• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.6
• /
• 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.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.26 no.3
• /
• pp.252-261
• /
• 2023

Analysis of dynamic characteristics and flight vibration test for unmanned aerial vehicles was studied by using dummy test body. The FEM model for dummy test body was supplemented by results of modal and random vibration test. The free end boundary condition to simulate flight environments was made by test setup using bungee cable. Prior to the flight vibration test using a dual electric vibration exciters, the test procedure to calculate quantitative vibration level was studied by using military specification. The actual test was successfully done by using the analysis and pretest results. From the analysis results, it was possible to determine the feasibility of the test by predicting the excitation force of the flight vibration test and to get the response of any point which could not be measured by the test. The results of this study will much contribute to the Test and Evaluation of unmanned aerial vehicles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.634-637
• /
• 2007

A weighted sound pressure level has been used to evaluate sounds test or sound quality test for a refrigerator up to present but the customer had different satisfactions of refrigerator sounds with different listening position. It means that there was a sound directivity caused by a position of fan or compressor. In this paper, we proposed a sound power spectrum guideline that represents total sound of refrigerator.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.3
• /
• pp.12-18
• /
• 2001

Frequency domain has been used to detect chatter vibration and to decide commencing point of chatter for the milling processes. For this, power spectrum of accelerations signal is analyzed in the frequency domain. Also, the power spectrum and surface roughness are measured, compared, and evaluated according to the depth of cut by experimental works. As a results, it is known that the commencing point of chatter can be decided the behavior of the maximum amplitude of the power spectrum of acceleration signal and there is a correlation between the power spectrum of acceleration signal and the surface roughness. In conclusion, the power spectrum of acceleration signal can be used as a useful information for detec-tion and estimation of chatter vibration in machining.

• Journal of KSNVE
• /
• v.7 no.3
• /
• pp.439-447
• /
• 1997

In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.534-538
• /
• 2008

The vehicle system is exposed to random source in service. Therefore, it is important to consider dynamic effect of the system. But, fatigue analysis is traditionally performed by using time signal of loading. To obtain dynamic effect of resonance, we carried out resonance durability analysis with frequency response and the dynamic load on frequency domain. The study shows that the damage considering resonant frequency of fuel tank system can be effectively estimated.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.2
• /
• pp.71-78
• /
• 1998

와(vortex) 박리는 고형물체가 유동내에서의 유체의 흐름을 방해할 때 발생하는 전 형적인 주기적 진동 현상이다. 본 연구에서는 삼각주형 실린더가 유동내에 유발하는 와 발 리 특성을 가시화 기법, 와에 의해 변조된 초음파의 파워 스펙트럼 및 유동관에서의 진동측 정 등을 통해 연구하였다. 가시화 관찰과 유동측정 실험 결과, 발생 와는 발생체 전면으로부 터 3d와 5d 사이에서 가장 안정성이 유지됨을 발견하였다. 넓은 레이놀즈 수(104≤Re≤106) 의 유동영역에서 액체와 기체원형유동의 측정 실험결과로부터 스트로우할(Strouhal) 수가 와발생체 폭(d)과 형상비(d/D)의 증가함수이며, 삼각주 단면의 높이에 반비례함을 알 수 있 었다. 또한 실험 결과로부터 실린더의 기하학적 치수로 삼각주형 실린더의 스트로우할 수를 예측할 수 있는 경험식을 제시하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.42-47
• /
• 2014

In this paper, fatigue life analysis of each structure was performed through theoretical analysis method at design stage in order to verify the success or failure of the store's acoustic noise durability according to the Method 515.5 standard of MIL-STD-810F. In addition, experimental analysis was carried out through the ground and flight test by manufacturing the measuring store, and verification of the sound durability was completed through the flight test after manufacture of the actual store. Furthermore, the commercial FEM code through the PSD calculation method applying measured SPL enables verify the durability of new store components development for the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.392-395
• /
• 2006

The configuration of coaxial co-rotating contained in shroud provides a useful model for investigating the characteristics of flow in the HDD. Reynolds number is defined as $Re_R={\Omega}{R_o}^2/{\upsilon},\;Re_H={\Omega}R_oH/{\upsilon}$ in present study. An experimental investigation was performed for turbulence profiles and PSD distribution and vortices frequency behavior for various range of $Re_R=2.43{\times}10^4{\sim}3.61{\times}10^5$. A laser Doppler anemometry (LDA) is used to obtain the velocity field of unobstructed co-rotating disks flow. Airflow pattern visualization between inner and outer region was compared with turbulence profiles measured from LDA. Outer detached shear layer and dead-zone without oscillating velocity fluctuation to circumferential mean were quantitively traced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.10a
• /
• pp.416-421
• /
• 2013

In this paper, the design concept of the transport of defense equipment and processes were established. And the transport of large radar equipment design were investigated. Detailed design of moving equipment with reference to the U.S. military standard was performed.Damping system of the moving equipment by using a simulation designed to predict In order to minimize shock and vibration in the vehicle due to the irregular road surface is transmitted through. Analysis of the damping system was verified using the driving test.