경사 제직성의 객관적 추정

김종성,임정호,김환국,허유,Kim, Jong-S.,Lim, Jung-H.,Kim, Hwan-Gook,Huh, You 한국섬유공학회 2011 한국섬유공학회지 Vol.48 No.3

New types of fibers or yarns are often in the development of high-quality textile products. However, their processability is difficult to estimate or evaluate and is detemlined subjectively by experienced engineers or technicians. Therefore a measurement was developed to define more objectively the processability of yarns, especially the weavability of warp yarns. Warp yarn tensions were measured on a test rig to collect information on weavability. Hair occurrence, entanglement of warp yarns, yarn breakages, and warp tension relaxation were measured and combined with weighting factors to establish a weavability index of the warp yarns. The weighting coefficients were chosen according to the experience of users. Weavability index has the potential to allow the prediction of a yarn's performance it is woven. An example use of the index is discussed.

롤러 드래프트의 조작 설정과 슬라이버 굵기의 변동 특성

김종성,허유,Kim, Jong-S.,Huh, You 한국섬유공학회 2011 한국섬유공학회지 Vol.48 No.4

Fibers' length distributions were shown to affect their linear density. They depended on processing conditions such as draft roller adjustment and draft ratio. Random variational signals were applied as input bundles and output linear densities were simulated at various draft roller adjustments and draft ratios using the dynamic model equipped with various velocity variance models for fiber length distribution. Draft roller adjustment and draft ratio led to process resonance and increased irregularity in the output linear density. Increasing draft roller adjustment reduced linear density in CV%, while process resonance occurred at draft roller adjustments of 1.1-1.25 times of the maximal fiber length. Length distributed bundles had lower fundamental frequencies (longer fundamental wavelengths) than uniform fibers. High draft ratios induced greater irregularities in the output bundles, with process resonance occurring at draft ratios of 20-30. Draft ratios above 30 led to output linear density including wide ranging regularly oscillatory components of irregularity that corresponded to integer multiples of the fundamental frequency.

마찰 정방에서 드럼 표면상에서의 집속체 굵기 분포

김종성,허유,Kim, Jong-S.,Lehmann, Beata,Huh, You 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.3

This study is dealing with the friction yarn formation process, where the fiber fleece is transformed into a bundle. The bundling procedure can be thought of as the fiber stapling and rolling on the friction drum, of which the dynamics can be described on the basis of the mass conservation. On the basis of the dynamic model obtained the bundle thickness on the friction drum was simulated according to the step and sinusoidal changes in the input fleece thickness. Results showed that the bundle radius response to the step change of the input fleece thickness can be approximately described with the characteristics of an integrating system with the amplitude limit. The sinusoidal change of the input fleece thickness yielded the bundle radius change that depended on the input change frequency. Under certain frequencies of the input fleece thickness change the yam take-up speed could amplify the output yam irregularity, which confirms the possible existence of the process resonance.

집속체 유동계의 안정성 해석

김종성,허유,Kim, Jong-S.,Huh, You 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.2

Bundle flow occurs in the processes where material with long shape in comparison with its cross-section is used and the process products often undergo thickness fluctuation due to the flow dynamics. This study deals with investigating the stability of a bundle flow by means of theoretical simulation. Introducing perturbation in the flow state demonstrated that the eigenvalues of the linearized flow dynamic system, determining the stability of the flow state, were dependent on the model parameters and the draft ratios. The stability diagram revealed that the stable area of the parameters became narrower as the draft ratio increased, which indicates that the state of the bundle flow is sensitive to the input bundle properties. As the fiber cohesion of the bundle or the draft ratio increased, the flow was apt to change to an unstable state. Especially there existed a specific value of the draft ratio that represented a characteristic measure, addressing the criterion of the bundle flow stability. The bundle flow dynamics was insistently stable under the condition of the draft ratio less than the characteristic value, no matter what values of the parameters were given.

섬유장 분포를 고려한 연신 집속체의 굵기 모사

김종성,허유,Kim, Jong-S.,Huh, You 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.6

Bundle consists of fibers that have a length distribution, which influences the flow dynamics in a roller drafting process. Since the dynamic behavior of bundle in the flow system can lead to the thickness variation of the output, the fiber length distribution was taken into the dynamic model describing the bundle flow, and the dynamic characteristics and the output bundle thickness were investigated by simulation, while the process factors such as the draft gauge and the draft ratio were considered. Introducing velocity variance models for different fiber length distributions and a simplified sinusoidal velocity variance into the bundle flow dynamics, the output bundle thicknesses were compared each other. The state variables in a steady state showed that the bundle with a uniform fiber length can get a stronger jerk than the bundle with a fiber length distribution, when crossing over the front roller nip line. The bundle flow dynamics could be characterized by oscillatory behavior with a decaying magnitude or an increasing magnitude with an upper limit, which is dependent on the process variables. It was confirmed theoretically that as the draft gauge increases, the output bundle thickness becomes more uniform, while the draft ratio has the opposite effect on the out-put. The critical draft gauge that defines the bordering zone between unstable and stable behavior of the output bundle thickness was about 1. 25 times of the maximum fiber length. The critical draft ratio revealed different results for bundles with a uniform fiber length and a fiber length distribution: for the uniform fiber length the critical draft ratio has a value below than 25, for a fiber length distribution it lies in the zone greater than 25, which demonstrates that the fiber length distributed bundle is roller drafted better that the uniform fiber length bundle. The simplified velocity variance model could be effectively applied to describe the flow dynamics that consists of bundles with a fiber length distribution or even with a uniform fiber length.

롤러 연신 슬라이버의 굵기 변동과 비선형 조작 특성

김종성,서문원,허유,Kim, Jong-S.,Suh, Moon-Won,Huh, You 한국섬유공학회 2009 한국섬유공학회지 Vol.46 No.1

This study set the target to systemize the roller drafting operation and performed the characteristic analysis by simulation of the effect of the draft ratio, an important process variable, on the output sliver thickness, based on the bundle flow model. The simulative result showed that the output sliver thickness possesses a fixed point for a value of draft ratio in the range of the linear stability. As the draft ratio increases, the drafted sliver thickness changes in a periodical way, which corresponds to the critical case in a linearized system. Then for the further increase of the draft ratio the output sliver thickness has an initial increase of the deviation from the stationary value, which is justified for an unstable system, but when time elapses long, the increase of the amplitude is limited in a certain range, showing a closed trajectory in the phase plane. This dynamic characteristics is called the limit cycle behavior. Eventually the sliver output from the roller draft operation varies in the characteristics of the linear density for the draft ratio; a fixed point occurs, and then the fixed point disappears, as the draft ratio increases, which is a typical Hopf bifurcation phenomenon. The existence of the draft wave can be thus justified as a limit cycle behavior due to the non-linearity of the bundle flow system.

1 방향 유동계에서의 섬유군 거동 특성

김종성,임정호,허유,Kim, Jong S.,Lim, Jung Ho,Huh, You 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.4

This study deals with the dynamic characteristics of staples flowing in a one-directional flow field, when external forces exerted on the staples are generated at both the ends of the flow field. Based on a theoretical model describing fiber bundle flow dynamics, we introduced the effect of staple length on model parameters such as the speed variance of individual staples and the kinematic viscosity of staples through a beard diagram. Simulations for investigating the dynamic behaviors of the staple flow variables, namely, the average speed of the staples and the linear density of the staple bundle, were conducted numerically with respect to time and position in the flow field under predetermined conditions. The results indicated that the output linear density of the staple bundle has a periodic change, which could be explained by the dynamic behavior of the staples in the flow field. The dynamic distribution of the average speed of staples has a continuously increasing profile, which changes with time. Thus, the change in speed distribution leads to fluctuations in the linear density of the staple bundle. The acceleration of the staple bundle also fluctuated with time, which got stronger while approaching the exit of the flow field. This indicates that the output staple bundle could be very sensitive to the disturbances occurring near the exit. The fluctuation in output linear density was influenced by the length of the flow field. When the length of the flow field is short (the ratio of the field length to the maximum staple length is approximately 1.1), the fluctuation in linear density has a single peak in the amplitude spectrum. However, when the flow field becomes longer (the ratio of the field length to the maximum staple length is approximately 1.5), the spectrum of the linear density fluctuation shows multiple peaks.

동적 안정성 하에서의 드래프트 불균제 특성

김종성,허유,서문원,Kim, Jong-S.,Huh, You,Suh, Moon-W. 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.3

Factors influencing the product quality of the roller drafting operation can be referred to as the arrangement of the bundle fibers and the bundle thickness. However, the movement of individual fibers cannot be exactly controlled during the processing. The state of the bundle flow in the processing can be disturbed easily due to the change of the raw material or the process conditions, which can be attributed to the fact that the bundle flow dynamics is different from the continuum. Uncontrollable bundle fibers lead to the irregularity of the output bundle thickness. This study reports on the characteristics of the draft irregularity by simulation, when the system has the dynamic stability on the basis of the bundle flow dynamic model. Results reveal that the thickness variation of the drafted bundle depends on the model parameters; a uniform thickness or a periodical variation in thickness appears. The draft irregularity can take place more sensitive to the input bundle thickness than to the draft ratio in a limited range of the output bundle thickness variation. The thickness irregularity can commonly characterized by the fundamental frequency, even though the system has the parameters that assure it to be stable. The range of the irregularity frequency band, above which the thickness variation disappears, is dependent on the disturbing source, but the upper limit of the frequency range reads 5 times of the fundamental frequency that is defined by the transient characteristics of the bundle flow system.

연조 슬라이버의 선밀도 거동 해석. II. 연조비와 롤러 간격 효과

임정호,김종성,허유,Lim, Jung Ho,Kim, Jong S.,Huh, You 한국섬유공학회 2018 한국섬유공학회지 Vol.55 No.6

The behavioral characteristics of sliver linear density under roller drafting operation were investigated in this study. A theoretical model describing the dynamic behavior of the staples flowing in a single direction was applied. While the model parameters remained constant, the process parameters including draw ratio and roller distance were varied. Simulations of the dynamic behavior of the drawn sliver linear density showed that it was dependent on the process conditions, and the effects varied depending on the staple length distribution. For uniform length staples, the linear density of the drawn sliver showed periodic changes at a steady state when the drawing roller distance was long. For the short drawing zone, the drawn sliver exhibited a constant steady state linear density. Increasing the draw ratio caused the linear density to change periodically which resulted in an increase in the CV% of the drawn sliver linear density. For length distributed staples, the linear density was sensitive to the draw ratio. At a low draw ratio, for example, DR=4, the drawing zone length did not affect the sliver linear density, and a constant linear density was observed. However, at high draw ratios, for example, DR=12, the drawing zone length affected the linear density behavior of the drawn sliver, showing periodic changes in the steady state. Thus, high draw ratios and long drawing zones caused a drastic increase in the CV% of the quasi-steady state linear density. In general, the two passes of sliver in a drawing operation with low draw ratio resulted in improved properties, that is, a more even linear density of the drawn sliver than that obtained using single drawing pass with a high level draw ratio, which drastically increased the linear density.

마찰 정방에서 굵기 동역학의 실험적 확인

임정호,김종성,허유,Lim, Jung-H.,Kim, Jong-S.,Huh, You 한국섬유공학회 2011 한국섬유공학회지 Vol.48 No.5

Dynamics of the bundle thickness in a friction yarn formation process was ascertained experimentally from the view point of the thickness of in-process bundle and output bundle. By changing the thickness of input fleece the thickness distribution of the in-process bundle on the friction drum and the irregularity of the output bundle in a steady state were measured. The experimental results were then compared with the simulation results derived on the basis of the dynamic model, while a step signal and a sinusoidal signal were applied. Experimental results turned out to be in a good agreement with the simulation result, which indicates that the theoretical model describes the dynamics of the frictional bundling process very good. The cross-sectional area of the in-process bundle increased linearly to the drum position in response to a step change in the input fleece thickness, which indicates that the friction bundling process can be though of as an integrating system with an interval. The periodic change in the input fleece thickness yielded also a good correspondence of the experimental results with those from the simulation. However, the thickness behavior of the output friction yarn for the periodic change in input fleece thickness demonstrated the dependency on the take-up speed of the output bundle.