Factors Influencing Impact Echo Simulations in Thick Concrete Structures

Impact Echo (IE) simulations with heterogeneous concrete models have been very rare in the past. However, they could prove to be a valuable tool for enhancing physical understanding and improving data evaluation through artificial intelligence for future IE testing. Such improvements would result in more accurate condition assessments in industrial applications, such as for the inspection of nuclear power plant containment structures, among others. This study presents and discusses parameters influencing the outcome of IE simulations using the elastodynamic finite integration technique (EFIT). These parameters include the effective wave speed in concrete, which depends on the degree of heterogeneity. Additionally, the study explores wave scattering in the Rayleigh limit, identified as a primary noise source during actual IE measurements and discusses approximations for the source function, which ensure stability of the simulations. Lastly, the damping properties of the simulated concrete are discussed, recognizing the challenges in simulating elastic wave damping in low-frequency regimes. Following the discussion of these influencing parameters, the study presents results from 2D and 3D IE simulations of a test specimen, comparing them to real inspection data. Generally, results from 3D simulations exhibit a good agreement with measurement data in various aspects, whereas applications for 2D simulations are more limited yet also valuable.