• Journal of Mechanical Science and Technology
• /
• v.14 no.10
• /
• pp.1028-1040
• /
• 2000

A numerical method is presented for the dynamic analysis of military tracked vehicles of high mobility. To compute the impulsive dynamic contact forces which occur when a vehicle passes on a ground obstacle, the track is modeled as the combination of elastic links interconected by pin joints. The mass of each track link, the elastic elongation of a track link between pin joints by the track tension, and the elastic spring effects on the upper and lower surfaces of each track link have been considered in the equations of motion. And the chassis, torsion bar arms, and road wheels of the vehicle are modeled as the rigid multi bodies connected with kinematic constraints. The contact positions and the contact forces between the road wheels and track, and the ground and the the track are simultaneously computed with the solution of the equations of motions of the vehicle consisting of the multibodies. The iterative scheme for the solution of the multi body dynamics of the tracked vehicle is presented and the numerical simulations are conducted.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.826-830
• /
• 2007

The effects of the statistical properties of the Coulomb friction coefficients on the dynamic responses of a galloping quadruped robot are investigated in this paper. In general, the Coulomb friction coefficients are assumed to be deterministic for a controller design to achieve required motion characteristics. However, the friction coefficients between the ground and the robot legs are not constant in reality. Therefore, statistical characteristics of the friction coefficients need to be considered for a multi-body modeling of the robot galloping on the ground. The effects of the statistical properties on the dynamic responses of the quadruped robots are investigated.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.4
• /
• pp.544-550
• /
• 2003

The contact analyses of arbitrary shaped spatial bodies are important in the study of multi-body dynamics. This paper presents a method fur calculating contact force between bodies in space. At each integration time step, the proposed method finds potential contact points on bodies and then calculates the penetration, the velocity of penetration, and the contact force. A continuous analysis method is adopted to calculate the contact force. To get contact points accurately on their outlines, a new algorithm is developed. The proposed algorithm is tested and compared the results of DADS. As applications, the contact of two steel balls, spatial pendulums, and the problem of a ball and bat are demonstrated.

• Tribology and Lubricants
• /
• v.23 no.5
• /
• pp.187-194
• /
• 2007

The profile of the roller in the axial direction is the main design factor in order to increase endurance life against the contact fatigue due to the stress concentration along the edge of the roller. Even under the elas-tohydrodynamic lubrication (ehl) conditions, the stress concentration along the edge of the roller greatly worsens the fatigue life both for the roller and contacting body. In this study, roller contacts of finite axial length are studied for the film thickness and pressure of ehl. For the real contact behaviors under the ehl conditions, multigrid and multi-level method is applied so that much higher loading conditions can be investigated. Several axial profiles of roller are investigated to verify how both ehl film and pressure are generated and some of them are recommended for the ehl contact condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.607-612
• /
• 2004

Disc brake noise continues to be a major concern throughout the automotive industry despite efforts to reduce its occurrence. Eliminating vibrations during braking is an important task for both vehicle passenger comfort and reducing the overall environmental noise levels. There are several classes of disc brake noise, the major ones being squeal, judder, groan, and moan. In this study, analytical model for moan noise of rear disk brake is investigated. Modeling of the disc brake assembly to take account of the effect of different geometrical and contact parameters is studied through the use of multi-body model. The contact stiffness of the caliper and torque member plays an important role in controlling brake vibration. Therefore, a suitable material pair at the caliper/body contact has been made. An ADAMS model of a rear disc brake system was integrated with a flexible suspension trailng arm from MSC/NASTRAN. A fully non-linear dynamic simulatin of brake system behavior, containing rigid and flexible bodies, was performed for a Prescribed set of operating conditions. Simulation results were validated using data from vehicle experimental testing.

• Journal of the Society of Naval Architects of Korea
• /
• v.60 no.4
• /
• pp.288-295
• /
• 2023

This paper deals with the dynamic simulation method for analysis of driving characteristics of aircraft and towing vehicles (TUG) on carrier vessel in wave motions. For prompt deployment in a short period of time, optimization of the movement of carrier aircraft becomes a major issue. In this regards, strategy studies using real-time simulation technology and optimal decision-making technologies are being conducted. In the present work, the dynamic characteristics of carrier aircraft and TUG connected by towbar or towbarless mechanism were investigated by means of multi-body dynamics model. Meanwhile, for real-time simulation, Dugoff's model of tire loads calculation was adopted. Through comparative analysis it was confirmed that the similarity of results between the multi-body contact model and the tire load calculation model can be achieved by coefficients tuning.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.1
• /
• pp.1-7
• /
• 2010

The paper proposes a multi-body dynamic simulation to numerically evaluate the generated axial force(G.A.F) and plunging resistant force(P.R.F) practically related to the shudder and idling vibration of an automobile. A numerical analysis of two plunging types of CV joints, tripod joint(TJ) and very low axial tripod joint(VTJ), is conducted using the commercial program DAFUL. User-defined subroutines of a friction model illustrating the contacted parts of the outboard and inboard joint are subsequently developed to overcome the numerical instability and improve the solution performance. The Coulomb friction effect is applied to describe the contact models of the lubricated parts in the rolling and sliding mechanisms. The numerical results, in accordance with the joint articulation angle variation, are validated with experimentation. The offset between spider and tulip housing is demonstrated to be the critical role in producing the 3rd order component of the axial force that potentially causes the noise and vibration in vehicle. The VTJ shows an excellent behavior for the shudder when compared with TJ. In addition, a flexible nonlinear contact analysis coupled with rigid multi-body dynamics is also performed to show the dynamic strength characteristics of the rollers, housing, and spider.

• Journal of Drive and Control
• /
• v.21 no.1
• /
• pp.22-30
• /
• 2024

Gearboxes designed for reciprocating motion operating mechanisms operate under conditions where both the load and speed undergo continuous variations. When conducting durability tests on gearboxes designed for such applications, operating the target gearbox under conditions similar to the intended usage is essential. The gearbox must be operated for the required number of cycles to validate its durability under conditions mirroring its intended usage. This study devised an accelerated test method for gearboxes, which reduces operating angles and operational strokes. The reliability of the accelerated test was verified by comparing the stresses imposed on the gears under general and acceleration conditions through multi-body dynamic simulations. The results confirmed that the maximum contact stress levels under normal and accelerated conditions were within a 0.1% error range, indicating a minimal difference in the gear damage rates. However, a difference in the maximum contact stress results between the normal and accelerated conditions was observed when inertial forces acted on the output shaft due to the operational acceleration of the gearbox. Therefore, when conducting this acceleration test, caution should be exercised to ensure that the operational load on the gearbox, which affects inertia, does not significantly deviate from the conditions observed under normal operating conditions.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.1
• /
• pp.55-62
• /
• 1996

The dynamic photoelastic technique has been utilized to investigate the possibility of relieving the large local singular stresses which are induce in the corner of a right angled indenter. The indenter compresses a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effect of geometric changes to the indenter in terms of the diameter (d) and the location (ℓ) of the notch on the relieving of the dynamic contact stresses are investigated. A multi-spark-high speed camera with twelve sparks was used to take dynamic photographs. The contact singular stresses were found to be released by introducing the relief notch along the indenter. The optimal location and geometry of the relief notch need further experimental investigation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.7
• /
• pp.2097-2107
• /
• 1996

The dynamic photoelastic technique had been utilized to investigate the possibillity of relieving the large local singular stresses induced at the corner of a right- angle- indenter. The indenter compressed a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effects of the geometric changes of the indenter in terms of the diameter (d) and the location (1) of the stress relieving notch on the behavior of the dynamic contact stresses were investigated. The influence of stress relieving notches positioned along the edge of the semi-infinite body on the dynamic contact stresses were also studied by changing the diameter (D) and the location (L) of the notch. A multi-speak-high speed camera with twelve sparks were used to take photographs of full field dynamic isochromatic fringe patterns. The contact singular stresses were found to be released significantly by the stress relief notches both along the indenter and the edge of the semi-infinite body. The optimal position and geometry of the stress relieving notches were obtained with the aid of limited experimental results.