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Determination of defect sizes with the help of structural-health-monitoring methods based on guided waves

: Tschöke, Kilian; Weihnacht, Bianca; Gaul, Tobias; Schulze, Eberhard; Schubert, Lars; Neubeck, Robert

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Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. -DGZfP-, Berlin; European Federation for Non-Destructive Testing -EFNDT-:
7th European-American Workshop on Reliability of NDE 2017. Proceedings. Online resource : September 4 - 7, 2017, Potsdam, Germany
Online im WWW, 2017
Paper 25, 8 pp.
European-American Workshop on Reliability of NDE <7, 2017, Potsdam>
Conference Paper, Electronic Publication
Fraunhofer IKTS ()
structural health monitoring; guided wave; acousto Ultrasonic; acoustic emission; isotropic and anisotropic material; defect size

Numerous industrial areas request the permanently monitoring for damage of components with the least possible number of sensors. These industrial areas are construction engineering (e.g. bridge monitoring), renewable energies (e.g. monitoring of wind turbine rotor blades), chemical industry (e.g. monitoring of pipelines and storage tanks), mechanical engineering, vehicle manufacturing, aerospace industry (e.g. monitoring of lightweight structures) and others more. The diagnosis of components for internal failures can be carried out with different NDE methods depending on the material and the defect size. Examples of such methods are X-ray, the pulse-echo-ultrasonic method, for certain kinds of materials magnetic processes, eddy current methods, as well as radar and Terahertz methods. However, these methods are of limited suitability for permanent monitoring because of their limited range within the material to be monitored. For permanent monitoring of components guided acoustic waves (also called Lamb waves) are most useful because of their large range within solid materials. Changes inside the material have great influences on the propagation conditions of the guided waves. Acoustic sensors are able to monitor large components even at a great distance from each other. Sensors and devices for the measurement of guided waves are already available. However, precise instructions for the use of these systems and the description of substitute defects are missing. The aim of the government-funded research project QuantSHM is now to overcome these constraints of monitoring systems in order to allow the monitoring methods to be widely accepted. Basically, research results of two fields of application will be presented. In particular these are acousto ultrasonic methods for isotropic materials (e.g. steel, pipelines) and acoustic emission methods for anisotropic materials (e.g. composites, rotor blades). Defect sizes can be clearly correlated with the defect size for isotropic materials whereas damaged areas are clearly addressed by acoustic emission for anisotropic materials.