Coupling AE Monitoring with Discrete Element Fracture Models

The monitoring and analysis of acoustic emissions related to fracture can be a trade-off between the simplistic yet practical empirical relationships and the more tedious yet fundamental relationships. In an intermediate area between these extremes, we are using acoustic emissions to monitor progressive fracture energy of small specimens of clear-grained wood. The wood specimens were modeled using a statistically variable lattice to represent material heterogeneity and disorder. The central hypothesis of the work is that a microfracture event captured by AE should correspond to the fracture of lattice elements in the simulation. Furthermore, the energy of the AE event should correspond to the local fracture energy released in the lattice simulation. By coupling lattice simulations with laboratory tests, we were able to establish a ratio between the cumulative fracture energy released in the simulation with the relative energy monitored by the AE system up to peak load. The magnitude of this ratio varies with failure mode, but in all cases, the shape of the cumulative AE energy captured mirrors the shape of the cumulative lattice fracture energy released. The results allow us to better match lattice element properties with the physical microstructure that the lattice elements are meant to represent.