A fixing frame applied with Foam Cored CFRP Sandwich Composite (FCCSC) that replaces SAPH440 steel used in the fixing frame for hydrogen storage was designed, and its structural safety was evaluated. In the design of the fixing frame, FCCSC was implemented by PMI foam core, a Bakelite mount, and Carbon Fiber Reinforced Plastics (CFRP) using woven carbon fiber prepreg. Unlike the steel fixing frame, the FCCSC-applied fixing frame had a cross-section of hollow-rectangular, and its validity was confirmed through finite element analysis. Structural analysis of the designed FCCSCapplied fixing frame and steel fixing frame was performed. Under the extreme load condition of 9G acceleration, the steel fixing frame showed the lowest safety factor of 1.14 based on the yield strength in the opposite direction of gravity. On the other hand, the FCCSC-applied fixing frame showed a safety factor of 7.6 at the maximum principal stress and 3.15 at the shear stress. Through this result of structural analysis, it was verified that the FCCSC-applied fixing frame, which was 25.8% lighter than the steel fixing frame, was 1.8 times safer.
Recently, competition in the manufacturing industry related to the preoccupation of new markets has drastically changed due to the increase in small quantity batch production products. Besides, business models utilizing 3D printing technology suitable for flexible manufacturing are gaining interest. As 3D printing technology is becoming more common, Design for Additive Manufacturing is also in the spotlight. However, the productivity of 3D printing technology is still insufficient in terms of mass production. In this study, the possibility of innovation in mass production process that combines 3D printing technology is presented through the case of innovation in manufacturing productivity of medium-speed engine cylinder head through the integration of sand 3D printing technology. It outlines how sand 3D printing technology is applied to cylinder head mass production processes, how the quality of cylinder head products can be improved compared to conventional pattern-based molding methods, and how productivity can be maximized by reducing process time and human error through hybrid production method with sand 3D printed integrated design cores. In conclusion, this paper presents the effectiveness of sand 3D printing technology which can secure product competitiveness by increasing the production capacity of mass production process, reducing production costs, improving quality, and reducing loss.
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The sanding device support bracket is part of the axle box and is one of the railway vehicles parts that must withstand extremely harsh environments. Conventional welded structure type brackets were cracked at welds during operation, requiring design changes. To minimize harsh environments and manufacturing errors, this review was conducted from the design stage, and design changes were made through several trial and error. In this paper, the optimal design was derived by performing topology optimization on the model designed and manufactured through trial and error and applied to the actual vehicle. The comparison of the existing model with the empirically designed model confirmed the improvement of the optimal design using the topology optimization. The optimized design was verified by the analysis and the vibration test of IEC 61373 was satisfied. The test parts based on the optimal design were applied to the actual vehicle and the performance was verified. In the optimum design process, the shape and material as well as the weight analysis were performed and finally the brackets were designed to be light in weight and improved in strength.
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When a building is detonated, the debris generated collides with the ground with very high energy and bounces back. This phenomenon is called ricochet. Ricochet increases risk by increasing the moving distance of the debris. The ricochet of debris is affected by the shape of the debris. In this paper, the behavior and moving distance of debris along the shape of debris were studied. For various initial conditions, the ricochet of debris was studied through the FEM, and the results were fitted to a 3D curved surface to predict the speed and angle after the ricochet. The moving distance of the debris was calculated using the trajectory formula considering the drag coefficient using the MATLAB. The ricochet of debris is affected by the contact area with the medium. As the contact area increases, the reflection angle increases because of the increase of the repulsive force. As the size of the debris increases, the energy loss also increases because of the increasing of the contact area. Thus, the moving distance of the cylinder debris is shorter than that of the sphere debris.
When a building explodes, debris generated bounces after hitting the ground with high energy. It is called the ricochet phenomenon. Ricochet phenomena increase the risk of damage by increasing the moving distance of the debris. The ricochet of debris is impacted by the type of medium. In this paper, the behavior and travel distance of debris after ricocheting are studied according to the type of medium. For various initial conditions, the ricochet of the debris was studied through FEM, and the resulting values were fitted to the 3D curved surface, to predict the speed and angle after the ricochet. The trajectory of the sphere was calculated with the flight formula, considering drag force by using the MATLAB. The ricochet of debris is impacted by the contact area with the medium. As the contact area increases, the reflection angle increases due to the increase of the repulsive force. As the size of the debris increases, the contact area increases and the energy loss increases, but it moves further because of the increase of the weight and kinetic energy. The type of media around the building can be used as an appropriate means of controlling the travel distance of the debris.
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A Study of Moving Distance of Ricocheted Debris for Various Debris Shape with Air Drag Coefficient Yoon Keon Kim, Woo Chun Choi Journal of the Korean Society for Precision Engineering.2020; 37(3): 209. CrossRef
The development of the lightweight sandwich plate with periodically repeated cores is one of hot issues to reduce the weight of the part. The behavior of the sandwich plate under static and dynamic loads is greatly influenced by the design of the cores. The aim of this paper is to investigate the effects of the corrugated angle on low velocity impact characteristics of the lightweight sandwich plate with corrugated cores. The corrugated core with the fold surface is designed to improve the joining characteristics between cores and skin sheets. The corrugated angle of the corrugated cores ranges from 45o to 90o. Specimens are manufactured from the fused deposition modeling (FDM) process. The characteristics of the fabricated specimen are investigated. Impact experiments are performed using a drop impact tester with a stretching type of fixture and the hemispherical nose of the impact head. From the results of the experiments, the influence of the impact energy and corrugated angle on the failure pattern of the lightweight sandwich plate is examined. The effects of the corrugated angle on critical impact energies for different failure patterns are investigated. Finally, the failure map of the lightweight sandwich plate with corrugated cores is estimated.
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It is generally accepted that mechanical properties of sandwich composite are affected by curing pressure variation. For the present study, the effects of curing pressure variation on the compressive properties of balsa wood sandwich composite were investigated. For this purpose, a compressive test was conducted using balsa wood and honeycomb core sandwich composite, applying 40 psi and 60 psi curing pressure conditions. The results showed that compressive load of balsa wood sandwich composite applying 60 psi curing pressure condition is higher than applying a 40-psi curing condition. This phenomenon is due to an increase in the adhesive strength of the balsa wood sandwich composite as the curing pressure increases, thereby improving the compressive strength. Deboning and local buckling were observed on fracture surfaces of all balsa wood sandwich composite, but only global buckling was observed at honeycomb core sandwich composite.
The flexural characteristics of corrugated sandwich panels are anisotropic and depend on its corrugation geometry and load position. The objective of this paper is to examine the influence of corrugation angle and load position on the flexural characteristics of plastic sandwich panels with trapezoidal corrugated cores subjected to ASTM three-point bending via finite element analysis. The stress distributions at mid span have been plotted to determine the stress concentration at different corrugation angle and load position. The specific flexural stiffness and modulus have been estimated from the loaddisplacement and stress-strain curves, respectively. The failure of the specimen due to stress or strain limit has been examined via maximum limit stroke. Results have shown that the specific flexural stiffness and modulus improve as the corrugation angle decreases. The load position has influenced the flexural characteristics due to the occurrence of local bending and local tension.
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A Study on the Effects of the Corrugated Angle on Low Velocity Impact Characteristics of the Lightweight Sandwich Plate with Corrugated Cores Produced by FDM Process Yong Hun Jang, Dong-Gyu Ahn, Bo Sung Shin Journal of the Korean Society for Precision Engineering.2017; 34(12): 939. CrossRef
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