STRUCTURAL HEALTH MONITORING BASED ON IMPEDANCE

摘要

For an important defect sensitive structure in service, damages will be inevitable to occur in them due to the action of design loads and other varieties of burst factors, which will unceasingly deteriorate the health state of structure and will form a threat to normal use and safe of the whole structure. Therefore it is of necessity to carry out monitoring on the health state of structures. Conventional NDE methods, however, have unacceptable limits.Some of these techniques are time-consuming and inconvenient for service structure. The impedance based health monitoring is also a nondestructive testing, which can realize monitoring and finding minor changes in structural integrity. The impedance based structural monitoring utilizes both the direct and converse versions of the piezoelectric effect simultaneously to obtain an impedance signature for the structure. The PZT is driven by a sinusoidal voltage sweep. Since the patch is bonded to the structure, the structure is deformed along with it and produces a local dynamic response to the vibration. The area that one patch can excite depends on the structure and material. The response of the system is transferred back to the piezoelectric patch resulting in an electrical response. Of course, the presence of damage causes the response of the system to change. The electrical response is then analyzed, and damage is indicated by a phase shift or magnitude change in the impedance. Then the impedance based method is utilized to assess a damaged concrete beam and bolts looseness. Based on the experimental results it can be concluded that the impedance method has the potential to be used for damage detection of structure.