• 한국레이저가공학회지
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• 제4권3호
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• pp.30-39
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• 2001

This work was tamed out to apply a laser welding technique in joining between a Zn coated low carbon steel plate(SECC) and a free cutting carbon steel shaft(SUM24L) with or without W coating. Experiments were carried out and analysed by applying the FD(factorial design)method to obtain the optimum Laser welding condition. Optical microscopy, SEM, TEM and XRD analyses were performed in order to observe the microstructures in the fusion zone and the HAZ. Mechanical properties of the welded specimens were examined by microhardness test, tensile test and twist test. There was no flawed Zn in the fusion zone by EDS analysis. This means that during the welding process, Zn gas could be eliminated by appropriate shielding gas flow rate and butt welding gap. Ni coating itself did not influence on the tensile strength and hardness. However, twist bending strength and the weld depth of the Ni-coated free cutting carbon steel were lower as compared with those of the uncoated free cutting carbon steel. It was attributed to a lower absorbance of laser beam to the shin Ni surface. According to the results of the factorial design tests, the twist bending strength of welded specimens was primarily affected by pulse width, laser power, frequency and speed.

• 한국기계가공학회지
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• 제15권1호
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• pp.26-33
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• 2016

In this study, a new method to develop a fixed diamond wire for silicon wafer machining by the multi-wire cutting method was developed. The new twist diamond wire has improved performance with high breaking strength and chip flutes structure. According to these characteristics, the new twist diamond wire can be used in the higher speed multi-wire cutting process with a long lifetime. Except the design of the new structure, the twist diamond wire is coating by electroless-electroplating process. It is good for reducing breakage and the falling-off of diamond grains. Based on the silicon material removal mechanism and performance of the wire-cutting machine, the optimal processing condition of the new twist diamond wire has been derived via mathematical analysis. At last, through the tensile testing and the machining experiments, the performance of the twist diamond wire has been obtained to achieve the development goals and exceed the single diamond wire.

• 한국의류산업학회지
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• 제5권4호
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• pp.408-412
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• 2003

The micro structure of POY was modified and a wool-like touch yarn of composite fibers with different shrinkage was made. With this yarn 12 different fabrics with wool like touch were prepared. The characteristic physical property changes of the fabrics examined are as follows: 1. In all cases, the initial high shrinkage stages were observed in hot water treatment and the 3D images of complex multilayer of typical doubling fibers with different shrinkage were also observed in hot air treatment of 170C. 2. The tensile strength changes of satin and plain fabrics with the change of twist count showed similar behavior. However, WT's were slightly higher and RT's was lower in twill and satin fabrics than those in plain fabric. 3. Since a slight decrease of B's of twill fabric found with increasing twist count under given experimental condition, it could be influenced on the anti-drape stiffness was decreased and flexibility was increased. 4. A significant decrease of G values was observed in the twist count 800-1000 T.P.M However, in the twist count higher than 1000 T.P.M G values observed were kept nearly constant. 5. MIU of plain and twill fabrics showed a drastic decrease at the twist count higher than 1000 T.P.M.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.18-33
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• 2008

This paper presents design optimization of a new Active Twist Rotor (ATR) blade and conducts its aeroelastic analysis in forward flight condition. In order to improve a twist actuation performance, the present ATR blade utilizes a single crystal piezoelectric fiber composite actuator and the blade cross-sectional layout is designed through an optimization procedure. The single crystal piezoelectric fiber composite actuator has excellent piezoelectric strain performance when compared with the previous piezoelectric fiber composites such as Active Fiber Composites (AFC) and Macro Fiber Composites (MFC). Further design optimization gives a cross-sectional layout that maximizes the static twist actuation while satisfying various blade design requirements. After the design optimization is completed successfully, an aeroelastic analysis of the present ATR blade in forward flight is conducted to confirm the efficiency in reducing the vibratory loads at both fixed- and rotating-systems. Numerical simulation shows that the present ATR blade utilizing single crystal piezoelectric fiber composites may reduce the vibratory loads significantly even with much lower input-voltage when compared with that used in the previous ATR blade. However, for an application of the present single crystal piezoelectric actuator to a full scaled rotor blade, several issues exist. Difficulty of manufacturing in a large size and severe brittleness in its material characteristics will need to be examined.

• 감성과학
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• 제5권3호
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• pp.67-74
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• 2002

Testing device was newly designed and built to measure the dynamic contact angle. The measurement was made using microscope interfaced with computerized image analysis system while the dynamic condition being controled using Instron. As specimens for the experiment, two different types of fibers, i.e., hydrophilic and hydrophobic, were prepared. In case of hydrophilic fiber, the increase of twist level gave the increase of contact angle. However, in hydrophobic yarn the increase of twist level gave the decrease of contact angle. When saline was used as a telling liquid, the increase of the concentration gave the increase of contact angle. The results rationalized clearly on the basis of known concepts could be used in designing fabric structure for the improvement of comport performance.

• International Journal of Internet, Broadcasting and Communication
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• 제15권1호
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• pp.145-149
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• 2023

In this study, the spectrum changes induced from the doping of phosphor micro particles in a twist nematic liquid crystal cell was observed. The experimental results show that the achromatic transmission can be observed with a proper driving condition, which may be applied to the design of an achromatic liquid crystal device. In this paper, we tried to figure out the spectrum changes induced from the doping of phosphor micro particles. The experimental result of the phosphor powder doped twist nematic liquid crystal cell shows that the achromatic transmission and the wavelength linearly dependent transmission both can be observed with some proper driving conditions, respectively. The result is useful on developing an achromatic liquid crystal device and it can be applied for Vihicle lamp.

• 소성∙가공
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• 제23권8호
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• pp.501-506
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• 2014

Progressive shearing with blanking dies is commonly employed to produce large quantities of tiny sheet metal electronic parts. Sheet metal pins, which are narrow and long, that are sheared with a progressive die set are often twisted. The twist in the sheet metal pins, which usually occurs in the final shearing operation, generally decreases with increasing blank holding force. The blank holding forces in all shearing operations are not the same because of different shearing positions and areas. In the current study, the optimal layout of the springs in a progressive die set to minimize the twist of the sheet metal pin is proposed. In order to find the holding force acting on the tiny narrow blanks produced with the proposed springs during the shearing process, the equivalent area method is used in the structural analysis. The shearing of the sheet-metal pin was simulated to compute the twist angle associated with the blank holding force. The constraint condition satisfying the pre-set blank holding force from the previous shearing operations was imposed. A design of experiments (DOE) was numerically implemented by analyzing the progressive die structure and by simulating the shearing process. From the meta-model created from the experimental results and by using a quadratic response surface method (PQRSM), the optimal layout of the springs was determined. The twist of sheet metal pin associated with the optimal layout of the springs found in the current study was compared with that of an existing progressive die to obtain a minimal amount of twist.

• 한국염색가공학회지
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• 제22권2호
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• pp.173-179
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• 2010

In this study, we determine the stretch and shrinkage properties of conjugated yarns. The shrinkage(%) and elasticity(%) were determined by applying twist conditions of 0, 350, 800, 1000, 1200, 1400, 1600, 2000 T/M (twisting per meter). It is found that the shrinkage(%) and elasticity(%) gradually decreased with increasing T/M. Especially the elasticity(%) dramatically decreased over 1400 T/M condition. In contrast, it is showed that the handle and drapery properties decreased below 1000 T/M, which indicates that the optimal T/M condition could be 1000~1400. The effect of shrinkage(%) and elasticity(%) with different steam setting temperatures (60, 70, 80 and $90^{\circ}C$) was also determined. The shrinkage(%) decreased with increasing setting temperature, while the elasticity not changed. In this context, the optimal steam setting temperature could be $80^{\circ}C$ because it is not easy to weave with the yarns which was set below $80^{\circ}C$. The elasticity(%) decreased with increasing the density of warp and weft. To produce soft handle, excellent drapery and good stretch fabrics, the warp density needs to be reached by 90% of the ideal warp density. In the case of NaOH treatments to the fabrics, the elasticity(%) increased with increasing weight reduction. Therefore, this study have demonstrated that the conjugated yarns with core yarn and the SDY CD(cation dyeable spindraw yarn) as an effect yarn would be appropriate to produce excellent mixture-yarn, which displays clean appearance, good handle and excellent elasticity, The optimized conditions are as follows; 1000~1200 twist per meter, $80^{\circ}C$ steam setting temperature, 90% of ideal warp density and relaxation condition treated with 5g/l NaOH concentration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.85-92
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• 2007

This paper presents a design optimization of a new Advanced Active Blade Twist (AATR-II) blade incorporating single crystal Macro Fiber Composites (MFC) and conducts vibratory loads reduction analysis using an obtained optimal blade configuration. Due to the high actuation performance of the single crystal MFC, the AATR blade may reduce the helicopter vibration more efficiently even with a lower input-voltage as compared with the previous ATR blades. The design optimization provides the optimal cross-sectional configuration to maximize the tip twist actuation when a certain input-voltage is given. In order to maintain the properties of the original ATR blade, various constraints and bounds are considered for the design variables selected. After the design optimization is completed successfully, vibratory load reduction analysis of the optimized AATR-II blade in forward flight condition is conducted. The numerical result shows that the hub vibratory loads are reduced significantly although 20% input-voltage of the original ATR blade is used.

• 한국전산구조공학회논문집
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• 제27권4호
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• pp.223-230
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• 2014

본 논문에서는 FSI해석을 이용하여 비정형 초고층 빌딩의 풍응답 특성을 연구하였다. 해석모델은 Twist모델이며, 뒤틀림 각도와 풍가속도의 상관관계에 대해 연구 중점을 두었다. 먼저 단방향 해석을 수행하여 100년 재현주기 풍속에 대한 최대 횡 변위를 구하고, 제한조건을 만족하는 탄성계수를 산출한다. 그리고 양방향 해석을 수행, 시간이력해석을 통해 산출된 탄성계수와 임의의 밀도를 가지는 풍가속도를 예측하게 된다. 정방형 모델은 높이 400m, 변장비 1:1, 세장비 8로 설정, 뒤틀림 모델은 0도에서 90도까지 15도 간격으로, 90도에서 360도까지 90도 간격으로 비틀어 회전시켰다. 형상에 따른 풍가속도 예측 결과, 정방형 모델이 뒤틀림 모델보다 크게 산출되어 풍진동 영향에 더 민감한 것을 검증하였다.