Research On Damage Identification Of Plate Structure Under Ambient Excitation

Affected by the harsh marine environment,the safety of ships and marine structures during service has always been the focus of attention.If damage can be detected in the early stage of structural damage,it will not only save a lot of maintenance costs,but also avoid major safety accidents.Therefore,the application of structural health monitoring(SHM)to Naval Architecture and Ocean Engineering has attracted increasing attention from researchers.Structural damage identification is a key step in structural health monitoring.Using structural vibration response signals to detect damage has always been a research hotspot.Among them,the structural strain response has the advantages of fast recognition rate and high sensitivity to local damage.It is widely used in structural damage recognition.Previous damage identification research focused on finding new damage indicators to improve the efficiency of damage identification.However,this paper focuses on the structural strain measurement technology,and proposes a strain measurement method,which has been verified by experiments to effectively improve the efficiency of damage identification.Specific research contents are as follows:In this paper,the finite element method is used to derive the strain mode,and it is proved that the strain mode and the displacement mode have similar mathematical expressions.Based on this,the Vibration differential equation of multi-degree-of-freedom linear proportional damping structure with strain as the variable is obtained.then the structural strain response and strain frequency response function are obtained,and the theoretical principle of the modal parameter identification method(NExT-ERA and peak picking method)is derived based on the strain response.This paper makes a detailed mathematical derivation of Wheatstone bridge theory,and proposes a cross-shaped strain measurement method based on Wheatstone bridge theory.This is an innovation of this paper.The cross strain measurement method has two circuit connection methods,which are introduced in detail,and the modal parameters of the clamped aluminum plate under these two measurement methods are analyzed and compared by finite element method.Compared with the traditional half-bridge strain measurement method,this method has the following advantages: the sensor can realize temperature self-compensation,and improves the utilization efficiency of the sensor.In this paper,the experiment of strain modal parameter identification and damage identification of the clamped aluminum plate is designed.In this experiment,the random hammering method is used to simulate the natural environment excitation,and the local mass is added to simulate the damage.Through operating modal parameter identification experiment,the modal parameters of the structure are obtained,and compared with numerical simulation,a good results are obtained.In the damage identification experiment,this paper compared the two circuit connection methods of the cross strain measurement method,and compared the cross strain measurement method with the traditional half-bridge strain measurement method.The effectiveness of the strain measurement method proposed in this paper is verified.