Active Lamb Wave Damage Monitoring And Evaluation Using Projection Of Reflection Field

Structural health monitoring is a hot topic both in engineering and academic domain, because itis meaningful to ensure the structural safety and reduce the disaster or the loss of personnel property.And damage monitoring and evaluation technology is an important content and one of the keyproblems of structural health monitoring. Lamb wave reflection field projection method wasanalyzed theoretically based on the influence of damage on Lamb wave propagation, and it wasvalidated experimentally in typical damage monitoring and evaluation.The main works in this dissertation include:(1) The concept of structural health monitoring was presented. The application and recentdevelopment were summarized. Damage evaluation technology was especially introduced anddescribed.(2) The basic concept of active monitoring technique based on Lamb wave was discussed. TheLamb wave propagation in structure was studied theoretically. Signal processing methods on Lambwave structural responses were also mentioned. Based on the analysis of relationship between thelength of one-dimensional crack damage and the reflection field of Lamb wave,damage evaluationmethod based on the Lamb wave reflection field was proposed.(3) The realizing technology of damage monitoring and evaluation based on Lamb wavereflection field projection was analyzed and validated experimentally. After Lamb wave monitoringsignal was activated in the aluminum plate, Lamb wave structural responses were collected throughlinear sensor network, and the energy envelope of structural responses using Hilbert was extracted.The reflection field of Lamb wave was reconstructed at the location of the corresponding sensorsbased on compensation method for Lamb wave attenuation. It can be used to further monitor andevaluate one-dimensional crack damage.(4) The location and evaluation of unknown direction crack damage based on phased arraytheory was researched further. Simple two-dimensional damage monitoring and evaluationtechnology was analyzed and verified by the experiment. The monitoring results indicated highaccuracy.The research showed that Lamb wave reflection field projection method was practical fortypical damage monitoring and evaluation.