• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.06a
• /
• pp.87-87
• /
• 2006

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.6
• /
• pp.146-152
• /
• 2017

In order to make 3-D glass from 2-D glass for mobile device windows, a mold is used for heat forming. In this process, the temperature of the glass is very important. However, measuring the temperature of the glass inside the mold is very difficult owing to the mold structure and the high temperature. The purpose of this study is to measure the temperature inside the mold by using Process Temperature Control Rings (PTCR) and to compensate for temperature differences in the heat forming machine and inside the mold. The measuring method uses the ceramic material's shrinkage characteristics, which makes it possible to measure the temperature inside the mold at various locations.

• Journal of the Korean Society of Industry Convergence
• /
• v.22 no.4
• /
• pp.405-413
• /
• 2019

In this study, a progressive process was performed to fabricate the inner fin of a high-efficiency heat exchanger. A forming simulation was also carried out on the concavo-convex of the inner fin, forming a simulation based on elastic-plastic finite element method. The forming analysis where the speed of the press descended and ascended was set to five seconds showed that the effective stress was at a maximum of about 69 MPa in the curved portion where the bending occurred. Therefore, the die was designed based on the simulation results, and the inner fin die was installed on the 400-ton capacity press. After that, the inner fin fabrication experiment was conducted under the same condition as the simulation. Crack was not found from the curved portion of the concavo-convex of the inner fin. The profile of the concavo-convex of the prepared inner fin measured 6.7~6.8 mm in depth, 2.65~2.7 mm in width, and 0.3 mm in thickness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.269-273
• /
• 2003

There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.

• Transactions of Materials Processing
• /
• v.13 no.1
• /
• pp.84-89
• /
• 2004

There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.

• Transactions of Materials Processing
• /
• v.21 no.7
• /
• pp.447-452
• /
• 2012

This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.12
• /
• pp.1201-1208
• /
• 2009

Dome stretching tests and tension tests were performed to evaluate the formability of a copper alloy used for manufacturing the regenerative cooling chamber. The test specimens were prepared to investigate the effect of heat treatment and direction of specimens on the formability. The test results show that forming limit values are increased by the heat treatment of the material but the variation of the forming limit values by manufacturing direction is negligible compared to the heat treatment effect, and forming limit values are also different according to the test methods. These results indicate that the high temperature heat treatment of the material before bulging is a very important process to deform the inner cylindrical structure of the regenerative cooling chamber into a nozzle shape by the bulging process without necking or fracture and the test methods also have a great effect on a evaluation of the formability. The forming limit diagram obtained in this study would be utilized to the design of regenerative cooling chamber nozzles.

• Transactions of Materials Processing
• /
• v.33 no.3
• /
• pp.161-168
• /
• 2024

Aluminum alloy sheets, compared to conventional steel sheets, face challenges in press forming due to their lower elongation. To enhance their formability, extensive research has focused on forming technologies at elevated temperatures, specifically warm forming at around 300℃ and hot forming at approximately 500℃. This study proposes that the formability of aluminum alloy sheets can be significantly enhanced using a multi-stage hot forming technique. The research also investigates whether the strength of the A6061 aluminum alloy, known for its precipitation hardening, can be maintained when formed below the precipitate solid solution temperature. In the experiments, the A6061-T6 sheet underwent heating and rapid cooling between 250 and 500℃. The mechanical properties were evaluated at each stage of the process. The findings revealed that when the initial heat treatment was below 350℃, the strength of the material remained unchanged. However, at temperatures above 400℃, there was a noticeable decrease in strength coupled with an increase in elongation. Conversely, when the secondary heat treatment was conducted at temperatures of 350℃ or lower, the strength remained comparable to that of the initial heat treated material. However, at higher temperatures, a reduction in strength and an increase in elongation were observed.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.3
• /
• pp.199-205
• /
• 2016

A thin sheet of metal with corrugated structures has been utilized in various devices: heat exchangers, separators in fuel cells, and many others. However, it is not easy to fabricate thin corrugated structures using a single-step stamping process due to their geometrical complexity. To solve this problem, firstly, a plate type heat exchanger was redesigned to attain the optimal value of aspect ratio and the optimal shape of corrugated structures for the actual loading conditions. A forming analysis of the corrugated plate was then carried out to determine the process parameters. From this work, the optimal value of aspect ratio was found to be 4.6. In addition, the process parameters of heat exchanger forming were optimized using the optimal value of aspect ratio, and the analytical results were evaluated through experiments. The results obtained indicated good agreements between them.

• Transactions of Materials Processing
• /
• v.12 no.4
• /
• pp.364-369
• /
• 2003

Non-heat treated steels are attractive in the steel-wire industry since the spheroidization and quenching-tempering treatment are not involved during the processing. However, non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, three different steels such as dual phase steel, low-Si steel, and ultra low carbon bainitic steel were used to study their mechanical properties and the cold formability. The cold formability of three steels was investigated by estimating the deformation resistance and the forming limit. The deformation resistance was estimated by calculating the deformation energy, and the forming limit was evaluated by measuring the critical strain revealing crack initiation at the notch tip of the specimens. The results showed that deformation resistance was the lowest in the low-Si steel, and the forming limit strains of ultra low carbon bainitic steel and low-Si steel were higher than that of commercial SWRCH45F steel.