25-08-2017, 09:32 PM
Rotating Electromagnetic Field for Crack Detection in Railway
Tracks
p-1611--electromagnetic_field_railway_crack_detection.pdf (Size: 236.14 KB / Downloads: 108)
INTRODUCTION
In order to improve manufacturing quality and ensure public safety, components and structures
are commonly inspected for early detection of defects or faults which may reduce their structural
integrity. Non Destructive Testing and Evaluation (NDT/E) techniques present the advantage of
leaving the specimens undamaged after inspection. NDT/E involves treating defect detection and
characterization as inverse problems. In experimental NDT/E, the available measurement data are
exploited in order so some clues may emerge in the inspection signal that are possibly representative
of structural modi¯cation of specimens, like cracks, °aws and phase transformations that develop to
discontinuous deformations. NDT/E in the ¯eld of defects identi¯cation in metallic elements plays a
remarkable role with special regard to those sectors where the material integrity is strictly required.
As a consequence, the detection of defects in metallic materials, together with the relevant shape
classi¯cation, provides the operator with useful information on the actual mechanical integrity of
the specimen. It is presently possible to perform forward numerical simulations [1{3] very precisely
and rapidly and concerning di®erent applications of the NDT/E.
REMARKS AND CONCLUSIONS
On the basis of the numerical method presented in this paper, we developed a ¯nite element pro-
cedure for the analysis of the rotating magnetic ¯eld for the detection of railway tracks. For our
analysis, we used a 2D section of the railway and simulated di®erent sizes of defects according to the
ISO rules. Speci¯cally, exploiting the Ferraris e®ect, a 2D time dependent model has been studied to
evaluate the distortion of the magnetic ¯eld density due to the defect presence: Rotating Magnetic
Field provides a good overall accuracy in discriminating defect presence, as our experimentations
demonstrate. At the same time, the procedure should be validate for other kind of defects, with dif-
ferent geometries or orientations. The same approach should ¯nd useful applications like: Detection
of third-layer cracks, above all concerning alodine rivets within the framework of aging aircrafts'
inspection, or micro-crack and micro-voids detection in welding process. Anyway, the presented
results, which also can be considered as preliminary results, are very encouraging and they suggest
the possibility of increasing and generalizing the performance model with a physical realization of
a rotating ¯eld eddy current sensor. The authors are actually engaged in this direction.