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잔향 수조에서의 시간 이력 수음 신호 간 교차상관을 이용한 수중 음속 계측 방법에 관한 실험적 검증
이주엽,김국현,박성주,조대승 대한조선학회 2024 大韓造船學會 論文集 Vol.61 No.1
Underwater sound speed is an important analysis parameter on an estimation of the underwater radiated noise (URN) emitted from vessels. This paper aims to present an underwater sound speed measurement procedure using a cross-correlation of time-domain acoustic signals and validate the procedure through an experiment in a reverberant water tank. For the purpose, time-domain acoustic signals transmitted by a Gaussian pulse excitation from an acoustic projector have been measured at 20 hydrophone positions in the reverberant water tank. Then, the sound speed in water has been calculated by a linear regression using 190 cross-correlation cases of distances and time lags between the received signals and the result has been compared with those estimated by the existing empirical formulae. From the result, it is regarded that the presented experimental procedure to measure an underwater sound speed is reliably applicable if the time resolution is sufficiently high in the measurement.
이태훈(Tae-Hun Lee),김용식(Young-Sik Kim),이정석(Jeong-Seok Lee) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.4
비파괴검사 분야에 대한 시뮬레이션은 다양한 결함에 대한 신호의 예측과 검사 절차 개발에 사용되어진다. 특히 비파괴검사 전용 시뮬레이션 툴인 CIVA는 정확도가 높고 빠른 계산이 가능하며, 비파괴평가 기술과 동일한 형태의 화면 표시와 시각적으로 개선된 3차원 그래픽 유저 인터페이스를 제공한다. CIVA 소프트웨어 개발자가 내부적으로 타당성 검증을 시행하겠지만, 사용 이전에 소프트웨어의 정확도를 평가하는 독립적인 유효성 검증 연구가 필요하다. 이러한 목적으로 이번 연구에서는 CIVA를 이용하여 원자로 상부 헤드 관통관 검사에 사용되는 보정시험편에 대하여 TOFD 신호를 시뮬레이션하고, 실제 검사 신호와 비교하여 시뮬레이션 신호의 정확도와 적용 범위에 대하여 검증하였다. 종합적으로, A-scan 신호, B-scan 이미지, 깊이 측정 측면에서 CIVA 시뮬레이션 결과와 실험 결과 간에 전반적으로 일치를 보였다. The simulation of nondestructive testing has been used in the prediction of the signal characteristics of various defects and in the development of the procedures. CIVA, a simulation tool dedicated to nondestructive testing, has good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with an NDE technique. Even though internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the assessment of the accuracy of the software prior to practical use. In this study, time of flight diffraction signals of ultrasonic inspection of a calibration block for reactor vessel head penetrations were simulated using CIVA. The results were compared to the experimentally inspected signals. The accuracy of the simulated signals and the possible range for simulation were verified. It was found that, there is a good agreement between the CIVA simulated and experimental results in the A-scan signal, B-scan image, and measurement of depth.
Inconel 617 재료의 소형펀치 실험을 이용한 수소취화처리재의 탄-소성 거동 및 파괴인성 유추
김낙현(Nak Hyun Kim),김윤재(Yun Jae Kim),윤기봉(Kee Bong Yoon),마영화(Young Hwa Ma) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.6
금속 재료의 수소취화 현상에 대한 분석은 수소플랜트의 안전성 평가를 위해 매우 중요하다. 수소환경하 취화된 재료의 기계적 물성과 파괴인성은 구조 건전성 평가에 가장 기본적이며 중요한 자료이다. 본 논문은 최근에 개발된 유한요소 해석 기반 현상학적 손상해석을 소형펀치 실험에 적용하고 Inconel 617 재료의 대기 중 소형펀치 실험결과와 비교 함으로써 손상해석 기법의 적용 타당성을 보였다. 또한 역변환 기법을 사용하여 소형펀치 실험으로부터 인장물성을 예측하고 인장실험으로부터 구한 재료물성과 비교하여 적용 가능성을 검증하였다. 검증된 결과를 바탕으로 수소취화된 시편에 대한 소형펀치 실험결과에 역변환 기법과 손상해석을 적용하여 수소취화 된 재료의 기계적물성과 파괴인성을 예측하였다. The hydrogen embrittlement of metallic materials is an important issue from the viewpoint of structural integrity. In this regard, the estimation of mechanical properties and fracture toughness under hydrogen conditions provides very important data. This study provides an experimental validation of the approach for simulating the small punch of Inconel 617 using finite element damage analysis, as recently proposed by the authors, and applies an inverse method for the determination of the constitutive tensile behavior of materials. The mechanical properties obtained from the inverse method are compared with those obtained from the tensile test and validated. The mechanical properties and fracture toughness are predicted by using the inverse method and finite element damage analysis.
야외 환경에 노출된 입체 구조물에 대한 열적외선 신호 예측 소프트웨어 개발 및 실험적 검증 연구
김동건(D.G. Kim),권구용(K.Y. Kwon),장현성(H.S. Jang),연윤모(Y.M. Yeon),하남구(N.K. Ha) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
This paper contains experimental validation of surface temperature and IR(infrared) signal prediction performance for a 3D object placed in an outdoor environment as part of a software development process to predict thermal infrared signals based on computational thermal analysis with considering 3D thermal conduction and unsteady state. For experimental validation, CUBI targets, which are introduced as major verification cases abroad, were produced and installed on the experimental site. Also, thermocouple wires, infrared cameras, a solar tracker and a weather station were installed on the experimental site. Performance validation was carried out step by step, and as the first step, the suitability of the algorithm applied to the developed software was determined through comparison and analysis of prediction results for surface temperature. As a second step, the self-emitted radiance calculation result and the solar and sky reflected radiance calculation algorithm were validated through the analysis of the prediction result for infrared signals. In addition, by assigning the same input conditions to the other commercial software with similar concepts and comparing the calculated results together, the limitations of modeling inevitably appear in the comparison between modeling and measurement were considered. As a result of the validation, it is judged that the thermal infrared signal prediction performance of the software developed through this study is applicable to stereoscopic objects placed in an outdoor environment. In the future, it is necessary to prepare to become software with higher reliability through performance validation of 3D objects that have more complex forms or contain heat sources.
해상용 3축 위성 안테나 다물체 동역학 및 제어 모델의 실험적 검증
김현일(Hyun-il Kim),김성수(Sung-Soo Kim),원문철(Mooncheol Won),윤진섭,Ki-sang Hwang 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Simulation based design technique is vary effective to design such antenna, since the development cost can be reduced. According to the design procedure, multibody model has been refined to carry our multibody dynamics and control simulations. Based on the design, actual hardware prototype has been fabricated. Before the actual marine test of the prototype is performed with an experimental boat, validation of the computer model have been carried out in order to study every possible cases with the experimental boat. For such validation purpose, ship motion simulator which can generate roll-pitch-yaw motion of the ship is used.
강성욱,김민지,이요셉,유승한 한국자동차공학회 2023 한국 자동차공학회논문집 Vol.31 No.9
As the development of control systems used to improve vehicle driving stability becomes more advanced, determining the intervention time of the control logic has become increasingly important. Oversteer is one of the critical factors in determining the lateral stability of a vehicle. Therefore, not only autonomous vehicles, but all vehicles require accurate predictions and judgments for oversteer to ensure driving safety. In this paper, a neural network-based artificial intelligence methodology was used to predict the presence or absence of oversteer. While previous research has been painstakingly conducted with complex judgment conditions and lookup tables, the oversteer decision model based on artificial neural networks of this paper can save time and cost because it can determine whether oversteer occurs without having to consider different individual variables. This model has been validated by using real vehicle experimental data under different driving scenarios.
중형 트럭 KEY ON/OFF 시 엔진 마운팅 진동 해석
국종영(Jongyoung Kuk),문일동(Ildong Moon),강경완(Kyungwan Kang),현상학(Sanghak Hyun),강영춘(Youngchun Kang) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system have direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key on/off of a heavy truck by experiment and simulation. The analysis model consists of the engine, body including frame, front and rear suspensions and tires. The force element between body and suspension is modeled as a combination of suspension spring and damper, and the unsprung mass has roll and pitch. The engine shake obtained from experiment was compared with the result of computer simulation, and by using the verified computer model, parametric study of the body shake on engine key on/off is performed with changing the stiffness of engine mount rubber, the engine mount angle, and position of engine mounts.
음향블랙홀 보를 이용한 비틀림 진동 감쇠기의 설계 및 실험적 확인
이두호(Dooho Lee),배시완(Si Wan Bae),김선용(Sun-Yong Kim) 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.2
In this study, a novel type of torsional vibration damper was proposed and experimentally verified. The torsional vibration damper is composed of acoustic black hole (ABH) beams arranged in the outward radial direction and a base structure to fix the root of the ABH beam. The effective frequencies of the proposed torsional vibration damper are not limited to a narrow frequency range but all frequency ranges beyond a cut-off frequency. The proposed torsional vibration damper was fabricated and examined on a test-bed for torsional vibration. The experimental results showed that the proposed torsional vibration damper reduces all vibrational peaks in the magnitude generated owing to torsional modes.