A magnetic-field transducer based on a magnetic-field-controlled electrochemical cell

Abstract

It is known that in order to obtain positive results during a magnetic powder inspection, a ferromag netic suspension must be characterized by certain parameters, such as the concentration, size of ferromag netic particles, their magnetic properties, viscosity and several other properties given in the corresponding standard [1].Along with its mechanical properties, the suspension has electrical parameters whose values can depend on the magnetic field; during an inspection this is used in order to obtain additional quantitative data on the results of the inspection. It was shown in [2] that the measurement of electrical resistivity in the flaw zone during a magnetic inspection can give, in addition to visual indications, information about the parameters of a flaw. In [3], measurement of the galvanic currents of a suspension of a specific com position, which vary during the application of a magnetic field, was proposed. A magnetic field transducer was also proposed in [3]. In this transducer, the measured value and voltage of galvanic currents in a fer romagnetic suspension, which result from the action of the magnetic field of a flaw on one of the trans ducer electrodes placed in the suspension, are used for the indication of the magnetic fields of flaws.Such a transducer is intended for the indication of only nonuniform magnetic fields (the magnetic field of a flaw is among them) and cannot be used for measuring uniform magnetic fields as long as the mea suring electrodes of a transducer, which are under the same conditions, do not disturb the potential bal ance between the electrodes, since in this case the galvanic currents are at a minimum.In this study, we consider a magnetic field transducer that is an electrochemical cell that is used for the indication of both nonuniform and uniform magnetic fields. This is done via an arrangement of compo nents within the transducer construction that differs from that used in [3].The transducer (Fig. 1) consists of a vessel, 1, in which two similar copper electrodes, 2, are placed. The right hand section, 3, is filled with a ferromagnetic suspension; the left hand section, 4, is filled with a dispersed medium that is present between electrodes, 5, located in the middle of the space. The con struction of the transducer is similar to that used in [3].Thus, in contrast to the transducer that was used in [3], in which a suspension uniformly fills the vessel bottom and is in contact with both electrodes, the present transducer contains a suspension only around one of electrodes; an electrochemical current is induced via a potential drop between the dispersed medium, 4, and the suspension, 3. Since the properties (magnetic and electrical) of the suspension vary during the application of a magnetic field, the potential difference of the electrodes, 2, which are con nected with the media, 3 and 4, also changes.Abstract-An electrochemical cell in which the electrolyte is a ferromagnetic suspension of a specific composition containing acidic electrolytic components was proposed for...

Effects of surface roughness on magnetic flux leakage testing of micro-cracks

“…With the development of manufacturing level, higher accuracy of MFL detection is strongly required [12,13]. Much attention is focused on a wide variety of factors, including the lift-off of the sensor, scanning velocity, B-H curves of the material, magnetization as well as the geometry of defects in relation to the inspection signals [13][14][15][16][17][18][19]. However, all the work on the factors mentioned above is conducted based on the simple and sketchy hypothesis that the surface of the workpiece is absolutely smooth.…”