• Journal of KSNVE
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• v.5 no.1
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• pp.75-83
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• 1995

The fluctuation of the engine torque appears to be the major source of the torsional vibration of the automotive driveline. The reduction of this torsional vibration has become a significant problem, due to an increase in the fluctuation of the torque of recent light weighted and high powered engines, along with the requirements of higher performance. The torsional vibration of the automotive driveline can be reduced by smoothing the fluctuation by adjusting the torsional characteristics of the clutch-disc. This paper presents an experimental and theoretical research on the clutch-disc torsional characteristics for the reduction of the torsional vibration at driving. The effects of clutch-damper on diminishing the torsional vibration were investigated experimentally. A dynamic model for the automotive driveline was developed, and the engine torque of the model were evaluated with experimental data. By executing a simulation using the model, it has become possible to obtain the clutch-disc torsional characteristics and the clutch-disc torsional characteristics for reducing the torsional vibration has been suggested. The results are as follows: (1) By exceuting simulations using nonlinear model of four degrees of freedom, a design technique to determine the clutch-disc torsional characteristics for reducing the torsional vibration at driving was developed. (2) The influence of barious torsional characteristics of the clutch has been studied in examining design parameters, which indicates that the domain to minimize the torsional vibration at driving depends on the characteristics of the clutch-damper, i. e., spring constant and hysteresis.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.113-120
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• 2013

This paper proposes a design optimization approach for core of solenoid actuators by combining optimization techniques with the finite element method (FEM). A solenoid is an important element part which hydraulically controls a transmission system, etc. The demanded feature of the solenoid is that it performs an electromagnetic force output being constant regardless of the stroke and being proportional to coil current. The plunger compresses a spring with a minimum force of 12 N over an 1.7 mm travel. The orthogonal array, analysis of variance (ANOVA) techniques and response surface optimization, are employed to determine the main effects and their optimal design variables. The methodology is demonstrated as a optimization tool for the core design of a solenoid actuator.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.301-310
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• 2016

There are differences in seismic behavior between non-skewed bridges and skewed bridges due to in-plane rotations caused by pounding between the skewed deck and its abutments during strong earthquake. Many advances have been made in developing design codes and guidelines for dynamic analyses of non-skewed bridges. However, there remain significant uncertainties with regard to the structural response of skewed bridges caused by unusual seismic response characteristics. The purpose of this study is performing non-linear time history analysis of the bridges using abutment-soil interaction model considering pounding between the skewed deck and its abutments, and analyzing global seismic behavior characteristics of the skewed bridges to assess the possibility of unseating. Refined bridge model with abutment back fill, shear key and elastomeric bearing was developed using non-linear spring element. In order to evaluate the amplification of longitudinal and transverse displacement response, non-linear time history analysis was performed for single span bridges. Far-fault and near-fault ground motions were used as input ground motions. According to each parameter, seismic behavior of skewed bridges was evaluated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.126-129
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• 2010

MEMS(micro electro-mechanical systems) inertial switch which is applicable to the ignition Safe-Arm- Unit of propulsion system is devised. The MEMS inertial switch is designed according to the general design procedure for conventional mechanical elements. Unlikely conventional MEMS accelerometer, threshold inertial switching mechanism is adopted which makes a MEMS element an abrupt switching in a certain acceleration level. By comparing the design data and test results of the specimen a small discrepancy in switching acceleration level is found which is presumably due to the nonlinear characteristics of the beam spring and the flexure hinge which are the main parts of the MEMS inertial switch.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.327-346
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• 2017

Laminated plates have many applications in different industrials. Buckling analysis of these structures with the nano-scale reinforcement has not investigated yet. However, buckling analysis of embedded laminated plates with nanocomposite layers is studied in this paper. Considering the single-walled carbon nanotubes (SWCNTs) as reinforcement of layers, SWCNTs agglomeration effects and nonlinear analysis using numerical method are the main contributions of this paper. Mori-Tanaka model is applied for obtaining the equivalent material properties of structure and considering agglomeration effects. The elastic medium is simulated by spring and shear constants. Based on first order shear deformation theory (FSDT), the governing equations are derived based on energy method and Hamilton's principle. Differential quadrature method (DQM) is used for calculating the buckling load of system. The effects of different parameters such as the volume percent of SWCNTs, SWCNTs agglomeration, number of layers, orientation angle of layers, elastic medium, boundary conditions and axial mode number of plate on the buckling of the structure are shown. Results indicate that increasing volume percent of SWCNTs increases the buckling load of the plate. Furthermore, considering agglomeration effects decreases the buckling load of system. In addition, it is found that the present results have good agreement with other works.

• Steel and Composite Structures
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• v.23 no.6
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.57-65
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• 2000

In this paper, a model reference adaptive control for the atomic force microscope (AFM) of tapping mode is investigated. The dynamics between the AFM system and al sample is mathematically modeled as a second order spring-mass-damper system with oscillatory inputs. The attractive and repulsive forces between the tip of the AFM system and the sample are derived using the Lennard-Jones potential energy. By non-dimensionalizing the displacement of the tip and the input frequency, the chaotic behavior near a resonance frequency is better depicted through the non-dimensionalized equations. Four nonlinear analysis techniques, a phase portrait, sensitive dependence on initial conditions, a power spectral density function, and a Pomcare map are investigated. Because the equations of motion derived in this paper involve unknown parameter values such as the damping effect of the air and the interaction constants between materials, the standard model reference adaptive control is adopted. Two control objectives, the prevention of chaos and the tracking of reference signal, are pursued. Simulation results are included.

• Journal of The Korean Astronomical Society
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• v.24 no.2
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• pp.151-159
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• 1991

Using the photographic imagery of the SO galaxy NGC 5102, the equivalent luminosity profile and the fractional integrated luminosity curve have been derived. Several photometric parameters of the galaxy, such as a total magnitude ($B_T$), equivalent radius ($r^*_e$), effective surface brightness (${\mu}^*_e$), and concentration indices ($C_{21}$, $C_{32}$) were derived from the luminosity profiles. According to the decomposition method from the nonlinear least squares fitting, photometric parameters of the bulge (${\mu}_e$, $r_e$) and the exponential disk (${\mu}(0)$, ${\alpha}^{-1}$), and the bulge to total luminosity ratio (B/T) were obtained. The derived central disk surface brightness (${\mu} (0)\;=\;22.06\;{\pm}\;0.18\;mag/\Box"$) and the evaluated B/T ratio (= 0.52) of the NGC 5102 are close to the mean values (${\mu} (0)\;=\;21.65\;{\pm}\;0.3\;mag/\Box"$, B/T=0.63) of the SO galaxies. Analysis showed that a lens-like hump is embedded in the equivalent luminosity profile of the NGC 5102.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.244-247
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• 2005

Although several artificial disc designs have been developed for the treatment of discogenic low back pain and used clinically, biomechanical change with its implantation seldom studied. To evaluate the effect of artificial disc implantation on the biomechanics of lumbar spinal unit, nonlinear three-dimensional finite element model of L1-L5, S1 was developed and strain and stress of vertebral body and surrounding spinal ligaments were predicted. Intact osteoligamentous L1-L5, S1 model was created with 1-mm CT scan of a volunteer and known material property of each element were applied. This model also includes the effect of local muscles which was modeled with pre-strained spring elements. The intact model was validated with reported biomechanical data. Two models implanted with artificial discs, SB Charite or Prodisc, at L4/5 via anterior approach were also developed. The implanted model predictions were compared with that of intact model. Angular motion of vertebral body, force on spinal ligaments, facet joint contact force with $2\sim12$ Nm flexion-extension moment.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.209-218
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• 2004

The purpose of this paper is to suggest a practical and simple method for the identification of the joint mechanical properties and to apply it to human knee joints. The passive moment at a joint was modeled by three mechanical parts, that is, a gravity term, a linear damper term and a nonlinear spring term. Passive pendulum tests were performed in 5 fat and 5 thin men. The data of pendulum test were used to identify the mechanical properties of joints through sequential quadratic programming (SQP) with random initial values. The identification was successful where the normalized root-mean-squared (RMS) errors between the simulated and experimental joint angle trajectories were less than 10％. The parameter values of mechanical properties obtained in this study agreed with literature. The inertia, gravity and the damping constant were greater at fat men, which indicates more resistance to body movement and more energy consumption fer fat men. The suggested method is noninvasive and requires simple setup and short measurement time. It is expected to be useful in the evaluation of joint pathologies.