• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.177-184
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• 2022

The present study aims to investigate the influence of Zn addition on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-9%Al and Mg-9%Al-1%Zn alloys. To obtain large DPs volume fractions in the microstructure, the alloy specimens were solution-treated at 688 K for 24 h followed by water quenching, and then aged at 413 K for 48 h. The aged Mg-9%Al-1%Zn alloy had higher DPs content than the Mg-9%Al alloy, indicating that the Zn addition plays a beneficial role in enhancing age-hardening response. The DPs in the Zn-containing alloy possessed the higher hardness than those of the Zn-free alloy. Microstructural examination revealed that the increased hardness of the DPs resulting from the Zn addition is closely associated with the lower α-(Mg)/β(Mg₁₇Al₁₂) interlamellar spacing and the higher volume fraction of β phase layer of the DPs.

• Design & Manufacturing
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• v.16 no.3
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• pp.50-57
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• 2022

The qualities of the products produced by injection molding are strongly influenced by the process variables of the injection molding machine set by the engineer. It is very difficult to predict the qualities of the injection molded product considering the stochastic nature of the manufacturing process, since the processing conditions have a complex impact on the quality of the injection molded product. It is recognized that the artificial neural network(ANN) is capable of mapping the intricate relationship between the input and output variables very accurately, therefore, many studies are being conducted to predict the relationship between the results of the product and the process variables using ANN. However in the condition of a small number of data sets, the predicting performance and robustness of the ANN model could be reduced due to too many input variables. In the present study, the ANN model that predicts the length of the injection molded product for multiple combinations of process variables was developed. And the accuracy of each ANN model was compared for 8 process variables and 4 important process inputs that were determined by the feature selection. Based on the comparison, it was verified that the performance of the ANN model increased when only 4 important variables were applied.

• Journal of Sensor Science and Technology
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• v.30 no.4
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• pp.236-242
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• 2021

In this paper, we report the fabrication of the tip-on-gate of a field-effect-transistor (ToGoFET) probe using a standard complementary metal-oxide-semiconductor (CMOS) process and the performance evaluation of the fabricated probe. After the CMOS process, I-V characteristic measurement was performed on the reference MOSFET. We confirmed that the ToGoFET probe could be operated at a gate voltage of 0 V due to channel ion implantation. The transconductance at the operating point (Vg = 0 V, Vd = 2 V) was 360 ㎂/V. After the fabrication process was completed, calibration was performed using a pure metal sample. For sensitivity calibration, the relationship between the input voltage of the sample and the output current of the probe was determined and the result was consistent with the measurement result of the reference MOSFET. An oxide sample measurement was performed as an example of an application of the new ToGoFET probe. According to the measurement, the ToGoFET probe could spatially resolve a hundred nanometers with a height of a few nanometers in both the topographic image and the ToGoFET image.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.6
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• pp.295-302
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• 2022

The present study aims to investigate the effect of Al content on microstructure and hardness of discontinuous precipitates (DPs) formed by continuous cooling (CC) in Mg-8%Al and Mg-9.5%Al alloys. The DPs had a wide range of (α+β) interlamellar spacings, which may well be attributed to the different transformation temperatures during CC. The higher Al content gave rise to the higher level of interlamellar spacings of the DPs, and thicker and larger amount of β phase layer in the DPs. It is noticeable that the Mg-9.5%Al alloy exhibited higher hardness of the DPs than the Mg-8%Al alloy, but the ratio of increase in hardness of the DPs compared to that of the as-cast state was similar regardless of the Al content. The reason was discussed based on the differences in microstructures of the DPs for the Mg-8%Al and Mg-9.5%Al alloys.

• Food Science and Industry
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• v.55 no.3
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• pp.326-336
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• 2022

Since the food industry, including the agricultural production, is the largest industrial sector in Myanmar, the Myanmar government and industry have a strong willingness to develop the food manufacturing industry despite the limitations of investment, production and technological level. Particularly, the Myanmar government recognizes that the agricultural product-based food industry is an essential element for national economic growth, and is promoting various policy efforts for the industrial development. Therefore, the overall status of the food industry in Myanmar has been reviewed in this study. Also, the TASK (Technology Advice and Solutions from Korea) project in the food processing sector as an ODA (official development assistance) program has been specifically addressed in order to strengthen bilateral cooperation between Korea and Myanmar in the near future.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1315-1324
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• 2022

The need for remanufacturing ships and various mechanical components continues to increase along with environmental problems. Research on remanufacturing is being carried out in various fields, but research on cleaning is quite insufficient. In particular, there is no research on the cleaning-ability of diverse mechanical components. In order to increase the life cycle of mechanical components, remanufacturing must be considered from the step of design. Particularly, it is also very important to evaluate the degree of easiness in cleaning to remove various pollutants generated by long-term use quickly as well as easily. In this study, the degree of easiness in cleaning is defined as cleaning-ability. In fact, remanufacturing components can be easily done only when cleaning-ability is set high from the step of design. The purpose of this study is to evaluate the cleaning-ability of ships and various mechanical components. The details of easiness in cleaning are cleaning and drying identification, accessibility to cleaning tools, convenience in cleaning, and convenience in drying. This study presents a quantitative procedure to evaluate cleaning-ability, derived various factors influencing each of the details of easiness and their ranges, and gave scores to the factors according to their ranges. The weight was also calculated for the details of easiness in cleaning and the factors. Lastly, this researcher suggests a scoring procedure to evaluate cleaning-ability quantitatively and the total weight of cleaning-ability.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.287-293
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• 2021

This study was intended to investigate the influence of Al content on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-8.7%Al and Mg-10%Al alloys. In order to obtain large amount of DPs in the microstructure, the alloy specimens were solution-treated at 688K for 24 h followed by water quenching, and then aged at 418K for 48h. The Mg-Al alloy with higher Al content was characterized by higher volume fraction of DPs at the same aging condition, lower interlamellar spacing of the DPs, thinner β phase layer and higher β phase content in the DPs. This is closely related to the higher velocity of discontinuous precipitation process resulting from the higher Al supersaturation in the α-(Mg) matrix. The Mg-10%Al alloy showed higher hardness of the DPs and greater difference in hardness between as-cast state and DPs than the Mg-8.7%Al alloy.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.302-308
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• 2021

The aim of this study was to investigate the dependence of the hardness and thermal conductivity on the volume fraction of discontinuous precipitates (DPs) in the Mg-9.3%Al alloy with (α-(Mg)+DPs) dual phase structure. In order to obtain various DPs volume fractions, the alloy was solution-treated at 688 K for 24 h and then aged at 418 K for up to 144 h. The volume fraction of DPs increased from 0% to 63% with an increase in the aging time up to 72 h, over which, continuous precipitation was observed within the α-(Mg) grains. It is noticeable that the hardness and thermal conductivity of the alloy increased linearly with the volume fraction of DPs. The improved hardness and thermal conductivity with respect to volume fraction of DPs are closely associated with the higher hardness of the DPs with fine (α+β) lamellar structure and the lower Al concentration in the α phase layer of the DPs, respectively.

• Journal of Korea Foundry Society
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• v.42 no.6
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• pp.347-357
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• 2022

In this study, 3D visualization of the packing behavior of the charge material in a foundry was attempted. It was simulated based on the practical conditions of the charge material and the melting furnace. It was confirmed whether the 3D visual simulation realistically implements the packing behavior of the manufacturing site. The realistic packing state by the 3D visual simulation was compared with the ideal packing state. It was analyzed in which case the difference between the two packing states occurred. The advantages of applying the 3D visual simulation to the manufacturing process were investigated, and various application plans in the casting industry were proposed.

• Design & Manufacturing
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• v.16 no.4
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• pp.46-51
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• 2022

The piercing process of creating holes in sheet metals for mechanical fastening generates high shear force. Real-time monitoring technology could predict tool damage and product defects due to this severe condition, but there are few applications for piercing high-strength aluminum. In this study, we analyzed the load signal to predict the punch's wear level during the process with a piezoelectric sensor installed piercing tool. Experiments were conducted on Al6061 T6 with a thickness of 3.0 mm using piercing punches whose edge angle was controlled by reflecting the wear level. The piercing load increases proportionally with the level of tool wear. For example, the maximum piercing load of the wear-shaped punch with the tip angle controlled at 6 degrees increased by 14% compared to the normal-shaped punch under the typical clearance of 6.7% of the aluminum piercing tool. In addition, the tool wear level increased compression during the down-stroke, which is caused by lateral force due to the decrease in the diameter of pierced holes. Our study showed the predictability of the wear level of punches through the recognition of changes in characteristic elements of the load signal during the piercing process.