• 제목/요약/키워드: vibration acceleration magnitude

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헬기 탑재용 전자장비의 동특성 분석 절차 (Dynamic Characteristic Analysis Procedure of Helicopter-mounted Electronic Equipment)

  • 이종학;권병현;박노철;박영필
    • 한국소음진동공학회논문집
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    • 제23권8호
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    • pp.759-769
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    • 2013
  • 기동중인 헬리콥터는 공기역학적인 현상에 의하여 발생하는 불규칙 진동과 회전날개의 작동으로 인한 정현파 진동이 합성되어 발생하는 진동, 작업 및 착륙 시 발생하는 충격, 그리고 갑작스런 기동 시 발생하는 가속도와 같은 동적 하중에 노출 된다. 이때 발생하는 진동과 같은 동적 하중은 기체내부로 전달되어 헬리콥터운용에 필요한 전자장비를 가진 한다. 과거에 이러한 현상을 최소화하기 위하여 진동크기 감쇠시키기 위한 완충기를 전자장비의 장착대에 적용하여 왔다. 그러나 헬리콥터의 경우, 저주파에서 정현파 가진이 발생하므로 완충기 적용은 오히려 장착 플레이트 및 전자장비 부품의 파손을 발생시킬 수 있다. 이 연구에서는 완충기를 제거한 장착대를 동적 하중에 강건하며 전자장비에 전달되는 진동크기를 최소화 하도록 설계하였다. 완충기를 제거한 장착 대를 적용 시, 무게와 부피를 획기적으로 줄일 수 있으며 전자장비를 기체에 체결하는 나사 수가 적어짐에 따라 체결작업에 필요한 시간이 감소되는 장점을 갖는다. 최적화 해석에 적용되는 동적 하중을 선정하기 위하여 진동, 충격, 가속도하중을 비교 분석하여 가장 결정적인 동적 하중인 진동에 의한 하중을 선정하였다. 전체모델 유한요소 해석을 통하여 전자장비의 동적 거동을 분석하고 최적화 해석에 필요한 단순화 모델을 구축하였으며, 모달 테스트를 통해서 동특성을 검증하였다. 위상 최적화를 적용하여 강성대비 체적비가 큰 장착대의 형상을 도출한 후 고유진동수, 응력을 제약조건으로 무게가 최소화 되도록 하는 파라미터 최적화를 수행하여 장착대의 최종 형상 및 치수를 결정하였다. 개선모델은 체적 및 질량이 약 13 % 감소하였으며 사용시간은 규격대비 9.2배 증가하였다. 마지막으로 최적화된 장착대를 운용중인 실제 장비에 적용하여 진동환경에 대한 안정성을 평가하였다.

Seismic structural demands and inelastic deformation ratios: Sensitivity analysis and simplified models

  • Chikh, Benazouz;Laouami, Nacer;Mebarki, Ahmed;Leblouba, Moussa;Mehani, Youcef;Kibboua, Abderrahmane;Hadid, Mohamed;Benouar, Djillali
    • Earthquakes and Structures
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    • 제13권1호
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    • pp.59-66
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    • 2017
  • Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

지진 진앙지에서 지진 진동의 거리별 실측치와 발파 진동과의 비교분석에 관한 연구 (A Study on the Comparative Analysis of Seismic Waves and Blast Vibration Measurements by Distance from the Earthquake Epicenter)

  • 이승훈;신영철;강동현;임대규;김기묵;김동연;이진옥;이천식
    • 화약ㆍ발파
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    • 제42권3호
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    • pp.23-37
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    • 2024
  • 최근 국내에서 발생하는 지진으로 인해 건물, 구조물 등에 피해를 입는 경우가 자주 발생하고 있다. 그러나 지진은 언제 발생할지 알 수 없기 때문에, 지진 발생 시 자동화 계측기를 사전에 설치하지 않으면 진동 특성 값을 알기가 힘든 것이 사실이다. 다행히 6개 발파 현장에 자동화 계측기를 설치하고 있어서 이번에 지진 진동과 발파 진동 특성을 비교하고자 한다. 최근 2024년 6월 12일(수) 08시 26분에 전북 부안군 남남서쪽 4km 지역에서 발생한 규모 4.8의 지진에 대한 지진 진동 특성과 국내 발파 현장에서의 지진 진동과 발파 진동 실측값 등을 비교해 보았다. 또한, 이번 기회에 지진에 대한 발생 원인 및 피해 규모도 파악해 보고, 지진 진앙지로부터 여러 지역에 설치된 자동화 계측기로부터 나오는 특성값을 분석하여 감쇠 정도가 어느 정도 되는지도 알아보았다. 이를 통해 향후 발파 시 진동으로 인한 보호 물건 피해 등을 비교하여 현장에서 발생하는 민원을 사전에 대처하는 데 도움을 주고자 한다.

대형 컨테이너 선박의 유탄성 실선 계측 데이터 분석 Part I - 모달 파라미터 추정 (Full Scale Measurement Data Analysis of Large Container Carrier with Hydroelastic Response, Part I - Identification of Modal Parameters)

  • 김병훈;최병기;박준석;박성건;기혁근;김유일
    • 대한조선학회논문집
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    • 제55권1호
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    • pp.37-44
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    • 2018
  • To understand the dynamic characteristics of the vessel with hydroelastic response, it is very important to estimate the dynamic modal parameters such as mode shapes, natural frequency, and damping ratio. These dynamic modal parameters of full scale ship are a priori unknowns, hence to be estimated directly based upon the full scale measurement data. In this paper, dynamic modal parameters were extracted by signal processing of acceleration and strain data measured from a large container ship whose loading capacity is 9400TEU. The mode shapes of the vibrating hull were identified using the proper orthogonal decomposition and the vibration response of hull was decomposed into its modal magnitudes. Natural frequencies of specific modes were derived via Fourier transform of these modal magnitude. Also, the free decay signal of the vibrating hull was obtained through the random decrement technique and the damping ratio was estimated with accuracy.

연비 향상을 위한 반력 생성형 에코페달의 설계와 성능검증 (Design and Performance Validation of Tactile Force Generating Type Eco-pedal to Improve Fuel Economy)

  • 김지수;탁태오
    • 대한기계학회논문집A
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    • 제40권11호
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    • pp.963-970
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    • 2016
  • 본 연구는 가속페달에 반력을 생성하여 운전자의 경제운전을 유도하기 위한 에코페달의 설계와 성능 검증을 다룬다. 에코페달의 제어로직은 사전에 설정된 "허용가속도"를 바탕으로 현재 속도에서 허용되는 연료소비량을 정하고 이를 실제 연료소비량과 비교하여 에코페달의 작동을 결정하는 방식을 제안하였다. 폐달 반력은 운전자가 충분히 인지하되 불쾌감을 느끼지 않아야 하며, 차량의 정상 거동에 간섭이 없어야 한다. 스텝형과 램프형 반력 등과 같이 페달 답력이 급속하게 증가하는 형태의 반력은 반력 작동이 멈춘 직 후 운전자의 답력에 의한 급작스러운 가속 현상 때문에 적용이 어렵고, 이러한 문제가 없는 진동형 반력을 채택하였다. 진동형 반력의 주파수, 진폭, 작동시간은 운전자의 주관적 평가와 연비 향상 효과를 고려하여 결정하였다. 본 연구에서 제안된 에코페달을 차량에 장착하여 주행시험을 실시한 결과 고속도로와 시내주행에서 각각 13%와 15%의 연비향상 효과를 보여주었다.

평행식 진동탄환 암거 천공기의 연구(III)-견인력, 토크, 동력 및 모멘크에 관한 모형시험- (A Study on Balanced -type Oseillating Mole-Drainer(III)-Model Test for Draft Force, Torque, Power and Moment)

  • 김용환
    • Journal of Biosystems Engineering
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    • 제1권1호
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    • pp.1-6
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    • 1976
  • This paper is the third one of the study on balanced type oscillating mole-drainer, the first one was presented in No 9. Gyeongsang College Report and the second one in Vol. 17, No.4 of the KSAE. In the first part of this study, the characteristics of traction forces between the nonoscillating earth working equipments and oscillating ones was compared. A model of the balanced type oscillating mole-drainer, which composed of a mechanism that may reduce the machine vibration, was designed following the dimensional analysis and similitude technique. The model test was carried out to clarify the balancing mechanism of the oscillating parts and other parts of the machine. In the light of the results from the model tests, a prototype machine was made for experimental purpose. Results from the field test by a reported in the near future. In the second report, the model tests were carried out under the same soil conditions, i.e, . oscillating frequency, running velocity, and oscillating amplitude, etc. It was clear that use of balanced type oscillating model could substantially reduce the vibration of the whole system of the machine, when compared with the nonoscillating type model. In this paper(the third report), results of investigation on the traction force, power requirement, and moment. etc, is presented. Analysis of variance technique was used for analyzing the effect of the frequency, amplitude, and running velocity on the draft force, torque, power requirements, and moments. The results obtained from the model tests are as follows, 1) By practicing a balanced-type oscillating mole-drainer, it was possible to reduce the traction resistance by 55.1-61. 2 percent of traction resistance, however, was 1.75 - 1.95 times greater than the value of resistance which was induced by use of a mole-drainer with single bullet. The resistance of rear shank against soil was considered as a main causing factor of the above results. 2) As the oscillation frequency was increased, the traction resistance was decreased. Considering on the effect of oscillation the greater the amplitude, and the slower the running velocity was, the greater the reduction ratio of traction resistance was. 3) The ratio of the traction resistance of oscillating mole-drainer to that of non-oscillating one could be represented as a function of dimensionless variable (V/$Af$). The results from the tests were well agreed with the reported results from the experim ents on oscillation plow or hoe. 4) By taking a lower value of (V/$Af$), reducing the traction resistance was possible. This fact meant, however, that the efficiency of mole drain practice would be lower. 5) It was experimentally confirmed under the same condition of soil that the variable (R/$rD1^3$) could be represented as a function of a variable($V^2/gD$) when a non\ulcornerocillating mole-drainer was used. 6) When a oscillating mole-drainer was used, the variable(R/$rD_1^{3}$) could be represented as a function of two variables ($v^2/gD_1$) and (V^2/gD_1$). 7) The torque was not affected by a change of frequency. However, a relation of proportionality existed between torque and amplitude, running velocity, and ratio of bullet diameter. When a balanced type oscillating mole-drainer with two bullets was used, torque was increased by 52.8-78. 4 percent and total power requirement was also increased. 8) Total power requirement was increased linearly in accordance with the increasing frequency, 41.96 percent of total power was used for oscillating action. The magnitude of total power requirement was 1. 8-9. 4 times greater than that of a non-oscillating mechanism. In the view point of power requirement, it was not advisable to increase the frequency, amplitude, running velocity, and ratio of bullet diameter at the same time. 9) Only the positive moment occured in the rear shank. Change of the diameter of a rear bullet, could not affect the balancing against the soil resistance. It was necessary for rear bullet to have a large resistance against soil only when the rear bullet was in backward motion. 10) Within an extent of the experimental base, optimum limits for several design factors were A=0.5cm, $f$=22.5Hz, V=O. 05m/sec, and $\lambda$=1.0 By adapting these values traction resistance was reduced by 40 percent and vibration acceleration wa s reduced by 60 percent. Even though the total , power requirements for operating a balanced type oscillation mechanism was greater ~than that of non-oscillating one, using a oscillating mechanism would be more effective. Because a balanced type oscillating mechanism is used, tractive resistance will be reduced and then the lighter . tractive equipment could be used.

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