The Local Defect Resonance of Elliptically Shaped Defects

Speaker:
Joas, Sebastian; Institut für Kunststofftechnik - University of Stuttgart; Germany

Authors:
Rahammer, M.; University of Stuttgart; Germany
Joas, S.; University of Stuttgart; Germany
Kreutzbruck, M.; University of Stuttgart; Germany

ID: ECNDT-0420-2018
Download: PDF
Session: Composite Material - UT 1
Room: G1
Date: 2018-06-14
Time: 11:10 - 11:30

The concept of local defect resonance in non-destructive testing utilizes the natural frequency vibration of plate-like defects excited by external sound sources. The defect area is considered fully clamped with a locally reduced stiffness. While natural frequencies of plates have been of interest for a long time, the applicability to local defect areas emerged only recently and was validated both mathematically and experimentally. At first only circular and square defect areas were considered. In this contribution a wider range of defects is taken into account by presenting a closed form forward solution for elliptically shaped defects with variable semi axis ratios and lengths. FEM and experimental data confirm the calculations made for flat bottom holes in isotropic plastic. A practical application in the form of a delaminated glass fiber reinforced plastic is demonstrated in which the estimated resonance frequency matches the experimental result within 6%.