液体アンモニア処理木材の割裂破壊におけるAEの挙動

抄録

The acoustic emission (AE) signals associated with the cleavage fracture process were measured during fracture toughness tests of Sugi (Cryptomeria japonica) and Red lauan (Shorea negrosensis) woods. In addition, the effects of liquid ammonia treatment on the fracture toughness and the AE parameters such as event count, amplitude distribution and spectrum were examined.
The following results were obtained;
The AE total count, N_T under the tests up to the maximum load in Sugi was larger than that of Red lauan wood. For both woods, N_T of radial direction (crack surface: TL plane) was larger than that of tangential direction (RL plane). After the liquid ammonia treatment, AE events were decreased considerably, and N_T in Sugi and Red lauan were reduced to one fifth and half, respectively.
From the AE amplitude distribution analysis, the difference in distribution profile between RL- and TL-cracking was observed in untreated Sugi, but not observed in treated Sugi, nor in treated and untreated Red lauan.
The characteristics of AE spectra in TL and RL planes were examined, but any good result could not be obtained.
The fracture toughness, G_IC of TL and RL planes in Red lauan were approximately 0.42 and 0.25N/cm, respectively. After treating with liquid ammonia, G_IC was increased with the treatment time. The G_IC of TL plane had a constant value (1.43N/cm) after 8 hours of the treatment, and the G_IC of RL plane took a maximum value (0.97N/cm) at 15 hours.