• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.294-304
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• 2003

An experimental analysis using three-dimensional laser Doppler velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.131-136
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• 2002

A computational analysis using Reynolds stress model in FLUENT is conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan at design condition ($\phi$=0.25) and off-design condition ($\phi$=0.21 and 0.30). The roll-up of tip leakage flow starts near the minimum static wall pressure position, and the tip leakage vortex developes along the centerline of the pressure trough within the blade passages. Near tip region, a reverse flow induced by tip leakage vortex has a blockage effect on the through-flow. As a result, high momentum region is observed below the tip leakage vortex. As the blade loading increases, the reverse flow region is more inclined toward circumferential direction and the onset position of the rolling-up of tip leakage flow moves upstream. Because the casing boundary layer becomes thicker, and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with blade loading increasing. The computational results show that a distinct tip leakage vortex is observed downstream of the blade trailing edge at $\phi$=0.30, but it is not observed at $\phi$=0.21 and 0.25.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.351-354
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• 2015

In this study, alumina plates 9~25 μm in size were used as thermal fillers, and epoxy resin was used as a polymer matrix. Oriented alumina plate/epoxy composites were prepared using a rolling method. The effect of ordering alumina plates increased with alumina plate size. The thermal conductivity and flexural strength of the composites were investigated. The horizontal thermal conductivity of the oriented composite was significantly higher than the vertical thermal conductivity. The horizontal thermal conductivity of the 75 wt% alumina content was 8.78 W/mk, although the vertical thermal conductivity was 1.04 W/mk. Ordering of the alumina plate using a rolling method significantly improved the thermal conductivity in the horizontal direction. The flexural strengths of the ordered alumina/epoxy composites prepared at different curing temperatures were measured.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.211-220
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• 2004

It is well known that the geometry of the articular surface has a major role in determining the position of articular contact and the lines of action for the contact forces. The contact force calculation of the knee joint under the effect of sliding and rolling is one of the most challenging issues in this field. We present a 3-D human knee joint model including sliding and rolling motions and major ligaments to calculate the lateral and medial condyle contact forces from the recovered total internal reaction force using inverse dynamic contact modeling and the Least-Square method. As results, it is believed that the patella, muscles and tendon affect a lot for the internal reaction forces at the initial heel contact stage. With increasing flexion angles during gait, the decreasing contact area is progressively shifted to the posterior direction on the tibia plateau. In addition, the medial side contact force is larger than the lateral side contact force in the knee joint during normal human walking. The total internal forces of the knee joint are reasonable compared to previous studies.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.595-600
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• 2011

This paper investigates the effect of strain rate on the anisotropic deformation behavior of advanced high strength steel sheets. Uniaxial tensile tests were carried out on TRIP590 and DP780 steel sheets at strain rates ranging from 0.001/sec to 100/sec to determine yield stresses and r-values at various loading angles from the reference rolling direction. R-values were determined by the digital image correlation technique. Hill48 and Yld2000-2d yield functions were tested for their capability to describe the plastic deformation anisotropy of the materials. Initial yield loci were constructed using the Yld2000-2d yield function, which adequately described the anisotropic behavior of the materials. The shape of the initial yield loci was found to change with different strain rate, and the anisotropic behavior decreased with increasing strain rate.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1281-1282
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• 2007

Effect of tension coating on reducing iron losses of thin grain-oriented 3% Si-Fe steel sheets was investigated. Conventional grain-oriented electrical steel sheets have a forsterite coating layer and a tension coating layer in order to apply tensile stress to the rolling direction of the sheets. However the proposed coating method in this paper is to form only a tension coating layer on the both surfaces of the sheets. Iron losses with the tension coating were reduced by 8% under the condition of 1.7 T and 60 Hz. Consequently the proposed tension coating is applicable to $80{\mu}m$-thick 3% Si-Fe steel sheets.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.3-12
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• 1984

Up to now, it has been common to treat the maneuvering motion of a ship as a 3-degree-freedom motion i.e. surge, sway and yaw on the sea surface, for the simplicity and mathematical calculation, and it is quite acceptable in the practical point of view. Meanwhile, considering the maneuverability of a ship under the special conditions such as in irregular waves, in wind or at high speed with small GM value, it is required that roll effect must be considered in the equation of ship motion. In this paper the author tried to build up the 4-degree-freedom motion equation by adding roll. And then, applying the M.M.G.'s mathematical model and with captive model test results the roll-coupled hydrodynamic derivatives were found. With these the author could make some simulating program for turning and zig-zag steering. Through the computer simulations, the effect of roll to the ship maneuver became clear. The effect of the wind force to the maneuverability was also found. Followings are such items that was found. 1) When roll is coupled in the maneuvering motion, the directional stability becomes worse and the turning diameter becomes smaller as roll becomes smaller as roll becomes larger. 2) When maneuver a ship in the wind, the roll becomes severe and the directional stability becomes worse. 3) When a ship turns to the starboard side, the wind blowing from 90 degree direction to starboard causes the largest roll and the largest turning diameter, and the wind from other direction doesn't change the turning diameter. 4) When a ship is travelling with a constant speed with rudder amidship, if steady wind blows from one direction, the ship turns toward that wind. This phenomenon is observed in the actual seaways.

• Journal of the Korean Wood Science and Technology
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• v.51 no.4
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• pp.239-252
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• 2023

In this study, bending and compression strength tests were performed to investigate effect of composition of layer layout of Larix cross-laminated timber (CLT) on mechanical properties. The Larix CLT consists of five laminae, and specimens were classified into four types according to grade and composition of layer. The layer's layout were composited as follows 1) cross-laminating layers in major and minor direction (Type A), and 2) cross-laminating external layer in major direction and internal layer applied grade of layer in minor direction (Type B). E12 and E16 were used as grades of lamina for major direction layer of Type A and external layer of Type B according to KS F 3020. In results of the bending test of CLT using same grade layer according to layer composition, the modulus of elasticity (MOE) of Type B was higher than Type A. In case of prediction of bending MOE of Larix CLT, the experimental MOE was higher than 1.00 to 1.09 times for Shear analogy method and 1.14 to 1.25 times for Gamma method. Therefore, it is recommended to predict the bending MOE for Larix CLT by shear analogy method. Compression strength of CLT in accordance with layer composition was measured to be 2% and 9% higher for Type A using E12 and E16 layers than Type B, respectively. In failure mode of Type A, progress direction of failure generated under compression load was confirmed to transfer from major layer to minor layer by rolling shear or bonding line failure due to the middle lamina in major direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.145-153
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• 1991

A numerical simulation of the nonsteady state rolling process in the plane strain condition is presented in the basis of the rigid-plastic finite element method by considering large deformation. In order to apply the large deformation theory to the numerical method for sheet rolling problems, constitutive equation relating 2nd-Piola Kirchhoff stress and Lagrangian strain which reflect geometrical nonlinearity is used. To confirm the validity of the developed algorithm, the analysis of the neutral flow region, roll separating force, torque, pressure and stress/strain distributions on the workpiece is conducted from the bite of the material until the steady state is reached. The computed results of the roll force and torque in the present finite element analysis are lower than those corresponding to small strain theory. The pressure distribution at the work piece-roll interface is found to show the typical 'friction hill' type only. The peak value in near the neutral region, however, is good agrements with the existing results. the neutral region, however, is good agrements with the existing results. The frictional force at the roll interface provide detailed information about the neutral point where the shear forces change direction. In addition, the analysis also includes the effect and influence of material condition, strip thickness, work roll diameter, as well as roll speed and lubricant on each deformation process.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.39-44
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• 2011

This study was to investigate the effects of stress ratio and anisotropy on Fatigue Crack Propagation(FCP) behavior of rolled magnesium alloy AZ31B. The experimental materials were a Mg-Al-Zn magnesium alloy. The FCP test was conducted on compact tension specimen by a servo-hydraulic fatigue testing machine in air at room temperature. Compact tension specimens were prepared from the extruded parallel and vertical rolling direction. The test condition was frequency of 10Hz and sinusoidal load stress ratios are 0.1 and 0.7. The FCP rates was automatically measured by a compliance method. In the case of the FCP of AZ31B, the FCP of both direction of LT and TL by anisotropy of specimens are almost same value. In lower stress ratio, the FCP of the LT, TL specimens are increased in lower ${\Delta}K$ region but higher ${\Delta}K$ regions are almost same value. Finally, the result of observed the surface crack, it expressed the quasi-cleavage fracture in lower ${\Delta}K$ region and straight mark on the aspect of the facet in high ${\Delta}K$ region.