• Journal of Magnetics
• /
• v.13 no.1
• /
• pp.34-36
• /
• 2008

For the measurement of the magnetic field distribution with high spatial resolution and high accuracy, the magnetic field sensing probe must be non-magnetic, but the MFM probe and sub-millimeter-meter size Hall probe use a ferromagnetic tip and block, respectively, to increase the sensitivity. To overcome this drawback, we developed a micro-size search coil magnetometer which consists of a single turn search coil, Terfenol-D actuator, scanning system, and control software. To reduce the noise generated by the stray ac magnetic field of the actuator driving coil, we employed an even function $\lambda$-H magnetostriction curve and lock-in technique. Using the developed magnetometer, we were able to measure the magnetic field distribution with a magnetic field resolution of 1 mT and spatial resolution of $0.1mm{\times}0.2mm$ at a coil vibration frequency of 1.8 kHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.364.1-364
• /
• 2002

This work is concerned with the damage size estimation by using propagating bonging wave signals in a beam. To this end, we apply the continuous wavelet transforms to the incident waves and the reflected waves from a small damage in a long cylindrical beam. In particular, we propose to use the relative magnitudes of the two kinds of waves along the ridges in the wavelet transformed time-frequency planes. (omitted)

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.2
• /
• pp.144-149
• /
• 2004

The objective of this investigation is to develop an efficient method to generate and measure torsional waves in non-ferromagnetic waveguides by using magnetostrictive transducers. In existing methods using a nickel strip that is attached circumferentially to the test specimen, large current input to the magnetostrictive transducer often generates undesired wave modes in addition to the desired torsional wave. However, we propose a new method to generate the torsional waves without being accompanied with other undesirable wane modes regardless of the input current magnitude. The specific transducer configuration is suggested and its performance is also checked through a series of experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.9
• /
• pp.841-848
• /
• 2010

Previous experimental results show that the magnetostrictive transducer has the peculiar characteristic with relation to their reversible magnetization and its practical usage will be hindered by this phenomena. In this paper, the idea of anhysteretization is adopted in order to solve this problem. The experimental results reveal that the anhysteretization can get rid of the extraordinary phenomena which are occurred by the change of biasing magnetic field. The effects of two important parameters, which are the amplitude and the decaying time of this process, on the anhysteretization are investigated experimentally. Finally the best operating condition is proposed in order to maximize the sensitivity under the anhysteretization.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.383-388
• /
• 1994

Ultrasonic sensor for evaluating plastic anisotropy was developed. Magnetostrictive type EMAT is sensor to transmit and receive the Lamb wave using magnetostriction. It is suitable for on line processing because of transmitting and receiving ultrasonic without contact ODCs(orientation distribution coefficients), W $_{400}$. W $_{420}$. W $_{440}$. were respectively calculated using zeroth order Lamb wave velocities, the calculated ODCs was used for evaluating plastic anisotropy, the results was compared for mean values of destructive tests. Besides, the Lorentz EMAT for generating longitudinal wave and two shear waves simultaneously and the Lorentz type EMAT for measuring SH wave velocities were made. ODCs were calculated using the measured resonant modes and velocities. the results of two methods show possibility of an line processing measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.549-553
• /
• 2002

Although the magnetostrictive sensors have received much attention in recent years. the investigations on the selection of a desired mode have not been reported. The purpose of this investigation is to present a technique to select a desired mode in a solid ferromagnetic cylinder using a non-contact magnetostrictive sensor. To achieve this goal. we propose new bias magnet configurations to select longitudinal and flexural waves. A few experimental results confirm the validity of the present investigation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.544-548
• /
• 2003

The objective of this investigation is to develop an efficient method to generate and measure torsional waves in non-ferromagnetic waveguides by using magnetostrictive transducers. In existing methods using a nickel strip that is attached circumferentially to the test specimen such as aluminum pipes, large current input to the magnetostrictive transducer often generates undesired wave modes in addition to desired torsional wave. However, we propose an improved method to generate the torsional waves without being accompanied by other undesirable wave modes regardless of the input current magnitude. The specific transducer configuration and its performance will be presented in the present investigation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2006.05a
• /
• pp.185-187
• /
• 2006

This study deals with characterization and the application of magnetoelasticity as a device which measures existing steel stress. Available method of measuring existing stress needs break the concrete and cut the steel bar. But Proposed method doesn't need to cut the steel bar. A successful application of magnetoelasticity depends on the linearity of the relationship between the elastic and magnetic response due to loading. To investigate the correlation between two, steel bars are loaded in tension under uniaxial loading while the magnetic reading is recorded. Results showed linearity or partial-linearity of the elastic behavior of steel bars in relation to magnetic change. In the paper, the various factors affecting the measurements are also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.08a
• /
• pp.107-109
• /
• 2003

The magnetostriction of FeCoGe/phenol composites is measured under the external magnetic field. A few Measurement are carried out by using the electrical-resistance strain gage, the Wheaton Bridge for eliminating the unnecessary voltage, the lock-in-amplifier for the signal amplification and noise filtering. When the external magnetic field is applied to the longitudinal direction against those samples which is the 10wt.% phenol in composites, the theoretical maximum strain of 120ppm is obtained. According to the larger strain than that of others solid state actuators and piezoelectric actuators. FeCoGe/phenol composites could be useful as an actuator.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.3
• /
• pp.336-341
• /
• 2012

Deformations in a cage-induction machine are investigated with simulations. The contribution of the Maxwell stress in the air gap and coil regions of the machine on the deformation is studied by comparing results obtained with and without inclusion of the stress into the calculation. The work attests the acceptability of an energy-based magneto-mechanical model for a 2D mesh of two different rotating electrical machines.