• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.828-834
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• 2002

In this paper, for the mixed mode fatigue problem, the method of determining testing load was proposed. It is based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E 647-00. The application method of maximum tangential stress criterion and the stress intensity factor for the finite width specimen was proposed. In the result of applying the method to mixed mode fat gut test for A5052 H34, it obtained the satisfactory experimental results on the stable crack growth.

• Structural Engineering and Mechanics
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• v.12 no.2
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• pp.157-168
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• 2001

In this paper, experimental investigation into the behavior of reinforced concrete (RC) columns tested under large lateral displacement with four different types of loading arrangements is presented. Each loading arrangement has a different system for controlling the consistency of the loading condition. One of the loading arrangements used three units of link mechanism to control the parallelism of the top and bottom stub of column during testing, and the remaining employed eight hydraulic jacks for the same purpose. The loading systems condition used in this investigation were similar to the actual case in a moment-resisting frame where the tested column was displaced in a double curvature. Ten model column specimens, divided into four series were prepared. Two columns were tested monotonically until collapse, and unless failure took place at an earlier stage of loading, the remaining eight columns were tested under cyclic loading. Test results indicated that the proposed system to keep the top and bottom stubs parallel during testing performed well.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.177-181
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• 2016

Hot shearing is a method of producing various high-quality planar machine parts by using reduced punch load. In order to predict the results of this process, the deformation behavior of work material at elevated temperatures need to be studied. In this research, a tensile test was carried out for 5052 aluminum alloy at high temperatures of $240-540^{\circ}C$ and strain rates of 0.001-0.1/s. The results of the tensile tests were studied to predict the deformation of the alloy during the hot shearing process. The results showed that hot shearing within a temperature range of $340-440^{\circ}C$ and a strain rate rage of 0.001-01/s will be the most effective in reducing punch load and increasing the sheared edge in the case of 5052 aluminum alloy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.539-546
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• 2004

Conventional robot manipulators actuated by motors with the speed reducer such as the harmonic drive have weakness in the load capacity, since the speed reducer does not have enough strength. To overcome this, a new type of the robot actuator based on the four-bar-link mechanism driven by the ball screw was proposed and constructed. Also, a new type of a revolute-jointed robot manipulator composed of the developed actuators was developed. The base axis is actuated by the motor with the conventional speed reducer, but the other axes are actuated by the proposed actuators. The kinematics and dynamics of the robot were analyzed, and the performance test of the robot was made. Through the test results, the performance of superior load capacity versus the robot weight is shown.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.245-246
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• 2002

The objective of this study is to evaluate corrosive wear resistance of metals used for bearings and gears in seawater. Sliding wear test of ferrous and copper materials against $Al_2O_3$ were carried out in artificial seawater using an electrochemical potentiostat. As the results, the wear rate and the coefficient of friction of the copper materials are lower than those of the ferrous materials. The corrosive wear of stainless steel is remarkably affected by normal load and sliding speed in view of tribological characteristics including adhesion and corrosion products.

• Structural Engineering and Mechanics
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• v.44 no.3
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• pp.325-337
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• 2012

In this article, the multi-objective optimization of cylindrical aluminum tubes under axial impact load is presented. The specific absorbed energy and the maximum crushing force are considered as objective functions. The geometric dimensions of tubes including diameter, length and thickness are chosen as design variables. D/t and L/D ratios are constricted in the range of which collapsing of tubes occurs in concertina or diamond mode. The Non-dominated Sorting Genetic Algorithm-II is applied to obtain the Pareto optimal solutions. A back-propagation neural network is constructed as the surrogate model to formulate the mapping between the design variables and the objective functions. The finite element software ABAQUS/Explicit is used to generate the training and test sets for the artificial neural networks. To validate the results of finite element model, several impact tests are carried out using drop hammer testing machine.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.35-36
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• 2008

In this paper, we studied the long term durability estimation for crystalline photovoltaic module while exposing to mechanical stress. Solar cell and PV module have many different kinds of stresses from cell to module fabrication. For this reason, some solar cell shows micro crack that decrease crystallization. In here, we expose artificial mechanical load on surface of PV module. Through this, the periodic external force on PV module might give an negative effect. The further analysis is described in the following paper.

• Advances in nano research
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• v.15 no.4
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• pp.285-294
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• 2023

This study is aimed to investigate the electrically conductive properties of epoxy nanocomposites exposed to an acidic environment under various mechanical loads. For simultaneous assessment of the acidic environment and mechanical load on the electrical conductivity of the samples, the samples with and without carbon nanotubes were exposed to the acidic environment under three different loading conditions for 20 days. Then, the aged samples' strength and flexural stiffness degradation under crude oil and bending stress were measured using a three-point flexural test. The aged samples in the acidic environment and under 80 percent of their intact ultimate strength revealed a 9% and 26% reduction of their electrical conductivity for samples with and without CNTs, respectively. The presence of nanoparticles declined flexural stiffness by about 16.39%. Scanning electron microscopy (SEM) images of the specimen were used to evaluate the dispersion quality of CNTs. The results of this study can be exploited in constructing conductive composite electrodes to be used in petroleum environments such as crude oil electrostatic tanks.

• Journal of Navigation and Port Research
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• v.32 no.3
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• pp.251-255
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• 2008

Container cranes are vulnerable structure about difficult weather conditions bemuse there is no shielding facility to protect them from the strong wind. This study was carried out to analyze the wind load which have an effect on container crane according to the various wind direction. The container crane is a model of a 61-ton class that used broadly in the current ports. The external fluid field was figured as a cylinder which was set up $500m{\times}200m$. In this study, we applied mean wind load conformed to 'Design Criteria of Wind Load' in 'Load Criteria of Building Structures' and an external fluid field was divided as interval of 10 degrees to analyze effect according to a wind direction In this conditions, we carried out the computation fluid dynamic analysis using the CFX-10. As we compared computation fluid dynamic analysis with wind tunnel test, we analyzed the wind load which was needed to design the container crane.

• Advances in nano research
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• v.16 no.2
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.