• 소성∙가공
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• 제21권2호
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• pp.119-125
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• 2012

The present study addresses a direct patterning process on a plastic film using ultrasonic vibration energy. In this process, a tool horn containing micro-patterns is attached to an ultrasonic power supply, and is used with ultrasonic vibration to replicate micro-patterns on the surface of a plastic film. To improve the replication characteristics of the micro-patterns, the effect of the die shape of the ultrasonic patterning process was investigated with respect to the flow direction control. Finite element analyses were performed to predict the flow characteristics of the polymer with variations in die design parameters. Experiments were conducted using the optimally-designed die, from which it was possible to attain much improved pattern replication.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.655-658
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat-flux boundary conditions unlike many of the previous researches, which had adopted constant wall-temperature conditions. Therefore in the study, modified dimensionless numbers such as Stefan and Rayleigh were adopted to represent heat transfer results. The experimental results revealed that ultrasonic vibrations accompanied the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion, accelerating the melting process as much as 2.5 times, compared with the result of natural melting (i. e., the case without ultrasonic vibration). Such effects are believed to be a prime mechanism in the overall melting process when ultrasonic vibrations were applied. Subsequently, energy could be saved by applying the ultrasonic vibrations to the natural melting In addition, various time-wise dimensionless numbers provided a conclusive evidence of the important role of the ultrasonic vibrations on the melting phenomena of the PCM.

• 펄프종이기술
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• 제40권2호
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• pp.16-22
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• 2008

The pilot scale ultrasonic deinking was carried out in order to confirm the commercialization possibility of ultrasonic deinking. White ledger was used as a raw material and the results were compared to the results obtained from the conventional deinking. The fraction of smaller ink particle was increased and the improved ink removal efficiency was also obtained by the ultrasonic treatment. The brightness and breaking length of ultrasonic deinked pulp were superior to those of the conventional deinked pulp. Most interesting findings in this study were that the significant improvement in effluent quality and the reduction of chemicals and energy cost were obtained by the ultrasonic deinking.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1846-1857
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• 2021

Ultrasonic nondestructive testing is important for monitoring the structural integrity of dissimilar metal welds (DMWs) in pressure vessels and piping in nuclear power plants. However, there is a low probability of crack detection via inspection of DMWs using ultrasonic waves because the grain structures (grain orientations) of the weld area cause distortion and splitting of ultrasonic beams propagating in anisotropic media. To overcome this issue, the grain orientation should be known, and a precise ultrasonic wave simulation technique in anisotropic media is required to model the distortion and splitting of the waves accurately. In this study, a method for nondestructive prediction of the DMW grain orientations is presented for accurate simulation of ultrasonic wave propagation behavior in the weld area. The ultrasonic wave propagation behavior in anisotropic media is simulated via finite-element analysis when ultrasonic waves propagate in a transversely isotropic material. In addition, a methodology to predict the DMW grain orientation is proposed that employs a simulation technique for ultrasonic wave propagation behavior calculation and an optimization technique. The simulated ultrasonic wave behaviors with the grain orientations predicted via the proposed method demonstrate its usefulness. Moreover, the method can be used to determine the focal law in DMWs.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.1879-1884
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• 2014

최근 미세접합 기술이 다양한 사회에서 주목받고 있다. 미세접합 기술은 레이저 접합 초음파 접합 등이 있다. 그러나 미세 접합의 연구가 많이 부족한 실정이다. 이에 본 논문에서는 초음파 접합장치 구동 시 열평형 상태에서 압전소자에 열영향을 최소화하기 위해 냉각관을 설계하였다. 또한 냉각관이 설계된 초음파 접합 장치를 이용하여 접합 실험을 실시하였다. 다꾸찌 실험계획법을 이용하여 실험을 실시하였으며, 기초실험을 통해 공정변수와 반응 변수를 설정하였다. 접합 실험의 신뢰도를 검증하기 위하여 접합 계면의 미세조직을 관찰하였고, 인장실험을 통해 접합 강도를 확인하였다.

• 한국해양공학회지
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• 제13권3호통권33호
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• pp.92-99
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• 1999

High temperature and pressure materials in power plant are degraded by creep damage, if they are exposed to constant loads for long times, which occurs in load bearing structures of pressurized components operationg at elevated temperatures. Many conventional measurement techniques such as replica method, electric resistance method, and hardness test method for measuring creep damgage have been used. So far, the replica method is mainly used for the inspection of high temperature and pressure components. This technique is, however, restricted to applications at the surface of the testpieces and cannot be used to material inside. In this paper, ultrasonic evaluation for the detection of creep damage in the form of cavaties on grain boundaries or intergranular microcracks were carried out. And the absolute measuring method of quantitative ultrasonic velocity technique for Cr-Mo material degradation was analyzed. As a result of ultrasonic tests for crept for specimens, we founded that the sound velocity was decreased as increase of creep life fraction(${phi}c$) and also, confirmed that hardness was decreased as increase of creep life fraction(${phi}c$).

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.41-46
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• 2002

The general purpose of this paper is Evaluation of material properties in spring steels by investigate correlation between ultrasonic attenuation and virker's hardness, charpy impact properties, microstructures. The three test speciments of the $490{\times}90 mm$ plates and 20 mm thick are used but differ in heat treatment, one is rolled plate, the second is quenched and then tempered, and the third is quenched. ultrasonic attenuation were obtained at fifteen locations on the plates. In order to investigate the correlation between hardness ( especially, HV ) and the attenuation, the virker's hardness and the microstructures were observed for three spring steels. also the charpy impact test were carried out at the room temperature in order to investigate the relationship between impact properties and the attenuation. The experimental results obtained from three different spring related to the heat treatment conditions and attenuation coefficient is increased with increasing the hardness(HV). Ultrasonic attenuation coefficients have shawn are ability to distinguish among spring steels.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.664-668
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• 2003

Transducer for ultrasonic linear motor with the symmetric and anti-symmetric modes was studied. The ultrasonic linear motor consists of two Langevin type piezoelectric vibrators that cross at right angles with each other in tip. In order to excite symmetric and anti-symmetric modes, the transducer must have a phase shift of 90 degree in space and time. Therefore, the tip of transducer moves on an elliptical motion. In this paper, the finite element analysis was used to optimize dimension and displacement of the transducer. The ultrasonic motor was fabricated using the simulated result and the driving characteristics were measured. No-load velocity was 0.28[m/s] and the maximum efficiency was 30[%] in resonance frequency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.324-324
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• 2008

Piezoelectric ceramics is an active element that makes stator to vibrate to generate rotational force in ultrasonic motors. In drive of ultrasonic motors, many factors that affect to the resonance characteristics of piezoelectric ceramics exist. For example, those factors are bonding condition with elastic body, the magnitude of electric field, the normal force for frictional drive and the emission of heat due to vibration and friction and so on. Therefore, it is important to research the inclination of property variation of piezoelectric ceramics in circumstance that has complex elements. In this paper, we focused and analyzed the resonance characteristics of ultrasonic motor due to the magnitude of the driving voltage and normal force.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.705-709
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• 2004

In this study, the foot-spa driving circuit using ultrasonic vibrator was manufactured The used ultrasonic vibrator was PSN-PMN-PZT ceramic with the radius of $25{\Phi}$ and the thickness of 2, 2.5, 3, 3.5 and 4mm, respectively. Resonent frequency for driving ultrasonic vibrator at the fabricated circuit was generated using the self exciting and the external exciting methods. Fabricated foot-spa showed the best condition at the resonent frequency of 1.130MHz and the ceramic thickness of 2.0mm. That is, when the foot-spa was operated for 360 min. at $0.5\ell$ water, temperature increase of water was $14^{\circ}C$ at the self exciting method and $16^{\circ}C$ at the external exciting methods, respectively.