• 소성∙가공
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• 제13권7호
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• pp.580-585
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• 2004

Almost all injection molds have multi-cavity runner system fur productivity and are designed with geometrically balanced runner system in order to minimize filling imbalance between cavity to cavity during processing. However, filling imbalances have been observed though geometrically balanced runner lay-out. Generally, these filling imbalances are due to thermal unbalance, viscosity, characteristic of polymers and so on. These kinds of filling imbalances have already been reported by Beaumont since 1997, but his research has mainly focused on filling imbalance at binary runner. In this study, we conducted an experimental study about the filling imbalances in unary branch runner as well as binary branch runner and inquired into the causes of filling imbalances. The results could be summarized as fellowing: Filling imbalances existed in multi-cavity mold with unary branch runner, it could be decreased by optimizing processing condition such as increasing injection rate, and it is almost proportion to each polymer's temperature sensibility.

• 한국음향학회지
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• 제30권4호
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• pp.223-230
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• 2011

한국종은 지면으로부터 일정한 간극을 두고 매달리며, 종 아래에 명동이라고 불리는 독특한 음향학적 요소를 갖고 있다. 간극과 명동의 적절한 설계는 공명효과에 의하여 종소리를 극적으로 증폭시킨다. 종체의 내부공동과 간극, 그리고 명동으로 구성된 음향공동계는 공명주파수와 모드를 갖는데, 공명주파수가 종체의 고유진동수에 일치하게 되면, 그 주파수성분이 크게 증폭된다. 이 연구는 성덕대왕신종을 대상으로 간극효과를 고려한 명동의 공명조건을 처음으로 제시한다. 공명조건을 구하기 위하여 신종의 실제 치수를 사용하여 SYSNOISE를 이용한 경계요소해석을 수행하였다. 또한, 계절에 따른 기온의 차이가 공명조건에 어떠한 영향을 미치는가를 규명하고, 가변형 명동의 개념을 제시함으로써, 현장에서 온도차를 보정하여 정확한 공명조건을 구현시킬 수 있는 방안을 제공한다.

• 한국분무공학회지
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• 제1권2호
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• pp.16-23
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• 1996

In case of a high-speed D.I. diesel engine. the injected fuel spray is unavoidable that the impinging on the wall of piston cavity and in this case the geometry of piston cavity has a great influence on the atomization structure and air flow fields. In the field of combustion and in many other spray applications, there are clear evidence of correlation between spray structure and emission of pollutants. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, a single spray was impinged on each cavity wall at indicated angle in a quiescent atmosphere at room temperature and pressure, as being the simplest case, and 3 types of piston cavity such as Dish, Toroidal and Re-entrant type was tested for analyzing the influence of cavity geometry. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation $\sigma(t)$ and variation factor (v.f.) was measured with the lapse of time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.601-602
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• 2012

• 대한기계학회논문집
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• 제7권3호
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• pp.294-300
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• 1983

The purpose of this study is to investigate the radiant emission characteristics of diffuse equi-lateral trapezoid groove cavity for the case of uniform surface temperature. The theoretically developed results for the apparent emissivity are presented and the values of apparent emissivity for the trapezoid groove cavity were compared with those of the V-groove cavity. In the experimental part of this study, the test models were manufactured from 100x 100x 15mm copper plates on which the equi-lateral trapezoid cavities were grooved. The inclined angles of the groove were 30,45 and 60 degrees and the ratio of groove depth to base surface width varied from 1 to 5 for each inclined angle. As a result of this work, it was found that the trapezoid groove cavity was more general form of V-groove and the apparent emissivity of trapezoid groove cavity was greater than that of V-groove cavity. The resulting equation for the apparent emissivity in the trapezoid groove cavity was valid for the angles greater than 40 degrees.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.211-219
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• 1996

In a small high-speed D. I. diesel engine, the injected fuel spray into the atmosphere of the high temperature is burnt by go through the process of break up, atomization, evaporation and process of ignition. These process are important to decide the emission control and the rate of fuel consumption and out put of power. Especially, in the case of injected fuel spray impinging on the wall of piston cavity, the geometry of piston cavity gives great influence the ignitability of injected fuel and the flame structure. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, the spray was impinged on the wall of 3 types of piston cavity such as Dish, Toroidal, Re-entrant type, in order to analyze the combustion process of impinging spray precisely and systematically. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation σ(t) and variation factor(vf) was measured with the lapse of time.

• 호남수학학술지
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• 제38권3호
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• pp.435-454
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• 2016

This paper investigates the effect of dual-phase-lags on a thermoviscoelastic orthotropic solid with a cylindrical cavity. The cylindrical cavity is subjected to a thermal shock varying heat and its material is taken to be of Kelvin-Voigt type. The phase-lag thermoelastic model, Lord and Shulman's model and the coupled thermoelasticity model are employed to study the thermomechanical coupling, thermal and mechanical relaxation (viscous) effects. Numerical solutions for temperature, displacement and thermal stresses are obtained by using the method of Laplace transforms. Numerical results are plotted to illustrate the effect phase-lags, viscoelasticity, and the variability thermal conductivity parameter on the studied fields. The variations of all field quantities in the context of dual-phase-lags and coupled thermoelasticity models follow similar trends while the Lord and Shulman's model may be different. The influence of viscosity parameter and variability of thermal conductivity is very pronounced on temperature and thermal stresses of the thermoviscoelastic solids.

• 천문학회지
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• 제20권1호
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• pp.27-47
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• 1987

In the present study a two-mode, separately concurring resonant cavity model is proposed for theoretical interpretation of the 3 minute umbral oscillation. The proposed model has been investigated by calculating the transmission coefficients of the waves propagating through the umbral photosphere (photospheric weak-field cavity) and chromosphere (chromospheric strong-field cavity) into the corona, for 3 different umbral model atmospheres by Staude (1982), Beebe et al. (1982) and Avrett (1981). In computing the transmission coefficients we made use of multi-layer approximation by representing the umbra] atmosphere by a number of separate layers with (1) temperature varying linearly with depth and (2) temperature constant within each layer. The medium is assumed to be compressible, non-viscous, perfectly conducting under gravity. The computed resonant periods, transmission spectra, phase spectra, and kinetic energy density of the waves associated with the oscillations are presented in comparison with the observations and their model dependent characteristics are discussed.

• 설비공학논문집
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• 제12권4호
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• pp.381-387
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• 2000

An experimental study on the stratified fluids was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in the square cavity. The same volume of water and silicon oil was filled in it. The experiments were performed with the variations of initial temperatures and cooling surface temperatures. And the effect of vertical or horizontal cooling surface positions in the square cavity was investigated. When the cooling surface temperatures were $-4^{\circ}C$ , the supercooling phenomena were observed for both cases of cooling surface positions in the full region regardless of the initial temperature of fluid. In the square cavity with horizontal cooling surfaces, the lower the initial temperatures were, the longer the supercooling durations were, and with vertical cooling surface the lower the initial temperatures were, the shorter the supercooling durations were.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.64-72
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• 2001

Weld line is one of serious troubles which are observed in a plastic part manufactured by a injection molding process. This is caused by many process factors, which are molding pressure, temperature, velocity, location of a injection gate, mold geometry and material properties. investigation on the effects of these process factors to the appearance of a weld line was carried out using a finite element method. Filling and packing analyses were carried out by modifying both the configuration of the injection gates and cavity thickness. Proper locations of the injection gates could be determined by considering molding pressure, temperature, velocity and frozen layer, and whereby the weld line was controled. In order to make a weak appearance of the weld line, flow velocity and flow front in a cavity were also investigated by modifying a cavity thickness. As a result, flow front was extended around the corner in the cavity by changing the flow velocity and hence the appearance of the weld line was much weakened.