Research On Wood Beam Damage Detection Technology Based On Modal Analysis And Piezoelectric Ceramics

As a renewable biomass engineering material,wood is widely used in wood frame construction.However,wood is prone to damage such as cracks,corrosion and mildew during use,which can reduce the mechanical properties of wood and thus affect the overall safety of wood structures.Therefore,there is a need for health monitoring and damage identification of wood structures.In this paper,two damage detection methods are proposed for the damage detection needs of wood beams,an important member of wood structures,as follows:(1)For the wood beam transverse crack damage detection needs,based on the modal strain energy change rate(MSEI),in order to overcome the modal vibration pattern obtained during the experiment contains certain noise interference,using the excellent noise reduction ability of DS evidence theory,a fusion damage index(FDI)based damage detection method is proposed;for the wood beam longitudinal crack damage detection needs,a damage detection method based on piezoelectric ceramic and small A damage detection method based on piezoelectric ceramics and small wave packets is proposed for longitudinal crack detection of wooden beams.(2)To initially verify the effectiveness of the transverse crack damage detection method,modal analysis models of undamaged and damaged free wooden beams were established based on ANSYS finite element analysis software,and the corresponding modal vibration patterns were extracted from the simulation analysis results,based on which the modal strain energy change rate and fusion damage index were calculated respectively.The results show that the fusion damage index has good noise immunity and accurate localization ability for single damage and two damages of mild,moderate and severe;the modal strain energy change rate has good recognition ability for the damage degree of wooden beams.To initially verify the effectiveness of the longitudinal crack damage detection method for wood beams,the COMSOL finite element analysis software was used to construct a machine-electrical multi-physical field coupled model of nondamaged and damaged wood beams and piezoelectric ceramics,and the corresponding stress wave signals were extracted by simulation analysis results and wavelet packet energy calculation was performed.The results show that the wavelet packet energy has a good detection and identification ability for the longitudinal crack damage degree of wood beams.(3)The commercial modal detection and stress wave analysis systems are generally expensive and single-functional.For this reason,based on the existing NI hardware platform and Lab VIEW and MATLAB software in the laboratory,a modal analysis-based transverse crack damage detection system and a piezoelectric ceramic-based longitudinal crack damage detection system for wood beams were designed and developed,respectively.The transverse crack damage detection system has the functions of vibration signal acquisition,display,saving,modal parameter extraction,MSEBI and FDI calculation,etc.The longitudinal crack damage detection system has functions such as stress wave signal acquisition,display,saving and wavelet packet energy calculation.(4)To further verify the effectiveness and practicality of the two damage detection methods,rectangular openings were artificially created in the camphor pine wood beam specimens to simulate the transverse crack damage and longitudinal crack damage of the wood beams.The designed and developed wood beam damage detection system was used to detect damage to nondamaged and damaged camphor pine free wood beams respectively,and the experimental results matched with the simulation results,which further verified the effectiveness and accuracy of the wood beam damage detection method proposed in this paper.