This study aimed to develop automotive radiator support parts by applying the press forming/drawing mold technology of 440 MPa high-tensile steel sheets. It is intended to develop a shape structure that does not generate shape and positional accuracy, deformation, wrinkles, or cracks by maintaining strong contact surface pressure on both sides of the blank material and freezing elastic recovery stress. Therefore, quality improvement and high productivity were secured by applying the forming/drawing method of high-strength steel sheets to the radiator support parts.
In this study, the production process of eccentric head bolts that fasten flanges for water supply pipe connections, which can only be achieved through the cold forging process, was improved. For axial forging, forming analysis was performed for a 200-ton header machine to check the raw material specifications, forming load, and metal flow improvements suitable for forming. The analysis found that the forging of high-strength bolts of M14×65 ㎜ with eccentric heads was possible under the maximum load condition of 137.2 tons with low carbon boron steel of ø13.8×89.7 ㎜ and 105.2 g. By mounting the prototype mold on the header machine, it was possible to prevent metal flow breakage, as shown by the trial mass production test. It was possible to improve the strength of the eccentric head bolt and reduce the weight of the input material through the cutting process. Therefore, manufacturing costs could be reduced.
The munitions industry uses high-strength carbon fiber composites imported from other countries because of the lack of the information about the properties that should be satisfied by the domestic high-strength carbon fiber composites. Verification of the applicability of domestic high-strength carbon fiber composites to the munitions industry requires comparison of the fiber strength transition rate between the carbon fiber composites imported from other countries and domestically. A strand test was performed to evaluate in the unit of a fiber the mechanical properties of the imported high-strength carbon fiber composites and domestically. Additionally, a composite pressure vessel was prepared using the filament winding method to perform a hydrostatic pressure test and calculate the fiber strength in the unit of a structure. Comparison of the fiber strength results showed that the fiber strength transition rates of the domestic carbon fiber composites H2550 and H3055, were 86.35 and 74.19%, respectively. Domestic carbon fiber composite material H2550 is expected to be replaceable in the munitions industry.
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Evaluation of Structural Integrity of 6.8 L Composite Pressure Vessel Manufactured by Domestic Carbon Fiber Nam Hoon Kim, Eun Bi Lee, Hyo Hun An, Kwang Bok Shin Journal of the Korean Society for Precision Engineering.2021; 38(12): 953. CrossRef
The importance of environmentally-friendly energy production has been growing globally, and studies on energy storage technologies are underway, to supply produced energy to consumers. Flywheel Energy Storage System (FESS) is physical energy storage technology, that stores generated electric energy into kinetic energy in the rotor. To design the FESS with a high-strength steel rotor, that is inexpensive, recyclable and easy to manufacture, mechanical and electrical components such as a rotor, bearings, etc. are required. Among these, safety of rotor and bearings is critical, because the rotor with high rotating speed may cause axis failure or fracture of the rotating body. Proper size of a rotor for required energy storage and radial, axial forces generated by the spinning rotor was calculated, considering gyroscopic forces acting on the rotating body. Based on the calculation, adequately sustainable angular ball bearings were selected. As a result, by conducting structural, modal and critical speed analysis, safety verification is presented pursuant to the American Petroleum Institute (API) publication 684.
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An Analytical Study on the Design of Housing Components for 10 kWh Flywheel Energy Storage System Deuk Kyu Lee, Beom Soo Kang Journal of the Korean Society for Precision Engineering.2020; 37(1): 59. CrossRef
In this paper, the reliability-based parameter study is carried out for the stamping process of a front rail roof member with the ultra high strength steel, considering the scatters of the material properties and the process parameters. With the reliability-based design optimization (RBDO) scheme, the springback tendency is investigated from the perturbation of the process parameters such as the sheet thickness, ultimate tensile strength, yield strength, Coulomb friction coefficient, and applied padding force. The amount of the elastic recovery along the height direction is quantified to describe the springback tendency from the analysis. The analysis shows the springback-amount scattering is not ignorable when the yield stress scatters within the similar range of the ultimate tensile strength. The analysis results fully explain the importance of controlling the scatters as well as the average yield-strength amount in the mass production of the stamped products.
We have designed the structural shapes of a spiral blade and the frame to be used in an Archimedes wind-power system with the objective of increasing its mechanical strength. A conical roll-bending forming process was introduced to fabricate a metallic spiral blade, based on an incremental stepwise approach. From this process, the complicated spiral blade was constructed, and it could be applied to the wind-power mill. We proposed a few structural design concepts for improvement of the mechanical strength of the blade and frame. Fixing rods between the blades increased the natural frequency of the blades three-fold, compared to the original model with no rods. Also, the strength of the frame was increased by introducing edge-flanges with a height greater than 20 mm. This study will be helpful to industrial engineers interested in the structural design of a wind-power system in understanding the structural design process.
As emission regulation of vehicles is being reinforced globally, the current requirement of the automobile industry are innovative green technologies that reduce the weight of the vehicle, thereby improving fuel consumption and the amount of exhaust gas emission. The application of ultra-high strength steel (UHSS) for vehicles has specifically been studied for light weight of vehicles. UHSS withstands greater loads than a general steel sheet of the same thickness. The spring-back and formability of the UHSS are also worse than general steel sheet due to their high elasticity and high yield strength. Various methods applied for processing UHSS include roll-forming and hot-press forming. However, these processes have not only high installation cost but also low productivity. This study therefore developed the cold-press forming method to overcome these disadvantages. The objective of this study is to determine the optimum conditions of the cold press required to form the upper seat track using UHSS. Forming analysis predicted the spring-back at each stage of the press forming. The prediction of spring-back was compared with the manufactured upper seat track by try-out, thereby reducing trial and error in the pressing process.
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Press Forming/Drawing Molding in the Radiator Support Mold Process of 440 MPa High Strength Steel Sheets Dong-Hwan Park, Tae-Gil Lee, Hyuk-Hong Kwon Journal of the Korean Society for Precision Engineering.2024; 41(1): 71. CrossRef
Hot Stamping Parts Shear Mold Manufacturing via Metal Additive Manufacturing Myoung-Pyo Hong Applied Sciences.2022; 12(3): 1158. CrossRef
Impact Energy Absorption Capability Analysis of Locally Softened High-Strength Steel Bumper Beams Using Induction Heat Treatment Jongsu Kang, Myunghwan Song, Hyeongjun Jeon, Jae-Yong Lim Transaction of the Korean Society of Automotive Engineers.2019; 27(1): 39. CrossRef
Process Design of Automobile Seat Rail Lower Parts using Ultra-High Strength, DP980 Steel Dong-Hwan Park, Yun-Hak Tak, Hyuk-Hong Kwon Journal of the Korean Society of Manufacturing Process Engineers.2018; 17(2): 160. CrossRef
CP (Commercially Pure) titanium has been widely used in various industries such as in energy plants and bio-materials because of an excellent corrosion resistance and its non-toxicity to the human body. But there are limitations for usage as structural materials due to low strength. The tensile properties of CP titanium could be improved by microstructure refinement such as in a SPD (Severe Plastic Deformation) process. However, high strengthening of CP titanium wire is impossible by SPD processes like ECAP (Equal Channel Angular Pressing), HPT (High-Pressure Torsion), and the ARB (Accumulative Roll Bonding) process. The study purposes are to increase the strength of CP titanium wire by optimization of the cold drawing process and the harmonization with mechanical properties by heat treatments for the next forming process. The optimization process was investigated with regard to the design of drawing dies and the reduction ratio of cross sections. The elongations of high strength CP titanium were controlled by heat treatment.
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