RESEARCH ON WOOD DAMAGE FRACTURE CHARACTERISTICS BASED ON ACOUSTIC EMISSION RA-AF VALUE AND ENERGY CONCENTRATION

To study the acoustic emission (AE) characteristics and fracture properties of wood at different stress stages, three-point bending tests and real-time AE monitoring were carried out on Zelkova schneideriana and Pinus sylvestris var. in this paper. Different stress stages were classified according to AE ringing counts-cumulative AE ringing counts-load curves, damage modes of wood at different stages were identified based on distribution characteristics of RA-AF data, and fracture behavior of wood was predicted by energy concentration k. Results show that distribution characteristics of AE RA-AF data can characterize the types of cracks generated in each stress stage of wood. The crack modes generated by both specimens during three-point bending loading are tension shear composite cracks, and the proportion of tensile cracks is significantly higher than that of shear cracks, but during the elastic-plastic stage, Zelkova schneideriana specimens will produce a large number of shear cracks, whereas Pinus sylvestris var. specimens have predominantly tensile cracks, with only a small number of shear cracks produced before and after fracture. The sudden change in the energy concentration k curve between elastic-plastic deformation stage and fracture stage can be used as a precursor of damage for both specimens under three-point bending test conditions.