• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1371-1377
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• 2013

In this analysis, a method is presented to calculate the critical speed of a railway vehicle by using a multibody dynamic model. The contact conditions and contact forces between the wheel and the rail are formularized for the wheelset model. This is combined with the bogie model to obtain a multibody dynamic model of a railway vehicle with constraint conditions. First-order linear dynamic equations with independent coordinates are derived from the constraint equations and dynamic equations of railway vehicles using the QR decomposition method. Critical speeds are calculated for the wheelset and bogie dynamic models through an eigenvalue analysis. The influences of the design parameters on the critical speed are presented.

• Steel and Composite Structures
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• v.37 no.4
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• pp.493-501
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• 2020

The paper describes an optimization method based on the mathematical model of interaction within multibody 'bridge-track-cars" dynamic system. The interaction is connected with considerable dynamic phenomena influenced by high traffic speed (up to 400 km/h) on high-speed railroads. The trend analysis of a structure is necessary to determine the direction and resource of optimizing the system. Thus, scientific methods of decision-making process are necessary. The process requires a great amount of information analysis dealing with behavior and changes of the "bridge-track-cars system" that consists of mechanisms and structures, including transitions. The paper shows the algorithm of multi-criteria optimization that can essentially reduce weight of a bridge superstructure using big data analysis. This reduction is carried out in accordance with the constraints that have to be satisfied in any case. Optimization of real steel-concrete beam is exemplified. It demonstrates possibility of measures that are offered by the algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.50-61
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• 1994

A method for performing dynamic design sensitivity analysis of vehicle suspension systems which have three dimensional closed-loop kinematic structure is presented. A recursive form of equations of motion for a MacPherson suspension system is derived as basis for sensitivity analysis. By directly differentiating the equations of motion with respect to design variables, sensitivity equations are obtained. The direct generalize for the application of multibody dynamic sensitivity analysis. Based on the proposed sensitivity analysis, optimal design of a MacPherson suspension system is carried out taking unsprung mass, spring and damping coefficients as design variables.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.176-184
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• 2000

Recently, it becomes a very important issue to consider the mechanical systems such as high-speed vehicle and railway train moving on a flexible beam structure. Using general approach proposed in the first part of this paper, it tis possible to predict planar motion of constrained mechanical system and elastic structure with various kinds of foundation supporting condition. Combined differential-algebraic equations of motion derived from both multibody dynamics theory and Finite Element Method can be analyzed numerically using generalized coordinate partitioning algorithm. To verify the validity of this approach, results from simply supported elastic beam subjected to a moving load are compared with exact solution from a reference. Finally, parameter study is conducted for a moving vehicle model on a simply supported 3-span bridge.

• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.18-25
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• 2020

This study investigated the structural behaviors and safety of an electro-mechanical linear actuator and a load simulator with a plate spring. The material and dimensions of the plate spring were determined by theoretically calculating the stress and torsional angle for the rating load of the actuator. Thereafter, a flexible multibody dynamics (FMBD) analysis was conducted on the linear actuator and load simulator to confirm the performance of the load simulator and acquire the reaction forces acting on the actuator and simulator. The structural safety of the linear actuator and load simulator was evaluated via finite element analysis using the aforementioned reaction forces. Consequently, the proposed linear actuator and load simulator were determined to be structurally safe; however, the safety factors for the actuation rod and the housing on the actuator were excessively high. Therefore, the weight and cost must be reduced to improve their design parameters in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1489-1495
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• 2012

In this study, we perform the structural analysis of a floating offshore wind turbine tower by considering the dynamic response of the floating platform. A multibody system consisting of three blades, a hub, a nacelle, the platform, and the tower is used to model the floating wind turbine. The blades and the tower are modeled as flexible bodies using three-dimensional beam elements. The aerodynamic force on the blades is calculated by the Blade Element Momentum (BEM) theory with hub rotation. The hydrostatic, hydrodynamic, and mooring forces are considered for the platform. The structural dynamic responses of the tower are simulated by numerically solving the equations of motion. From the simulation results, the time history of the internal forces at the nodes, such as the bending moment and stress, are obtained. In conclusion, the internal forces are compared with those obtained from static analysis to assess the effects of wave loads on the structural stability of the tower.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.859-864
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• 2001

In a vacuum circuit breaker mechanism, a spring-actuated linkage system is used to satisfy the desired opening and closing characteristics of electric contacts. Because the opening and the closing dynamics of electric contacts is determined by such a linkage system, the stiffness, free length and attachment points of a spring become the important design parameters. In this paper, based on the dynamic model of the circuit breaker using a multibody dynamic program ADAMS, a optimal design procedure of determining the spring design parameters is presented. The proposed procedure is applied to the design of an opening spring for satisfying the specified opening characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.109-118
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• 2005

A functional suspension model is proposed as a kinematic describing function of the suspension that represents the relative wheel displacement in polynomial form in terms of the vertical displacement of the wheel center and steering rack displacement. The relative velocity and acceleration of the wheel is represented in terms of first and second derivatives of the kinematic describing function. The system equations of motion for the full vehicle dynamic model are systematically derived by using velocity transformation method of multi-body dynamics. The comparison of field test results and simulation results of the ADAMS/Car demonstrates the validity of the proposed functional suspension modeling method. This model is suitable for real-time vehicle dynamics analysis.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.116-122
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• 2011

A realtime simulator using an explicit integration method is introduced to improve the solving performance for the dynamic analysis of a wheeled vehicle. Because a full vehicle system has many parts, the development of a numerical technique for multiple d.o.f. and ground contacts has been required to achieve a realtime dynamics analysis. This study proposes an efficient realtime solving technique that considers the wheeled vehicle dynamics behavior with full degrees of freedom and wheel contact with soft ground such as sand or undersea ground. A combat vehicle was developed to verify this method, and its dynamics results are compared with commercial programs using implicit integration methods. The combat vehicle consists of a chassis, double wishbone type front and rear suspension, and drive train. Some cases of vehicle dynamics analysis are carried out to verify the realtime ratio.

• Structural Engineering and Mechanics
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• v.5 no.2
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• pp.209-220
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• 1997

The dynamic equations for an arbitrary cluster comprising rigid spheres or assemblies of spheres (subclusters) encountered in granular-type systems are considered. The system is treated within the framework of multibody dynamics. It is shown that for an arbitrary cluster topology the governing equations can be given in an explicit scalar from. The derivation is based on the D'Alembert principle, on inertial coordinate system for each body and direct utilization of the path matrix describing the topology. The scalar form of the equations is important in computer simulations of flow of granular-type materials. An illustrative example of a three-body system is given.