• Composites Research
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• v.33 no.3
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• pp.133-139
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• 2020

In this research, the vibration characteristics of composite quadcopter are analyzed, and avoidance design and analysis are performed to avoid resonance. The full platform of a commercial quadcopter with composite rotor arm is analyzed to see the vibration characteristics using FEM program. The manufactured stacking sequences of rotor arm is used for analysis, and the natural frequencies are compared with experimental results and simple analytic model results. It is also confirmed that the natural frequency of the particular mode is included within the operation range of the motor. The resonance avoidance design is carried out by selecting three variables from the existing model: stacking sequence, rotor-arm pipe length, and pipe thickness.

• Journal of KSNVE
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• v.10 no.1
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• pp.13-17
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• 2000

• Journal of the Korean Society for Precision Engineering
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• v.28 no.8
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• pp.951-958
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• 2011

In this paper, the purpose is to investigate the vibration characteristics and the design of resonance avoidance of the unmanned helicopter master. Based on the Euler-Bernoulli beam theory for helicopter master, the equation of motion is derived by using extended Hamilton's principle. It was studied about the natural frequency of helicopter master as the design variances(tip mass, length and diameter of master). Also, it was compared the theoretical results for natural frequency with the results of FE analysis. The results of this study showed the vibration characteristics of helicopter master for the design of resonance avoidance.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.321-329
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• 2018

Resonance phenomena occurs at large vertical pump which is operating to cool down the hot steam using sea water in the power plant. To avoid the resonance, the natural frequency needs to be isolated about 20% from motor operating speed. Yet, excessive vibration occurs especially at low tide. At first, natural frequency of the whole pump system and each part is calculated using ANSYS. As it is revealed in the previous journal papers that only circular pipe part is related to resonance, the FSI technique is applied for free vibration analysis. The natural frequency is reduced to 60% (compared to that) of the frequency measured in air as it is similar to other published results. And the frequency obtained by finite element analysis is almost same to that obtained from modal test. Based on the accurate finite element model and analysis, design change is tried to avoid the resonance by changing the thickness of pipe and base supporting plate. In stead of doing optimization process, design sensitivity is computed and used to find such designs to avoid resonance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.279-285
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• 2019

Transverse vibrations of a ship's aft end and deckhouse are mainly induced by transverse exciting forces from the main engine. Resonance should be avoided in the initial design stages when there is a prediction of resonance between the main engine and transverse modes of the deckhouse. Estimates of frequencies for resonance avoidance are possible from the specifications of the main engine and propeller, but the inherent vibration frequency of the structure around the engine room is not easy to estimate due to the variation in the shape. Experience-oriented vibration design is also carried out, which results in many problems, such as process delay, over-injection of on-site personnel, and iterative performance of the design. For the flexible design of 8,600 TEU container vessels, this study addressed the resonance problem caused by the transverse vibration of the main engine when only the main engine was changed from 12 cylinders to 10 cylinders without modification of the hull structure layout. Efficient structural reinforcement design guidelines are presented for avoiding resonances with the main engine lateral vibration and the structure around the engine room. The guidelines are expected to be used as practical design guidelines at design sites.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.642-643
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.881-882
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.327-328
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.336-341
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• 2012

The vertical-axis tidal current turbine (VAT) consisting of blades, struts to support blades, shaft, generator and so forth requires anti-resonance design against fluid fluctuation forces generated on blades to ensure its stable operation. In this study, a free vibration analysis program based on the finite element method is developed for efficient anti-resonance design of VAT in the preliminary design stage. In the finite element modeling, the VAT structure components are regarded as beam elements. Added masses due to the fluid and structure interaction of VAT evaluated by empirical formulas are considered as lumped mass elements. In addition, input parameters required for the analysis can be automatically prepared from the principal dimensions of VAT to make anti-resonance design more convenient. The validity of applied methods is verified by the comparison of the numerical results obtained from MSC/Nastran and the developed program for two VAT models.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.26-35
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• 2017

The high-cycle fatigue cracking and the resonance generated in operation of a centrifugal compressor are main cause of the impeller damage. In order to prevent the damage, the impeller is designed or modified to have sufficient strength to withstand the operating condition. The damage prevent design will lead to a change of the flow condition and the performance characteristics of the compressor. In this study, the computational analysis were performed to identify the flow and the performance characteristics. The cases are a scalloped and a increased the blade thickness models with a closed type impeller. As the analysis results, the value of head coefficient and total to total efficiency for the increased the blade thickness model was decreased by each 0.5% and 0.1% than the values of the baseline model. Each value for the scalloped model was increased by 0.4% and was decreased by 1.6%.