ROTATING ELECTROMAGNETIC FIELD FOR NDT INSPECTIONS
Reliable performance of a component or structure depends on its pre-service quality and in-service degradation under operating conditions. The importance of Non-Destructive Testing and Evaluation is ever increasing, above all in ensuring pre-service quality and monitoring in-service degradation, in order to avoid premature failure of the components/structures. There are many Non-Destructive Techniques based on various physical principles. In this work, our main objective is the characterization of anomalies such as defects, stresses and microstructural degradations in materials. Particularly, in this work we propose a Finite Element Method based approach for modelling a fast and accurate evaluation of defects in metallic materials able to easily detect defects, aside from the orientation. Within this framework, the paper proposes the application of a magnetic fleld rotating perpendicularly to the analysed specimen. We discuss a few case studies, starting from numerical simulations and flnally highlighting the importance of this approach in order to evaluate the structural integrity assessment.
Eddy current examination of steel wires
Abstract This paper describes an automatic eddy current instrument designed and produced at the Center of Technical Physics of la§i and set up at the Metal Works, Cimpia Turzii, Romania. The diameter of the wires tested by the apparatus ranged between 2 and 9 mm. The control frequency can be adjusted between 1 and 100 kHz and the phase may be changed in steps of 15°. The test frequency was established theoretically so that the variations in the normalized components of impedance were highest for crack-type flaws. The theoretical results are compared with experimental ones for wires made of steel B 80N, 7 mm in diameter. By using a coil with a fill factor of 0.8 and a control speed of 1.5 m s −1 it was possible to reveal cracks with depths of 0.05 mm and 0.012 mm long, as well as areas of structural alteration due to the appearance of ferrite phases within the martensitic mass.
3-D eddy current calculations using the magnetic vector potential
Two methods for using the magnetic vector potential for 3-D eddy current calculation are treated. One method uses the magnetic vector potential that is continuous over the entire region and generally accompanies the electric scalar potential. It has the advantage that no cutting is necessary for the multiply-connected-region problem. The other method uses the magnetic vector potential that is discontinuous across the interface surface between different media. This magnetic vector potential can be arranged so that the electric scalar potential does not appear in the equations when the conductivity is constant. It has the disadvantage that cutting is necessary for the multiply-connected-region problem. New boundary value problem formulations are given for both methods, precisely defining the interface and boundary conditions. >