Modelling of Crack Growth Based Acoustic Emission Release in Aluminum Alloys

Various theories in the past have addressed the correlation of material properties and the respective acoustic emission release during fracture. Whilst these theories yield good predictions for fundamental relationships, they neglect the dynamic displacements during crack formation. This paper presents first results for a new acoustic emission crack source model based on a finite element modelling approach which calculates the dynamic displacement field during crack formation. The specimen modelled is statically loaded until conditions for crack growth (e.g. local exceedance of material’s fracture toughness) are fulfilled. Crack growth is modelled by local degradation of the material properties in the crack process zone. The respective displacements generate the acoustic emission signal and allow detailed examination of the generation of acoustic emission signals. Subsequent to crack growth signal propagation in a simple tensile specimen is modeled. The signal propagation is modeled superimposed to the static displacement field. The influence of the crack propagation length, the static displacement field and material plasticity is investigated. It is demonstrated, that present analytical theories systematically underestimate the strength of acoustic emission sources. Strong discrepancy was found between the rise-times predicted by the present simulations and those assumed in analytical theories.