Structural Health Monitoring Based On Paremeter Identification Of Electromechanical Impedance Model

Structural health monitoring(SHM) technology based on Electro-Mechanical Impedance(EMI) measurements has a lot of advantages, such as high sensitivity of detecting tiny damage of structural, great anti-interference performance, convenience of signal acquisition. These result in a wide application foreground on metals, composites and concrete structures.EMI technology is applied to piezoelectric element self-diagnosis. It includes revising admittance model, adding damage factors on piezoelectric element destruction and debonding. Genetic algorithm was used to calculate the value of damage factor, and experiments have been done to prove whether the modified model is right. The consequences suggest that the modified admittance model can monitor both whether the element is destroyed and the extent of debonding.It is found that the sensitivity of electrical admittance technique which detects variation of structural stiffness is very precise through the numerical simulation of admittance formula. Then two aspects have been researched, including structure size and modulus of elasticity. The experiment of iron plate groove damage indicated that it is highly sensitive to detect stiffness degradation caused by the thickness reduction based on electrical admittance measurement. Aluminum plate affixing piezoelectric-panel has been analysed using finite element method, and it concludes that structural stiffness is proportional to structure modulus of elasticity. In the fatigue damage experiment of aluminum alloys, we have studied damage admittance signal with damage identification index, and demonstrated variation laws of structural stiffness and modulus of elasticity. The results show that using electrical admittance technique to monitor the fatigue damage of aluminum alloys is effective.At the final part, we have researched the relationship between electrical impedance signal and temperature. According to the test, temperature change can result in fluctuation of amplitude of impedance signal, as well as resonance frequency. Temperature compensation algorithm is proposed based on damage identification index, and on the basis of experiments, it concludes that impedance signal, with temperature compensation algorithm, can apply to structural health monitoring.