• Title/Summary/Keyword: Overall Vibration

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A Study on the Identification & Improvement of Dynamic Characteristics of Compressor Shell by Substructure Synthesis Method (부분구조합성법을 이용한 컴프레서 쉘의 동특성 규명 및 개선에 관한 연구)

  • Kim, Dong-Kyu;Kim, Jong-Bae;Go, Sang-Chul;Han, Kwang-Hee;Oh, Jae-Eung
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.5
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    • pp.99-106
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    • 1996
  • The noise of a compressor is a major contributor to overall noise radiated from the refrigerator. The major source of the noise is radiated by the vibration of the compressor shell. In this study, to identify the dynamic characteristics of compressor shell, a compressor shell is divided into several components and these are analyzed with a commercial FEM(Finite Element Method) package such as MSC/NASTRAN. Using substructure synthesis method, the dynamic characteristics of the total system is identified. The coherence of each component to the total system is computed by using strain and kinetic energy. To increase the frequency of the first resonance mode which is most effective mode to the noise of the compressor shell, the improving strategy of dynamic characteristics is suggested by changing mass and stiffness of the coherence component to the first mode.

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Experimental contribution analysis of external aeroacoustic noise sources to interior noise of automobile (자동차 외부 공기음향 소음원들의 실험적 실내 기여도 분석 기술 개발)

  • Lee, Myung Han;Ih, Kang Duck;Hwang, Seongil;Kim, Yong-Joe
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.5
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    • pp.300-308
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    • 2018
  • The contribution analysis of various external aeroacoustic noise sources to interior noise is important, enabling to design an automobile with a low interior noise level. With a new technique, the CD (Cholesky Decomposition), it is proposed to decompose an overall interior noise spectrum into multiple spectra, each representing the contribution of a specific noise source to the interior noise. In order to validate this method, three kinds of experiments were conducted. Furthermore, it is proposed to improve the CD-based contribution analysis method to be integrated with existing exterior microphone arrays in the wind tunnel. This method was validated with an experiment with two speakers.

Integrity Evaluation By IRT Technique And FEM Analysis of Spur Gear (스퍼 기어의 FEM 해석 및 IRT 기법을 적용한 건전성 평가)

  • Roh, Chi-Sung;Jung, Yoon-soo;Lee, Gyung-Il;Kim, Jae-Yeol
    • Tribology and Lubricants
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    • v.32 no.4
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    • pp.113-118
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    • 2016
  • As an economic, high quality, and highly reliable gear with low noise and low vibration is demanded, an overall finite element analysis regarding a gear is required. Also, an infrared thermography test, which is a quantitative testing technique, is demanded for safety and longer lifespan of gear products. In order to manufacture a gear product or to determine safety of a gear being used, it is necessary to precisely determine ingredients of a material constituting a gear and detect any internal defect. This study aims to realize a design that minimizes the spur gear displacement with respect to power during its rotation and ensures the spur gear control capacity by using a 3D model and the midasNFX program. This facilitates the assessment of the possibility of cracking by evaluating the stress intensity and focusing on the integrity of the spur gear. We prepare the specimen of the spur gear based on the possibility of cranking as per the result of the structural interpretation from an infrared ray thermal measuring technique. After cooling the spur gear, we perform experiments using thermography and halogen lamps and analyze the temperature data according to the results of the experiment. In the experiment which we use thermography after cooling, we find a rise in the temperature of the room. As a result, the defective part show temperatures lower than their surroundings while the normal parts have temperatures higher than the defective parts. Therefore, it possible to precisely identify defective part owing to its low temperature.

Seismic torsional vibration in elevated tanks

  • Dutta, Sekhar Chandra;Murty, C.V.R.;Jain, Sudhir K.
    • Structural Engineering and Mechanics
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    • v.9 no.6
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    • pp.615-636
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    • 2000
  • Some elevated water tanks have failed due to torsional vibrations in past earthquakes. The overall axisymmetric structural geometry and mass distribution of such structures may leave only a small accidental eccentricity between centre of stiffness and centre of mass. Such a small accidental eccentricity is not expected to cause a torsional failure. This paper studies the possibility of amplified torsional behaviour of elevated water tanks due to such small accidental eccentricity in the elastic as well as inelastic range; using two simple idealized systems with two coupled lateral-torsional degrees of freedom. The systems are capable of retaining the characteristics of two extreme categories of water tanks namely, a) tanks on staging with less number of columns and panels and b) tanks on staging with large number of columns and panels. The study shows that the presence of a small eccentricity may lead to large displacement of the staging edge in the elastic range, if the torsional-to-lateral time period ratio $({\tau})$ of the elevated tanks lies within a critical range of 0.7< ${\tau}$ <1.25. Inelastic behaviour study reveals that such excessive displacement in some of the reinforced concrete staging elements may cause unsymmetric yielding. This may lead to progressive strength deterioration through successive yielding in same elements under cyclic loading during earthquakes. Such localized strength drop progressively develop large strength eccentricity resulting in large localized inelastic displacement and ductility demand, leading to failure. So, elevated water tanks should have ${\tau}$ outside the said critical range to avoid amplified torsional response. The tanks supported on staging with less number of columns and panels are found to have greater torsional vulnerability. Tanks located near faults seem to have torsional vulnerability for large ${\tau}$.

Optimization of a Nuclear Fuel Spacer Grid Using Considering Impact and Wear with Homology Constraints (호몰로지 조건을 이용하여 충격과 마모를 고려한 원자로 핵연료봉 지지격자의 최적설계)

  • Lee, Hyun-Ah;Kim, Chong-Ki;Song, Kee-Nam;Park, Gyung-Jin
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.145-150
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    • 2007
  • The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods saftely. Therefore, the spacer gl1d set should have sufficient strength for the external impact forces. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to tile flow-induced vibration. The conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined and corresponding design parameters are selected. The overall flow of the design is defined according to the application of axiomatic design. The design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis because the contact area becomes wider.

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A Development of Multi-Emotional Signal Receiving Modules for Ubiquitous RCP Interaction (유비쿼터스 RCP 상호작용을 위한 다감각 착신기능모듈의 개발)

  • Jang Kyung-Jun;Jung Yong-Rae;Kim Dong-Wook;Kim Seung-Woo
    • Journal of Institute of Control, Robotics and Systems
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    • v.12 no.1
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    • pp.33-40
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    • 2006
  • We present a new technological concept named RCP (Robotic Cellular Phone), which combines RT and CP. That is an ubiquitous robot. RCP consists of 3 sub-modules, RCP Mobility, RCP interaction, and RCP Integration. RCP Interaction is the main focus of this paper. It is an interactive emotion system which provides CP with multi-emotional signal receiving functionalities. RCP Interaction is linked with communication functions of CP in order to interface between CP and user through a variety of emotional models. It is divided into a tactile, an olfactory and a visual mode. The tactile signal receiving module is designed by patterns and beat frequencies which are made by mechanical-vibration conversion of the musical melody, rhythm and harmony. The olfactory signal receiving module is designed by switching control of perfume-injection nozzles which are able to give the signal receiving to the CP-called user through a special kind of smell according to the CP-calling user. The visual signal receiving module is made by motion control of DC-motored wheel-based system which can inform the CP-called user of the signal receiving through a desired motion according to the CP-calling user. In this paper, a prototype system is developed far multi-emotional signal receiving modes of CP. We describe an overall structure of the system and provide experimental results of the functional modules.

Direct Non-stepwise Multiple Quantum Excitations in Translation-Vibration Energy Transfer (竝進-振動에너지 變換에 있어서의 多量子 直接 振動 勵起)

  • Yoo Hang Kim;Hyung Kyu Shin
    • Journal of the Korean Chemical Society
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    • v.20 no.2
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    • pp.97-110
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    • 1976
  • Effects of direct multiple quantum excitations in vibrational energy transfer were investigated. Vibrational transition probabilities for 0${\rightarrow}$2, 0${\rightarrow}$3, and 0${\rightarrow}$4 excitations were explicitly formulated including both direct 0→n excitations and stepwise single quantum processes. For the formulation the perturbing force was derived from the exponential potential including terms up to fourth order in the vibrational amplitude. The head-on collinear collision model between a harmonic oscillator and an incident particle was employed, and the formulation was based on the semiclassical approximation. Numerical results were obtained for five different collision systems (Ar${\cdots}$O-N, He${\cdots}$H-H, He${\cdots}$H-Cl, 5${\cdots}$1-2, 2${\cdots}$12-12). Comparison between the present results and those obtained using the linearized interaction potential showed that the overall effect of including the direct multiple quantum transition is to decrease the probabilities at low collision energies and to increase them at high energies. The present results were found to be significantly different from those obtained using the linearized potential for collision systems He${\cdots}$H-H, He${\cdots}$H-Cl, and 5${\cdots}$1-2. For systems Ar${\cdots}$O-N and 2${\cdots}$12-12 the differences were negligible.

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Vibration behavior of functionally graded sandwich beam with porous core and nanocomposite layers

  • Si, Hua;Shen, Daoming;Xia, Jinhong;Tahouneh, Vahid
    • Steel and Composite Structures
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    • v.36 no.1
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    • pp.1-16
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    • 2020
  • In steel-concrete composite beams, to improve the cracking resistance of the concrete slab in the hogging moment region, a new type of connector in the interface, named uplift-restricted and slip-permitted screw-type (URSP-S) connector has been proposed. This paper focuses on the behavior of steel-concrete composite beams with URSP-S connectors. A total of three beam specimens including a simply supported beam with URSP-S connectors and two continuous composite beams with different connectors arrangements were designed and tested. More specifically, one continuous composite beam was equipped with URSP-S connectors in negative moment region and traditional shear studs in other regions. For comparison, the other one was designed with only traditional shear studs. The failure modes, crack evolution process, ultimate capacities, strain responses at different locations as well as the interface slip of the three tested specimens were measured and evaluated in-depth. Based on the experimental study, the research findings indicate that the larger slip deformation is allowed while using URSP-S connectors. Meanwhile, the tensile stress reduces and the cracking resistance of the concrete slab improves accordingly. In addition, the overall stiffness and strength of the composite beam become slightly lower than those of the composite beam using traditional shear studs. Moreover, the arrangement suggestion of URSP-S connectors in the composite beam is discussed in this paper for its practical design and application.

Influence of masonry infill on reinforced concrete frame structures' seismic response

  • Muratovic, Amila;Ademovic, Naida
    • Coupled systems mechanics
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    • v.4 no.2
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    • pp.173-189
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    • 2015
  • In reality, masonry infill modifies the seismic response of reinforced concrete (r.c.) frame structures by increasing the overall rigidity of structure which results in: increasing of total seismic load value, decreasing of deformations and period of vibration, therefore masonry infill frame structures have larger capacity of absorbing and dissipating seismic energy. The aim of the paper is to explore and assess actual influence of masonry infill on seismic response of r.c. frame structures, to determine whether it's justified to disregard masonry infill influence and to determine appropriate way to consider infill influence by design. This was done by modeling different structures, bare frame structures as well as masonry infill frame structures, while varying masonry infill to r.c. frame stiffness ratio and seismic intensity. Further resistance envelope for those models were created and compared. Different structures analysis have shown that the seismic action on infilled r.c. frame structure is almost always twice as much as seismic action on the same structure with bare r.c. frames, regardless of the seismic intensity. Comparing different models resistance envelopes has shown that, in case of lower stiffness r.c. frame structure, masonry infill (both lower and higher stiffness) increased its lateral load capacity, in average, two times, but in case of higher stiffness r.c. frame structures, influence of masonry infill on lateral load capacity is insignificant. After all, it is to conclude that the optimal structure type depends on its exposure to seismic action and its masonry infill to r.c. frame stiffness ratio.

Modeling of wind and temperature effects on modal frequencies and analysis of relative strength of effect

  • Zhou, H.F.;Ni, Y.Q.;Ko, J.M.;Wong, K.Y.
    • Wind and Structures
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    • v.11 no.1
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    • pp.35-50
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    • 2008
  • Wind and temperature have been shown to be the critical sources causing changes in the modal properties of large-scale bridges. While the individual effects of wind and temperature on modal variability have been widely studied, the investigation about the effects of multiple environmental factors on structural modal properties was scarcely reported. This paper addresses the modeling of the simultaneous effects of wind and temperature on the modal frequencies of an instrumented cable-stayed bridge. Making use of the long-term monitoring data from anemometers, temperature sensors and accelerometers, a neural network model is formulated to correlate the modal frequency of each vibration mode with wind speed and temperature simultaneously. Research efforts have been made on enhancing the prediction capability of the neural network model through optimal selection of the number of hidden nodes and an analysis of relative strength of effect (RSE) for input reconstruction. The generalization performance of the formulated model is verified with a set of new testing data that have not been used in formulating the model. It is shown that using the significant components of wind speeds and temperatures rather than the whole measurement components as input to neural network can enhance the prediction capability. For the fundamental mode of the bridge investigated, wind and temperature together apply an overall negative action on the modal frequency, and the change in wind condition contributes less to the modal variability than the change in temperature.