• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.100-104
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• 2005

The injection molding is very effective process for various plastic products due to its high productivity. It is also good fur precise products like optical parts. Various thermoplastic materials are also available with this injection molding process. In recent, however, as the overall size of the product increases and micro or nano scale of patterns are applied to the products, we now have some problems such as low fidelity of the replication of the pattern, high molding pressure, or warpage from the in-mold stress. Injection/compression molding is studied to overcome those problems in molding large thin plate with micro pattern array on its surface. An injection compression mold is designed to 3 pieces mold for side gate. We install 4 pressure transducers and 9 thermocouples to measure the melt pressure and surface temperature in the cavity during the process. As a result, the maximum molding pressure for injection compression molding is reduced to 1/3 compared to injection molding and the uniformity of the pressure in the cavity is enhanced by about 15%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.321-325
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• 2008

In this paper, heat transfer changes due to the shock/boundary layer interaction were investigated on surfaces where secondary jet are injected. With an infra-red thermography, surface temperature was measured and the measured data was used to obtain the convective heat transfer. Heat transfer is enhanced with increment of momentum ratio. And normal injection case has a higher heat transfer value than that of 15 degrees inclined injection case. Secondary injection momentum ratio and injection angle affect the surface heat transfer distribution.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.742-754
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• 2020

Zircaloy cladding oxidation is an important phenomenon for both design basis accident and severe accidents, because it results in cladding embrittlement and rapid fuel temperature escalation. For this reason during the last decade, many experts have been conducting experiments to identify the oxidation phenomena that occur under design basis accidents and to develop mathematical analysis models. However, since the study of design extension conditions (DEC) is relatively insufficient, it is essential to develop and validate a physical and mathematical model simulating the oxidation of the cladding material at high temperatures. In this study, the QUENCH-05 and -06 experiments were utilized to develop the best-fitted oxidation model and to validate the SPACE code modified with it under the design extension condition. It is found out that the cladding temperature and oxidation thickness predicted by the Cathcart-Pawel oxidation model at low temperature (T < 1853 K) and Urbanic-Heidrick at high temperature (T > 1853 K) were in excellent agreement with the data of the QUENCH experiments. For 'LOCA without SI' (Safety Injection) accidents, which should be considered in design extension conditions, it has been performed the evaluation of the operator action time to prevent core melting for the APR1400 plant using the modified SPACE. For the 'LBLOCA without SI' and 'SBLOCA without SI' accidents, it has been performed that sensitivity analysis for the operator action time in terms of the number of SIT (Safety Injection Tank), the recovery number of the SIP (Safety Injection Pump), and the break sizes for the SBLOCA. Also, with the extended acceptance criteria, it has been evaluated the available operator action time margin and the power margin. It is confirmed that the power can be enabled to uprate about 12% through best-estimate calculations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.390-401
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• 2000

In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake $O_2$ concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake $O_2$ concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.35-41
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• 2013

In injection molding, the mold temperature is one of most important process parameters that affect the flow characteristics and part deformation. The mold temperature usually varies periodically owing to the effects of the hot polymer melt and the cold coolant as the molding cycle repeats. In this study, a pulsed mold temperature control was proposed to improve the part quality as well as the productivity by alternatively circulating hot water and cold water before and after the molding stage, respectively. Transient thermal-fluid coupled analyses were performed to investigate the heat transfer characteristics of the proposed pulsed mold heating and cooling system. The simulation results were then compared with those of the conventional mold cooling system in terms of the heating and cooling efficiencies of the proposed pulsed mold temperature control system.

• Composites Research
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• v.29 no.1
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• pp.7-15
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• 2016

The quality of polymeric automotive parts depends highly on an injection molding process, which causes various defects, such as warpage, sink marks, weld lines, shrinkage, residual stress, etc. This study is to determine the optimum processing parameters, such as packing pressure, mold temperature, melting temperature, and packing time for the manufacture of polycarbonate buttons in cars on the basis of FEM, the Taguchi method, and analysis of variance (ANOVA). As a result, the optimum processing parameters of buttons made of polycarbonate material were obtained as follows: 140 MPa of packing pressure, $105^{\circ}C$ of mold temperature, $292.5^{\circ}C$ of melting temperature and 1 second of packing time. A gain of S/N (signal to noise) ratio, 10.2, was obtained with the optimum values. Moreover, the melting temperature was found to be the most significant factor followed by the mold temperature.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.55-60
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• 2020

The injection molding technique is a processing method widely used for the production of plastic parts. In this study, the gate position, gate size, packing time, and melt temperature were optimized to minimize both the stress and deformation that occur during the injection molding process of medical suction device components. We used a central composite design and Latin hypercube sampling to acquire the data and adopted the response surface method as an approximation method. The efficiency of the optimization of the injection molding problem was determined by comparing the results of a genetic algorithm, sequential quadratic programming, and a non-dominant classification genetic algorithm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.60-63
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• 2003

Semi-solid forming is the process of stirring alloy during solidification, making the mixture of liquid and solid, solidifying it, reheating it to the solid-liquid coexistent temperature, and then injecting this semi solid slurry into dies. In the semi-solid die casting process, it is very important to find out the correlation of injection condition, microstructure and mechanical properties. Especially, an improper injection condition is the main cause of liquid segregation and non-homogeneous mechanical properties due to the difference of solid fraction according to the position of the products. To ensure the database requisite to the semi-solid die casting product, it is essential to acquire the mechanical properties considering liquid segregation to the injection condition. In this study, the effect of injection condition on liquid segregation, formability, microstructure and mechanical properties in a thin product was investigated.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.11a
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• pp.160-165
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• 2005

Bioventing efficiency was compared in a continuous and an intermittent(6hr injection and 6hr rest) air injection mode. Two lab-scale columns which packed with 5kg of soil artificially contaminated by diesel oil were operated. The columns were maintained at the $25^{\circ}C{\pm}2.5$ in order to minimize the effect of exterior temperature variation. The flow rate of air injection mode were maintained constantly at the flow rate of 10ml/min. The moisture of the columns was stably maintained at $60{\sim}80%$ of field capacity. The nutrient compounds were added to make C : N : P ratio as 100 : 10 : 1. The continuous and intermittent injection modes showed 67.56% and 69.63%reduction of initial TPH concentration during 90 days, respectively. The loss of diesel oil by volatilization in the continuous and intermittent injection modes were about 5% and 1%, respectively.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1640-1647
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• 2004

This study was to investigate the effects of water induction through the air intake system on the characteristics of combustion and exhaust emissions in an IDI diesel engine. The fuel injection timing was also controlled to investigate a method for the simultaneous reduction of smoke and NOx when water was injected into the combustion chamber. The formation of NOx was significantly suppressed by decreasing the gas peak temperature during the initial combustion process because the water played a role as a heat sink during evaporating in the combustion chamber, while the smoke was slightly increased with increased water amount. Also, NOx emission was significantly decreased with increase in water amount. A simultaneous reduction in smoke and NOx emissions was obtained when water was injected into the combustion chamber by retarding more 2$^{\circ}C$A of the fuel injection timing than without water injection.