• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.67-69
• /
• 2006

Since magnesium alloy has a limited formability at room temperature, forming should be carried out at the elevated temperature. If the initial grain size is small, superplasticity could be expected over $400^{\circ}C$. Using superplastic behavior, blow forming can be used to overcome the low formability of Mg alloys. In the present study, the optimization of blow forming of AZ31 alloy at the elevated temperature was investigated. Finite element simulation was carried out and verified with the blow forming experiments.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.2
• /
• pp.275-281
• /
• 1993

The new high temperature plasma source for spectrochemical analysis has been developed and characterized. In the development of new high temperature plasma sources for atomic emission spectrocopy, optimization of experimental variables is necessary to achieve the best analytical results. By means of a modified sequential simplex optimization method, six experimental variables were optimized. The line-to-background (L/B) ratio for Ca(II) at 393.37 nm was used as measure of the response function. The optimal experimental conditions were found to be at a current of 27.8 A, a plasma length of 28.8 mm, a sample uptake rate of 1.3 ml/min, a sample carrier gas flow rate of 0.7 ml/min, a plasma gas flow rate of 4.9 l/min, and an observation height of 6.4 mm above the top quartz tube.

• Journal of Biosystems Engineering
• /
• v.29 no.1
• /
• pp.53-58
• /
• 2004

The purpose of this study was to evaluate an optimization model to determine the operation conditions of the chestnuts flame peeling system. The results of this study were summarized as follows. The optimization model was developed and evaluated to represent the flame peeling characteristics of the domestic chestnuts. When the heating depth was selected for various utilization of the peeled chestnuts, the model could determine the optimal conditions of the hardness of the chestnut shells, the flame temperature, and the flame time to get the maximum peeling ratio of the chestnut flame peeling system. When the heating depth was limited to 2.2 mm, the optimization model determined the proper operation conditions and the maximum peeling ratio such as 1594 g/$\textrm{mm}^2$ of the hardness of the chestnut shells, 780$^{\circ}C$ of the flame temperature, 29 second of the flame time, and 98.1 % of the peeling ratio.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.10 s.241
• /
• pp.1139-1147
• /
• 2005

The shape optimal design of the plate-fin type heat sink with vortex generator is performed to minimize the pressure loss subjected to the desired maximum temperature numerically. Evaluation of the performance function, in general, is required much computational cost in fluid/thermal systems. Thus, global approximate optimization techniques have been introduced into the optimization of fluid/thermal systems. In this study, Kriging method Is used to obtain the optimal solutions associated with the computational fluid dynamics (CFD). The results show that when the temperature .rise is less than 40 K, the optimal design variables are $B_1=2.44\;mm,\;B_2=2.09\;mm$, and t=7.58 mm. Kriging method can dramatically reduce computational time by 1/6 times compared to SQP method so that the efficiency of Kriging method can be validated.

• Design & Manufacturing
• /
• v.16 no.1
• /
• pp.62-69
• /
• 2022

In the present study, the injection molding optimization of a large thick LH type elastic frames for the reduction of warpage was performed. Two kinds of fine and coarse finite element models were prepared to investigate the efficiency of analysis time and quality on simulation results. In order to derive injection molding conditions that can minimize distortion of parts, it was investigated that the effects of mold temperature, resin temperature, injection time, hold pressure switching time, holding pressure and the hold time on deformation characteristics using the design of experiments. The main influential factors on the warpage were found from the optimization simulation and the geometry data of the warpage result was converted into an initial model for injection simulation. It was shown that a coarse model with good mesh quality could be adapted for mold design since the total analysis time using the proposed model was reduced to 1/10. The suggested inversed warpage model produced the best minimized result of warpage.

• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1835-1844
• /
• 2022

Single-orifice plate is wildly utilized in the piping system of the nuclear power plant to throttle and depressurize the fluid of the pipeline. The cavitation induced by the single-orifice plate may cause some serious vibration of the pipeline. This study aims to find the optimal designs of the single-orifice plates that may have weak cavitation possibilities. For this purpose, a new single-orifice plate with a convergent-flat-divergent hole was modeled, a multi-objective optimization method was proposed to optimize the shape of a single-orifice plate, while computational fluid dynamics method was adopted to obtain the fluid physical quantities. The reciprocal cavitation number and the developmental integral were treated as cavitation indexes (e.g., objectives for the optimization algorithm). Two non-dominant designs ultimately achieved illustrated obvious reduction in the cavitation indexes at a Reynolds number Re = 1 ×10⁵ defined based on fluid velocity. Besides, the sensitivity analysis and temperature effects were also performed. The results indicated that the convergent angle of the single-orifice plate dominants the cavitation behavior globally. The optimal designs of single-orifice plates result in lower downstream jet areas and lower upstream pressure. For a constant Reynolds number, the higher temperature of liquid water, the easier it is to undergo cavitation. Whereas there is a diametric phenomenon for a constant fluid velocity. Moreover, the regression models were carried out to establish the mathematical relation between temperature and cavitation indexes.

• Journal of Hydrogen and New Energy
• /
• v.24 no.1
• /
• pp.50-60
• /
• 2013

High temperature proton exchange membrane fuel cells (PEMFCs) using phosphoric acid (PA) doped polybenzimidazole (PBI) membranes have been concentrated as one of solutions to the limits with traditional low temperature PEMFCs. However, the amount of reported experimental data is not enough to catch the operational characteristics correlated with cell performance and durability. In this study, design of experiments (DOE) based operational optimization method for high temperature PEMFCs has been proposed. Response surface method (RSM) is very useful to effectively analyze target system's characteristics and to optimize operating conditions for a short time. Thus RSM using central composite design (CCD) as one of methodologies for design of experiments (DOE) was adopted. For this work, the statistic models which predict the performance and degradation rate with respect to the operating conditions have been developed. The developed performance and degradation models exhibit a good agreement with experimental data. Compared to the existing arbitrary operation, the expected cell lifetime and average cell performance during whole operation could be improved by optimizing operating conditions. Furthermore, the proposed optimization method could find different new optimal solutions for operating conditions if the target lifetime of the fuel cell system is changed. It is expected that the proposed method is very useful to find optimal operating conditions and enhance performance and durability for many other types of fuel cell systems.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.587-590
• /
• 2000

The new core making method economized on core sand requested. The new method is heating core box until it reaches reasonable temperature and then spraying core sand with core binder into core box. Inner temperature distribution have to uniform in order to form core of uniform thickness. Therefore, in this study we treat of inner temperature distribution of core box in priority. First, determine proper torch number. Next, optimize the torch position to minimize the average of absolute deviation(AVEDEV) of inner temperature. The results are as followed : 1. The torch number that makes inner temperature distribution about $300^\circ{C}$ uniformly is 25. 2. When $S_H$ and $S_V$ is 0.7, the torch position is optimized and AVEDEV is 5.85.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.4
• /
• pp.51-56
• /
• 2008

Thermoforming is one of the most versatile and economical processes available for shaping polymer products, but obtaining a uniform thickness of the final product using this method is difficult. Heater power adjustment is very important because the thickness distribution depends strongly on the distribution of the sheet temperature. In this paper, the steady-state optimum distribution of heater power is first ascertained by a numerical optimization to obtain a uniform sheet temperature. The time-dependent optimal heater input is then determined to decrease the temperature difference through the direction of the thickness using the response surface method and the D-optimal method. The optimal results show that the time-dependent optimum heater power distribution gives an acceptable uniform sheet temperature in the forming temperature range by the end of the heating process.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2122-2125
• /
• 2008

Because the reheating furnace consumes a large amount of energy to heat up the slabs, it is very important to find an optimal temperature patterns in the furnace for energy saving as well as uniform target temperature at the exit of the furnace. In this study, the temperature profiles in the slab are determined by solving the transient one-dimensional heat conduction equation in conjunction with boundary conditions with total heat exchange factors. The optimal temperature patterns are obtained to minimize the fuel consumption with satisfying the predetermined constraint conditions. The design optimization is performed by using a genetic algorithm and the optimal results are validated with results obtained from the PIDO tool, called as P.I.A.n.O.