Research For Bolt Looseness Monitoring Based On The Piezoelectric Impedance Technology

There have a variety ways of connection between engineering structure, boltconnection has been used in practical engineering most widely. Bolt under the actionof cyclic load and forced vibration would lead to fatigue damage and bolt looseness.However bolt failure will cause disastrous consequence and major property damage.It is particularly important that bolt should monitored in the real-time online health.Piezoelectric impedance technology as a new type of structural health monitoringtechnology has been achieved rapid development in nearly20years. This technologywas widely used in structural health monitoring, include steel structure, concretestructure and important component. Bolt looseness experimental research based onthe piezoelectric impedance technology was conducted, the main content is list asfollows:1．This article has comprehensive analysis the main method of structural healthmonitoring and the piezoelectric impedance technology theory. The structural healthmonitoring research status at home and abroad based on the piezoelectric impedancetechnology,which have been used in the field of steel structure, concrete structure,cracks, bolt and other structure are discussed. The usage of different structuraldamage indexes in the structural health damage assessment are list. Some influencefactors of piezoelectric impedance technology are analyzed. This paper alsointroduce the finite element of piezoelectric coupling field analysis researchsituation and summarize the advantages of piezoelectric impedance technology.2．This paper introduce the concept of piezoelectric material and piezoelectriceffect, cited the piezoelectric equation to derived calculation formula of piezoelectricmaterial electrical admittance. Introduce damage index to quantitative analysis thedamage degree.3．This paper expounded the concept of finite element method and relatedsoftware, the piezoelectric coupling field analysis detailed process is described, this paper introduces the method for piezoelectric admittance extracting. Piezoelectricpatch-steel beam and piezoelectric patch-bolt finite element model are established,coupling models were conducted finite element piezoelectric coupling field analysis.Piezoelectric admittance and relevant data under different load is obtained, thechanges of admittance curve under different load is analyzed.4．The experiment platform of bolt looseness monitoring has been built, and thebolt looseness monitoring experiment based on piezoelectric impedance technologyis conducted, use the universal testing machine for bolt loading to simulate thechange of the bolt pre-tightening force. Piezoelectric admittance curve and thedamage index(RMSD) changed by the pre-tightening force is analyzed. Piezoelectricmaterial installation location and effect of structure contact surface roughness on thedamage index is analyzed.5．The research of one-piece intelligent bolt based on piezoelectric impedancetechnology is conducted, the piezoelectric materials was installed on differentsurface of respectively bolts and nuts. Electrical admittance data under differentforce is analyzed, and establish the relationship curve between the degree of boltlooseness and the pre-tightening force.