Simulation Of Micro Crack Damage Of Thin Metal Plate And Damage Feature Extraction Method

With the development of science and technology,the application requirements of plate type structure in different engineering fields are increasing.Subjected to high speed and high temperature effects,long-term effect of load,mutation effect,fatigue effect,material aging and corrosion and other factors,the decrease of structural strength and damage accumulation are inevitable.Crack damage is easy to occur in plate material.At home and abroad,establishing and improving a safety early warning system to detect and alert to the damage at an early stage is a hot topic in engineering and academic circles in recent years.The main research contents and innovation points are as follows.In this paper,in order to research the method identifying of the damage of the tiny crack in thin metal plate,the finite element numerical model of ultrasonic lamb wave excitation/receiving was established by coupling the PZT with the thin metal plate.The model is attached to the surface of a metal plate by using PZT chip material as an actuator and sensor.The actuator transmits ultrasonic guided wave through the damaged structure,and the scattering echo signal of damage is received by the sensor.Through the analysis of the received response signal and the extraction of the damage characteristics,effective monitoring of the health status of the structure can be guaranteed because of the detection of various changes in the process of transmission,such as energy decay,reflection,transmission and mode transformation.In the process of numerical simulation,the lamb wave signal of a metal plate with no damage and tiny crack damage are received,and then the wavelet packet is used to analyze it.The wavelet packet decomposition method is used to extract the time frequency data of each node at the bottom of the wavelet packet tree,and the energy spectrum of the wavelet packet is obtained,and the rule of the energy spectrum of the crack damage is found.The data and chart show that In the wavelet packet energy spectrum decomposition node values,the energy spectrum change value of significant points can characterize the length of damage,the greater the damage length,the larger the change of energy spectrum of the significant node is.The number of significant points can characterize the width of damage,the greater the width of damage,the more number of significantly nodes.The geometric data of simulation model in combination with the energy spectrum change value of significant points,it can locate the damage location.There is a linear correlation between the change of the small crack boundary and the change of the total energy spectrum of the crack damage model.Based on the above rules,this method can predict and evaluate the damage degree of micro cracks in thin metal plates The database based on a large number of comprehensive numerical simulations will provide effective detection and reference for the actual engineering of the thin metal plate micro crack damage.