Acoustic emission measurements and lattice simulations of microfracture events in spruce

Abstract

A statistical lattice model was developed to investigate the energy associated with damage and failure of wood. The model incorporates several important morphological aspects of wood such as grain direction, early wood percentage and grain geometry. The model was developed to investigate progressive damage under enforced boundary displacements and has been adapted to predict fracture energy related phenomena. In this particular study, notched specimens were loaded in uniaxial tension while monitored by a passive acoustic emission (AE) measurement system. The energy associated with the mechanical damage was measured by the AE instruments and compared with the energy released by ruptured elements in the lattice model. Cumulative energy release was tracked as a function of specimen load and deformation in both model and experiment. A ratio was established between the cumulative AE energy released at the first drop in load and the cumulative fracture energy released when the model load-deformation relationship becomes significantly nonlinear. An additional ratio was established between the total fracture energy measured prior to 50% of peak strain and the total fracture energy measured prior to peak strain. The magnitudes of these energy release ratios vary owing to a change in failure modes between the short model and the larger specimens; however, the shape of the AE energy release curve up to failure coincides well with that predicted by the model simulations.

Acoustic emission analysis of industrial plywood materials exposed to destructive tensile load

“…5c), its cumulative AE energy follows an almost exponential increase path (Fig. 8) and hence indicates the nonlinearity in damage evolution (Nagy et al 2010). In the case of plywood materials, the exponential increase in normalized cumulative AE activity (Fig.…”

Numerical modeling of timber with knots: the progressively damaged lattice approach vs. the equivalent damaged continuum

“…Introduced for wood by Landis et al (2002), this distinct view consists of modeling by a series of linear elements similar to the real wooden fibers. It was demonstrated that this approach provides satisfactory results at smaller scales, despite the higher complexity Brought to you by | University of Georgia Libraries Authenticated Download Date | 6/5/15 10:28 PM of construction and calibration (Davids et al 2003;Fournier 2005;Fournier et al 2007;Sedighi-Gilani and Navi 2007;Vasic and Stanzi-Tschegg 2007;Landis and Navi 2009;Nagy 2010;Nagy et al 2010). This approach facilitated the application of additional concepts in numerical wood models such as growth rings, mechanical variability, and heterogeneous failure patterns.…”

Random field generation of the material properties in the lattice discrete element method

“…Examples of the Continuum Mechanics approach are the classical model proposed by Ottosen, 2 examined later by Voyiadjis, 3 and the contributions of Li et al 4 and Lv et al 5 The lattice discrete element method (LDEM), used in this article, belongs to the second group. Other models that follow this approach were proposed by Schlangen and Van Mier, 6 Krajcinovic and Vujosevic, 7 Sagar and Prasad, 8 Nagy et al 9 and Rinaldi, 10 and Jivkov and Yates 11 and examine the relationships between different lattice arrangements with the material properties of an equivalent continuum, while Mastilovic and Rinaldi 12 present an extensive revision of different versions of the lattice approach.…”