• Journal of Biosystems Engineering
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• v.14 no.2
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• pp.67-79
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• 1989

This study was conducted to investigate the applicability of true model theory for pull prediction in a powered lugged wheel-soil system and to examine the possibility of using principles of similitude in investigating the dimensions of soil parameters pertinent to a powered lugged wheel-soil system concerning the pull prediction. The following conclusions were derived from the study; 1) The pull of prototype wheels proved to be predicted by those of the model wheels for the range of the dynamic weight tested. The pull curves of models and prototype were respectively very similar in the shape. From this basic knowledge, it was enabled to apply the similitude theory to the performance prediction of the true model. 2) A conditional equation which can be used for the prediction of pull of prototype by model test was derived as follows. $n_f=n_1^{-b}$ where $n_f$ : force scale = $w/w_m$ $n_1$ : length scale = ${\ell}/{\ell}_m$ b : exponent on the length dimension of the soil property ${\alpha}$ The range of the numerical value of b, which was determined by the least square method, was found to be -2.0~-2.6. 3) Considering a relatively wide variation of b values in the pull prediction, b is considered to be a function of many variales. Thus it was concluded that there are several soil properties which are pertinent to the powered lugged-wheel-soil system concerning the pull prediction, and these soil properties may have the different effects on the pull of model and protytype wheels, to give the different dimension on the soil parameters.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.61-66
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• 1992

This paper addresses on the determination of damping coefficients of an infinitely long squeeze film damper operating with an electro-rheological (ER) fluid. The ER fluid behaves as Bingham fluid with an electric field dependent yield shear stress. AS phenomenological model of the fluid is adopted for the relationship between the yield shear and the intensity of the electric field imposed on the fluid domain. The model is then incorporated with the governing equation and associated boundary conditions of the squeeze film damper executing a circula centered orbit for the expression of dimension- less damping coefficients. Numerical simulation is performed to evaluate the performance improvement of the proposed squeeze film damper.

• Journal of the Korean Society of Safety
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• v.21 no.6 s.78
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• pp.1-6
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• 2006

Subway platform is divided into Side-platform type and Center-platform type. In this study does quantitative fire risk assesment of subway platform types in numerical analysis by using CFD model. From the result of this study, 1) All exhaust mode was low-end result it seems most fire risk at Side-platform station. 2) All exhaust mode was low-end result it seems most fire risk at Center-Platform station. 3) When comparing same type exhaust mode of Side-platform and Center-platform that last thing was visible $9.1{\sim}72.34%$ low-end fire risk. Center-platform is more opera-tive than Side-platform that reduce fire risk when that was same dimension and external environment. Designer look upon a fire characteristic of subway platform types when he make smoke control air volume and platform area design.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.27-33
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• 2012

The relationship between the excitation frequency and the vortex shedding frequency is analyzed during the oscillation of the circular cylinder. Two-dimension unsteady Navier-Stoke's equation is calculated by using the Optimized High Order Compact (OHOC) scheme. The flow condition is Mach number 0.3 and Reynold's number 1000. From the results acquired by calculation, it can be inferred that, when the excitation frequency is near the vortex shedding frequency at the fixed cylinder wake, the oscillation frequency of lift and drag coefficients appears to lock-on. The lock-on refers to a phenomenon in which the aerodynamic coefficient appears as one primary oscillation frequency through excitation and its amplitude is amplified. In the non-lock-on zone, the excitation frequency is not in the lock-on mode anymore and beat is formed in which two or more primary oscillation frequencies of the aerodynamic coefficient are mixed together.

• International Journal of Highway Engineering
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• v.17 no.6
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• pp.37-45
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• 2015

PURPOSES : The purpose of this study is to validate the design criteria of the concrete modular road system, which is a new semi-bridge-type concept road, through a comparison of numerical analysis results and actual loading test results under static axial loads. METHODS : To design the semi-bridge-type modular road, both the bridge design code and the concrete structural design code were adopted. The standard truck load (KL-510) was applied as the major traffic vehicle for the design loading condition. The dimension of the modular slab was designed in consideration of self-weight, axial load, environmental load, and combined loads, with ultimate limit state coefficients. The ANSYS APDL (2010) program was used for case studies of center and edge loading, and the analysis results were compared with the actual mock-up test results. RESULTS : A full-scale mock-up test was successfully conducted. The maximum longitudinal steel strains were measured as about 35 and 83.5 micro-strain (within elastic range) at center and edge loading locations, respectively, under a 100 kN dual-wheel loading condition by accelerating pavement tester. CONCLUSIONS : Based on the results of the comparison between the numerical analysis and the full-scale test, the maximum converted stress range at the edge location is 32~51% of the required standard flexural strength under the two times over-weight loading condition. In the case of edge loading, the maximum converted stresses from the Westergaard equation, the ANSYS APDL analysis, and the mock-up test are 1.95, 1.7, and 2.3 times of that of the center loading case, respectively. The primary reason for this difference is related to the assumption of the boundary conditions of the vertical connection between the slab module and the crossbeam module. Even though more research is required to fully define the boundary conditions, the proposed design criteria for the concrete modular road finally seems to be reasonable.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.163-173
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• 2014

In this study, a modeling method is based on representing a road generation system with several rigid bodies, i.e, pad, shaft, torsional damper, oneway-clutch, gear system, and electricity generator. The simulation software is developed to evaluate the performance of a road generation system. It is used to determine parametric dimension for optimal design with the theoretically calculated results from the simulation software. The parametric dimensions are included as capacity, length, and angle of equipment. The transient responses at the conditions of low and high vehicle speed are compared with the calculated results as torque, power, out energy etc. Consequently, before manufacturing system, the analysis of simulation results shows that the proposed concept and system has efficiency and confidence.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.319-324
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• 2003

In general industrial rotating machinery is operated under 3,600 rpm as rotating speed and designed to have critical speed that is above operating speed. So, there was no problem to operate rotating machine under critical speed. But nowadays, they should be operated more than the frist critical speed as usual with the trend of high speed, large scale and hish precision in industries. In case of the large rotor assembly as the trend of large scale, using fitting method of disk or cylinder on shaft is rising for the convenience of assembly and cutting down of manufacturing cost. The shrink fitting is used to assemble lamination part on shaft for manufacturing of rotor of motor or generator in many cases and also is widely used for other machinery. In rotating system, which is compose of rotor and bearing, the critical speed is determined from inertia and stiffness for the rotor and bearings. In case of fitting assembly, analysis and design of the rotor is not easy because the rotor stiffness is determined depend on a lot of factors such as shaft material/dimension, disk material/dimension and assembled interference etc. Therefore designer who makes a plan for hish-speed rotating machine should design that the critical speed is located out of operating range, as dangerous factors exist in it. In order to appropriate design, an accurate estimation of stiffness and damping is very important. The stiffness variation depend on fitting interference is a factor that changes critical speed and if it's possible to estimate it, that Is very useful to design rotor-bearing system. In this paper, the natural frequency variation of the rotor depends on fitting interference between basic shaft and cylinder is examined by experimentation. From the result, their correlation is evaluated quantitatively using numerical analysis that is introduced equivalent diameter end the calculation criteria is presented for designer who design fitting assembly to apply with ease for determination of appropriate interference.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.275-280
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• 2008

A technique for reliability-based design optimization(RBDO) is developed based on the Bayesian approach, which can deal with the epistemic uncertainty arising due to the limited number of data. Until recently, the conventional REDO was implemented mostly by assuming the uncertainty as aleatory which means the statistical properties are completely known. In practice, however, this is not the case due to the insufficient data for estimating the statistical information, which makes the existing RBDO methods less useful. In this study, a Bayesian reliability is introduced to take account of the epistemic uncertainty, which is defined as the lower confidence bound of the probability distribution of the original reliability. In this case, the Bayesian reliability requires double loop of the conventional reliability analyses, which can be computationally expensive. Kriging based dimension reduction method(KDRM), which is a new efficient tool for the reliability analysis, is employed to this end. The proposed method is illustrated using a couple of numerical examples.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.989-999
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• 2006

In this paper, numerical analysis method to perform linear dynamic analysis of bridge considering the road surface roughness and bridge-vehicle interaction when vehicle is moving on bridge is presented. The vehicle and bridge are modeled as three-dimension where contact length of tire and pitching of tandem spring are considered and single truck with 2-axles and 3- axles, and tractor-trailer with 5-axles are modeled as 7-D.O.F., 8-D.O.F., and 14-D.O.F., respectively. Dynamic equations of vehicle are derived from the Lagrange's equation and solution of the equation is obtained by Newmark-${\beta}$ method. The surface roughness of bridge deck for this analysis is generated from power spectral density (PSD) function. Beam element for the main girder, shell element for concrete deck and rigid link between main girder and concrete deck are used. The equations of the motion of bridges are solved by mode-superposition procedures. The proposed procedure is validated by comparing the results with the experimental data by Whittemore and Fenves.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2546-2551
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• 2007

Weather Strip(W/S) is a rubber part to proof water, sound and dust for opening and shutting devices including vehicle doors. And it requires high dimension precision and durability to proof water, noise, vibration and etc. But ironically it itself makes some wind noise because of some protuberance with glasses. The air flow analysis of door part of vehicle makes it possible to calculate and find out the cause of wind noise. In previous analysis, we focus on the numerical air flow analysis of the automobile side part. We do 2D-C.F.D first and 3D second. Through simulations, we can calculate the amount of sound pressure level at the glass run and find out the effects of glass run to make wind noise. Finally we can improve shape of glass run to reduce wind noise although it is small amounts of sound pressure reduction compared with total vehicle noise level.