Abstract:

Abstract: Take two softwoods and two hardwoods as test materials, studied on microstructure evolves of non-flaw and crosswise crack-contained specimens under bending break process by acoustic emission (AE) technology, and using the AE characteristic parameters to distinguish several damaged types. The results indicate: the ratio of AE hits occurred of non-flaw specimens were small during the initiation of loading,and mainly appears low amplitude and low energy AE signals. As the load reached the peak and during the fracture stage, a large number of AE hits occurred and its amplitude and energy were high. Using the AE set monitor the entire damage-fracture process of crack-contained specimens under three-point-bended, may distinguish the crack tip to sidewise initiation and expansion on different stages obviously. AE signal characteristic related to damage pattern, the AE signals are large amplitude,large energy and long duration when cell-wall break, but AE signals are low amplitude, low energy and short duration as cell-wall interface damage,interlaminar fracture, cell yield and collapse damage. The Kaiser effect appears at lower loading level, but the Felicity effect appears at lower loading level.

Key words: Key words: wood, damage and fracture, acoustic emission characieristics, felicity effect