XIX Sympozjum Srodowiskowe PTZE - materialy.pdf

XIX Sympozjum PTZE, Worliny 2009
ANALYZING SURFACE CRACKS BY A MFL TESTER
Gergely Kovács, Miklós Kuczmann
Laboratory of Electromagnetic Fields,
Széchenyi István University, H-9026, Egyetem tér 1, Győr, Hungary
e-mail: kovacs.gergely1984@gmail.com
The aim of nondestructive testing methods is to obtain some information about the specimen
under test without any physical impression of the material. Here, only ferromagnetic materials
have been used in the measurements. One of these methods is the so-called Magnetic Flux
Leakage (MFL) method [1], which detects the gaps, cracks and flaws by the help of the
magnetic field supplied by a current source. It is well known that the ferromagnetic materials
drive the magnetic flux, but the generated flux emerges the gaps, and this effect can be
measured by the appropriate sensor, such as using a little coil or a Hall type sensor.
The magnetic flux leakage method is a type of nondestructive testing methods. MFL signals
can be measured in the vicinity of a material inhomogeneity. In this case only surface cracks
have been analyzed. The research has two parts. The first one is to build up a nondestructive
testing system in our laboratory; the second is to measure manufactured gaps in a specimen,
and to simulate this system by the Finite Element Method (FEM) [2, 3, 4].
Fig. 1. The measure apparatus
An apparatus has been built up, which can be used as a magnetic flux leakage tester (see Fig.
1). This measurement system is based on National Instruments Data Acquisition card (NI-
DAQ) and National Instruments LabVIEW software package [5]. The specimen can be
positioned in the x-y plane by using LabVIEW commands; the manufactured cracks are
81