• Transactions of Materials Processing
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• v.27 no.3
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• pp.139-144
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• 2018

Many studies have been conducted on the process of forming magnesium alloy sheets to reduce the body weights of vehicles. Magnesium has a lower specific gravity than steel and also has a higher specific strength. Mg alloy sheets have low formability and a lot of springback due to their limited ductility and low young's modulus. As the temperature increases, the yield strength of the material decreases. Warm forming increases the formability and minimizes the springback of a material by heating it and the die to reduce the required load at forming. In this study, the temperature of the AZ31B sheet was controlled in order to reduce springback and increase formability. However, as the temperature increased, the deformation characteristics of the material changed and the radius of curvature of the material increased. The load and springback amount required for forming were analyzed according to the temperature and the bottoming force in the bending deformation.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.237-242
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• 2001

Ti-6Al-4V alloy can be obtained the stability of organization and product treasure, the evaluation of the cutting ability and the mechanical characteristics after the heat treatment of annealing, solution and aging. The difficulty in machining titanium alloy is how treat the heat generated during the process. Because the heat conductivity of titanium alloy is regardfully low, the heat generated during grinding is accumulated in workpiece. and it causes the increasing of grinding wheel grits' wear and makes the ground surface rough. So, these characteristics in grinding of titanium alloy will change the mechanical properties of the titanium alloy. From this study. the mechanical characteristics of annealed one and solution and aging one treated Ti-6Al-4V alloy after grinding was concerned with checking out the bending strength and hardness. For the result, both of bending strength and hardness were increased at the burned area on the surface. Roughness value was remarkably high at the table speed of 10m/min.

• Journal of the Korean Geotechnical Society
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• v.36 no.3
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• pp.25-36
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• 2020

In this research, three-point bending tests were performed using a rectangular frozen specimen with various fine contents and notch offset distance from the center of the specimen to investigate the fracture characteristic of the frozen sand. Based on the test results, mode I fracture toughness was calculated, and mixed-mode (mode I + II) fracture characteristics were investigated using the fracture energy which was calculated until the maximum point of the load-displacement curve. As the fine contents increase, the peak load and mode I fracture toughness increase until 10% fine contents. Furthermore, as the notch offset distance increases, the fracture energy required for crack start also increases due to the increase in mode II load at the crack tip.

• Journal of Korean Neurosurgical Society
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• v.37 no.3
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• pp.217-222
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• 2005

Objective: To achieve optimal fit of implant, it is necessary to bend the implant during spine surgery. Bending procedure may decrease stiffness of plate especially made of titanium and stainless steel. Typically titanium suffers adverse effects including early crack propagation when it is bent. We investigate whether 6 degree bending of titanium plates would decrease the stiffness after full cyclic loading by comparing with non-bending titanium plates group. Methods: Authors experimented 40 titanium alloy plates of 57mm in length, manufactured by 5 different companies. Total 40 plates were divided into two groups (20 bent plates for experimental group and 20 non-bent plates for control group). Twenty plates of experimental group were bent to 6 degree with 3-point bending technique and verified with image analyzer. Using the electron microscope, we sought for a initial crack before and after 3-point bending. Mechanical testing by means of 6000 cyclic axial-compression loading of 35N in compression with moment arm of 35mm-1.1 Nm was conducted on each plate and followed by the electron microscopic examination to detect crack or fissure on plates. Results: The stiffness was decreased after 6000 cyclic loading, but there was no statistically significant difference in stiffness between experimental and control group. There was no evidence of change in grain structure on the electron microscopic magnification. Conclusion: The titanium cervical plates can be bent to 6 degree without any crack or weakness of plate. We also assume that minimal bending may increase the resistance to fatigue fracture in cervical flexion-extension movement.

• Composites Research
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• v.27 no.2
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• pp.37-41
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• 2014

Fiber reinforced composite materials have outstanding specific strength and specific stiffness. So the use of composite materials increases in various kinds of industrial fields including sports goods such as bicycles. Composite materials are used to make structural parts with various kinds of shapes. Specially, rectangular composite tubes are used to make a few of composite bicycle frames, but there has been a few of research on this issue. Rectangular composite tubes are designed to have appropriate radius of curvature and endure bending and torsional loads. In this research, nine kinds of rectangular composite tubes having aspect ratios 1:1, 1:1.5, 1:2 and radius of curvatures R5, R10, R15 were fabricated. The carbon fiber reinforced composite material was used to make tubes having same cross sectional areas. The stacking sequence of tubes is $[0/90/{\pm}45]s$. Experimental evaluation was accomplished to apply bending and torsional load to the tubes. Experimental results show that bending and torsional characteristics depend on radius of curvature and aspect ratio of rectangular composite tubes.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.23-32
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• 2007

The goal of this study is to perform several bending tests on a shape memory alloy bar and to analyze the characteristics of the bending behavior. The other goal is to verify the seismic performance of an SMA bar bending application. Single and double bending tests were conducted with varying loading speeds and maximum displacement. The loading and the unloading stiffness were estimated from the force-displacement curves and the equivalent damping ratio of each test was also assessed. In single bending, the SMA bar showed the stiffness hardening after the displacement of 32 mm. It is assumed that this phenomenon is due to the stress-induced-martensite hardening. The increasing loading speed did not influence on the stiffness of the single bending SMA bar. The stiffness of the double bending bar is about 5 times of that of the single bending. This study introduced a seismic application of SMA bending bars as seismic restrainers for bridges and showed its practicality. SMA bars in bending are used for seismic restrainers in a three-span-simply-supported bridge. They showed the effectiveness to reduce the responses of the bridge and the applicability for a seismic restrainer. The significance of this study is to provide basic knowledge of SMA bending and its seismic applications.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1231-1236
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• 2007

This study presents the static and dynamic actuating performances of a bending piezoelectric actuator with a thin sandwiched PZT plate under a static load. The stored elastic energy within the actuators which occurs during a curing process is obtained through a flexural bending test. An actuating performance is evaluated in terms of an actuating displacement at the simply supported condition. The results reveal that an actuator that consists of a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at the alternating current voltage, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling their performances.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.300-301
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• 2006

We studied about new module technology to solve warpage problems that produce bending of cell in the LCD (Liquid crystal display). Characteristics of cell gap and glass bending of applying heat Panel's PAD part and cell at various temperature was investigated. When applies heat and compresses PAD party only in case of compressing COG(Chip on Glass), uniformity of cell gap that happen by glass bending by temperature of these compressing COG In the PAD party is decreased. However, in case of compress COG. glass bending of applying heat Panel's PAD part and cell at various temperature produced 20um. But, uniformity of cell gap was not decreased. Therefore, it is considered that applying heat Panel's PAD part and cell could decrease uniformity of cell gap and bending of glass.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.870-879
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• 2007

In this study, various damage modes in bending unimorph piezoelectric composite actuators with a thin sandwiched PZT plate during bending fracture tests have been evaluated by monitoring acoustic emission (AE) signals in terms of waveform and peak frequency as well as AE parameters. Three kinds of actuator specimens consisting of woven fabric fiber skin layers and a PZT ceramic core layer are loaded with a roller and an AE activity from the specimen is monitored during the entire loading using an AE transducer mounted on the specimen. AE characteristics from a monolithic PZT ceramic with a thickness of $250{\mu}m$ are examined first in order to distinguish different AE signals from various possible damage modes in piezoelectric composite actuators. Post-failure observations and stress analyses in the respective layers of the specimens are conducted to identify particular features in the acoustic emission signal that correspond to specific types of damage modes. As a result, the signal classification based on waveform and peak frequency analyses successfully describes the failure process of the bending piezoelectric composite actuator exhibiting diverse failure mechanisms. Furthermore, it is elucidated that when the PZT ceramic embedded actuators are loaded mechanical bending loads, the failure process of actuator specimens with different lay-up configurations is almost same irrespective of their lay-up configurations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.880-888
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• 2007

This article describes the load capability of bending piezoelectric actuators with a thin sandwiched PZT plate in association with the stored elastic energy induced by an increased dome height after a curing process. The stored elastic energy within the actuators is obtained via a flexural mechanical bending test. The load capability is evaluated indirectly in terms of an actuating displacement with a load of mass at simply supported and fixed-free boundary conditions. Additionally, a free displacement under no load of mass is measured for a comparison with an actuating displacement. The results reveal that an actuator with a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators in terms of free displacement as well as actuating displacement due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at AC voltage, the actuating displacement is rather higher than the free displacement for the same actuating conditions. In addition, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric composite actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling the performance.