A Flexible Multi-body Dynamic Model for Analyzing the Hysteretic Characteristics and the Dynamic Stress of a Taper Leaf Spring

Il-Dong Moon,Ho-Sang Yoon,Chae-Youn Oh 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of 1~2 ㎜/sec and frequency of 132 ㎜. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.

다물체 동역학을 이용한 해상 풍력 발전 구조 해석 기법 개발

오재원(Jaewon Oh),배대성(Daesung Bae),조희제(Huije Cho),임채환(Chaewhan Rim),송진섭(Jinseop Song) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

Dynamics analysis of a floating wind turbine system is coupled with aero-elastic dynamics, hydro dynamics, multi body dynamics and control system. The aero-elastic dynamics code has been developed by NREL(National Renewable Energy Laboratory, USA). The hydro dynamics code has been developed by KIMM(Korea Institute of Machinery & Materials) and SNU(Seoul National University). Those codes have been merged on the commercial multi-body dynamics software of DAFUL made in VM(Virtual Motion). A wind turbine system consists of blade, hub, power train, nacelle, tower, platform, mooring. The blade and tower are modeled as multi-body system to apply an aero force and elastic force. Pitch and generator torque are controlled with PID controller. Added mass, damping, restoring, mooring and buoyancy forces are applied on the platform. This analysis method is verified by NREL OC3 model and FAST, developed in NREL. As a result, the two results agree well enough to verify the reliability.

Construction of simulation framework for dynamic analysis of a superconducting magnetic levitation train with flexible car bodies

하휘,박경수 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

Magnetic levitation (maglev) trains are eco-friendly and help to transport passengers efficiently and safely. Among two main types of maglev train, the EDS type is more appropriate for ultra-high-speed maglev trains. However, it has disadvantages with regard to vertical and lateral stability induced by external and internal vibrations. To analyze and evaluate the dynamics of ultra-high-speed maglev, we proposed a co-simulation framework for dynamic analysis of an EDS-type maglev with ultra-high-speed and all-flexible car bodies using couple-field analysis. First, electromagnetic forces were calculated with the superconducting coils and magnets using 2D analytic model. And a lookup table for electromagnetic forces was constructed with a large range of levitation from −100 mm to 100 mm and guidance from −50 mm to 50 mm. A rigid car body model was then constructed using a multi-body dynamics program. The flexible car body were modeled using the ANSYS program and converted using rigid body element (RBE2 element). The total simulation framework was constructed using MATLAB Simulink, and the dynamic models, electromagnetic model and lookup table were connected using a cosimulation process. The constructed co-simulation framework was used to investigate the dynamics of a high-speed train under conditions of random irregularity. As results, we found that the first bending and middle layer modes of the flexible car body mutually affected the vibration characteristics of the flexible car body compared to the rigid car body. In addition, flexible car bodies showed greater vibration than rigid car bodies because of elastic modal effects and additional vibration induced by the interactions of the car bodies.

Numerical estimation of dynamic transmission error of gear by using quasi-flexible-body modeling method

조성규,최주환,최진환,임성수 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.7

When the power transmission systems are designed or improved, an understanding of gear dynamics is essential and very important. Gear systems are not easy to investigate because gear noise has to be carefully controlled. As a result, when designing and developinggear transmission systems, it is very important to grasp the noise and reduce it. Also, it is necessary to make a clear distinction betweenrattle noises and whine noises. The rattle noise occurs by mainly hitting the tooth, and whine noise occurs by mainly rubbing the tooth inmeshing. Therefore, the whine noise is relatively related to high frequency characteristics. Our aim was to find a good way to evaluatewhine noise with a numerical approach. When the gear dynamics are investigated to evaluate the whine noise, the dynamic transmissionerror (DTE) can be utilized. But, it is very difficult to obtain the DTE results by means of not only experimental ways but also numericalcalculations. Although multi-body dynamics software has not been able to calculate the DTE practically yet, there is a possibility that thesoftware can get the DTE results. Therefore, we propose a numerical modeling method to obtain the DTE results by using multi-bodydynamics software (RecurDyn). To reduce the calculation time and represent flexibility, a rotational joint and force element with thebending stiffness are applied between gear teeth and trunk. Also the numerical results have been compared with the experimental data. The results show a good agreement with the experimental results.

철도를 활용한 선박이송시스템의 다물체 동역학 모델 구축

임재용(Jae Yong Lim),최두호(Dooho Choi),김정국(Jeongguk Kim),서승일(Sungil Seo) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10

본 연구에서는 철도를 활용한 선박 이송시스템의 선박 안정성 검증을 위한 다물체동역학 해석 모델을 구축하였다. 최근 한국철도기술연구원에서는 파나마운하와 같은 수로형운하를 대체할 수 있는 대형선박의 육상운송시스템을 제안한 바 있다. 이는 다수의 철로를 이용하여 대형선박을 육상구간에서 운송하는 기술로서 특수 다축화차 상에 선박을 선적하여 철로를 이용하여 이송하는 기술이다. 새롭게 제안된 시스템에 대하여 주행 중에 발생할 수 있는 가능한 주행 시나리오-급정지, 경사로 등판, 곡선부 주행-에 대해 선박의 안정성에 대한 검증이 필요하다. 따라서, 본 연구에서는 현재 검증연구가 진행되고 있는 10ton급 선박과 설계제작 중인 다축화차 시제품에 대하여 강체기반 다물체 동역학 모델을 구성하였으며, 안정된 선박 이송이 가능함을 검증하였다. 다물체 동역학 해석 프로그램 Daful을 이용한 본 해석 모델은 14레인을 이용한 대형선박이송시스템 검증으로 향후 확장될 것이다. In this study, a multi-body dynamics model of a ship transport system was constructed in order to ensure the stability of a ship. In recent years, Korea Railroad Research Institute (KRRI) proposed ‘Rail- Canal system’, in which a large vessel could be transported not along waterways but on land, so as to replace canals like the Panama canal. In the system, a large vessel of up to 100,000 ton Post-Panamax class was loaded on the specially-designed multi-axle freight cars, and pulled by a number of locomotives in multiple lanes. Prior to undertaking the innovative project, the system needs to be verified at various perspectives including the stability of ships. And thus, a multi-body dynamics model was constructed for two multi-axle freight cars and rails targeting on a currently investigating 10 ton class vessel, and simulated three possible driving scenarios – braking, uphill driving, driving on a curved track - using a commercially available software, Daful. It was shown that the designed multi-axle freight cars successfully transported the target ship without any significant rolling or deceleration. As a next step, the model will be extended to the largevessel transport system with fourteen lanes.

Stick-slip algorithm in a tangential contact force model for multi-body system dynamics

차호영,Juhwan Choi,류한식,최진환 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value,even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper,the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved.

A Flexible Multi-body Dynamic Model for Analyzing the Hysteretic Characteristics and the Dynamic Stress of a Taper Leaf Spring

Moon Il-Dong,Yoon Ho-Sang,Oh Chae-Youn The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of $1{\sim}2mm/sec$ and frequency of 132 mm. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.

Coupled Analysis of Thermo-Fluid-Flexible Multi-body Dynamics of a Two-Dimensional Engine Nozzle

WonJong Eun,JaeWon Kim,Oh-Joon Kwon,Chanhoon Chung,Sang-Joon Shin,Olivier A. Bauchau 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.1

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multibody dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.

대형 트레일러 차량의 범프 통과 시 유연다물체 동역학 해석

김정윤 (J. Y. Kim ),김흥수 (H. S. Kim ),김진곤 (J. G. Kim ) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6

This article deals with the transient analysis using multi-flexible body dynamics of a trailer vehicle, which is passing a bump on the flat road. In order to investigate the transient dynamic behavior of the trailer, we developed an equivalent finite element model for the trailer and a vehicle dynamic model for the truck using multi-body dynamics. The driving condition considered here is set as the trailer vehicle passes a bump on the flat road in 7km/h. And we investigate the time histories of vertical load and deflections on connecting points between the trailer and truck during the vehicle passes a bump. Due to the dynamic load resulted from the driving condition, additional stress concentrations are found in the trailer and the suspension connecting points between the trailer and rear axles along with kingpin.

Coupled Analysis of Thermo-Fluid-Flexible Multi-body Dynamics of a Two-Dimensional Engine Nozzle

Eun, WonJong,Kim, JaeWon,Kwon, Oh-Joon,Chung, Chanhoon,Shin, Sang-Joon,Bauchau, Olivier A. The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.1

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multi-body dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.