Numerical DEM simulation of the evolution of damage and AE preceding failure of structural components
The authors examine, by Monte Carlo simulation employing the Discrete Element Method (DEM), the occurrence of micro-fractures and the evolution of damage in concrete plates subjected to nominally homogeneous, monotonically increasing pure shear and uniaxial tensile stress states until complete failure.
It is assumed that the damage process and the corresponding Acoustic Emission (AE) events observed in the cases studied are illustrative of typical situations in structural components in which failure occurs abruptly when the structural strength under quasi static loading is reached, i.e. at an unstable equilibrium point in Lyapunov’s sense, causing rapid fracture propagation and complete structural failure.
It was found that in the cases under consideration, the fracture process may be divided in two stages, of which only in the first stage the distribution in time of AE events may be modeled as a Poisson process.
In the second stage the assumption of a stationary process must be abandoned and changes in the frequency of occurrence or in the amplitudes of AE events may be useful predictors of the system strength. For this purpose the authors suggest a scheme applicable to systems subjected to increasing loading, in which experimental data is available for the loading stage preceding failure.
Keywords: Acoustic emission, Damage evolution, Fracture