关键词: 声发射, 临界点, 无损检测, 山杨

Abstract:

The acoustic emission (AE) evolution process of David Poplar (Populus davidiana) samples was investigated by combining the two methods of mechanics testing and AE technique when the samples were imposed to the dynamic loads. By analysis of AE parameters and the elastic-viscosity of wood, the AE characterization under different loads was explored. The results are: 1) AE amplitudes are not continuous and leap from one another. The AE amplitudes and energy before fracture damage are lower than those after fracture damage. Moreover, while the material is fracturing the local maximum of AE amplitudes and AE energy appears. 2) With the time and loads changing, the increase speed of AE cumulative hits and AE cumulative energy can exactly identify complete elasticity, dominant elasticity with the coexist of elastic-plasticity and dominant plasticity with the coexist of elastic-plasticity of wood, which of the three stages are the most important feature of wood under loads. 3) The AE rate and amplitude can be employed to predict two “critical points" of wood fracture damage. The first point represents that the fibers begin to peel off from each other and a few of fibers begin to rupture, which means the material is in the state of slight danger. The other point represents lots of fibers begin to rupture, which means the material is in the state of serious danger. If loaded continuously the material will fracture.

Key words: acoustic emission(AE), critical points, non-destructive testing, Populus davidiana