Real-time defect imaging in plate-like structures using Guided Wave Tomography with portable sparse array in direct non-glued contact.

Speaker:
Mattei, Christophe; Creo Dynamics AB; Sweden

Authors:
Mattei, C.; Creo Dynamics AB; Sweden
Risberg, R.; Creo Dynamics AB; Sweden

ID: ECNDT-0016-2018
Download: PDF
Session: Modelling & data processing - Guided Waves
Room: J2
Date: 2018-06-13
Time: 13:30 - 13:50

Guided wave tomography of plate-like structures for SHM applications has extensively been reported. This family of techniques relies on the generation and detection of guided waves by a sparse array of sensors glued to the structure. Damage detection is performed by comparison of the signals acquired on the structure during or after operational loading with baseline signals acquired on the pristine structure before damage initiation.
This paper investigates an alternative mode of operation -suitable for NDT applications- where the sparse array is not permanently glued to the structure. An innovative concept for reconfigurable and portable sparse-array for pitch-catch generation and detection of low frequency flexural modes is presented. The portable array allows damage detection and location through a comparison of the signal with baseline signals acquired on a similar pristine reference part. A damage index derived from the correlation of the guided wave signals acquired on the part under inspection and on the reference part is calculated for all paths between the array probes. Imaging of the zone under inspection is performed from tomographic reconstruction of the damage indexes. This process provides a near real-time update of the imaged zone when the array is moved over the component.
The performance of a sixteen-channel system including a real-time tomographic reconstruction imaging process is discussed. The array is applied by the operator on the part and instantaneous imaging of a 25cm x 25cm zone within the array is displayed. Imaging of typical damage type such as impact delamination in CFRP or corrosion in steel is presented. The sensitivity of the technique is discussed from experimental results and FEM based simulations. Examples of imaging of defects in non-flat structure such as a hat profile are also presented.