT) in current tomography technology, this paper takes the damaged elastic plate as a research object and utilizes the acoustic emission (AE) technology with high frequency and high sensitivity to propose a discrete wave velocity field reconstruction technology based on multi-point lead break excitation and finite point AE response. This technique overcomes the problem of sparse discrete grid and low-quality wave velocity field reconstruction in the test area which is affected by the limited travel line number between excitation and response. First, a relationship model between material wave velocity, Young’s modulus and damage factor is established by applying theories of elasticity and damage mechanics. Second, based on the discretized elastic plate grid domain and the time-difference vectors between the discrete travel paths, a linear model for reconstructing the wave velocity field in the discretized grid domain is established, incorporating the wave slowness in the grid domain, the discrete unit length of the travel route, and the time differences. On this basis, based on the quantity of the discretized grid domain, a method is proposed to determine the number and position of multiple break lead excitation points on the elastic plate boundary based on finite AE sensor response points, which can make the augmented matrix rank of the reconstructed linear model based on the time difference vector not less than the coefficient matrix rank of its wave slowness. Third, a time parameter extraction method from lead break excitation to AE response is proposed by using the long short-time window time difference algorithm. In addition, the reconstruction analysis of wave velocity field by non-iterative algorithm of the plate structure can be realized by using the least squares algorithm. Finally, the effectiveness of wave velocity field reconstruction technology and damage location identification is verified by taking the elastic structure plate with hole defects as an experimental example, thus providing a convenient and accurate non-destructive testing method for overall health assessment of critical structural components in equipment