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Wireless Sensor Networks for Structural Health Monitoring

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Significance

Current industry practice uses conventional Non Destructive Evaluation methods such as eddy current, ultrasound, wet fluorescent magnetic particle testing, and magnetic Barkhausen noise at scheduled intervals to inspect a system's components during its downtime. The inspections are typically conducted manually by utilizing hand-held devices that capture data from remote-installed or hand-held sensors to be transported back to a central-repository for analysis. Although such methods are well established and provide detailed and precise information about damage location and shape, they are prone to operator errors, and require high cost to train personnel for conducting the inspection. Moreover, the maintenance schedules might not be adequate to detect an impending hazard. To overcome these shortcomings, cost-efficient techniques capable of accurate and continuous structural health monitoring are desirable for meeting the systems' uptime, reliability, and safety.
Wireless Sensor Networks (WSN) offer a promising solution for continuous Structural Health Monitoring of various industrial and civil structures. WSNs are inherently highly scalable and configurable and do not require high installation and maintenance cost. They allow transitioning from calendar based industrial maintenance to condition-based maintenance.


Objectives

The proposed research aims to develop a wireless multi-modal sensor network system for actuation and sensing to enable real-time monitoring of structural health. The sensing modalities that will be investigated in this research include passive techniques such as acoustic emission (AE) and active Lamb wave techniques. The main appeal of these techniques is that these modalities can be implemented using inexpensive PZT patches, which are surface mounted on the structure to be monitored without interrupting the structure’s operation.
An interface between sensor nodes and PZT patches will be developed for proper data acquisition using the underlying inspection technique. The Sensor nodes will then be programmed with embedded distributed algorithms for detecting and characterizing defects.

Structural Health monitoring system


Approach

A two tiered network with off-the-shelf sensor nodes, such as Iris motes, will be implemented. The sensor nodes can utilize multiple sensing mechanisms for monitoring damage. In particular, the AE sub-system will be used to continuously monitor the component-under-test, run preprogrammed algorithms on the collected data and determine occurrence and location of anomalous measurements.
Appropriate PZT sensors (also placed at fixed locations on the component) will then be triggered to generate guided waves that can inspect the targeted region of interest on the structure. The interaction of the guided acoustic waves with the component will be collected and communicated using a separate wireless communication channel or through the internet to a base-station where further analysis of data from multiple sensor nodes will be carried out for damage characterization.

Structural Health monitoring system