Abstract
The main problem about a railway analysis is detection of cracks in the structure.
If these de¯ciencies are not controlled at early stages they might cause huge economical problems
a®ecting the rail network (unexpected requisition of spare parts, handling of incident and/or
accidents). Within this framework, the early and continuous use of Non Destructive Tests can
be useful. In this context, Eddy Current Testing is increasing in importance and popularity.
Particularly, in this paper we exploit the measure of normal component, with respect to the
scanned surface, of magnetic ¯eld. Whilst the scienti¯c literature proposes a lot of solutions for
detecting sub-super¯cial defects, an open problem is related to the geometrical complexity of
the structure and the relevant di±culty of crack detection. In this paper, we propose a Finite
Element Method based approach for modelling a fast and accurate evaluation of the defect in
railways tracks. The modelled system is strongly versatile and the choice of electrical parameters
a®ect the design of new probes for this kind of inspection. In particular, we propose a solution
exploiting a rotating electromagnetic ¯eld with very encouraging results: The proposed model is
able to recognize deep and surface cracks even if their orientations is vertical to the longitudinal
direction of the sensor.
1. 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. With the evolution of computer
systems and numerical methods, the interest in NDT/E has grown so much as problems that a
few years ago appeared very di±cult to be practically solved, can now be approached by numerical
simulations. Cracks or other in-service expected discontinuities occurring in railway may lead to
fracture and thus to operational danger. Where necessary, operational safety is guaranteed by the
periodic non-destructive inspection of these components. Irregularities may not exceed a speci¯ed
and limited extension. Moreover, irregularities are closely related to operating speed, covering dis-
tance, quality of the track, acceleration, pro¯le wear, rail wear, sti®ness bogey, and so on. For this
reason, the initial inspection shall be exploited in order to observe all discontinuities or damages.
Our numerical simulations were carried out according to the requirements and advices of interna-
tional standards: European standard (EN), International Standard (ISO) and Unit Identi¯cation
Code (UIC). As the EN or ISO standards approach the acceptance of rolling stock components in
manufacturing stage and not directly in-service inspections, a study of UIC documents and expe-
rience achieved after 4 years inspections, in railway networks, focus the inspection requirements.
The available rolling stock standards concerning

Download full report
http://googleurl?sa=t&source=web&cd=1&ve...wnload.php%3Ffile%3DMDkwOTE4MDQ1OTU2fFZvbDZObzNQYWdlMjQydG8yNDYucGRm&ei=5NY3TtzRDcbOrQfB9_n2Dw&usg=AFQjCNEiUEocEdMREJvYkE3JSht1vHx_DQ&sig2=QStlMhx5P-MbzK9-1N3mvQ