정현파로 가진한 강제진동 해석과 응답특성

김종도,윤문철 중소기업융합학회 2020 융합정보논문지 Vol.10 No.7

가진 정현파 강제력에 의한 강제 진동의 특성이 연구되었고 또한, 주파수 영역에서 FRF의 수치 분석을 자세히 수행하였다. 이와 관련하여 강제 진동 모델에서 변위, 속도 및 가속도의 응답을 구하였다. 고유 주파수 주변 의 실수부와 허수부의 FRF 특성도 각 경우에 따라 구하였다. 시간 영역에서의 강제 진동의 응답분석은 정현파 강 제 진동의 특성을 식별할 수 있다. 변위, 속도 및 가속도 등의 응답을 얻기 위해 Runge-Kutta-Gill 방법의 수치해 석 기법을 수행하여 강제력 주파수에 따른 응답을 얻었고 이 주파수는 응답에 큰 영향을 미치지 않았다. 또한, FRF 는 강제 진동의 고유 특성을 나타내고 있으며 이러한 강제 진동 모델의 각 감쇠 조건에서 이러한 응답분석을 성공 적으로 자세하게 얻을 수 있었다. 상이한 질량, 감쇠 및 강성에 대한 수치 분석 후, 정현파 강제력에 의한 강제 진동 응답 특성을 강제력의 진폭 및 주파수를 동시에 고려하여 분석되었다. The characteristics of forced vibration with excited sinusoidal force was introduced. Also, numerical analyses and FRF in frequency domain were performed in detail. In this regard, the responses of displacement, velocity and acceleration were investigated in a forced vibration model. The FRF characteristics in real and imaginary part around natural frequency are also discussed. This response approach of forced vibration in time domain is used for the identification and monitoring of sinusoidal forced vibration. For acquiring a displacement, velocity and acceleration, a numerical technique of Runge-Kutta-Gill method was performed. For the FRF(frequency response function), These responses are used. Also, the FRF can represent the intrinsic characteristics of the forced vibration. These performed results and analysis are successful in each damped condition for the forced vibration model. After numerical analysis of the different mass, damping and stiffness, the forced vibration response characteristics with sinusoidal force was discriminated considering its amplitude and frequency simultaneously.

통계적 에너지 분석법의 FRF를 이용한 충격 응답 스텍트럼(SRS)의 결정

구성완,황철규,김인성 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.7

A method how to determine the shock response spectrum from the FRF of the statistical energy analysis( SEA ) is presented here. The system of 3 different Plates connected by bolt joints is selected simulating missile structural sections Joined together. First, the SEA model was rendered by SEA parameters which were determined from experimental SEA method. Then, the mobility power was input to the SEA model and we can verify the validity of the model in the medium to high frequency range checking the reproduction of output average velocity. And, the shock induced shock response spectrum(SRS) was obtained using SEA FRF and arbitrarily chosen experimental FRF. We have compared the thus obtained SRS with actually measured SRS and they were relatively in good agreement. In this paper, we used the measured SEA FRF and therefore we have got the SRS well agreed with actually measured SHS even in the low frequency range. If the SEA FRF of well verified SEA model is used, the good result will come out in SEA effective frequency range which is more important at SRS.

엔드밀 가공시 절삭력을 이용한 공구날 주파수 분석법

김종도(Jong-Do Kim),윤문철(Moon-Chul Yoon),조현덕(Hyun-Deog Cho) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.4

The mode analysis of end-milling was introduced using recursive parametric modeling. Also, a numerical mode analysis of FRF in end-milling at different conditions was performed systematically. In this regard, a REIVM(recursive extended instrumental variable method) modeling algorithm was adopted and natural modes of real and imaginary part were discussed. This recursive approach can be used for the on-line system identification and monitoring of an end-milling for this purpose. For acquiring a cutting force, an experimental practice was performed. And these end-milling forces were used for the calculation of FRF(Frequency response function) and its mode analysis. Also, the FRF was analysed for the prediction of end-milling system. As a results, this algorithm was successful in each condition for the detection of natural modes of end-milling. After numerical analysis of the FRF, the tooth passing frequency was discriminated in their FRF, power spectrum and mode calculation.

둔턱 진행 차량의 승객수와 속도에 따른 파워스펙트럼 특성분석

이혁(Hyuk Lee),김종도(Jong-Do Kim),윤문철(Moon-chul Yoon) 한국기계가공학회 2022 한국기계가공학회지 Vol.21 No.1

Vehicle vibration was introduced in the time and frequency domains using fast Fourier transform (FFT) analysis. In particular, a vibration mode analysis and characteristics of the frequency response function (FRF) in a sport utility vehicle (SUV) passing over a bump barrier at different speeds was performed systematically. The response behavior of the theoretical acceleration was obtained using a numerical method applied to the forced vibration model. The amplitude and frequency of the external force on the vehicle cause various power spectra with individual intrinsic system frequencies. In this regard, several modes of power spectra were acquired from the spectra and are discussed in this paper. The proposed technique can be used for monitoring the acceleration in a vehicle passing over a bump barrier. To acquire acceleration signals, various experimental runs were performed using the SUV. These acceleration signals were then used to acquire the FRF and to conduct mode analysis. The vehicle characteristics according to the vehicle condition were analyzed using FRF. In addition, the vehicle structural system and bump passing frequencies were discriminated based on their power spectra and other FRF spectra.

FRF 기반 부분구조합성법을 이용한 차량 진동성능 강건설계

원영우(Young-Woo Won),이두호(Dooho Lee) 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.2

In this study, a robust design procedure using the FRF-based substructuring (FBS) method was proposed for vehicle vibration performance. In the robust design procedure, global sensitivity analysis was used to obtain the design information of elastomers in structural systems considering uncertainties. The global sensitivity method combines the random balance design method for variance-based sensitivity information and the FRF-based substructuring (FBS) method for the calculation of vibrational responses, which establishes an efficient tool even in complex real structures. Moreover, a multi-objective optimization formulation was applied to obtain the optimal design of elastomers that give robust vibration responses. The objective functions were set to the mean and variance of the vibration responses. The Pareto optimal front was calculated using the non-dominated sorting genetic algorithm-II (NSGA-II). The genetic algorithm design variables were screened using the global sensitivity analysis results for the elastomers. These formulations were applied to a passenger car problem to obtain the optimal design of the engine mount systems. The numerical results showed that the newly introduced feature enhanced the calculation performance and the proposed procedure can be applied successfully in real complex structural problems.

하이브리드 주파수 응답함수 합성법을 이용한 차체 소음 예측 및 저감 연구

노희민(Hee-Min Noh) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Virtual FRF를 이용한 채터강성 해석에 관한 연구

강성운(Seong-Un Kim),정낙신(Nak-Shin Jeong),이강재(Kang-Jae Lee),양민양(Min-Yang Yang) 한국생산제조학회 2009 한국생산제조시스템학회 학술발표대회 논문집 Vol.2009 No.5

The prediction of chatter stable region is a significant requirement for the manufacturing industry. Usually, the chatter stability lobes are obtained by measuring the frequency response function(FRF) of a machining center using impulse test or exciter test. However, these tests are not only spent much time, but also performed after machining center is manufactured. This paper presents virtual FRF using by F.E.M for the prediction of chatter stable region. The proposed method enables a designer to estimate the chatter resistance of machine tools at the early stage of design.

Virtual FRF를 이용한 채터강성 해석에 관한 연구

김성운,정낙신,이강재,양민양 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-

The prediction of chatter stable region is a significant requirement for the manufacturing industry. Usually, the chatter stability lobes are obtained by measuring the frequency response function(FRF) of a machining center using impulse test or exciter test. However, these tests are not only spent much time, but also performed after machining center is manufactured. This paper presents virtual FRF using by F.E.M for the prediction of chatter stable region. The proposed method enables a designer to estimate the chatter resistance of machine tools at the early stage of design.

A DAMAGE IDENTIFICATION METHOD FOR THIN CYLINDRICAL SHELLS

오혁진(H. Oh),조주용(J. Cho),이우식(U. Lee) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the dynamic equations of the damaged cylindrical shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM requires only the FRF-data measured in damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.

엔드밀 가공시 절삭조건에 따른 진동응답 특성

김종도(Jong-Do Kim),김광희(Kwang-Heui Kim),윤문철(Moon-Chul Yoon) 한국기계가공학회 2024 한국기계가공학회지 Vol.23 No.5

Vibration during end-milling is a forced vibration that occurs when the end mill blade impacts the workpiece and is processed. In other words, it can be viewed as a model of forced vibration caused by an external excitation force with an impact frequency according to the number of end mill blades, a vibration characteristic that changes depending on the amplitude and frequency of the cutting force, which varies depending on the cutting force conditions during end milling. Therefore, the end milling model should be defined as a second-order system to obtain the displacement, speed, and acceleration. Additionally, by expressing this vibration model as a differential equation and performing a numerical analysis, the time and frequency responses can be analyzed. In particular, the FRF(frequency response function) was analyzed to reveal the natural frequency of the system and the characteristics of the impact frequency applied to the workpiece by the end mill. Considering the impact force caused by the four-tooth cutter as an excitation force, the natural frequency, surrounding modes, power spectrum, real and imaginary parts of the FRF and the characteristics of each mode were analyzed in detail. After numerical analysis of the different mass, damping, and rigidity of the end milling, it can distinguish several modes that occur depending on the amplitude and frequency of the end milling force. Also, the response can be determined according to the dynamic force conditions during machining and the forced-vibration response characteristics was analyzed systematically.