• Design & Manufacturing
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• v.2 no.5
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• pp.39-42
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• 2008

The Paper discussed the effects of working electric current and pulse when using super hardend alloy drill as corona electrode. The discharge effect can be obtained very precisely in the ranges of 1A - 2A in working current. $12{\mu}s-14{\mu}s$ in dis charge pulse on time width and $8{\mu}s-10{\mu}s$ in discharge pulse off time.

• Journal of the Korean institute of surface engineering
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• v.35 no.3
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• pp.141-148
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• 2002

Fe-C alloy layers were produced by pulse plating and the properties were compared with those produced by D.C. plating. When the pulse on time ($T_{on}$ ) was the same, both the duty cycle and peak current density($I_{p}$ ) had little influence on the carbon content and the hardness of the layer. The structure and hardness of the direct current plating were similar to those of the pulse current plating. However, the ductility was enhanced when the pulse current was applied due to the release of residual stress during the pulse off time($T_{off}$).).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.159-159
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• 2015

금속의 기계적 강화방법인 결정립미세화의 일종으로 미세한 쌍정을 도입하여 기계적강도를 향상시키면서 전기전도도는 감소시키지 않는 방안으로 nanotwin 구조의 Cu가 보고되고 있다. Nanotwin 구조는 FCC결정구조에서 특정 결정면을 [(111) mirror plane]을 기준으로 정합계면을 유지하면서 원자층의 배열이 역전되는 구조가 수~수십나노 수준의 간격으로 이뤄진 미세조직을 의미한다. 전해도금법을 이용한 nanotwin Cu의 형성방법으로는 pulse 파형을 사용하는데, pulse파형의 on time동안의 높은 전류밀도로 인해 발생한 도금층의 stress가 off time동안에 release되면서 nanotwin구조가 형성되는 것으로 보고되고 있다. Nanotwin형성 조건으로 보고된 pulse 도금 조건은 수에서 수십밀리초의 on time에 duty cycle($t_{on}/(t_{off}+t_{on})$)이 1/100~1/10 수준이다. 본 연구에서는 전기이중층의 이온고갈에 필요한 회복시간인 수에서 수십 밀리초 보다 짧은 시간인 마이크로 초($1{\mu}s$, $10{\mu}s$ 및 $100{\mu}s$)의 pulse 전류를 인가하였을 때에 발생하는 구리 도금층의 미세조직의 변화에 대해 알아보고자 한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.255-256
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• 2007

• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.51-54
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• 2019

The electrodeposition of rhodium (Rh) on silicon substrate at different current conditions were investigated. The cracks were found at high current density during the direct current (DC) plating. The pulse current (PC) plating were applied to avoid the formation of cracks on the deposits. Off time in the pulse plating relieved the residual stress of the Rh deposits and consequently the current conditions for the crack-free Rh deposits were obtained. Optimum pulse current (PC) condition is 5:5 (on:off) for the crack-free Rh electroplating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.314-314
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 40vol.% of Zirconium Diboride(hereafter, $ZrB_2$) powders with Silicon Carbide(hereafter, SiC) matrix. TheSiC+40vol.%$ZrB_2$ composites were manufactured through Spark Plasma Sintering(hereafter, SPS) under argon atmosphere, uniaxial pressure of 50MPa, heating rate of $100^{\circ}C$/min, sintering temperature of $1,500^{\circ}C$ and holding time of 5min. But one on/off pulse sequence(one pulse time: 2.78ms) is 10:9(hereafter, SZ10), and the other is 48:8(hereafter, SZ48). The physical and mechanical properties of the SZ12 and SZ48 were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via X-Ray Diffraction(hereafter, XRD) analysis. The apparent porosity of the SZ10 and SZ48 composites were 9.7455 and 12.2766%, respectively. The SZ10 composite, 593.87MPa, had higher flexural strength than the SZ48 composite, 324.78MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had Positive Temperature Coefficient Resistance(hereafter, PTCR).

• Journal of Welding and Joining
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• v.26 no.6
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• pp.48-53
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• 2008

Although Magnetic Pulse Welding(MPW) is not a recently developed technique, it has gained the attention of the automotive industry. MPW has become an accepted welding process because it enables the joining of similar, and dissimilar materials, with a very short cycle time, without the need for filler metal and gases. In this study, the effect of the stand-off distance on the weld strength has been investigated. The compressive strength of the MPW joints was evaluated using UTM. The interface of weld, IMC composition and morpology were studied by SEM and EDS. It was concluded that the stand-off distance and the voltage are the main parameters influencing the strength of weld. In case of too high stand-off distance, it influenced harmful effect because of the resistance of deformation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.485-501
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• 1997

Pressure control is possible driving a simple ON/OFF 3-way valve of hydraulic servo system by pulse width modulation signal. But the pressure varies according to the duty ratio and carrier frequency and repeated on-off action induces pressure fluctuation. So equations for mean pressure and ripple amplitude are theoretically derived as a function of on/off time, the system parameters which decide the pressure characteristics are arranged and they are verified by experimental study. As the result selection criteria for the major design parameters are established and the basic strategy to suppress the unnecessary fluctuation can be provided for a hydraulic pressure control system using these type of valves.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.109-116
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• 1998

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone (MPWMD). The pneumatic system using on-off valves has advantage of simple construction and low cost compared with a system with servo-valves. The performance of the proposed control method is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control compared to the conventional PWMD algorithm. It is also shown that the use of the proposed MPWMD algorithm for the position control significantly reduces the number of valve switching and noise.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.3
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• pp.255-261
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• 2007

By using numerical analysis methods, through transmission type pulsed eddy current (PEC) testing is modeled and PEC signal responses due to varying material conductivity, permeability, thickness, lift-off and pulse width are investigated. Results show that the peak amplitude of PEC signal gets reduced and the time to reach the peak amplitude is increased as the material conductivity, permeability, and specimen thickness increase. Also, they indicate that the pulse width needs to be shorter when evaluating the material conductivity and the plate thickness using the peak amplitude, and when the pulse width is long, the peak time is found to be more useful. Other results related to lift-off variation are reported as well.