• Transactions of the KSME C: Technology and Education
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• v.3 no.2
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• pp.125-130
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• 2015

Using flexible multibody system dynamic method, the rigid-flexible coupling multibody dynamic analysis model of the drum brake system was developed, and the kinematic and dynamic simulation of the system was processed as its object of study. Simulations show that the friction will increase with the dynamic friction coefficient, but high dynamic friction coefficient will cause the abnormal vibration and worsen the stability of the brake system, even the stability of the whole automobile. The modeling of flexible multi-body can effectively analyze and solve complex three-dimensional dynamic subjects of brake system and evaluate brake capability. Further research and study on this basis will result in a convenient and effective solution that can be much helpful to study, design and development of the brake system.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.17-23
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• 1998

The objective of this study is to investigate the dynamic behaviors of KHSR(Korea High-Speed Railway) bridge supported by elastomeric bearings subjected to high-speed vehicles. The effects of damping on the dynamic behaviors are also studied. The train composed of two power cars, two motor cars and eighteen passenger cars are simulated using constant moving forces for simplicity and effectiveness in the analysis. Direct integration method are used to solve the dynamic equation of motion. The bridge analyzed is real bridge with 2@40m span and concrete continuos box girder. The bridge is model led using frame element in three dimensional space. From the results of this study, the effects of elastomeric bearing on the dynamic responses of bridge(especially vertical accelerations) may cause undesirable behaviors. Damping are very important in the dynamic behaviors of the bridge subjected to high-speed railways. And so, dynamic analysis of steel bridge for high-speed railway supported by elastomeric bearings should be performed carefully.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.46-52
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• 1996

In this paper, an analytical method is proposed to find the dimensions of impact stresses with using the dimensions of impact loading parameter regardless of mass of impactor, velocity of impactor, and plate thickness. In analytical method of Impulsive stresses, the three-dimensional dynamic theory of elasticity using rectangular coordinates and the potential theory of displacement are utilized, and when the measurement of Impact loading is difficult especially for a steel ball colliding on an infinite plate, the impact loading can be obtained by using the classical plate theory and Hertz’s contact theory. And in the numerical analysis, the fast Fourier transform (F. F. T.) algorithm and the numerical inverse Laplace transformation are used because the analysis of impact loading Is difficult to obtain solutions by using the thress-dimensional dynamic theory of elasticity.

• Journal of KSNVE
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• v.5 no.2
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• pp.215-224
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• 1995

In this paper, the three-dimensional finite element model is established to investigate the structural dynamic characteristics of rotor blade using a finite element analysis. Six natural frequencies and mode shapes are calculated by computer simulation. The first three flapping modal frequencies, the first two lead-lag modal frequencies, and the first feathering modal frequency are validated through comparison with the modal test results of the fixed rotor blade. The computer simulation results are found in good agreement with experimentally measured natural frequencies. The important results are obtained as follows: (1) Natural frequencies are changed due to the variation of rotational speed and fiber angle of rotor blade, (2) Weak coupling between flapping mode shape and lead-lag mode shape are detected, (3) Centrifugal force has more effect on flapping modal frequency than lead-lag modal frequency.

• Journal of Power System Engineering
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• v.19 no.5
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• pp.80-85
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• 2015

The unsteady-state, incompressible and three-dimensional large eddy simulation(LES) was carried out to analyze the structure of turbulent flow fields according to the operating loads of three-dimensional small-size axial fan(SSAF). LES shows the best prediction performance in comparison with any other Reynolds averaged Navier-Stokes(RANS) method because static pressure coefficients analysed by LES show a little bit larger than measurements including all flow coefficients. Also, it can be known that the wake of SSAF is divided into from axial flow to radial flow before and behind stall region according to the increase of static pressure through LES analysis.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.301-318
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• 2017

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.99-104
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• 2009

This article describes the analysis of stable grasping for multi-fingered robot. An analysis method of stable grasping, which is based on the three-dimensional acceleration convex polytope, is proposed. This method is derived from combining dynamic equations governing object motion and robot motion, force relationship and acceleration relationship between robot fingers and object's gravity center through contact condition, and constraint equations for satisfying no-slip conditions at every contact points. After mapping no-slip condition to torque space, we derived intersected region of given torque bounds and the mapped region in torque space so that the intersected region in torque space guarantees no excessive torque as well as no-slip at the contact points. The intersected region in torque space is mapped to an acceleration convex polytope corresponding to the maximum acceleration boundaries which can be exerted by the robot fingers under the given individual bounds of each joints torque and without causing slip at the contacts. As will be shown through the analysis and examples, the stable grasping depends on the joint driving torque limits, the posture and the mass of robot fingers, the configuration and the mass of an object, the grasp position, the friction coefficients between the object surface and finger end-effectors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.935-941
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• 2006

The hysteretic behavior of steel structure under cyclic and dynami loading such as earthquake is different to that under static loading. Because structural steels on dynamic deformation is different to static deformation with respect with mechanical characteristics and stress-strain relationship. Therefore, to accurately predict the hysteretic behavior of steel structures such as circular steel columns under cyclic and dynamic loading, the difference of loading carrying capacity and deformation according to loading rate, assumed static and dynamic deformation state, must be investigated. In this study, numerical analyses of circular steel column using SM490 for change of loading rate and diameter-thickness ratio(D/t) were carried out by using three-dimensional elastic-plastic finite element analysis and dynamic cyclic plasticity model of SM490 developed by the authors. Characteristics of hysteretic behavior of circular steel column using SM490, load carrying capacity and energy dissipation ratio, were clarified by analysis results.

• Computers and Concrete
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• v.18 no.5
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• pp.1019-1039
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• 2016

In this paper, a parallel algorithm of nonlinear dynamic analysis of three-dimensional (3D) reinforced concrete (RC) frame structures based on the platform of graphics processing unit (GPU) is proposed. Time integration is performed using Newmark method for nonlinear implicit dynamic analysis and parallelization strategies are presented. Correspondingly, a parallel Preconditioned Conjugate Gradients (PCG) solver on GPU is introduced for repeating solution of the equilibrium equations for each time step. The RC frames were simulated using fiber beam model to capture nonlinear behaviors of concrete and reinforcing bars. The parallel finite element program is developed utilizing Compute Unified Device Architecture (CUDA). The accuracy of the GPU-based parallel program including single precision and double precision was verified in comparison with ABAQUS. The numerical results demonstrated that the proposed algorithm can take full advantage of the parallel architecture of the GPU, and achieve the goal of speeding up the computation compared with CPU.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.342-347
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• 2004

The dynamic responses of a PSC bridge for automated guide-way transit system are investigated by analytical approach of bridge-vehicle interaction. In this study, the dynamic responses, concerned with a spall on the surface of bridge are emphasized. A simply supported pre-stressed concrete bridge is adopted as a numerical example. Dynamics of three-dimensional dynamic interaction system between bridges and vehicles is considered in this study. The FE method and modal analysis is used for modeling a bridge for dynamic response analysis. An AGT vehicle is idealized as a model with 11DOFs including lateral motion. It was found that the dynamic responses of bridge can be affected by a spall of surface. Especially, the vibrations are increased much more when a spall is exist.