• Title, Summary, Keyword: 모달 시험

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Study on Modal Test Method for Vibration Characteristics of the Cylindrical Structure Filled with Liquid (액체가 채워진 원통형 구조물의 진동 특성 규명을 위한 모달 시험 방법 연구)

  • Kim, Gen-Sang;Kim, Mun-Guk;Kim, In-Gul;Park, Jae-Sang;Park, Soon-Hong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.8
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    • pp.621-630
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    • 2018
  • In the case of launch vehicles using liquid fuel, natural frequency changes due to fuel consumption after launch, and a modal test is essential to investigate its effect. However, when relying on modal test to characterize the free vibration characteristics, the testing time is excessively increased and accuracy is reduced. Therefore, this paper suggests a modal test method with finite element analysis to overcome these drawbacks. A cylindrical structure filled with liquid are considered as a study model, and modal tests and finite element analyses are performed. The modal tests are conducted by an impulsive method using an impact hammer and accelerometers. Through the comparison of the modal test and the finite element analysis results, the validity of the proposed modal test method is verified. In addition, the free vibration characteristics and the tendency for the cylindrical structure according to the liquid filled ratio were investigated.

Constructing Equations of Motion for a Dynamic System from Modal Parameters (모달 파라미터를 이용한 동적 시스템의 운동 방정식 구성)

  • Hwang, Woo-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.1
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    • pp.40-45
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    • 2007
  • Modal analysis or modal test is a routine process to get the modal parameters of a dynamic system. The modal parameters include the natural frequencies, damping ratios and mode shapes. This paper presents a method that can derive the equations of motion for a dynamic system from the modal parameters obtained by the modal analysis or modal test. The present method based on the relation between the eigenvalues and eigenvectors of the state space equation derives the mass, damping and stiffness matrices of the system. The numerical verifications for the simple mass-spring-damper system and the cantilevered beam prove the efficiency and accuracy of the present method.

Analysis of Durability of Torsion Beam Axle Using Modal Stress Recovery Method (모달 응력 회복법(Modal Stress Recovery)을 이용한 Torsion Beam Axle 내구해석)

  • Ko, Jun-Bok;Lim, Young-Hoon;Lee, Dong-Cheol
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.10
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    • pp.1339-1344
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    • 2010
  • MSM (Modal Superposition Method) is a technique for analyzing structural durability by taking the vibration characteristics into consideration. In this paper, MSR (Modal Stress Recovery) method, which is similar to MSM, was reviewed to check its validity as a durability analysis method. The MSR method directly calculates the modal displacement time history in multibody dynamics analysis; as a result, the total analysis time is shorter than that of MSM method. We conduct durability analysis using the MSR method and a durability test of a torsion beam axle that is affected by various road loads within the natural frequency of the beam axle. The analysis results for critical location and durability were in good agreement with the respective test results. Therefore, durability analysis using the MSR method is effective in predicting the durability of the structures of various dynamic systems.

Development of a Series Hybrid Propulsion System for Bimodal Tram (바이모달 트램용 직렬형 하이브리드 추진시스템 개발)

  • Bae, Chang-Han;Lee, Kang-Won;Mok, Jai-Kyun;You, Doo-Young;Bae, Jong-Min
    • The Transactions of the Korean Institute of Power Electronics
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    • v.16 no.5
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    • pp.494-502
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    • 2011
  • Bimodal tram is designed to run on a dedicated path in automatic mode using a magnetic track system in order to realize a combination of the accessibility of a bus and the constant regularity of a railroad. This paper presents design and test results of the series hybrid propulsion system of the bimodal tram on both test track and public road, which uses CNG (Compressed Natural Gas) engine and Lithium polymer battery pack. This paper describes the real-time data measuring equipment for the series hybrid propulsion system of the bimodal tram. Using this measurement equipment, the performance of the prototype vehicle's driving on test track and public road was verified and the fuel consumption and the efficiency of CNG engine have been investigated.

Test of the Series Hybrid Propulsion Power Unit of a Bimodal Tram (바이모달 트램의 직렬형 하이브리드 추진 전원장치 시험)

  • Bae, Chang-Han;Chang, Se-Ky;Mok, Jai-Kyun;Lee, Kwang-Won;Kim, Yong-Tae;Bae, Jong-Min
    • Proceedings of the KSR Conference
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    • pp.930-939
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    • 2009
  • A bimodal tram is being developed to combine the flexibility of a bus with the punctuality of a train. The propulsion system is a series hybrid type using a set of CNG engine generator and Li-polymer battery. This paper presents the experimental results of the series hybrid propulsion power unit using an active loader which can simulate powering and regenerative braking conditions of the propulsion equipments continuously. The power sharing scheme between PWM converter and a battery pack has been observed. The measurement results of DC link voltage and SOC(State Of Charge) of battery pack are presented.

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A Study on the Comparison of Structural Performance Test and Analysis for Design Verification of Bimodal Tram Vehicle Made of Sandwich Composites (샌드위치 복합재 적용 바이모달 트램 차체의 설계검증을 위한 구조 성능 시험 및 해석적 비교 연구)

  • Ko, Hee-Young;Shin, Kwang-Bok;Jeong, Jong-Cheol
    • Journal of the Korean Society for Railway
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    • v.12 no.4
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    • pp.518-525
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    • 2009
  • This paper describes the evaluation of structural performance test and finite element analysis to verify the design of Bimodal Tram made of sandwich composites. The sandwich composite applied to vehicle structure was composed of a aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. The load tests of vehicle structure were conducted for vertical load, compressive load, torsion and modal analysis according to JlS E 7105. The structural Integrity of vehicle was evaluated by the measurement of displacement, stress and natural frequency obtained from dial gauge, strain gauge and gravity sensor, respectively. And finite element analysis using ANSYS v11.0 was done to compare with structural test. The results showed that the displacement, stress and natural frequency were in an good agreement with those of structural analysis using the proposed finite element models.

A Study on the Prediction of the Mechanical Properties of Printed Circuit Boards Using Modal Parameters (모달 파라미터 정보를 활용한 PCB 물성 예측에 관한 연구)

  • Choo, Jeong Hwan;Jung, Hyun Bum;Hong, Sang Ryel;Kim, Yong Kap;Kim, Jae San
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.5
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    • pp.421-426
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    • 2017
  • In this study, we propose a method for predicting the mechanical properties of the printed circuit board (PCB) that has transversely isotropic characteristics. Unlike the isotropic material, there is no specific test standard for acquisition of the transversely isotropic properties. In addition, common material test methods are not readily applicable to that type of laminated thin plate. Utilizing the natural frequency obtained by a modal test and the sizing optimization technique provided in $OptiStruct^{(R)}$, the mechanical properties of a PCB were derived to minimize the difference between test and analysis results. In addition, the validity of the predicted mechanical properties was confirmed by the MAC (Modal Assurance Criteria) value of each of the compared mode shapes. This proposed approach is expected to be extended to the structural analysis for the design verification of the top product that includes a PCB.

A study on the applicability of newly developed stainless steel for weight reduction of carbody of intermodal tram (인터모달 트램 차체 경량화를 위한 신개발 스테인레스 강재 적용성 연구)

  • Seo, Sung-il;Kim, Jeong-guk;Jung, Hyun-seung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.3
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    • pp.457-463
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    • 2016
  • The newly developed super ductile duplex stainless steel (SDSS) has good strength and ductility, and it can be used to reduce weight and improve the fabrication efficiency of a carbody of a rolling stock. In this study, spot weldability tests were conducted to take advantage of SDDSS in a carbody for an intermodal tram. Specimens of various thickness (0.4 to 5.0 mm) were prepared to find the proper welding conditions, and tensile load tests were conducted to evaluate the tensile-shear strength of spot welded joints. Then, nugget diameters were measured to verify the quality. The tensile-shear strength was found to be proportional to the heat parameter. It was verified that the tensile-shear strengths and nugget sizes of the joints satisfy the standard requirements. The overall weldability tests confirmed that SDDSS can be used effectively for the carbody of an intermodal tram.