• Title/Summary/Keyword: Vibration characteristics

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Dynamic characteristics of single door electrical cabinet under rocking: Source reconciliation of experimental and numerical findings

  • Jeon, Bub-Gyu;Son, Ho-Young;Eem, Seung-Hyun;Choi, In-Kil;Ju, Bu-Seog
    • Nuclear Engineering and Technology
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    • v.53 no.7
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    • pp.2387-2395
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    • 2021
  • Seismic qualifications of electrical equipment, such as cabinet systems, have been emerging as the key area of nuclear power plants in Korea since the 2016 Gyeongju earthquake, including the high-frequency domain. In addition, electrical equipment was sensitive to the high-frequency ground motions during the past earthquake. Therefore, this paper presents the rocking behavior of the electrical cabinet system subjected to Reg. 1.60 and UHS. The high fidelity finite element (FE) model of the cabinet related to the shaking table test data was developed. In particular, the first two global modes of the cabinet from the experimental test were 16 Hz and 24 Hz, respectively. In addition, 30.05 Hz and 37.5 Hz were determined to be the first two local modes in the cabinet. The high fidelity FE model of the cabinet using the ABAQUS platform was extremely reconciled with shaking table tests. As a result, the dynamic properties of the cabinet were sensitive to electrical instruments, such as relays and switchboards, during the shaking table test. In addition, the amplification with respect to the vibration transfer function of the cabinet was observed on the third floor in the cabinet due to localized impact corresponding to the rocking phenomenon of the cabinet under Reg.1.60 and UHS. Overall, the rocking of the cabinet system can be caused by the low-frequency oscillations and higher peak horizontal acceleration.

Vibrational characteristics of sandwich annular plates with damaged core and FG face sheets

  • Xi, Fei
    • Steel and Composite Structures
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    • v.44 no.1
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    • pp.65-79
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    • 2022
  • The main goal of this paper is to study the vibration of damaged core laminated annular plates with FG face sheets based on a three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. In this study the effect of microcracks on the vibrational characteristic of the sandwich plate is considered. In particular, the structures are made by an isotropic core that undergoes a progressive uniform damage, which is modeled as a decay of the mechanical properties expressed in terms of engineering constants. These defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as "isotropic damage" and it is fully described by a scalar parameter. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular plate is assumed to have any arbitrary boundary conditions at the circular edges including simply supported, clamped and, free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution, and boundary conditions.

Application of Finite Element Analysis for Structural Stability Evaluation of Modern and Contemporary Sculptures: 'Eve 58-1' by Man Lin Choi

  • Kwon, Hee Hong;Shin, Jeong Ah;Cho, Nam Chul
    • Journal of Conservation Science
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    • v.38 no.4
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    • pp.277-288
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    • 2022
  • 'Eve 58-1', the subject of this study is a statue made of plaster and its structural stability was evaluated by utilizing the CAE program in order to prevent the risk of damage arising from impact and vibration that are generated during the packaging and transportation process given its material characteristics. CAE is an abbreviation for Computer Applied Engineering for realization by predicting changes at the time of application of virtual physical energy. It is applied by reflecting the physical property conditions and each boundary condition of plaster, and the digital images of the internal and external structure of the work were acquired through 3D scanning and CT analysis for interpretation by executing finite element modeling. When acceleration is applied to the work in the direction of its own weight, the left-right side and the front-rear side, it was possible to confirm a maximum displacement value of 15.24 mm in the head section of the front-rear side direction that has been tilted by approximately 27° from the Y-axis and the largest stress value of 12.46 MPa was at the left ankle section. The corresponding results confirmed that the left ankle section is the most vulnerable area and the section for which precautions need to be exercised and supplemented at the time of transporting the work by means of objective values.

In-situ Deposition Rate Measurement System to Improve the Accuracy of the Film Formation Process (성막 공정 정밀도 향상을 위한 실시간 성막 속도 측정 시스템)

  • Somi Park;Seung-Yo Baek;Hyun-Bin Kim;Jonghee Lee;Jae-Hyun Lee
    • Applied Chemistry for Engineering
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    • v.34 no.4
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    • pp.383-387
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    • 2023
  • The quartz crystal microbalance (QCM), commonly used in high vacuum deposition, becomes difficult to use when a thick film is deposited on the quartz, affecting the crystal's inherent vibration. In this study, a non-destructive optical measurement method was developed to measure the film's deposition rate during the in-situ film deposition process. By measuring the scattered laser intensity caused by the dimer in the parylene gas passing through the gas flow path, it was successfully confirmed that the ratio of the dimer in the parylene gas increases as the pyrolysis temperature decreases. Additionally, it was noted that the film's thickness and haze increase as the pyrolysis temperature decreases by confirming the characteristics of the visible parylene films. Through the research results, we aim to utilize the stable in-situ film deposition rate measurement system to control the precise film deposition rate of parylene films.

Electrochemical Properties of Sub-micron Size Si Anode Materials Distributed by Wet Sedimentation Method (습식 분급으로 입도 조절된 서브 마이크론 크기의 Si 음극활물질의 전기화학적 특성 분석)

  • Jin-Seong Seo;Hyun-Su Kim;Byung-Ki Na
    • Korean Chemical Engineering Research
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    • v.61 no.1
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    • pp.39-44
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    • 2023
  • In this study, the particle size of Si polycrystals was controlled through wet-sedimentation method, and changes in the capacity and cyclic characteristics of the Si anode material according to the particle size were observed. After wet-sedimentation of Si particles pulverized by a vibration mill, the non-uniform particle distribution of Si was uniformly controlled. The d50 of a sample in which Si was sedimented for 24 hours decreased to 0.50 ㎛. As a result of the electrochemical characteristic analysis, the Rct value representing the resistance in the electrode was significantly reduced due to the decrease in particle size. The unclassified Si sample exhibited a discharge capacity of 2,869 mAh/g in the first cycle, and decreased to 85.7 mAh/g after 100 cycles. The sample in which Si was classified for 24 hours showed a capacity of 3,394 mAh/g initially, and maintained a capacity of 1,726 mAh/g after 100 cycles. As the size of the Si particles decreased, the discharge capacity increased and the cycle life was also increased.

A Study on the Application of Smart Safety Helmets and Environmental Sensors in Ships (선박 내 스마트 안전모 및 환경 센서 적용에 관한 연구)

  • Do-Hyeong Kim;Yeon-Chul Ha
    • Journal of the Institute of Convergence Signal Processing
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    • v.24 no.2
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    • pp.82-89
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    • 2023
  • Due to the characteristics of ship structure, the compartment structure is complicated and narrow, so safety accidents frequently occur during the work process. The main causes of accidents include structural collisions, falling objects, toxic substance leaks, fires, explosions, asphyxiation, and more. Understanding the on-site conditions of workers during accidents is crucial for mitigating damages. In order to ensure safety, the on-site situation is monitored using CCTV in the ship, but it is difficult to prevent accidents with the existing method. To address this issue, a smart safety helmet equipped with location identification and voice/video communication capabilities is being developed as a safety technology. Additionally, the smart safety helmet incorporates environmental sensors for temperature, humidity, vibration, noise, tilt (gyro sensor), and gas detection within the work area. These sensors can notify workers wearing the smart safety helmet of hazardous situations. By utilizing the smart safety helmet and environmental sensors, the safety of workers aboard ships can be enhanced.

Case Study of Friction Piles Driven into Clayey Soils on the Central Coast of Vietnam (베트남 중부 연안의 대심도 점토지반에 시공된 강관 마찰 말뚝의 항타시공관리)

  • Seol, Hoon-Il
    • Journal of the Korean Geotechnical Society
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    • v.40 no.3
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    • pp.19-31
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    • 2024
  • In Korea, driven piles are generally penetrated up to weathered rock or harder strata. Friction piles have been used to some extent in the southwest coastal area with deep soils; however, friction piles are not extensively due to uncertainties about construction quality. The embedded pile construction method is primarily used due to noise and vibration complaints. However, in Southeast Asian countries (e.g., Cambodia, Myanmar, and Vietnam), where soft sediments are deep, the driven pile method is commonly used due to its economic advantages. Construction companies are increasingly entering overseas construction markets, e.g., Southeast Asia; thus, it is necessary to understand the behavior of driven friction piles in the soil and improve on-site engineering management to gain market competitiveness in these countries. In this study, the bearing capacity of friction piles driven into clayey coastal soils in Vietnam with time-dependent characteristics was evaluated based on the dynamic and static pile load tests. Based on the results, a modified Danish formula is proposed for on-site quality management.

Nonlinear free and forced vibrations of oblique stiffened porous FG shallow shells embedded in a nonlinear elastic foundation

  • Kamran Foroutan;Liming Dai
    • Structural Engineering and Mechanics
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    • v.89 no.1
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    • pp.33-46
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    • 2024
  • The present research delves into the analysis of nonlinear free and forced vibrations of porous functionally graded (FG) shallow shells reinforced with oblique stiffeners, which are embedded in a nonlinear elastic foundation (NEF) subjected to external excitation. Two distinct types of PFG shallow shells, characterized by even and uneven porosity distribution along the thickness direction, are considered in the research. In order to model the stiffeners, Lekhnitskii's smeared stiffeners technique is implemented. With the stress function and first-order shear deformation theory (FSDT), the nonlinear model of the oblique stiffened shallow shells is established. The strain-displacement relationships for the system are derived via the FSDT and utilization of the von-Kármán's geometric assumptions. To discretize the nonlinear governing equations, the Galerkin method is employed. The model such developed allows analysis of the effects of the stiffeners with various angles as desired, in addition to the quantitative investigation on the influence of the surrounding nonlinear elastic foundations. To numerically solve the problem of vibrations, the 4th-order P-T method is used, as this method, known for its enhanced accuracy and reliability, proves to be an effective choice. The validation of the present research findings includes a comprehensive comparison with outcomes documented in existing literature. Additionally, a comparative analysis of the numerical results against those obtained using the 4th Runge-Kutta method is performed. The impact of stiffeners with varying angles and material parameters on the vibration characteristics of the present system is also explored. The researchers and engineers working in this field may use the results of this study as benchmarks in their design and research for the considered shell systems.

Development of Improved String Model for Instruments with Anjok (안족이 있는 악기의 개선된 현의 모델 개발)

  • Cho, Sang-Jin;Chong, Ui-Pil
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.7
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    • pp.328-333
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    • 2007
  • In this paper, we describe characteristics of a movable bridge called the Anjok and propose an improved string model which has delay line controller in physical modeling of the Gayageum. Movable bridge, the Anjok determines the length of vibrating string and transmits the vibration of each string to the body of the Gayageum. We analyze the variations in frequency domain and implement the Anjok model as parametric form using the first-order polynomial fitting in logarithmic scale graph, because the length of string changes fundamental frequency. In order to implement the Anjok model, frequency fitting, tension fitting and frequency fitting using leaky integrator are used. The frequency fitting using leaky integrator has the best results among those. Proposed string model with the Anjok model can represent real tuning system of the real Gayageum and the proposed model could synthesize sounds which is similar to original sounds.

Experimental Identification of the Damping Characteristics of a Squeeze Film Damper with Open Ends and Central Groove (열린 끝단과 중앙 홈을 갖는 스퀴즈 필름 댐퍼의 감쇠 특성에 대한 실험적 규명)

  • Nam Kyu Kim;Tae Ho Kim;Kyungdae Kang
    • Tribology and Lubricants
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    • v.40 no.1
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    • pp.28-37
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    • 2024
  • This paper presents the development of a squeeze film damper (SFD) test rig and experimental identification of the effects of clearance, damper length, journal eccentricity ratio, excitation amplitude, oil supply pressure, and oil flow rate on the damping coefficients of a test SFD with open ends and a central groove. Test data are compared with predictions from a simple model developed for short SFDs with open ends and a central groove. The test results show a significant decrease in the damping coefficient with increasing clearance and a dramatic increase with damper length, which are in good agreement with the simple model predictions. According to the simple model, the damping coefficient is inversely proportional to the cube of the clearance and directly proportional to the cube of the length. An increase in the journal eccentricity ratio results in a dramatic increase in the damping coefficient by as much as 15 times that of the concentric case, particularly at low excitation frequencies. By contrast, the measured damping coefficient remains almost constant with changes in the excitation amplitude and supply pressure, which are not major factors in the damper design. In general, the test data agree well with the simple model predictions, excluding cases that show increases in the SFD length and journal eccentricity, which indicate significant dependency on the excitation frequency.