Title:

Ultrasonic Structural Health Monitoring of Overhead Transmission Lines

Speaker:

Prof. Lothar Gual

Affiliation:

University of Stuttgart

When:

Thursday, January 26, 2012 at 11:00:00 AM   Add to Calendar

Where:

Molecular Science and Engineering Building, Room 3201-A

Host:

Laurence Jacobs
laurence.jacobs@coe.gatech.edu

Abstract

In an effort to detect and localize damages in engineering structures, the research field of Structural Health Monitoring (SHM) has emerged rapidly. SHM involves regular evaluation of the structural state by means of integrated actuators and sensors. Among potential damage detection methods, ultrasonic wave-based techniques are widely used because of their versatility and affordability.

One target for SHM applications in the realm of civil engineering are cable structures, such as overhead transmission lines and stay cables in bridges. These are subject to static and dynamic loads, aging, corrosion and accidental events.

The proposed concept for SHM of overhead transmission lines is displayed in Figure 1: The excitation of ultrasonic waves in cylindrical media generates guided waves, which can propagate long distances. This allows for monitoring large sections of a cable with a single actuator and sensor. On the other hand, guided wave propagation in cylinders is multimodal, which complicates analysis and synthesis of wave motion.

This work addresses several aspects of guided wave propagation in cylindrical structures, with the objective of developing an SHM methodology for cable structures.

Wave propagation in cylinders is examined analytically and numerically and the distinct propagation modes are determined and visualized. Design of piezoelectric transducers for generation of waves in cable structures is discussed. On the basis of transfer functions of piezoelectric actuators, optimal excitation signals are computed.

The interaction of waves with defects is explored. Reflection and transmission at cracks is quantified with a modal decomposition method as well as transient Finite Element simulations and experiments.

Interaction of individual wires in a multi-wire strand is modeled with an energy-based method. It is shown that it is possible to detect damages in second-layer wires in a multi-wire cable due to the friction contact between neighboring wires.

This work demonstrates the feasibility of ultrasonic wave-based SHM for cable structures and provides methodologies and models to analyze and simulate the underlying wave propagation processes.

Biography

Professor Gaul's Biography was not available at this time.

Notes

Refreshments will be served.