• 대한기계학회논문집A
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• 제28권7호
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• pp.923-929
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• 2004

A magnetostrictive sensor is a sensor measuring elastic waves. Because of its unique non-contact measurement feature, the sensor receives more attentions in recent years. These sensors have been mainly used to measure longitudinal and torsional waves in ferromagnetic waveguides, but there increases an interest in using the sensor for flexural wave measurement. Since the performance of the sensor is strongly influenced by the applied bias magnetic field distribution, the design of the bias magnetic system providing the desired magnetic field is critical. The motivation of this investigation is to design a bias magnetic system consisting of electromagnets and yokes and the specific objective is to formulate the design problem as a bias yoke topology optimization. For the formulation, we employ linear magnetic behavior and examine the optimized results for electromagnets located at various locations. After completing the design optimization, we fabricate the prototype of the proposed bias magnetic system, and test its performance through flexural wave measurements.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.310.2-310
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• 2002

Terfenol-D is one of magnetostrictive materials which have the property of converting the energy in magnetic fields into mechanical movement and vice versa. We designed and fabricated a linear magnetostrictive actuator using Terfenol-D. It has 25mm diameter and 100mm long. To grasp the characteristics of it, a series of tests were performed in the range of 50㎐ below. Induced-strain actuation displacements of the actuator measured by test and predicted by magnetic analysis agreed well. (omitted)

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.418-424
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• 2009

This work is the attempt to give qualitative explanations to complex magnetic phenomena which are observed in the previously proposed magnetostrictive sensor capable of ultrasonic waves and rotational speed measurement. The law of approach is adopted as analysis tool in order to account for some extraordinary output patterns and proved to be effective. The distance between the anhysteretic curve current magnetic state and the variation of anhysteretic curve by stress mainly determine the sensor output shapes and their uniqueness. It is also experimentally verified that the precisely determined bias magnetic field strength can not only remove the unusual output parts but also maximize its sensitivity.

• 한국소음진동공학회논문집
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• 제14권2호
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• pp.144-149
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• 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.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1177-1183
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• 2009

The effects of biasing magnetic fields on the performances of magnetostrictive ultrasonic transducers are investigated. The transducers are patch-type ones which are used for SHM of plate structures. Various kinds of configurations of biasing magnets are covered experimentally. It is experimentally verified that how the biasing magnetic field deploys is the most significant factors on maximizing the transducer output. From the magnetostriction curve of nickel, it is concluded qualitatively that it is not the absolute values of biasing magnetic field but the slope of magnetostriction curve to be taken account of.

• 한국소음진동공학회논문집
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• 제20권12호
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• pp.1200-1209
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• 2010

The main subject of this paper is to develop analytic method with which output power or sensitivity variations of a magnetostrictive ultrasonic transducer can be estimated with no aid of experiments. After the bias magnetic field deployed over the patch is calculated using finite element analysis for magnetostatics, the representative value is extracted by averaging these field values. The operating point on the characteristic curve for magnetostriction is identified by this value and then the output performance is calculated from it. It is verified that the results from this simple model match well with those of its experimental version and some limits of this modeling technique are also considered.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.549-553
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.544-548
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.433-438
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• 2003

In this paper we explore the effectiveness of a magnetostrictive actuator(MSA) as a structural control device. A series of numerical and experimental tests are carried out with a simple aluminum beam only supported at each end by the actuator. After the equation of motion of the controlled system is obtained by the finite element method, a model reduction is performed to reduce the numbers of degree of freedom. A linear quadratic feedback controller is realized on a real-time digital control system to damp the first four elastic modes of the beam. Through some tests, we confirmed the possibility of this actuator for controlling beam-like structures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.548-549
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• 2014

Omni-directional shear-horizontal magnetostrictive patch transducers have a disadvantage that magnetic flux leakage into the plate when it is installed on a ferromagnetic plate. The leakage produces poor transduction efficiency and unwanted wave mode excitation which should be avoided in guided wave inspections of large plate-like structures. In order to resolve these problems, we newly developed a method to reduce the leakage into the plate. In the method, the patch and the magnet are vertically lifted off and their optimal positions are determined by numerical simulations. Also, the verification of the developed method is successfully verified by experiments.