• 한국정밀공학회지
• /
• 제21권5호
• /
• pp.114-121
• /
• 2004

Recently, the finite element absolute nodal coordinate formulation (ANCF) was developed for the large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. In this paper, a computation method of dynamic stress in flexible multi-body dynamics using absolute nodal coordinate formulation is proposed. Numerical examples, based on an Euler-Bernoulli beam theory, are shown to verify the efficiency of the proposed method. This method can be applied for predicting the fatigue life of a mechanical system. Moreover, this study demonstrates that structural and multi-body dynamic models can be unified in one numerical system.

• International Journal of Aeronautical and Space Sciences
• /
• 제18권1호
• /
• pp.70-81
• /
• 2017

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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.874-880
• /
• 2003

Many mechanical systems are over-constrained if only rigid bodies are used to model the system. One example of such system is a satellite system with solar panels. To avoid this over-constrained problem, solar panels can be modeled as flexible bodies. The CMS(Component Mode Synthesis) method is widely used to analyze the flexible multi-body system because it can considerably approximate the deformation of the flexible bodies using small number of well-selected mode. However, it is very difficult to decide the boundary condition and the selection of modes. In this paper, the methods for mode synthesis and setting the boundary condition are presented to analyze the flexible multi-body system with over-constraints. Finally, the reliability of proposed method is verified by solar panel's deployment test.

• 한국군사과학기술학회지
• /
• 제3권2호
• /
• pp.15-22
• /
• 2000

Shock and vibration characteristics of a tractor-trailer type vehicle system with air suspension and air coupler running on a single bump road are investigated. The vehicle system is modelled and solved to two types of models, i.e. rigid-multi-body and flexible-multi-body model, by ADAMS and NASTRAN software. And the shock impulse is given by a single bump model on the road. When the analysis results of the rigid-multi-body model is compared with those of the flexible-multi-body model, it is revealed that the vibration and accelerations of the latter model are more repetitive and larger than the former.

• 대한기계학회논문집 C: 기술과 교육
• /
• 제3권2호
• /
• pp.107-115
• /
• 2015

유연 다물체 동역학은 실제 시스템을 가능한 유사하게 수치화하여 해석할 수 있기 때문에 일반 동역학 연구에 대한 차세대 주제로 각광을 받고 있다. 이러한 유연 다물체 동역학에 대한 해석 기술은 리커다인이라는 상용 소프트웨어에 효과적으로 적용되어 있는데, 특히 강체와 유연체를 통합하여 하나의 솔버에서 해석을 할 수 있는 특징을 가지고 있다. 본 논문에서는 이러한 리커다인의 유연 다물체 동역학 솔버의 기술들을 살펴보고자 한다. 기본적으로 리커다인의 유연 다물체 동역학 해법은 동시회전 기법을 사용하는 증분 유한요소 정식화를 기존의 순환공식을 이용한 동역학 정식화에 결합함으로써 구현되어 진다. 이 과정에서 강체와 유연체 사이의 조인트나 힘 요소 등의 효율적 처리를 위해 가상 바디와 유연체 조인트 개념이 사용된다.

• Structural Engineering and Mechanics
• /
• 제37권5호
• /
• pp.475-487
• /
• 2011

In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initial solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.

• 한국공작기계학회논문집
• /
• 제11권2호
• /
• pp.80-86
• /
• 2002

Previous method of computer simulation to predict the dynamic response of a vehicle has been based on the assumption that vehicle structure is rigid. If the flexibility of the vehicle structure becomes too large to ignore, rigid body assumption will no longer give good estimation of the dynamic characteristics. Therefore, in order to predict more precise vehicle dynamic characteristics, flexible multi-body dynamic analysis of a vehicle is necessary. This paper investigates dynamic characteristics of vehicle systems with flexible frames numerically. Joint reaction forces, vertical accelerations, pitch accelerations are analyzed for the vehicle systems with various flexible frames using multi-body dynamic analysis code and finite element analysis code.

• 동력기계공학회지
• /
• 제13권5호
• /
• pp.40-45
• /
• 2009

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.

• Journal of Mechanical Science and Technology
• /
• 제20권10호
• /
• pp.1638-1645
• /
• 2006

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.

• 한국군사과학기술학회지
• /
• 제4권1호
• /
• pp.13-19
• /
• 2001

It is known that displacements, velocities and accelerations of the tractor- trailer type vehicle system in shock & vibration analysis by the flexible-multi-body dynamics including the flexibility of structure are bigger and more repetitive than them by the rigid-multi-body dynamics, and it is necessary to prove above results by the experimental field test. Therefore, in this paper, theoretical analysis by the flexible-multi-body dynamics and experimental field test for a tractor-trailer type vehicle system are conducted and their results are compared with each other. Because of unexpected metal contact and impact in the air coupler part in the field test, some accelerations measured from the experimental field test are bigger than them analyzed from the theoretical analysis, but most accelerations are well coincide with each other in the amplitudes and trends. Thus more refined dynamic analytical models for some special type vehicle systems will be possible in the future.