• Title/Summary/Keyword: Modal dynamic analysis

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A Study on the Dynamic Stability of Heavy Press Considering Rotational Speed (회전 속도를 고려한 대형 프레스의 동적 안정성에 관한 연구)

  • Shin, Min Jae;Kim, Chae Sil;Keum, Chang Min;Kim, Jae Min
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.8
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    • pp.623-628
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    • 2016
  • This article describes the determination of the dynamic stability for a heavy press, particularly considering rotational speed. A finite element model of the driving parts for the heavy press was generated. We also applied boundary conditions and dynamic loads considering the driving conditions. Modal analysis was conducted using the finite element construction model. Therefore, no resonance was identified with the comparison between the results of the modal analysis and vibration excitation frequency by the gear tooth. In addition, the stress distribution of the driving parts for press was determined using transient analysis. As compared to the yield strength of the material, the dynamic stability the heavy press was confirmed.

Construction stage effect on the dynamic characteristics of RC frame using operational modal analysis

  • Arslan, Mehmet Emin;Durmus, Ahmet
    • Computers and Concrete
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    • v.12 no.1
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    • pp.79-90
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    • 2013
  • In this study, dynamic characteristics such as natural frequencies, mode shapes and damping ratios of RC frame is determined for different construction stages using Operational Modal Analyses method under ambient vibration. Full scaled, one bay and one story RC frames are selected as an application for different construction stages such as plane, brick in-filled and brick in-filled with plaster. The RC frame is vibrated by natural excitations with small impact effects and the response signals are measured using sensitive accelerometers during ambient vibration tests. Measurement time-frequency span and effective mode number are determined by considering similar studies in literature. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, output-only system identification technique is employed namely; Enhanced Frequency Domain Decomposition technique in the frequency domain. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of RC frames.

Dynamic Analysis of Micro Cantilever Beams Undertaking Electrostatic Forces (정전기력을 받는 마이크로 외팔보의 동적 해석)

  • 정강식;문승재;유홍희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.315-319
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    • 2004
  • Static and dynamic responses of micro cantilever beam structures undertaking electrostatic forces are obtained employing Galerkin's method based on Euler beam theory. Variations of static and dynamic responses as well as resonant frequencies are estimated for several sets of beam properties and applied voltages. It is shown that the applied voltage influences the deflection and the modal characteristics significantly. Such information can be usefully employed for the design of MEMS structures.

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Dynamic Analysis of Vehicle Sub-frame (차량용 서브프레임의 동특성 해석)

  • Lee, B.H.;Kim, C.J.;Kim, G.H.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.12 s.105
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    • pp.1332-1339
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    • 2005
  • The vibration of Powertrain are one of the import design characteristics of a vehicle. Powertrain is mostly mounted to the front subframe and powertrain mounting has an important role in determining the vehicle vibration characteristics. In this paper, the accuracy of the vibration analysis for the front subframe is discussed. The dynamic characteristic of subframe are measured from vehicle test and the finite element model updating are performed that natural frequency, mass and MAC of the experimental and theoretical modal analysis are compared. The subframe mounting stiffness are obtained the iteration method based on the vibration of subframe from vehicle test. Finally, the result of dynamic analysis which is operated dynamic load is compared with experimental one of vehicle test.

Modal analysis and multi-objective optimization of lightweight analysis of the main beam of the concrete spreader

  • Zhang, Shiying;Song, Bo;Zhang, Ke;Chen, Hongliang;Zou, Defang;Liu, Chang;Zhu, Chunxia;Li, Dong;Yu, Wenda
    • Computers and Concrete
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    • v.28 no.5
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    • pp.465-478
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    • 2021
  • On the premise of ensuring that the static performance of the concrete spreader is met, the first-order natural frequency of the concrete spreader is increased, and the weight of the main beam is reduced. ANSYS is used as an analysis tool to perform modal analysis on the concrete spreader. The natural frequency, mode shape and modal test verification will be obtained to ensure the accuracy of finite element model analysis. Using the ANSYS designxplorer module, the size of the main beam is set, and the response surface model between the parameter variables and the optimization objective is established according to the experimental design points. Screening algorithm and MOGA algorithm are used to multi-optimize the stress, first-order natural frequency and girder weight, and the optimal solution is obtained by comparison. The results of modal analysis are consistent with those of the experiment, and a set of optimal solutions is obtained through the optimization algorithm. The optimal solution obtained can meet the purpose of increasing the first-order natural frequency of the concrete spreader and reducing the weight of the main beam under the premise of ensuring the overall dynamic and static performance of the concrete spreader.

Ambient vibration testing of Berta Highway Bridge with post-tension tendons

  • Kudu, Fatma Nur;Bayraktar, Alemdar;Bakir, Pelin Gundes;Turker, Temel;Altunisik, Ahmet Can
    • Steel and Composite Structures
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    • v.16 no.1
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    • pp.21-44
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    • 2014
  • The aim of this study is to determine the dynamic characteristics of long reinforced concrete highway bridges with post-tension tendons using analytical and experimental methods. It is known that the deck length and height of bridges are affected the dynamic characteristics considerably. For this purpose, Berta Bridge constructed in deep valley, in Artvin, Turkey, is selected as an application. The Bridge has two piers with height of 109.245 m and 85.193 m, and the total length of deck is 340.0 m. Analytical and experimental studies are carried out on Berta Bridge which was built in accordance with the balanced cantilever method. Finite Element Method (FEM) and Operational Modal Analysis (OMA) which considers ambient vibration data were used in analytical and experimental studies, respectively. Finite element model of the bridge is created by using SAP2000 program to obtain analytical dynamic characteristics such as the natural frequencies and mode shapes. The ambient vibration tests are performed using Operational Modal Analysis under wind and human loads. Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods are used to obtain experimental dynamic characteristics like natural frequencies, mode shapes and damping ratios. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge was updated considering the material properties and boundary conditions. It is emphasized that Operational Modal Analysis method based on the ambient vibrations can be used safely to determine the dynamic characteristics, to update the finite element models, and to monitor the structural health of long reinforced concrete highway bridges constructed with the balanced cantilever method.

Effects of Flange Joint on the Dynamic Characteristics of the External Cylindrical Grinding Wheel Spindle (외경연삭 휠 주축의 진동특성에 미치는 플랜지 결합부의 영향)

  • Kim, Sun-Min;Ha, Jae-Hoon;Lee, Sun-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.10
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    • pp.118-125
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    • 1999
  • In the grinding process, generally, the exciting forces with high frequency can be generated due to the wheel wear and the grinding process. As the grinding speed increases, the precise investigation about the wheel dynamic characteristics is required. Conventionally the wheel-spindle has been considered with lumped model in dynamic modeling. With this lumped model, the significant mode resulted from the shell mode of wheel can be readily ignored. This paper suggests the new analysis model which includes the shell mode of wheel in modeling the wheel-spindle assembly. Furthermore, based on the suggested model, the effects of the bolt tightening force and the taper tightening force on the dynamic properties are investigated by the finite element modal analysis and the experimental method. As a result of investigation, the shell mode vibration of wheel affects the dynamic characteristics of the spindle assembly. Also, the vibration modes of the spindle assembly are significantly affected by the joint tightening forces.

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Dynamic Behavior Analysis of Driving Part in CHIP MOUNTER (CHIP MOUNTER 구동부의 동적 거동 해석)

  • 박원기;박진무
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.471-474
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    • 2001
  • Recently, due to demands of faster speed and extra features for the chip mounters, there has been ever-demanding needs for the basic technology. Until four or five years ago, chip mounters placing 0.3sec/chip were considered to be in the high speed category, but since then it has become a borderline for categorizing high speed machines capable of placing 0.1sec/chip. In this study, in order to analyze the vibration of head generated by the dynamic behavior of x-frame, FEM model is composed and modal analysis is performed to identify the dynamic characteristics of the structure. Those results are compared with the modal test in order to verify the model. In this paper, Several other factors, such as definition of dynamic accuracy, static accuracy and tolerance of the axis settling range, that might affect the dynamic behavior the head are discussed.

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MODAL CHARACTERISTIC ANALYSIS OF THE APR1400 NUCLEAR REACTOR INTERNALS FOR SEISMIC ANALYSIS

  • Park, Jong-Beom;Choi, Youngin;Lee, Sang-Jeong;Park, No-Cheol;Park, Kyoung-Su;Park, Young-Pil;Park, Chan-Il
    • Nuclear Engineering and Technology
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    • v.46 no.5
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    • pp.689-698
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    • 2014
  • Reactor internals are sensitive to dynamic loads such as earthquakes and flow induced vibration. Thus, it is essential to identify the dynamic characteristics to evaluate the seismic integrity of the structures. However, a full-sized system is too large to perform modal experiments, making it difficult to extract data on its modal characteristics. In this research, we constructed a finite element model of the APR1400 reactor internals to identify their modal characteristics. The commercial reactor was selected to reflect the actual boundary conditions. Our FE model was constructed based on scale-similarity analysis and fluid-structure interaction investigations using a fabricated scaled-down model.

On the Dynamic Response of Laminated Circular Cylindrical Shells under Dynamic Loads (동하중을 받는 복합재료 원통셸의 동적거동 해석)

  • 이영신;이기두
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.11
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    • pp.2684-2693
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    • 1993
  • The free vibration and dynamic response of cross-ply for CFRP and GFRP laminated circular cylindrical shells under dynamic loadings are investigated by using the first-order shear deformation shell theory. The modal analysis technique is used to develop the analytical solutions of simply supported cylindrical shells under dynamic load. The analysis is based on an expansion of the loads, displacements and rotations in a double Fourier series which satisfies the and boundary conditions of simply support. Analytical solution is assumed to be separable into a function of time and a function of position. In this paper, the considered load forces are step pulse, sine pulse, triangular(1, 2, 3) pulse and exponential pulse. The solution for a given loading pulse can be found by involving the convolution integral. The results show that the dynamic response are governed primarily by the natural period of the structure.