• 한국군사과학기술학회지
• /
• 제25권6호
• /
• pp.596-605
• /
• 2022

In this study, analysis of dynamic characteristics and flight vibration was performed to unmanned aerial vehicles. The analysis model was supplemented by performing a dynamic characteristic test and a random vibration test using manufactured dummy aerial vehicle. For the dynamic characteristic test, a bungee cable was used to implement the free end boundary condition. Prior to the flight vibration test using a multiple electric shaker, a random vibration test was performed to predict the excitation force during the actual flight vibration test. It was judged that the actual test could be predicted more accurately by supplementing the analysis model from the test results. In addition, it was possible to determine the feasibility of the test by predicting the excitation force of the flight vibration test.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.826-831
• /
• 2002

In order to investigate the dynamic characteristics of real structure, many dynamic engineer had been interested in modal test however it is not easy to perform dynamic test of large structure because of many difficulties such as unsatisfied excitation force in global mode frequency range, measurement of dynamic force and so on. Therefore. new type vibration exciter with variable stiffness support system and dynamic force was developed to provide a improved experimental environment for a large and complex structure. The developed exciter improved from two viewpoint, dynamic performance and utility convenience. its characteristics was shown in this paper.

• Journal of Mechanical Science and Technology
• /
• 제17권11호
• /
• pp.1732-1738
• /
• 2003

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the under-test, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.

• Advances in aircraft and spacecraft science
• /
• 제5권2호
• /
• pp.165-175
• /
• 2018

Jet Propulsion Laboratory has traditionally performed system level vibration testing of flight spacecraft. There have been many discussions in the aerospace community for more than a decade about spacecraft vibration testing benefits or lack thereof. The benefits and potential issues of fully assembled flight spacecraft vibration testing are discussed herein. The following specific topics are discussed: spacecraft screening test to uncover workmanship problems for launch dynamics environments, force- and moment-limited vibration testing, potential issues with structural frequency identification using base shake test data, and failures related to vibration shaker testing and ways to prevent them.

• Journal of international Conference on Electrical Machines and Systems
• /
• 제3권4호
• /
• pp.389-393
• /
• 2014

This paper presents one of the methods for design to reduce the noise and vibration of 200kW motor for electric propulsion ship. One of the important factors affecting vibration of the motor is the resonance. The natural frequency and natural mode of the 200kW motor is analyzed by using FEM tool and impact test equipment to avoid the resonance. Also, compare FEM result with impact test result to make a reliable FE model of 200kW motor. In order to find out the effect of the noise and vibration of the motor by electromagnetic excitation force, conduct electromagnetic-structure coupled analysis. These characteristics are much useful to design 200kW motor for electric propulsion ship.

• 한국항공우주학회지
• /
• 제50권11호
• /
• pp.791-800
• /
• 2022

능동 진동 제어 시스템(Active vibration control system, AVCS)을 이용하여 헬리콥터 기체의 능동 진동 제어 시 우수한 진동 제어 성능을 얻기 위하여서는 진동 상쇄 하중 발생기의 개수, 위치 및 하중 방향의 조합의 최적화가 중요하다. 따라서 고려 가능한 모든 하중 발생기의 조합에 대하여 헬리콥터 기체에 대한 AVCS의 진동 제어 성능을 조사하기 위해 Exhaustive 시험 기법을 적용한 AVCS 프레임워크를 구축하였다. 로터 진동 하중 해석, 기체 진동 응답 해석 및 AVCS 시뮬레이션 연구를 수행하기 위해 DYMORE II, MSC.NASTRAN 및 MATLAB Simulink 등 다양한 프로그램을 사용하였다. 이를 이용하여 비행 속도 158 knots의 UH-60A 헬리콥터에 대한 AVCS 적용을 위한 CRFG 조합을 최적화하였다. 최적의 CRFG 조합이 적용된 AVCS를 통해 UH-60A 헬리콥터의 4P 기체 진동 응답을 능동 제어한 결과, 기체의 주요 위치에서 4P 기체 진동 응답이 19.35~98.07%만큼 감소될 수 있었다.

• 대한물리의학회지
• /
• 제3권3호
• /
• pp.145-149
• /
• 2008

Purpose : The purpose of this study was evaluate the effects of vibration on joint position sense. Methods : The subjects were divided into vibration group(n=20) and control group(n=20). Vibration group was given local vibration on elbow joint for 15 minutes and control group was given resting 15 minutes by resting position. All subjects of each group were tested pre-post on maximal grip force and joint position sense. Results : Maximal grip force test and joint position sense test of vibration group was showed a significant difference between pre and post(p<0.05). Conclusion : There was a different change on maximal grip force and joint position sense.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.377-382
• /
• 2016

In this paper, influence of vibration on cogging torque and Radial Magnetic Force(RMF) imbalance was investigated in the IPM type BLDC motor. Design of cogging torque reduction and the RMF equilibrium was proceed applied to Design of Experiment(DOE). Vibration test results, the RMF imbalance was confirmed that a significant impact of vibration.

• 한국재난정보학회 논문집
• /
• 제8권2호
• /
• pp.197-203
• /
• 2012

최근 환경 공해 저감에 대한 사회적 요구가 높아짐에 따라 구조물의 방음, 방진 설계가 더욱 중요해지고 있다. 이 논문에서는 최근 개발된 수직형 면진장치의 기본 개념 및 성능 확인 실험 결과를 제시하였다. 개발된 면진장치는 PTFE 재질 마찰면의 마찰작용을 이용하여 수직방향의 진동을 감쇠시키고 수평 및 수직으로 배치된 폴리우레탄 소재의 스프링을 통하여 복원력을 제공하는 구조이다. 성능확인 실험은 하중 재하 속도에 변화에 따른 성능 변화추이를 파악하기 위한 실험과 고정하중이 적용된 후 발생되는 진동하중 작용 시 가정된 하중-변위 특성을 확인하기 위한 실험으로 구성하였다.

• 소음진동
• /
• 제5권1호
• /
• pp.95-106
• /
• 1995

Flow-induced vibration in heat exchanger (or fuel rod) in nuclar power plant can cause dynamic interactions between tubes and tube supports resulting in fretting-wear. To increase the reliability and design life of heat exchanger components, design criteria that establish acceptable limits of vibration and minimize fretting wear are necessary. The fretting-wear rate is dependent upon material combination, contact configuration, environmental conditions and tube-to tube support dynamic interaction. It is demostrated that the fretting -wear rate correlates well with tube-to-support contact force or work rate. The tube-to-support dynamic interaction, which consists of dynamic contact forces and tube motion, is used to relate single-span wear data to real heat exchanger configurations consisting of multi-span tube bundles. This paper describes the test facility to measure tube-to-support dynamic impact force and reports its dynamic characteristics through the four impact tests - a force transduces independent and external impact tests, central ring inside impact test and additional cylinder impact test. Through the tests the impact parameter change dependent upon the material difference of impacting ball is studied, and the impact parameters of Force Transducer Assembly components are measured. And also the dynamic behavior of Force Transducer Assembly is analyzed. The force measurement technique herein is shown to provide a reasonable measure of dynamic contact forces.