基于声发射临界慢化特征的木材断裂前兆OA

To predict the micro and macro failure behavior of wood under load,a prediction approach of wood damage precursors based on the b-value(describe the frequency distribution characteristics of acoustic emission signals)of the acoustic emission(AE)signal and the critical slowing down(CSD)characteristics was proposed.Firstly,to analyze the impact of load application rate on the wood failure process,two loading rates of 2 mm/min and 5 mm/min were employed in the wood three-point bending experiment,and AE signals released during the damage process of wood specimens were collected at a sampling rate of 500 kHz.Subsequently,an improved b-value calculation approach based on the classifica-tion of AE signal amplitude was proposed,and the AE signals generated during the experiment were divided into three levels,and the process of crack generation and development inside the wood specimen under load was described accord-ingly.Finally,in accordance with the principle of CSD,a prediction method of wood fracture precursors based on the length correlation coefficient and variance of AE signal was presented.The results demonstrated that the combination of different levels of b-values can reflect the fracture features and the generation of microcracks in the damage process of the specimen.CSD occurred when wood cracked at both the micro and macro levels,which was manifested in the increase of the correlation coefficient and variance of AE signal.At different loading rates,when the load reached approximately 80%of the ultimate yield strength,all the specimens displayed a significant CSD phenomenon.