Lamb Wave Based Crack Damage Quantitative Imaging Method

Since that crack damage in metal structures was highly concealed and harmful,quantitative crack detection technology was one of the current research hotspots in structural health monitoring.However,existing guided wave based structural damage monitoring using piezoelectric arrays usually ignore crack direction information and can't effectively evaluate crack damage.This paper deeply analyzes the influence of cracks on the propagation of Lamb wave monitoring signals,and introduces ring piezoelectric array and active Lamb wave RAPID imaging technology to study the crack damage quantitative monitoring technology.The proposed cross-orthogonal scanning method is used to make up for the limitations of traditional RAPID imaging technology for cracks.This article conducts research and experiments from the following four aspects.(1)Described the research background,research content and current status of structural health monitoring(SHM)technology at home and abroad,focusing on related technologies and imaging methods based on wave non-destructive monitoring.(2)Described the basic principles of waves,analyze the dispersion characteristics of waves and the excitation process and parameter settings.Describe the principle of probabilistic damage reconstruction algorithm(RAPID).(3)Modeling,parameter setting,and simulation calculation are carried out through finite element analysis software,and the mechanism of through-hole damage and crack damage on the direct wave of the response signal is analyzed.Through simulation experiments,we found the related limitations of crack damage in algorithm imaging.(4)According to the difference of crack damage to the response signal change under the orthogonal monitoring path,a cross scanning method is proposed to determine the crack direction,and then the damage difference coefficient(SDC)of the monitoring path of parallel or nearly parallel cracks is determined.The value is corrected to strengthen the reconstruction information of the crack direction,and then realize the image reconstruction and quantitative evaluation of the crack damage.(5)Analyze the interaction between multiple cracks by improving the PZT layout array.For multiple cracks in special locations,the cross scanning method will fail.A single crack area is determined by sectorization,the direction of a single crack is located using three points,and the SDC value of damage paths passing through multiple cracks at the same time is corrected,so as to avoid the mutual influence caused by the monitoring path passing through multiple damage areas at the same time.Then monitor and evaluate the damage of multiple cracks at different locations on the structure.The experimental results show that the cross-scanning method and the improved RAPID imaging method proposed in the study can better identify cracks and multiple crack directions,and can also quantitatively display the crack length,which has a wide range of research prospects.