基于声发射技术研究木材表面裂纹对应力波能量衰减特性的影响OA北大核心

Cracks in wood have a non-negligible effect on the propagation characteristics of stress waves.It is significant to inves-tigate the energy change law for the crack depth identification in wood.Pinus sylvestris var.mongholica Litv.wood was used as the specimen in the study,and different numbers of cracks were made on different specimens.The depth of cracks was gradually in-creased from 0 to 90 mm with an increment of 10 mm each time.Firstly,an acoustic emission(AE)sensor was used to collect the stress wave generated on the surface of the specimen by the pencil lead breaking,and its time-frequency characterization was per-formed.Secondly,the energy attenuation model of the stress wave in different frequency bands was established based on discrete wavelet analysis.The results showed that,the percentage of AE signals with frequency components of 125 to 250 kHz in the transient wave decreased significantly with increasing crack depth.As the number of cracks increased,the coefficient indicating the attenuation degree in the energy attenuation model after wavelet reconstruction of the AE signal increased from 0.73 to 1.09.In addition,with the increase of crack depth,the energy decay of the wavelet signal with frequency components of 31.25 to 62.5 kHz was obviously slow.And the crack region determined by the energy attenuation model can cover the location of the actual crack.