• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1196-1201
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• 1993

Test of Caterpillar Challenger 65 tractor which has rubber tracks, and articulated four wheel drive tractor with dual wheels and a mechanical front wheel drive tractor were conducted on an unplowed and plouwed wheat stubble field. The following parameters were analyzed : tractive efficiency (ηv), net tractive coefficient ($\phi$n), slip ($\sigma$) , drawbar pull(Fv), drawbar power (Pv) and forward velocity(v). The maximum net tractive coefficient was established at the tractive efficiency of 0.60 on the unplowed wheat stubble field : for the Challenger 65 tractor 0.855 ; 4WD 0.624 and MFWD 0.534 and on the plowed wheat stubble field with the tractive efficiency of 0.40 for the Challenger 65 tractor 0.82 : 4WD 0.57 and for tractor MFWD 0.48.

• Elastomers and Composites
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• v.45 no.4
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• pp.280-285
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• 2010

The CIIR blends with SBR, NBR and BR were prepared with various mixing ratios. The mechanical and physical properties of these blends, such as frictional coefficient, abrasion resistance, compression set, and specific gravity, were measured. In the permanent compression set measurement, the blends at the composition of 75 wt% CIIR showed the highest value, which means the lowest resistance to deformation. As SBR, NBR and BR blends with CIIR, the coefficient of friction of the mixtures showed a tendency to decrease in arithmetic average. In the case of blending CIIR with BR in order to increase the friction force, the negative effect due to reduction in abrasion resistance was greater than the positive effect of the improvement of the traction force caused by increasing friction coefficient.

• Structural Engineering and Mechanics
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• v.60 no.2
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• pp.313-335
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• 2016

In this article, a four-variable refined plate theory is presented for buckling analysis of functionally graded plates subjected to uniform, linear and non-linear temperature rises across the thickness direction. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. Young's modulus and Poisson ratio of the FGM plates are assumed to remain constant throughout the entire plate. However, the coefficient of thermal expansion of the FGM plate varies according to a power law form through the thickness coordinate. Equilibrium and stability equations are derived based on the present theory. The influences of many plate parameters on buckling temperature difference such ratio of thermal expansion, aspect ratio, side-to-thickness ratio and gradient index will be investigated.

• Wind and Structures
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• v.20 no.2
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• pp.143-168
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• 2015

A numerical model for analyzing air-train-track interaction is proposed to investigate the dynamic behavior of a high-speed train running on a track in crosswinds. The model is composed of a train-track interaction model and a train-air interaction model. The train-track interaction model is built on the basis of the vehicle-track coupled dynamics theory. The train-air interaction model is developed based on the train aerodynamics, in which the Arbitrary Lagrangian-Eulerian (ALE) method is employed to deal with the dynamic boundary between the train and the air. Based on the air-train-track model, characteristics of flow structure around a high-speed train are described and the dynamic behavior of the high-speed train running on track in crosswinds is investigated. Results show that the dynamic indices of the head car are larger than those of other cars in crosswinds. From the viewpoint of dynamic safety evaluation, the running safety of the train in crosswinds is basically controlled by the head car. Compared with the generally used assessment indices of running safety such as the derailment coefficient and the wheel-load reduction ratio, the overturning coefficient will overestimate the running safety of a train on a track under crosswind condition. It is suggested to use the wheel-load reduction ratio and the lateral wheel-rail force as the dominant safety assessment indices when high-speed trains run in crosswinds.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.159-165
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• 2003

Most engineers interested in stress singularities have focused mainly on the research of power stress singularities for v-notched cracks in dissimilar materials. The logarithmic stress singularity was discussed a little in Bogy's paper. The power-logarithmic stress singularity was reported by Dempsey and Sinclair. It was indicated that the logarithmic singularity is only a special case of power-logarithmic stress singularities. Then, Dempsey reported specific cases which have power-logarithmic singularities even fur homogeneous boundary conditions. It was known that logarithmic stress singularities for v-notched cracks in dissimilar materials occurs when the surfaces of a v-notched crack have constant tractions. In this paper, using the complex potential method, the stresses and displacements having logarithmic stress singularities were obtained and the coefficients vectors were calculated by a numerical program code: Mathematica. It was shown that our analysis models don't have logarithmic stress singularities under the constant tractions, although the coefficient vectors are existing.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.583-590
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• 1998

This study was performed to determine the kinetic friction coefficient bulk density, dynamic and static angle of repose, and terminal velocity of the chopped rice straw in the moisture range of 8~23%, which could be used for better design and operation of the processing machinery and handling facilities. Friction coefficient was determined from the horizontal traction force measured by pulling the container holding the mass of rice straw on the various plate materials. Bulk density was measured with an apparatus consisting of a filling funnel and a receiving vessel. Dynamic angle of repose was calculated from the photos of bulk samples piled by gravity flow on a circular platform. Static angle of repose was determined by measuring the side angle of the bulk material which was left in the cylindrical container after natural discharge of the bulk sample through a circular hole in the bottom plate. Kinetic friction coefficients of rice straw on the PVC, mild steel, stainless steel, and galvanized steel were in the range of 0.303~0.434, 0.222~0.439, 0.204~0.448, and 0.206~0.407, respectively. and indicated linear increase with moisture content. The effects of moisture change on the friction coefficients were in the order of PVC, mild steel, galvanized steel, and stainless steel. Bulk density, dynamic and static angle of repose, and terminal velocity were in the range of 56.8~60.3 kg/m$^3$, 41.4~45.9$^{\circ}$, 94.4~100.8$^{\circ}$, and 1.07~4.48 m/s, respectively, and were increased linearly with the moisture content.

• Journal of Biosystems Engineering
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• v.30 no.4 s.111
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• pp.229-234
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• 2005

Kinetic friction coefficient, bulk density, dynamic and static angle of repose, and terminal velocity of rice husk at the moisture range 7 to $23\%$ w.b. were determined. It could lead to better design and operation of the processing machinery and handling facilities. Friction coefficient was determined from the horizontal traction force measured by pulling the container holding a mass of rice husk on various plate materials. Dynamic angle of repose was calculated from the photos of bulk samples piled by gravity flow on a circular platform. Static angle of repose was determined by measuring the side angle of the bulk material which was left in a cylindrical container after natural discharge of the bulk sample through a circular hole in the bottom plate. Kinetic friction coefficients of rice husk were in the range of $0.254\~0.410,\;0.205\~0.520,\;0.229\~0.400,\;and 0.133\~0.420$ on PVC, mild steel, galvanized steel, and stainless steel, respectively. Bulk density, dynamic and static angle of repose, and terminal velocity were in the range of $91.7\~98.3$ $kg/m^3$, $40.2\~47.6^{\circ},\;52.8\~83.7^{\circ},$ and $1.36\~1.73$ m/s, respectively. These physical properties of rice husk increased linearly as the moisture content increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.512-519
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• 2016

In this study, the tire road friction estimation(TRFE) algorithm for controlling the rear wheel driving force of a 4WD vehicle during acceleration is developed using a standard sensor in an ordinary 4WD passenger car and a speed sensor. The algorithm is constructed for the wheel shaft torque, longitudinal tire force, vertical tire force and maximum tire road friction estimation. The estimation results of shaft torque and tire force were validated using a torque sensor and wheel force transducer. In the algorithm, the current road friction is defined as the proportion calculated between longitudinal and vertical tire force. Slip slop methods using current road friction and slip ratio are applied to estimate the road friction coefficient. Based on this study's results, the traction performance, fuel consumption and drive shaft strength performance of a 4WD vehicle are improved by applying the tire road friction estimation algorithm.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.621-625
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• 2012

Conventionally, to measure derailment coefficient of a railway wheel, strain gauges for lateral force measurement are attached to both side of the wheel. But narrow gap between railway wheel and traction motor makes it difficult to attache the strain gauges at the inner side of wheel. In this study, to overcome the hard accessibility to the strain gauge points by narrow gap, a new Wheatstone bridge connection method is presented by attaching all the strain gauges at the outer side of wheel with a new bridge connection. We evaluate the running safety of railway vehicles in accordance with railway safety regulations. The experimental results obtained shows higher sensitivity than conventional methods and the derailment coefficient measurement procedure becomes simpler.

• Journal of Biosystems Engineering
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• v.23 no.1
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• pp.1-12
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• 1998

This study was intended to investigate experimentally the effect of inflation pressure on tractive performance of bias-ply tires for agricultural tractors. Traction tests were conducted at the three velocities of 3, 4, and 5.5km/h under few different surface conditions using a 13.6-28 6PR bias-ply tire as driving wheel of the test tractor. When the inflation pressure was reduced from 250kPa to 40kPa by a decrement of either 30 or 50kPa depending upon the test surface conditions, some of the test results showed that the tractive coefficient and efficiency were increased maximally by 40% and 17％, respectively, at 20% slippage. However, it was failed to derive any consistent rules depicting the effect of inflation pressure of bias ply tires on the tractive performance of tractors.