华中科技大学硕士学位论文基于Lamb波的主动结构健康监测系统研究姓名：刘洋申请学位级别：硕士专业：系统分析与集成指导教师：王乘20050507摘要经过长期使用土木航空大型管道和大型储物罐等结构中难免会产生大量局部损伤及微裂纹为了使结构和材料处于良好的使用状态必须开发一套科学有效的结构健康监测系统StructuralHealthMonitoringSystem简称SHMSSHMS可以分为主动SHMS和被动SHMS两种被动SHMS通过被动传感器进行监测和数据处理仅仅监听通过结构振动产生的信号在主动监测系统中使用附在结构表面或嵌入结构中的激励器和传感器通过激励器激发激励信号在结构中引入弹性应力波利用对传感器的接收信号的分析处理可以有效地探知结构中的损伤情况本文研究在主动SHMS中引入Lamb波进行探伤这种探伤方式具有探测距离远探伤效率高速度快以及适用的类型比较多等优点具体工作如下讨论了适合在主动SHMS中激励和接收Lamb波的激励传感器传统的超声波发生装置体积庞大安装复杂不适合在分布式智能结构中广泛应用而压电晶体激励传感器具有价值低廉体积小质量轻并且抗干扰能力强等优点非常适合在主动SHMS中应用因为Lamb波具有多种模式本文通过对Lamb波探伤模式的研究分析了利用A0模式的Lamb波进行单模式探伤代替以往的多模式多次探伤的可行性根据以上的理论分析构造了利用附在金属板上的压电激励器在结构中产生A0模式的Lamb波并通过嵌入或附着在结构中的压电传感器进行接收的实验架构使用Mindlin板理论和有限差分法对Lamb波传播进行了仿真研究提出了一种基于TDOA模型的损伤定位算法利用该算法可以获得损伤部位坐标的显式表达式计算速度快功耗小并能够对损伤区域的大小做出估计仿真计算结果和实验结果证明该算法能够提供实时的主动损伤检测同时可以准确快速地对结构中可能存在的单点损伤或者损伤比较集中的区域进行定位和粗略的量化关键词SHMS,无损检测,压电晶体,Lamb波,Mindlin板理论,TDOA,损伤定位IVAbstractWithpayingmoreandmoreattentiontothattheintegrityofin-servicestructuresneedstobeinspectedtodeterminetheirphysicalconditionthroughouttheirlifetime,wehavediscussedactiveStructuralHealthMonitoringSystem(SHMS)usinginterrogativeLambwavesinthisthesis.SHMScanbeeitherpassiveoractive.PassiveSHMSinfersthestateofthestructureusingpassivesensors(loading,stress,environmentalcondition,performanceindicators,acousticemissionfromcracks,etc.)thataremonitoredovertimeandfedbackintoastructuralmodel.PassiveSHMSonly“listens”tothestructurebutdoesnotinteractwithit.ActiveSHMSisdifferentfrompassiveSHMSbecauseitusessensorstointerrogatethestructureinordertodetectdamagepresence,extent,andintensity.Activesensorsactuponthestructureinmuchthesamewaythatconventionalnondestructiveevaluation(NDE)transducersdo.Unlikepassivesensors(whichonlylistentothestructure),activesensorsinteractdirectlywiththestructureandfinditsstateofhealthandreliability.ActiveSHMSusinginterrogativeLambwaveswouldbeabletocoverlargeareasfromonesinglelocation.Suchsystemswouldbecost-effectiveandefficient.Furthermore,wehavediscussedthetransducersusinginSHMS.ConventionalultrasonictransducersareinappropriateforSHMSapplicationsduetotheircost,weight,andsize.Conventionalultrasonictransducerscouldnotbeembeddedinlargenumbersintoastructurewithoutincurringimportantcostandweightpenalties.ForSHMSapplications,newtypesofLamb-wavetransducerssuchaspiezoelectricwafertransducersmustbedeveloped,theymustbesmall,lightweight,unobtrusive,andlowcost.Ontheotherhand,thekeyrequirementsofanadvancedSHMSaretheabilitytodetectdamagingevents,characterizethenature,extentandseriousnessofthedamages.InthisthesisthroughdiscussingthepropagationofLambwaveswithMindlinPlateTheory(MPT)andFiniteDifferenceAlgorithm,adamagelocalizationconceptusingellipsesmethodisproposedbasedonthepropagationofLambwaves,whichareexcitedandreceivedbysurface-mountedorembeddedpiezoelectrictransducers.Usingthemethodcanprovideexplicitsolutionsandcandrawaconclusiononthedamagearea.Numericandtheoryanalysisbasingonthewaves’differencearrivaltimeoftransducersthathasbeenV
