ISBN:
9788361956358
Content:
The present contribution addresses the underlying theory of the non destructive testing technique Lorentz force eddy current testing (LET) [1-2]. The technique is applied on moving nonmagnetic conductors to detect buried defects and inclusions by means of the Lorentz force acting on a magnet system which is in relative motion with respect to the object under test. The fundamentals of motion induced eddy currents are described by evaluating analyticaI expressions of the Lorentz force and eddy current density of a cylindrical conductor moving through a ring magnet system. The reaction of the magnetic field generated by the induced eddy currents is taken into account in the present analysis in order to provide accurate predictions even for high velocities. The presented results are supported by finite-element simulations. In the presence of a defect, the induced eddy currents and hence, the Lorentz force acting on the magnet is perturbed. This response depends on the geometry and magnetization direction of the applied magnet system. In an optimization framework, the magnet system is optimized in order to maximize the absolute defect response signal. The optimal design depends on the defect parameters such as its size and Iocation and hence on the predefined detection goal. Distinct cases of subsurface and deep lying defects are studied and optimal designs are presented. Further studies are related to investigations on the role of uncertainties in the input parameters on the resulting Lorentz force. ln this sense, the remanence of the magnet, the lift-off distance as well as the conductivity and velocity of the specimen were modelled as uniform distributed random variables. The uncertainty intervals are estimated by our laboratory setup. A non-intrusive generalized polynomial chaos expansion [3] is performed by means of numerical simulations in order to quantify the impact of each of the input uncertainties. Most important parameters are identified in order to improve the accuracy of our laboratory setup.
In:
International Interdisciplinary PhD Workshop, IIPhDW 2015, 14-17 May 2015, Międzyzdroje, Poland, Warsaw : Electrotechnical Institute, 2015, (2015), Seite 78-79, 9788361956358
In:
year:2015
In:
pages:78-79
Language:
English
Author information:
Weise, Konstantin 1986-
Author information:
Ziolkowski, Marek
Author information:
Brauer, Hartmut 1953-
