• Title, Summary, Keyword: 시스템다이나믹스

Search Result 181, Processing Time 0.049 seconds

Development of a Simplified Vulnerability Analysis Program for Naval Vessel (함정 간이 취약성 해석 프로그램 개발에 대한 연구)

  • Shin, Yun-Ho;Kwon, Jeong-Il;Chung, Jung-Hoon
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.50 no.6
    • /
    • pp.383-389
    • /
    • 2013
  • Analysis and review of survivability is one of the most important aspects when naval vessels are designed. Because aiming points of threat towards the naval vessels in the battle field could not be estimated exactly, probabilistic and statistic approach is frequently introduced to evaluate and enhance the vessel survivability. Some commercial survivability analysis programs are used to perform the analysis for enhancement of susceptibility, vulnerability and recoverability but, they are usually classified and impossible to be exported to other countries because of their national security. In this paper, a simplified vulnerability analysis program is developed to evaluate the vulnerability of the warship in aspects of structure, redundancy and its mission capability at the conceptual design stage. To verify the developed program, the analysis results were compared with those of the commercial program MOTISS(Measure of Total Integrated System Survivability).

A Study on the Statistical Model Validation using Response-adaptive Experimental Design (반응적응 시험설계법을 이용하는 통계적 해석모델 검증 기법 연구)

  • Jung, Byung Chang;Huh, Young-Chul;Moon, Seok-Jun;Kim, Young Joong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.347-349
    • /
    • 2014
  • Model verification and validation (V&V) is a current research topic to build computational models with high predictive capability by addressing the general concepts, processes and statistical techniques. The hypothesis test for validity check is one of the model validation techniques and gives a guideline to evaluate the validity of a computational model when limited experimental data only exist due to restricted test resources (e.g., time and budget). The hypothesis test for validity check mainly employ Type I error, the risk of rejecting the valid computational model, for the validity evaluation since quantification of Type II error is not feasible for model validation. However, Type II error, the risk of accepting invalid computational model, should be importantly considered for an engineered products having high risk on predicted results. This paper proposes a technique named as the response-adaptive experimental design to reduce Type II error by adaptively designing experimental conditions for the validation experiment. A tire tread block problem and a numerical example are employed to show the effectiveness of the response-adaptive experimental design for the validity evaluation.

  • PDF

A Review on the Blast Resistant Design for Glazing and Window Systems Subject to High-explosive Loadings (공기 중 폭발하중에 대한 창호시스템의 방폭설계 절차에 관한 고찰)

  • Huh, Young-Cheol;Chung, Tae-Young;Oh, Sung-Keun
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.20 no.12
    • /
    • pp.1229-1235
    • /
    • 2010
  • Anti-terrorism design for public buildings as well as military facilities is important to minimize the mass casualties from terrorist attacks. Also, well designed glazing and window systems can reduce the potential injury of human caused by scattering fragment of a glazing. In this paper, blast resistant design for glazing and window systems is investigated based on the U.S. Standard. The design procedures include minimum requirements for the design, standard practice for design evaluation of the glazing and standard test method for evaluation of the performance.

Modeling the Dynamics of Wildbird's Avian Influenza Using the System Dynamics (시스템다이나믹스를 이용한 철새의 AI 전파 모델)

  • Park, Young-wook;Won, Dong-gyu;Choi, Sung-Bae
    • Proceedings of the Korea Contents Association Conference
    • /
    • /
    • pp.1130-1135
    • /
    • 2009
  • Avian Influenza is an infectious desease of birds. The infection can cause a wide spectrum of symptoms in birds, ranging from mild illness to a rapidly fatal diseases which might bring a tremendous economic loss to poultry farms[1]. It can also give fatal diseases to human. Therefore it is important to surveil wildbirds that are primary transportation of avian influenza. This report showed a relationship between avian influenza and a habitat of wildbirds using system dynamics, and concluded with suggestion for surveilance.

  • PDF

Performance Analysis of Oil-lubricated Thrust Collars in Integrally Geared Compressors (증속 기어 압축기용 스러스트 칼라의 윤활 성능 해석)

  • Lee, Donghyun;Kim, Byungok;Sun, Kyungho
    • Tribology and Lubricants
    • /
    • v.34 no.5
    • /
    • pp.169-174
    • /
    • 2018
  • A multi-stage compressor (MSC) is comprised of several impellers installed in the pinion gear shaft driven by a main bull gear. In the pinion shaft, a thrust collar (TC) is installed to support the thrust load. The TC makes the lubrication system simpler in the MSC; therefore, it is widely used in similar kinds of machinery. Typically, TCs are installed on both sides of the bull gear and pressure is developed in the lubricated area by creating a taper angle on the TC and bull gear surface. In the current study, we developed a numerical analysis model to evaluate the performance of the TC considering its design parameters. We sloved the Reynolds equation using the finite element method and applied the half Sommerfeld condition to consider cavitation. Based on the pressure calculated in the lubricated area, we calculated the power loss and minimum film thickness. In addition, we calculated stiffness and damping using perturbation method. We performed parametric studies using the developed model. The results of the analysis show that the maximum pressure presents in the center area of the TC and it increases with the taper angle. The area over which pressure is developed decreases with the taper angle. The results also show that there is an optimum taper angle providing minimum power loss and maximum film thickness. Additionally, the stiffness and damping decrease with the taper angle. As the applied load increases, the power loss increases and the minimum film thickness decreases. However, the stiffness and damping increase with the applied load.

Rotordynamic Performance Analysis and Operation Test of a Power Turbine for the Super critical CO2 Cycle Application (초임계 CO2 발전용 파워 터빈의 회전체 동역학 해석 및 구동 시험)

  • Lee, Donghyun;Kim, Byungok;Sun, Kyungho;Lim, Hyungsoo
    • Tribology and Lubricants
    • /
    • v.33 no.1
    • /
    • pp.9-14
    • /
    • 2017
  • This paper presents a rotordynamic analysis and the operation of a power turbine applied to a 250 kW super-critical $CO_2$ cycle. The power turbine consists of a turbine wheel and a shaft supported by two fluid film bearings. We use a tilting pad bearing for the power turbine owing to the high speed operation, and employ copper backing pads to improve the thermal management of the bearing. We conduct a rotordynamic analysis based on the design parameters of the power turbine. The dynamic coefficients of the tilting pad bearings were calculated based on the iso-thermal lubrication theory and turbine wheel was modeled as equivalent inertia. The predicted Cambell diagram showed that there are two critical speeds, namely the conical and bending critical speeds under the rated speed. However, the unbalance response prediction showed that vibration levels are controlled within 10 mm for all speed ranges owing to the high damping ratio of the modes. Additionally, the predicted logarithmic decrement indicates that there is no unstable mode. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation, and we monitor the shaft vibration and temperature of the lubricant during the test. In the steady state, we record a temperature rise of $40^{\circ}C$ between the inlet and outlet lubricant and the measured shaft vibration shows good agreement with the prediction.

Stability Analysis of Floating Ring Bearing Supported Turbocharger (플로팅 링 베어링으로 지지된 터보차저 로터의 안정성 해석)

  • Lee, Donghyun;Kim, Youngcheol;Kim, Byungok
    • Tribology and Lubricants
    • /
    • v.31 no.6
    • /
    • pp.302-307
    • /
    • 2015
  • The use of turbocharger in internal combustion engines has increased as it is a key components for improving system efficiency without increasing engine size. Because of increasing demand, many studies have evaluated rotordynamic performance so as to increase rotation speed. This paper presents a linear and nonlinear analysis model for a turbocharger rotor supported by a floating ring bearing. We constructed rotor model by using the finite element method and approximated bearings as being infinitely short. In the linear model, we considered fluid film force as stiffness and damping element. In nonlinear analysis, calculation of the fluid film force involved solving the time dependent Reynolds equation. We verified the developed model by comparing the results to those of previous research. The analysis results show that there are four unstable modes, which are rigid body modes combining ring and rotor motion. As the rotating speed increases, the logarithmic decrement shows that certain unstable modes goes into the stable area or the stable mode goes into the unstable area. These unstable modes appear as sub-synchronous vibrations in nonlinear analysis. In nonlinear analysis frequency jump phenomenon demonstrated in several experimental studies appears. The analysis results also showed that frequency jump phenomenon occurs when the vibration mode changes and the sequence of unstable mode matches the linear analysis result. However, the natural frequency predicted using linear analysis differs from those obtained using nonlinear analysis.