• 한국의상디자인학회지
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• 제16권1호
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• pp.117-123
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• 2014

This paper examined dyeing using sulfur dye with nylon and the characteristics of high gauge knitting for generating high functionality including light weight, wind resistance and elasticity using fine nylon threads. Yarn tension, stitch field and knitting speed of high and fine gauge knitting were measured. The influence of reducing agents on sulfur dye, optimum dyeing conditions and fastness features in nylon dyeing were analyzed. The analysis results are presented below. When nylon (Hyoseong, 40d/34f) and spandex (Hyoseong, 20d) for use as hosiery yarn were used to knit high gauge and flat weave, 44 gauge, the effective knitting conditions were a stitch field over 8.2cm in 1 course length, yarn tension of less than 5g and knitting speed below 18rpm. Nylon dyeing using sulfur dye showed effective results when a rongalite reducing agent was used at more than 10% o.w.f. and dyeing was maintained at $98^{\circ}C$ for 30 minutes. For dyeing nylon and spandex composite using sulfur dye, color fastness in washing, water, daylight and friction were higher than Class 4 or 5, which indicated a superior property. The analysis results verified that the existing problems in nylon dyeing could be solved by using sulfur dyes that don't use heavy metals due to superior fastness and therefore quality, high gauge nylon knit products could be produced.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.337-344
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• 2000

A modified k-$\epsilon$ model is proposed for calculation of transitional boundary layer flows. In order to develop the eddy viscosity model for the problem, the flow is divided into three regions; namely, pre-transition region, transition region and fully turbulent region. The pre-transition eddy-viscosity is formulated by extending the mixing Length concept. In the transition region, the eddy-viscosity model employs two length scales, i.e., pre-transition length scale and turbulent length scale pertaining to the regions upstream and the downstream, respectively, and a university model of stream-wise intermittency variation is used as a function bridging the pre-transition region and the fully turbulent region. The proposed model is applied to calculate three benchmark cases of the transitional boundary layer flows with different free-stream turbulent intensity ( $1\%{\~}6\%$ ) under zero-pressure gradient. It was found that the profiles of mom velocity and turbulent intensity, local maximum of velocity fluctuations, their locations as well as the stream-wise variation of integral properties such as skin friction, shape factor and maximum velocity fluctuations are very satisfactorily Predicted throughout the flow regions.

• 한국의사학회지
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• 제26권2호
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• pp.135-148
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• 2013

This study analyzed surface-chemical transitions in manufacturing process of traditional acupuncture as proposed method by Dongeuibogam. The manufacturing process of traditional acupuncture from a used iron for a long time was divided by primary medicinal herbs treatment, secondary medicinal herbs treatment and tertiary treatment using by dog meat. The traditional acupuncture research process was measured according to the characteristics and changes of the specimens at each processing step of the manufacturing process. The following devices were used to Surface analysis. Scanning electron microscopy (SEM), Energy Dispersive Spectrometer (EDS), X-ray diffraction analyzer (XRD). As a result, medicinal herbs removed impurities on the surface and raised the antibacterial effect in the manufacturing process of traditional acupuncture. Furthermore, the ingredients of medicinal herbs were coated on the surface of the iron. Dog meat influenced to prevent surface corrosion, reduce friction when the acupuncture was inserted. Although the process empirically obtained, a glimpse of the wisdom of our ancestors was revealed. These ancestral wisdom can be expected to apply today, when used in manufacturing process of a modern stainless steel acupuncture to compensate for the defective part.

• 대한기계학회논문집A
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• 제21권5호
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• pp.746-755
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• 1997

This paper addresses the systematic procedure using sequential approach for the analysis of the coupled thermo-mechanical behavior of a steady rolling tire. Not only the knowledge of mechanical stresses but also of the temperature loading in a rolling tire are very important because material damage and material properties are significantly affected by the temperature. In general, the thermo-mechanical behavior of a pneumatic tire is highly complex transient phenomenon that requires the solution of a dynamic nonlinear coupled themoviscoelasticity problem with heat source resulting from internal dissipation and friction. In this paper, a sequential approach, with effective calculation schemes, to modeling this system is presented in order to predict the temperature distribution with reasonable sccuracies in a steady state rolling tire. This approach has the three major analysis modules-deformation, dissipation, and thermal modules. In the dissipation module, an analytic method for the calculation of the heat source in a rolling tire is established using viscoelastic theory. For the verification of the calculated temperature profiles and rolling resistance at different velocities, they were compared with the measured ones.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.603-608
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• 2001

A certain amount of MBS rubber was added to improve toughness of PVC which has a strong tendency of being brittle, producing a mixture, PVC/MBS, from which test specimens were prepared. PVC has strong chemical resistance, oil resistance, frame retardancy and high mechanical strength. Also, it is relatively inexpensive to produce, but shows weakness to impact and difficult for processing. MBS, a typical toughening agent for PVC is generally known, when added in a small amount, to improve impact resistance and to minimize difficulties during the processing of the PVC without adversely affecting the positive aspects of the PVC. In this investigation, attempts were made to observe and determine the variations in elastic and damping constants of the PVC depending on the amounts of MBS added to the mixture, PVC/MBS, and also on the thicknesses of the specimens. An acoustic resonance technique was used for the tests in this investigation. It serves as a method to characterize properties of materials set in vibrational motions, which is initiated by low level stresses generated by externally supplied acoustic energy. Substantial variations were observed in the test results with the addition of the MBS to the PVC. Generally, the magnitudes of elastic constants decrease while the damping capacity improves when MBS rubber was added.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3095-3104
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• 1996

The tribological characteristics of TIN and DLC coated VCR drums were compared to conventional aluminum drums using a custom built accelerated testing set-up under varying temperature and humidity. It is found that the coated drums exhibit superior frictional properties at elevated temperature and high humidity compared to bare aluminum drum. Futhermore, the coated drums maintained their initial surface conditions over a wider range of temperature and humidity variation. As for the damage incurred to the tape, DLC coated drum was the most favorable of the three types of drums.

• 한국기계가공학회지
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• 제14권5호
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• pp.22-27
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• 2015

Processing of low toughness graphite material requires high-speed machine tools and DLC coating. In this study, results of investigation of the tool wear and machining properties of the DLC coating according to the thickness, and the machining time of the tool used for the machining of graphite electrodes, were as follows. 1. DLC coating thickness shows a larger wear amount of the tool center in accordance with thickness; the wear amount of the tool increases in proportion to the machining time. 2. The difference between the amount of wear depending on the processing time shows edge portions larger than the tool wear amount in the center. This amount of wear of the tool edge is formed since the rotating torque is in contact with the graphite material surface significantly more than the central portion. 3. The thicker the DLC coating, the more the coating tool eliminated of the coating area by the interface between the cemented carbide tool being coated with an increased friction of the graphite material and the DLC coating area.

• Geomechanics and Engineering
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• 제12권6호
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• pp.983-1001
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• 2017

The extent by which economy and safety concerns can be addressed in earth retaining structure design depends on the accuracy of the assumed failure surface. Accordingly, this study attempts to investigate and quantify mechanical backfill properties that control failure surface geometry of cohesionless backfills at the active state for translational mode of wall movements. For this purpose, a small scale 1 g physical model study was conducted. The experimental setup simulated the conditions of a backfill behind a laterally translating vertical retaining wall in plane strain conditions. To monitor the influence of dilative behavior on failure surface geometry, model tests were conducted on backfills with different densities corresponding to different dilation angles. Failure surface geometries were identified using particle image velocimetry (PIV) method. Friction and dilation angles of the backfill are calculated as functions of failure stress state and relative density of the backfill using a well-known empirical equation, making it possible to quantify the influence of dilation angle on failure surface geometry. As a result, an empirical equation is proposed to predict active failure surface geometry for cohesionless backfills based on peak dilatancy angle. It is shown that the failure surface geometries calculated using the proposed equation are in good agreement with the identified failure surfaces.

• 열처리공학회지
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• 제29권6호
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• pp.284-291
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• 2016

High temperature alloy steel such as Ni-Cr-Mo-V material has excellent properties of high strength and high heating resistance. It has been used for several military weapon components such as gun barrel of a warship, turbine rotor and turbine disk for nuclear power plant. Being curious about this material required excellent wear resistance and durability in extreme environmental conditions. A dry wear test at the ambient air and Ar gas conditions in the room temperature were performed in this study. What's more a lubricant wear test at different temperature was conducted. In addition that DLC was coated on Ni-Cr-Mo-V alloy steel substrate with a thickness of $3{\mu}m$, a property of it was compare with lubricant conditions. All the coefficient of friction and wear volume, comparing with DLC coated specimens. The test parameters were selected as follows: 10 N for normal load; 80 rpm for sliding wear speed; and 300 m for the sliding wear distance.

• 대한기계학회논문집B
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• 제27권7호
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• pp.853-858
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• 2003

The suitable estimation of the filter width in the dynamic eddy viscosity model were investigated in high Reynolds number channel flow. In this study, the improvement on matters by optimizing the test filter shape was attempted through the numerical experiment. The way that select optimum test filter width is recommended. Some test filters, one is based on a discrete representation of the top-hat filter and another are based on a high-order filtering operation, are evaluated in simulations of the turbulent channel flow at Reynolds number 1020, based on friction velocity and channel half width. It appears that the estimation of test filter width practically can decrease the dissipative nature of dynamic eddy viscosity model with explicit test filter. It shows that the value of the filter width ratio used in the dynamic procedure must match the properties of the test filter actually used in the calculation.