Structural Health Monitoring And Damage Localization Based On EMI Technology

Whether all the special equipments and large engineering structures can run safely or not is always the key point that people care about. There are many non-destructive test(NDT) methods developed based on the principle of sound, light,, electricity, magnetism etc. While testing, plant or equipments should be shut-down, and testers with rich professional experience are needed as well. Since NDT can not get the health condition of the equipment in service, it is urgent for people to find a health monitoring method with wide range of application and high reliability.This thesis has done the analysis and experimental research about plate-like structure damages localization and monitoring application of bolt looseness based on electro-mechanical impedance (EMI) technology. Static and dynamic analysis on circular wafer PZT by applying ANSYS is made to study the charge distribution and impedance spectroscopy under different excitation frequencies and accomplish the research about monitoring on plate-like structure damages and mechanical bolt-set looseness by using EMI technology. Specific researches are done as follows:1. Analyzes the characteristics of common structural health monitoring approaches and the defects of NDT methods; demonstrates the high application potential of SHM based on EMI technology and significance of damage identification;2. Introduces the research actuality about EMI technology in and abroad, the characteristics of the piezoelectric element and its basic principles when conducting structural health monitoring; focuses on the theoretical model establishment;3. Makes static, dynamic and harmonic response analysis on circular wafer-PZT piezoelectric element by using numerical simulation software ANSYS to intuitively get its own features which provide reference for subsequent experiments;4. Sets up a test platform which takes impedance analyzer, PZT piezoelectric element and plate-like structure as the core, studies in-depth about applying EMI method on health monitoring of plate-like structure; selects the damage coefficient by suitable algorithm and establishes and the relationship between damage extension and coefficient; makes use of function fitting to obtain the relationship between monitoring distance of PZT and damage coefficient;5. Studies mechanical bolt-set looseness monitoring based on PZT and find the suitable coefficient of bolt looseness; studies the monitoring of bolts component based on distributed PZTs, and use the BP neural network method to realize the precise positioning of the loosened bolt.