• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.892-897
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• 2002

The research was requested by Meridian Rail Corporation in United States. The Swing Motion Bogie can application by Korea style if synthesize study result of bogie strength evaluation, bogie dynamic characteristics analysis, actual test(maximum speed, derailment coefficient, lateral force, vertical force, vibration acceleration, steady state lateral acceleration) etc..

• 한국기계가공학회지
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• 제13권6호
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• pp.82-87
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• 2014

Small MR dampers with a simple structure were designed and manufactured. The Bingham model was used to represent the dynamic characteristics of the damper, and the parameters of the model were estimated from experimental data which were obtained by harmonic tests. The value of the estimated yield shear force remains positive when no electric current is applied, and it increases slowly with the current. The estimated viscous damping coefficient has a value close to zero when no electric current is applied, and it increases almost linearly with the current.

• 대한가정학회지
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• 제26권3호
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• pp.93-102
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• 1988

Rheological properties of cowpea and mung bean starch gels and pastes were investigated and compared with Instron Universal Testing machine and Brabender Viscometer. As the result of puncture test of gels, yield point force of mung bean starch gel was higher than that of cowpea starch gel. Compression coefficient of cowpea starch gel calculated by Bourne's equation was lower than that of mung bean starch gel. the stress relaxation test showed that viscoelastic properties of cowpea and mung bean starch gels may be represented by six element Maxwell model consisting of three Maxwell element in parallel. Cowpea and mung bean starch pastes showed bingham pseudoplastic behavior in 3, 5, 6, 7 and 8%. The consistency index in 7∼8% of cowpea starch paste were lower than those of mung bean starch paste. concentration dependence on consistency index and yield stress in mung bean starch were higher than those of cowpea starch. The yield stress of starch pastes was significantly correlated with yield point force by puncture test (r=0.996).

• 오토저널
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• 제10권3호
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• pp.38-44
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• 1988

It is important to control the axial forces of high tension bolts such as the automobile, construction machine, aircraft, marine engine bolts. However, the direct method to measure the axial forces of bolts practically have not been found out. The ultrasonic techniques is based on the principles that the bolt tensile elongation and ultrasonic velocity changes are proportional to the axial force below the yield point of the materials. From the result of the experiment, the coefficient of acoustoelasticity k could be measured as - 11.18*10$_{-5}$m $m^{2}$k $g_{f}$./.

• Journal of Biosystems Engineering
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• 제40권3호
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• pp.201-211
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• 2015

Purpose: Designing equipment for processing, sorting, and other post-harvest operations of agricultural products requires information about their physical properties. This study was conducted to investigate some of the mechanical and physical properties of Moringa oleifera L. pods and seeds. Methods: Properties such as the length, width, thickness, bulk density, porosity, mass, static coefficient of friction, and angle of repose were determined as a function of moisture content. Statistical data and force-deformation curves obtained at each loading orientation and moisture level were analyzed for bioyield point, bioyield strength, yield force, rupture point, and rupture strength using a testrometric machine. Result: The basic dimensions (length, width, and thickness) of moringa pods and seeds were found to increase linearly from 311.15 to 371.45 mm, 22.79 to 31.22 mm, and 22.24 to 29.88 mm, respectively, in the moisture range of 12 to 49.5% d.b. The coefficient of friction for both pods and seeds increased linearly with an increase in moisture content on all the surfaces used. The highest value was recorded on mild steel, with 0.581 for pods and 0.3533 for seeds, and the lowest on glass for pods, with a value of 0.501, and of 0.2933 for seeds on galvanized steel. The bioyield and rupture forces, bioyield and rupture energies, and deformation of the pods decreased with an increase in moisture content to a minimum value, then increased with further decrease within the moisture content range, while the yield force increased to a maximum value and then decreased as the moisture content increased. Conclusion: These results will help to determine the most suitable conditions for processing, transporting, and storing moringa pods, and to provide relevant data useful in designing handling and processing equipment for the crop.

• 한국지진공학회논문집
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• 제20권2호
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• pp.125-134
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• 2016

In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb's friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between low-and fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

• Tribology and Lubricants
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• 제16권2호
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• pp.75-83
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• 2000

The present paper proposes a new type of an electro-rheological squeeze film damper (ER SFD) of which the damping capacity can be controlled by the application of electric field. The new ER .SFD- is sealed with slotted rings having electrodes at the inside of the constant gap. The ER SFD can provent the problem of electric short which might be occurred in a previous ER SFD. Reynolds lubrication equation for a Newtonian fluid and the end leakage equation for ER fluids are numerically solved to get the pressure distributions and the damping coefficients of the ER SFD. The results show that the damping coefficients greatly increase with increasing the yield shear stress of ER fluid. In addition, the unbalance response analysis of a flexible rotor supported on the new ER SFD implies that the rotor system can be operated with the minimum of rotor amplitude and force transmissibility by controlling the yield shear stress of ER fluids properly.

• 대한기계학회논문집A
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• 제22권1호
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• pp.102-110
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• 1998

The analysis of lateral hydrodynamic forces in the leakage path between a shrouded pump impeller through wear-ring seal and its housing is presented. Governing equations are derived based on Bulk-flow and Hirs' turbulent lubrication model. By using a perturbation analysis and a numerical integration method, governing equations are solved to yield leakage and rotordynamic coefficients of force developed by the impeller shroud and wear-ring seal. The variation of rotordynamic coefficients of pump impeller shroud and wear-ring seal is analyzed as parameters of rotor speed, pressure difference, shroud clearance, wear-ring seal clearance, and circumferential velocity at the entrance of impeller shroud for a typical multi-stage centrifugal pump.

• Geomechanics and Engineering
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• 제8권3호
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• pp.461-476
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• 2015

Rankine's theory of earth pressure cannot be directly employed to c-${\phi}$ soils backfill with a sloping ground subjected to complex loadings. In this paper, an analytical solution for active earth pressures on retaining structures of cohesive backfill with an inclined surface subjected to surcharge, pore water pressure and seismic loadings, are derived on the basis of the lower-bound theorem of limit analysis combined with Rankine's earth pressure theory and the Mohr-Coulomb yield criterion. The generalized active earth pressure coefficients (dimensionless total active thrusts) are presented for use in comprehensive design charts which eliminate the need for tedious and cumbersome graphical diagram process. Charts are developed for rigid earth retaining structures under complex environmental loadings such as the surcharge, pore water pressure and seismic inertia force. An example is presented to illustrate the practical application for the proposed coefficient charts.

• 한국표면공학회지
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• 제49권1호
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• pp.104-109
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• 2016

Graphite's thermal stability facilitates its widespread use as crucibles and molds in high temperatures processes. However, carbon atoms can be rather easily detached from pores and outer surfaces of the graphite due to the weak molecular force of the c axis of graphites. Detached carbon atoms are known to become a source of dust during fabrication processes, eventually lowering the effective yield of products. As an effort to reduce these problems of dust scattering, we have fabricated SiC composites by employing Si vapor infiltration method into the pores of graphites. In order to understand the diffusion process of the Si vapor infiltration, Si and C atomic percentages of fabricated SiC composites are carefully measured and the diffusion law is used to estimate the diffusion coefficient of Si vapor. A quadratic equation is obtained from the experimental results using the least square method. Diffusion coefficient of Si vapor is estimated using this quadratic equation. The result shows that the diffusion length obtained through the Si vapor infiltration method is about 10.7 times longer than that obtained using liquid Si and clearly demonstrates the usefulness of the present method.