• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.356-362
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• 2007

Magnetostrictive materials have been used for linear actuators due to its large strain, large force output with moderate frequency band in the presence of magnetic field. However their performance analysis is difficult because of nonlinear material behaviors in terms of coupled strain-magnetic field dependence, nonlinear permeability, pre-stress dependence and hysteresis. This paper presents a finite element analysis technique for magnetostrictive linear actuator. To deal with coupled problems and nonlinear behaviors, a simple finite element approach is proposed, which is based on separate magnetic field calculation and displacement simulation. The finite element formulation and an in-house program development are illustrated, and a simulation model is made for a magnetostrictive linear actuator. The fabrication and performance test of the linear actuator are explained, and the performance comparison with simulation result is shown. Since this approach is simple, it can be applied for analyzing magnetostrictive underwater projectors and ultrasonic transducers.

• Journal of environmental and Sanitary engineering
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• v.14 no.1
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• pp.54-61
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• 1999

The industrial techniques of ultrasound have been used in the various fields, such as cleaning, medical surgery, emulsification, cell disruption etc. Especially the application of cell disruption was interested in the field of disinfection process in water by ultrasonic irradiation. It has been recognized that the ultrasounds are irradiated in aqueous solution, cavitation bubbles are generated and shock waves of high temperature and pressure are emitted as the bubbles are developed and finally broken, which function as a energy source to promote reaction efficiencies of various kinds of chemical reactions such as disinfection reaction in water. Therefore, this study was performed to apply the ultrasound for the disinfection method of infected drinking raw water and to discuss the limiting factors such as pH, sample volume and reaction temperature influenced on the removal efficiency of E. coli from experimental analysis of the results obtained in bench-scale plant. For the experiments to measure the influence of reaction parameters in the ultrasonic disinfection process, escalated reactivity of aqueous solutions was excellent when pH in aqueous solution was low, and sample volume was small. On the contrary, the reactivity of disinfection became elevated when reaction temperature was high. It was found that the rate constant of disinfection reaction was applied by Chick's law, reaction kinetics of Chick's law was irreversible and pseudo-first order at all the tested conditions.As a conclusion it appeared that the technology using ultrasonic irradiation can be applied to the treatment of disinfection in infected water which are difficult to be treated by conventional methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.4
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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.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.37-42
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• 2010

The stay cylinder weld at the steam generator of Korean Standard Nuclear Power Plants is safety class I component and is subjected to be inspected by the volumetric examination such as ultrasonic method. As accessibility of this area is limited due to the narrow space and high radiation, the existing manual inspection method involves various difficulties. Moreover operators may be exposed to internal contamination by contaminated dust during the surface buffing process to improve the inspection reliability of this area. Recently the new automatic inspection system for stay cylinder welds has been developed. The inspection system basically consists of a driving assembly, data acquisition device and signal processing units. The driving assembly is classified by 1) the scanner for inspecting and buffing the weld, 2) pillars for guiding the scanner and 3) the base frame for loading and supporting pillars. The scanner has 4 sensor modules to inspect in 4 refracted angles and 4 incident directions. These components can be inserted into the skirt of the stay cylinder through the manway hole and assembled easily by one-touch in the skirt. Data acquisition device and signal processing units developed in previous works are also newly upgraded for better processing of data analysis and evaluation. The system has been successfully demonstrated not only in the mock-up but also in the field. In this paper, newly developed inspection system for the stay cylinder weld of the steam generator is introduced and their field applications are discussed.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.338-346
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• 2016

Purpose: The purpose of this research is to improve the reliability of the composite material blades used for the wind power generator, by applying the phased array ultrasonic testing technique out of the many nondestructive test into the blades. Method: The wind power generation composite blades are used, as a case study, in order to evaluate the reliability of the phased array ultrasonic testing technique. Defects that are most likely occurred in the field are injected into the different locations of the three different types of artificial test pieces and then phased array ultrasonic testing technique are applied to evaluate the reliability of its effectiveness. Result: As a result of the analysis of the defect signals by applying the A scan and B scan simultaneously, depth and width of the defect could be obtained. An area of defect was proportional to the amount of energy by color in B scan image. The larger amount of energy, reflected amount of energy was appeared in the order of red, orange, yellow, blue color. Conclusion: The most reliable testing method to detect the defect in composite blades for wind power generation is considered to be the combination of the other destructive testing technique with the phased array ultrasonic testing since the PAUT alone could not detect all range of the defects in the blades.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.119-128
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• 2020

An ultrasonic multiple scattering simulation using cross-section of fine dust particles were proposed. These days, along with awareness of air pollution, social interest in fine dust is increasing. In the construction field, awareness of fine dust is increasing, and research on preparing various countermeasures is underway. The light scattering method fine dust meter currently in use is affected by environmental factors such as relative humidity, and reliability problems in terms of accuracy are continuously reported. However, the transmission of ultrasonic waves can directly reflect the physical change of the medium based on the mechanical wave. Using these advantages of ultrasonic waves, fine dust measurement simulation was performed using the scattering cross section and ultrasonic multiple scattering theory. The shape data of the fine dust particles were collected using a SEM (Scanning Electron Microscope), and a cross-section according to the fine dust particles was derived through numerical analysis. As a result of signal processing, the error for the number density corresponding to each cross-section is minimum 19, maximum 3455.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.1-8
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• 2016

An experimental study was performed for the combustion-field visualization of the burner which burns the liquid hydrocarbon fuel atomized by an ultrasonic oscillator. Configurations of the flame and combustion-field were caught by both high-speed camera and thermo-graphic camera, and those images were analyzed in detail through a post-processing. As a result, the combustion-field grew and reaction-temperature rose due to the strengthening of combustion reaction with the increasing flow-rate of carrier-gas. In addition, a phenomenon of flame flickering was discussed through the comparative analysis of the variational behaviors between the visible flame and IR (Infrared) flame-field.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.67-73
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• 2017

For the bio-fuel conversion of algae, several processes are needed including cultivating, agglomeration, extracting and conversion to the bio-fuel. The production cost for each process makes the total production cost of algae bio-fuel conversion. The production cost of algae bio-fuel has still higher than that of the other commercial bio-fuel. The reduction of production cost for each process enables the competitive price as a bio-fuel. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources. The present research is investigated for the elucidation of algae behavior in the water with the ultrasonics wave. For this purpose, the unsteady computational fluid dynamic analysis has been conducted in the ultrasonic pressure field. The velocity, pressure and algae concentration changes with time have been analysed to clarify the mechanism of algae separation by ultrasonic wave.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.341-348
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• 2016

Harbor facilities require long-term durability and safety, and also maintain the performance requirement until the durability life. However, existing harbor facilities are becoming superannuated with durable years and durability is declined by erosion of the sea and damage from sea. In addition, harbor facilities will be in demand for the expansion of harbor and offshore structures with rising economic power by enhancement of domestic industry and increase of import and export. Therefore, in this study, two kinds of nondestructive test (NDT) techniques (schmidt rebound hammer and ultrasonic sensor) are verified for the effective maintenance of underwater concrete structures including harbor facilities. Sea field applicability of Schmidt hammer and ultrasonic sensor was verified by comparing field test result with sea field test result and also deduced the compressive strength estimation equation by depth of the water. On the basis of the sea field test result, compressive strength estimation equation which was deduced by multiple regression analysis indicated highest accuracy compared to other equations, especially it will be more likely to be used in underwater because of the depth of water correction. In the future, if schmidt hammer and ultrasonic sensor which were invented as waterproofing are used with ROV (Remotely Operated Vehicle), it will be possible to make a diagnosis of high reliability for underwater concrete structures and set up a ubiquitous concept of NDT system.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.317-323
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• 2010

The manual ultrasonic examination for the nuclear power plant piping welds has been demonstrated by using KPD(Korean Performance Demonstration) generic procedure. For automated ultrasonic examination, there is no generic procedure and it should be qualified by using applicable automated equipment. Until now, most of qualified procedures used pulse-echo technique and there is no qualified procedure using phased array technique. In this study, data acquisition and analysis software were developed and phased-array transducer and wedge were designed to implement phased array technique for nuclear power plant in-service inspection. The developed procedure are qualified for performance demonstration for the flaw detection, length sizing and depth sizing. The qualified procedure will be applied for the field examination in the nuclear power plant piping weld inspection.