• Advances in materials Research
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• v.5 no.3
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• pp.193-203
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• 2016

Compared to metal-to-metal tribology, polymer tribology presents further complexity as it is more prone to be influenced by operating conditions. Over the past two decades, progress in the field of wear of polymers has led to the establishment of more refined wear mechanisms. The current paper establishes the link between different load parameters and the wear rate of polymers, based on experimental investigations. A pin-on-plate reciprocating tribometer was used to examine the wear behaviour of polyamide sliding against a steel counterface, under constant and fluctuating loads, in dry conditions. In addition, the influence of controlled imperfections in the polymer surface upon its wear rate were examined, under cyclic and steady loading, in order to better understand surface fatigue wear of polymers. The imposed imperfections consisted of vertical artificial deep crack (slit) perpendicular or parallel to the direction of sliding. The study concludes with the followings findings; in general, wear of polymers shows a significant tendency to the type of applied load. Under cyclic loads, polymers show an increase in wear rate compared to those tested under static loads. Such increase was found to increase with the increase in cyclic load frequency. It is also demonstrated that surface cracks results in higher wear rates, particularly under cyclic loads.

• Composites Research
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• v.16 no.6
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• pp.23-32
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• 2003

Applications of advanced composite material in construction field are tending upwards and development of all composite material bridges is making progress rapidly in home and abroad due to their high strength to weight ratio. This paper formulated the dynamic responses of the laminated composite structures subjected to moving load and analyzed the various dynamic behaviors using the finite element method. The nondimensionalized natural frequencies of a simply supported square-laminated composite plate are considered for verifications. Mode superposition and Newmark direct integration method are applied for moving load analysis. For structural models, dynamic magnification factor calculated for various velocities of the moving load and displacements characteristics of laminated composite structures due to the moving load are investigated theoretically Numerical results are presented to study the effects of lamination scheme, stacking sequence, and fiber angle for laminated composite structures during moving load. The various results on moving load and lamination through numerical analysis will present an important basic data for development and grasp the behavior of all composite material bridges.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.708-713
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• 2014

Trusses are widely used for wooden houses in the areas where wood construction in generalized for residential housings such as North America, Australian, New Zealand. In Korea, joist and rafter system is generally used because of the production cost, transportation cost and lack of experience required for truss manufacturing. In this study, roof trusses and flat trusses were manufactured by using oriented strand board (OSB) gusset plates for field assembly and tested under bending load to obtain the allowable loads. The allowable load and the actual load of 6m span roof trusses were 10.60 kN and 5.26 kN, respectively, which is regarded to be sufficient for use in construction. The allowable load and the actual load of 6m span floor flat trusses were 7.18 kN and 7.43 kN, respectively. For flat trusses, the allowable load is slightly lower than the actual load but the difference in very small, and it is thought that flat trusses can be used for construction by applying small change of structures and members.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.481-492
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• 2018

The steel-plate concrete composite beam is composed of a steel plate, concrete and shear connector to combine two inhomogeneous materials. In general, the steel plate is assembled by welding an existing composite beam. In this study, the SPC beam was composed of folding steel plates and concrete, without a headed stud. The folding steel plate was assembled by a high strength bolt instead of welding. To improve the workability in a field construction, a hat-shaped cap was attached to the junction with a slab. Monotonic load testing under two points was conducted under displacement control mode to analyze the flexural strength of the SPC beam using a cap as the shear connector. Five specimens with shear connector types, protrusion length, and different thickness of steel plates were constructed and tested. The experimental results were analyzed through the relationship between the shear strength ratio and flexural strength in KBC 2009. The test results showed a shear strength ratio of more than 40 %. In the case of using a cap-like specimen as the shear connector, the flexural strength was 70% of the value calculated as a fully composite beam. In addition, the cap showed a smaller shear strength than the stud, but the cap served as a shear connection. When the thickness of the steel plate was taken as a variable, the steel plate exhibited a bending strength of approximately 70% compared to a fully formed steel plate, and exhibited similar deformation performance. Local buckling occurred due to incomplete composite behavior, but local buckling occurred at a 5% higher strength for a relatively thick steel plate. The buckling width also decreased by 15%.

• Steel and Composite Structures
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• v.42 no.2
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• pp.243-256
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• 2022

A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1-continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.95-101
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• 2009

The generator for gas turbine power generation consists of the rotor which generates magnetic field, the winding coil which is the path for the field current and the wedge and retaining ring which prevents the radial movement of the coil. Relatively severe deformation was observed at the coil end section during the inspection of the generator for peaking-load operation, and the thermal-electricity and the centrifugal force were evaluated by the simple modeling of the windings to find the cause. But the simulation stress was not sufficient to induce the coil plastic deformation. The analysis result seems to be applicable to the base-load generators which runs continuously without shut down up to a year, but there had been more deformation than simulated for the generator which is started up and shut down frequently. The cause of the coil deformation was the restriction of the expansion and shrinkage. The restriction occurs when the winding coil shrinks, and the stress overwhelms the yield stress and cause the plastic deformation. The deformation is accumulated during the start-ups and shut-downs and the thermal growth occurs. The factors which induce the coil restriction during the expansion and shrinkage should be reduced to prevent the unallowable deformation. The resolutions are cutting off the field current earlier during the generator shut-down, modifying the coil end section to remove the stress concentration and making the insulation plate inserted between the coil end section and the retaining ring have the constant thickness.

• Journal of the Society of Disaster Information
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• v.3 no.2
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• pp.147-169
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• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.17-22
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• 2003

The present study was conducted to obtain the fundamental knowledge on the manufacturing and operating characteristics of a small scale CPL (Capillary Pumped Loop) heat pipe. CPL heat pipes are able to transfer heat effectively at any orientation in a gravitational field over long distances. An experimental model with an evaporator of a circular plate shape was designed and manufactured and its operating performances were tested. A Bronze powder sintered metal plate of 3 mm thick and $\Psi$ 50 mm was used as wick and ethanol was used as working fluid. An experimental apparatus was set up to ascertain the operating conditions oi CPL at different heat load and an surrounding temperature at the condenser was maintained about 13$^{\circ}C$.

• Korean Journal of Materials Research
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• v.17 no.11
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• pp.580-586
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• 2007

To enhance the reliability of a newly designed reciprocating compressor applied in a domestic compressor, accelerated life tests were developed using new definitions of the sample size and the $B_1$ life index. In $1^{st}$ accelerated life testing, the compressor was locked due to the fracture of the suction reed valve. The failure modes and mechanisms of the suction reed valve in the accelerated tests were found to be similar to that of the failed product in the field. The root cause of the failure was the overlap between the suction reed valve and the valve plate in the suction port. The missing parameters in the design phase were modified by expanding the trespan size, introducing tumbling process, changing the material and thickness for the valve, introducing a ball peening and brushing process for the valve plate. In $2^{nd}$ accelerated life testing, the compressor was locked due to the interference between the crank shaft and thrust washer. The corrective plan was to heat treat the crank shaft. The $B_1$ life of the compressor improved from 1.5 to 12.9 years.

• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.355-360
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• 2019

In this study, the structural stability of the railway level crossing system using rubber panel for high speed lines was investigated by applying the specification for wind load conditions (Train gust) of high speed train (300km/h and 360km/h). A finite element analysis using three-dimensional modeling was carried out by applying the field conditions that was installed with the complicated configuration of the rubber plate panel system. As a result of this study, the structural stability of the rubber plate panel system for high speed train gust was analytically verified.