• Journal of the Korean Society for Heat Treatment
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• v.10 no.1
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• pp.47-54
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• 1997

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occuring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Ni on the damping capacities and mechanical properties are investigated in 3.9%C-0.3% Cu gray cast iron. At 0.2% Ni content, specific damping capacity showed the maximum value, and decreased with further increase in Ni content, Graphite continuity also showed same behavior. This indicates that the specific damping capacity has a close relation with graphite continuity. On the other hand, the damping capacity in pearlite matrix showed superior to that in ferrite. In contrast, with increasing the Ni content, both tensile strength and hardness increased due to the decrease of graphite length and eutectic cell size.

• Journal of Drive and Control
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• v.16 no.3
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• pp.33-41
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• 2019

This study presents the development of a lifetime test bench for the strain wave reducer which is a precision gear reducer of the robot to realize fault diagnosis and failure prognostics. To this end, the lifetime test bench was designed to detect the vertical forward/reverse direction rotation load. Through the lifetime test bench, it is possible to apply the same load spectrum from robot working scenarios. We developed a data integration gateway for fault data collection. Through the development of dedicated software for fault diagnosis and failure prognostics, these data from vibration, noise and temperature sensors were collected and analyzed along with the operation of the lifetime evaluation.

• Journal of Drive and Control
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• v.16 no.2
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• pp.43-50
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• 2019

The objective of this study was to reverse engineer a swash plate type piston pump mounted on a wheeled armored vehicle and to analyze the structure of the pump case. From the analysis, the weak parts were identified and corrected in the final design. Each element corresponding to the piston pump case was analyzed. The analytical method was given static boundary conditions, load conditions and confirmed displacement, strain, stress, and safety factor. Plastic deformation and damage were also confirmed and the component elements redesigned through structural analysis Structural analysis and vibration analysis were carried out for the components of the piston pump case. The piston pump model was finally modified by structural analysis and vibration analysis results for each component assembly, and a prototype was designed. Durability test and environmental test were carried out and the test results satisfied all of the requirements. Therefore, the analytical method presented in this study can be utilized as a methodology for element component design in the development of various piston pumps.

• Wind and Structures
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• v.35 no.5
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• pp.337-351
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• 2022

As central-slotted box decks usually have excellent flutter performance, studies on this type of deck mostly focus on the vortex-induced vibration (VIV) control. Yet with the increasing span lengths, cable-supported bridges may have critical wind speeds of wind-induced static instability lower than that of the flutter. This is especially likely for bridges with a central-slotted box deck. As a result, the overall aerodynamic performance of such a bridge will depend on its wind-induced static stability. Taking a 1400 m-main-span cable-stayed bridge as an example, this study investigates the influence of a series of deck shape parameters on both static and flutter instabilities. Some crucial shape parameters, like the height ratio of wind fairing and the angle of the inner-lower web, show opposite influences on the two kinds of instabilities. The aerodynamic shape optimization conducted for both static and flutter instabilities on the deck based on parameter-sensitivity studies raises the static critical wind speed by about 10%, and the overall critical wind speed by about 8%. Effective VIV countermeasures for this type of bridge deck have also been proposed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.237-242
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• 2022

Acquiring high-quality images in control and measurement systems is one of the important factors. Among image acquisition technologies, SFF (Shape from Focus) is a technology for recovering a 3D shape by acquiring 2D images with different focus levels by moving an object at a predetermined step size along the optical axis. For SFF, when an object is moved at a constant step size, mechanical vibration, referred as jitter noise, occurs in each step along the optical axis. In this paper, a new state estimation filter is designed and applied for reducing the jitter noise. For the application of the proposed method, the jitter noise and focus curves are modeled as Gaussian function. Experimental results demonstrate the effectiveness of proposed method.

• Earthquakes and Structures
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• v.24 no.4
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• pp.237-245
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• 2023

Based on novel Galerkin's technique, the theoretical study gives a prediction to estimate the vibrations of FG rotating cylindrical shell. Terms of ring supports have been introduced by a polynomial function. Three different laws of volume fraction are utilized for the vibration of cylindrical shells. Variation frequencies with the locations of ring supports have been analyzed and these ring supports are placed round the circumferential direction. The base of this approach is an approximate estimation of eigenvalues of proper functions which are the results of solutions of vibrating equation. Each longitudinal wave number corresponds to a particular boundary condition. The results are given in tabular and graphical forms. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. There is a new form of frequencies is obtained for different positions of ring supports, which is bell shaped. Moreover, on increasing the rotating speed, the backward frequencies increase and forward frequencies decreases.

• Advances in nano research
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• v.14 no.4
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• pp.303-312
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• 2023

In this study, the bifurcation analysis of functionally graded material is done using exponential volume fraction law. Shell theory of Love is used for vibration of shell. The Galerkin's method is applied for the formation of three equations in eigen value form. This eigen form gives the frequencies using the computer software MATLAB. The variations of natural frequencies (Hz) for Type-I and Type-II functionally graded cylindrical shells are plotted for exponential volume fraction law. The behavior of exponent of volume fraction law is seen for three different values. Moreover, the frequency variations of Type-I and -II clamped simply supported FG cylindrical shell with different positions of ring supports against the circumferential wave number are investigated. The procedure adopted here enables to study vibration for any boundary condition but for brevity, numerical results for a cylindrical shell with clamped simply supported edge condition are obtained and their analysis with regard various physical parameters is done.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.751-764
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• 2023

In practical engineering such as aerial refueling pipes, the boundary of the fluid-conveying pipe is difficult to be completely immovable. Pipes under movable and immovable boundaries are controlled by different dominant nonlinear factors, where the boundary mobility will affect the nonlinear dynamic characteristics, which should be focused on for adopting different strategies for vibration suppression and control. The nonlinear dynamic instability characteristics of functionally graded fluid-conveying pipes lying on a viscoelastic foundation under movable and immovable boundary conditions are systematically studied for the first time. Nonlinear factors involving nonlinear inertia and nonlinear curvature for pipes with a movable boundary as well as tensile hardening and nonlinear curvature for pipes with an immovable boundary are comprehensively considered during the derivation of the governing equations of the principal parametric resonance. The stability boundary and amplitude-frequency bifurcation diagrams are obtained by employing the two-step perturbation- incremental harmonic balance method (TSP-IHBM). Results show that the movability of the boundary of the pipe has a great influence on the vibration amplitude, bifurcation topology, and the physical meanings of the stability boundary due to different dominant nonlinear factors. This research has guidance significance for nonlinear dynamic design of fluid-conveying pipe with avoiding in the instability regions.

• Korean Journal of Artificial Intelligence
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• v.11 no.4
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• pp.21-27
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• 2023

This paper discusses a deep learning-based road surface analysis system that collects data by installing vibration sensors on the 4-axis wheel bearings of a vehicle, analyzes the data, and appropriately classifies the characteristics of the current driving road surface for use in the vehicle's control system. The data used for road surface analysis is real-time large-capacity data, with 48K samples per second, and the A2B protocol, which is used for large-capacity real-time data communication in modern vehicles, was used to collect the data. CAN and CAN-FD commonly used in vehicle communication, are unable to perform real-time road surface analysis due to bandwidth limitations. By using A2B communication, data was collected at a maximum bandwidth for real-time analysis, requiring a minimum of 24K samples/sec for evaluation. Based on the data collected for real-time analysis, performance was assessed using deep learning models such as LSTM, GRU, and RNN. The results showed similar road surface classification performance across all models. It was also observed that the quality of data used during the training process had an impact on the performance of each model.

• Structural Engineering and Mechanics
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• v.61 no.5
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• pp.675-684
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• 2017

In this paper, a hybrid seismic response control (HSRC) system was developed to control bridge behavior caused by the seismic load. It was aimed at optimum vibration control, composed of a rubber bearing of passive type and MR-damper of semi-active type. Its mathematical modeling was driven and applied to a bridge model so as to prove its validity. The bridge model was built for the experiment, a two-span bridge of 8.3 meters in length with the HSRC system put up on it. Then, inflicting the EI Centro seismic load on it, shaking table tests were carried out to confirm the system's validity. The experiments were conducted under the basic structure state (without an MR-damper applied) first, and then under the state with an MR-damper applied. It was also done under the basic structure state with a reinforced rubber bearing applied, then the passive on/off state of the HSRC system, and finally the semi-active state where the control algorithm was applied to the system. From the experiments, it was observed that pounding rather increased when the MR-damper alone was applied, and also that the application of the HSRC system effectively prevented it from occurring. That is, the experiments showed that the system successfully mitigated structural behavior by 70% against the basic structure state, and, further, when control algorithm is applied for the operation of the MR-damper, relative displacement was found to be effectively mitigated by 80%. As a result, the HSRC system was proven to be effective in mitigating responses of the two-span bridge under seismic load.