Study On The Evolution Characteristics And Prediction Methods Of Acoustic Emission Of Waterlogged Archaeological Wooden Relic,and Equipment Development

Because the porosity of waterlogged archaeological wooden relic is higher than that of modern wood,it has stronger hygroscopicity.However,it is extremely susceptible to the influence of environmental relative humidity fluctuations,resulting in uneven distribution of moisture content,which leads to stress concentration,which causes many forms of damage such as fractures and distortions of the cultural relics.This phenomenon is not conducive to the long-term preservation of waterlogged archaeological wooden relic.In order to understand the damage and deterioration mechanism and related evolution characteristics of waterlogged archaeological wooden relic,in order to be able to propose protection schemes,it is necessary to develop a system that can accurately and real-time monitor the structure stability of waterlogged archaeological wooden relic online.Therefore,this paper focuses on the protection of the existing Song Dynasty shipwreck,conducts a study on the structural stability of waterlogged archaeological wooden relic,and initially develops a monitoring system.In this paper,the Chinese fir is taken as the research object.Based on the experimental study of the damage evolution law of Chinese fir,the damage evolution equation of Chinese fir is established and the Crack instability propagation prediction method is proposed.At the same time,using acoustic emission technology(AET)to develop an online monitoring system for the structural stability of waterlogged archaeological wooden relic,which aims to provide a theoretical basis and device basis for the structural health monitoring of waterlogged archaeological wooden relic.The main contents of this article are as follows:1.Propose EEMD-related analysis-Fast ICA fusion method.When using acoustic emission technology to monitor the Song Dynasty shipwreck,it was found that the interference of the monitoring environment,electrical equipment,and other blind source signals caused aliasing distortion of the acoustic emission signal.In response to the above problems,this paper uses a combination of multiple signal processing methods to separate the Song Dynasty shipwreck's damage signal.The results show that this method can effectively separate the damage signal from the Chinese fir acoustic emission signal.2.A method for estimating the acoustic emission signal strength of Chinese fir damage sources was proposed.In order to obtain the true value of the signal intensity of the damage source,an experimental study on the attenuation characteristics of the acoustic emission signal in wood was carried out.Therefore,this paper discusses the attenuation characteristics of acoustic emission signals at different frequencies,different distances and different texture angle,and establishes a method for estimating the acoustic emission signal strength of Chinese fir damage sources through regression analysis.3.Acoustic emission characteristic parameters that characterize the evolution of wood damage are extracted.In this paper,the acoustic emission parameter analysis method is used to test the damage evolution process of Chinese fir under different conditions.The results show that:(1)Ringing count can be used as a characteristic parameter of acoustic emission reflecting the law of damage evolution of Chinese fir.The change of accumulated ring counting of acoustic emission can reflect the damage status of Chinese fir at each stage.(2)Fracture of Chinese fir fibers can cause changes in the amplitude of acoustic emission,so changes in amplitude can predict wood fracture.4.The mesoscopic-macro damage evolution equation of Chinese fir was established.in order to track the damage evolution of wood under dynamic load in real time,the relationship between AE characteristic parameters and wood damage variables was studied.The Chinese fir is equivalent to be composed of multiple hexagonal tubular structures(RVE)with the same properties,and a wood modeling method of homogenization-statistic distribution is proposed.On this basis,the mesoscopic-macro damage evolution equation of Chinese fir with cumulative ringing count as the characteristic parameter was established.It provides a theoretical basis for tracking the evolution law of the Song dynasty shipwreck's damage.5.Proposed a method for Crack instability propagation prediction of Chinese fir.Using the amplitude as the characteristic parameter of acoustic emission,and based on the Griffith energy criterion and acoustic emission method,the stability status information of the cracked wood was obtained.The evaluation of the crack state of the cracked body using the acoustic emission characteristic parameters is realized.6.Developed an online monitoring system for the stability of waterlogged archaeological wooden relic based on acoustic emission technology.On the premise of ensuring no damage to the song dynasty shipwreck,a hardware system capable of performing full-field or key parts on the stability of waterlogged archaeological wooden relic was developed.At the same time,the supporting monitoring software was developed based on Lab VIEW platform.According to the principle of minimum intervention for the protection of cultural relics,the experiment determined the acoustic emission sensor coupling agent suitable for waterlogged archaeological wooden relic,and developed a device with sound insulation function.The monitoring system was used to monitor the Song Dynasty shipwreck throughout the year,and the system was stable.Studies have shown that the accumulated ringing counting can reflect Song dynasty shipwreck's damage law,and the humidity control strategy is formulated based on the accumulated ringing counting change law.