• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1183-1189
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• 2015

This study focuses on the design of the tapered joints of a wind power turbine. The main variables of the tapered joint are the transmitted torque, shaft diameter, contact area of the tapered ring, and tightening torque of the bolts, which applies a compressive pressure from the hub to the shaft. The stress distribution of the taper fit was calculated under axisymmetric plane strain conditions because of the small taper angle. The axial displacement of the clamp can be calculated from the radial elastic deformation and the taper angle. The stress field of each ring is obtained from the cylinder stress equation. To verify the accuracy of the calculation, finite element (FE) analysis was performed, and the results of the calculation and FE analysis were compared. The hoop stress of the tapered surface showed a discrepancy of approximately 10, but the trends of the stress distributions of each component and the relative movement obtained by FE analysis were in good agreement with the analytical calculation results.

• Steel and Composite Structures
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• v.35 no.3
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• pp.343-351
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• 2020

The present research deals with the multi-dual-phase-lags thermoelasticity theory for thermoelastic behavior of transversely isotropic thermoelastic thin circular plate The Laplace and Hankel transform techniques have been used to find the solution of the problem. The displacement components, stress components, and conductive temperature distribution are computed in the transformed domain with the radial distance and further determined in the physical domain using numerical inversion techniques. The effect of rotation and two temperature are depicted graphically on the resulting quantities.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.752-757
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• 2001

To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The ranked bidirectional evolutionary structural optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2931-2936
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• 2013

This paper presents results for the calculation of transport properties of noble gases (He, Ne, Ar, Kr, and Xe) at 273.15 K and 1.00 atm using equilibrium molecular dynamics (EMD) simulations through a Lennard-Jones (LJ) intermolecular potential. We have utilized the revised Green-Kubo formulas for the stress (SAC) and the heat-flux auto-correlation (HFAC) functions to estimate the viscosities (${\eta}$) and thermal conductivities (${\lambda}$) of noble gases. The original Green-Kubo formula was employed for diffusion coefficients (D). The results for transport properties (D, ${\eta}$, and ${\lambda}$) of noble gases at 273.15 and 1.00 atm obtained from our EMD simulations are in a good agreement with the rigorous results of the kinetic theory and the experimental data. The radial distribution functions, mean square displacements, and velocity auto-correlation functions of noble gases are remarkably different from those of liquid argon at 94.4 K and 1.374 $g/cm^3$.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.604-610
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• 1999

Vibration of a rotor-bearing system driven by an electric motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the air-gap. With the advent of new high-energy magnets together with high precision motor applications, magnetic sources of vibration are becoming more serious. This paper investigates the transient whirl responses of a rotor system with purely mechanical origins and compares it with that of magnetically coupled origins. A perturbation method is applied to model the magnetic field associated with rotor eccentricity. Electromagnetic forces are obtained by the Maxwell stress method, which utilizes the analytical expression of radial flux density distribution. The FEM was applied to a rotor-motor system to illustrate magnetically coupled effects in rotor dynamics. Results show that magnetically coupled sources significantly affect the vibration of the rotor-motor system.

• Macromolecular Research
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• v.9 no.3
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• pp.129-142
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• 2001

To efficiently demonstrate the molecular motion, physical properties, and mechanical properties of polycarbonates, we studied the differences between bisphenol-A polycarbonate(BPA-PC) and tetramethyl bisphenol-A-polycarbonate(TMBPA-PC) using molecular modeling techniques. To investigate the conformations of BPA-PC and TMBPA-PC and the effect of the conformation on mechanical properties, we performed conformational energy calculation, molecular dynamics calculation, and stress-strain curves based on molecular mechanics method. From the result obtained from conformational energy calculations of each segment, the molecular motions of the carbonate and the phenylene group in BPA-PC were seen to be more vigorous and have lower restriction to mobility than those in TMBPA-PC, respectively. In addition, from the results of radial distribution function, velocity autocorrelation function, and power spectrum, BPA-PC appeared to have higher diffusion constant than TMBPA-PC and is easier to have various conformations because of the less severe restrictions in molecular motion. The result of stress-strain calculation for TMBPA-PC seemed to be in accordance with the experimental value of strain-to-failure ∼4%. From these results of conformational energy calculations of segments, molecular dynamics, and mechanical properties, it can be concluded that TMBPA-PC has higher modulus and brittleness than BPA-PC because the former has no efficient relaxation mode against the external deformations.

• Steel and Composite Structures
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• v.38 no.2
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• pp.189-211
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• 2021

An analytical solution is presented to analyze the thermoelastoplastic response of a rotating thick-walled cylindrical pressure vessel made of functionally graded material (FGM). The analysis is based on Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. The uncoupled theory of thermoelasticity is used, and the plane strain condition is assumed. The material properties except for Poisson's ratio, are assumed to vary nonlinearly in the radial direction. Elastic, partially plastic, fully plastic, and residual stress states are investigated. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the vessel. It is assumed that the inner surface is exposed to an airstream and that the outer surface is exposed to a uniform heat flux. Tresca's yield criterion and its associated flow rule are used to formulate six different plastic regions for a linearly hardening condition. All these stages are studied in detail. It is shown that the thermoelastoplastic stress response of a rotating FGM pressure vessel is affected significantly by the nonhomogeneity of the material and temperature gradient. The results are validated with those of other researchers for appropriate values of the system parameters and excellent agreement is observed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.912-921
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• 1999

Shear stress acting on the arterial wall by blood flow is an important hemodynamic factor influencing blocking of blood vessel by thickening of an arterial wall. In order to study the effects of wall elasticity on the wall shear rate distribution in an artery-divergent graft anastomosis, a rigid and a elastic model are manufactured. These models are placed in a pulsatile flow loop, which can generate the desired flow waveform. Flow visualization method using a photochromic dye is used to measure the wall shear rate distribution. The accuracy of measuring technique is verified by comparing the measured wall shear rate in the straight portion of a model with the theoretical solution. Measured wall shear rates depend on the wall elasticity and flow waveform. The mean and maximum shear rate in the elastic model are lower than those in rigid model, and the decreases are more significant near the end of a divergent tube. The reduction of mean and maximum of wall shear rate in an elastic model are up to 17 percent.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.304-311
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• 2001

This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.479-486
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• 2011

In this study, we conducted experiment and finite element analysis on the flexural behavior of the round concrete panels according to the evaluation method of biaxial flexural tensile strengths. The Round Panel Test (RPT) and the Biaxial Flexure Test (BFT) were used to determine the biaxial flexural strength of round plain concrete panels. In order to understand the stress distribution on the panels, we measured load-strain relationship at the center of the panels' bottom surface. Test results show that fracture pattern in RPT and BFT panels are similar, and the tensile stress distribution is uniform in all directions at the center of the bottom surface of the panels for both RPT and BFT. The distribution of stresses in two test specimens coincided with the analysis result. The average biaxial flexural strength of RPT is about 29% greater than those of the BFT. The coefficient of variations (COV) of the RPT and BFT for the biaxial flexure strength is 8%, 6%, respectively, which indicates that BFT method is useful and reliable for determining biaxial flexural strengths of the concrete.