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M. Vospernig, M. Reiterer, R. Heuer:
"Damage process monitoring on the hot spot of a real steel component by means of ultrasonic guided waves";
in: "Life-Cycle and Sustainability of Civil Infrastructure Systems", A. Strauss, D. Frangopol, K. Bergmeister (ed.); Taylor & Francis Group, London, 2012, ISBN: 978-0-415-62126-7, 1447 - 1454.

Ultrasonic guided waves (UGW) are a very potential Structural Health Monitoring (SHM)
method. This paper presents the basic technology and concept for UGW, using an array of structure integrated
sensors. The influence of structural changes in terms of stress distributions to the sensitive ultrasonic signals is
investigated. To determine the bandwidth of the influence, numerical simulations are made. The results are used
to differentiate between structural changes through operation and a real damage. This technique is applied to an
experimental fatigue test on a HE-A 160 cantilever I-beam. A notch is introduced by a weld in the investigated
area to cause crack to appear and grow under the cyclic harmonic load. The excitation is realized by a single
mass exciter. Parallel the ultrasonic sparse sensor array is continuously recording the signal changes. Thus the
crack can be located and its growth can be observed. The compensation of operational effect within the sensor
signals and crack breathing is demonstrated.