Determination of effective properties of concrete by Finite Element simulations for ultrasonic NDT
ABSTRACT The ultrasonic testing of concretes is strongly affected by their inhomogeneous structure, which determines wave propagation velocities and causes attenuation. The work presented here aims at determining the effective properties of a concrete using time-domain Finite Element simulations. Numerical samples of concrete, represented as a mortar matrix containing aggregates, are randomly generated. The propagation of plane waves through these samples is simulated using Finite Elements for space discretization, and an explicit time scheme for time integration. The obtained ultrasonic field is processed to extract effective velocities and attenuations. The whole procedure has been implemented as new simulation modules in a development version of the CIVA platform. A module performing high-order Finite Element calculations in two dimensions had been the subject of a joint study between CEA and EDF. This communication introduces another tool, based on low-order computations on regular grids. It can perform two or three-dimensional calculations. These tools aim at providing input data for propagation calculations, and at validating analytical models. Cross-validation results obtained with the two approaches for two-dimensional configurations are presented. Results obtained with the low-order code in three dimensions are also shown. Theoretical results obtained with the Waterman and Truell model are included for comparison.