• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.747-756
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• 2007

The hydropneumatic suspension units, which have applied to the tracked vehicles, have the spring and damping function in the unit. The nonlinear characteristics such as roadwheel rotation effects, gas behavior changes, hydraulic damping characteristics, hysterisis, and frictional forces have been ignored or simplified to analyze the mathematical models in many areas. This study describes the dynamic characteristics and the nonlinear behaviors of hydropneumatic suspension unit considering the nonlinear effects such as the nonlinear spring and nonlinear damping through the simulation and the experiment. The utility of nonlinear analysis through the higher-order spectral analysis is also presented.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.262-271
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• 2004

Hydropneumatic suspension unit is an important part of tracked vehicles to absorb external impact load exerted from the non-paved road and the cannon discharge. Its absorption performance is strongly influenced by both damping and spring forces of the unit. In this paper, we numerically analyze the damping characteristics of the in-arm-type hydropneumatic suspension unit (ISU) by considering four distinct dynamic modes of the ISU damper: jounce-loading, jounce-unloading, rebound-loading and rebound-unloading. The flow rate coefficients determining the oil flow rate through the damper orifice are decided with the help of independent experiments. The wheel reaction force, the flow rate at cracking and the damping energy are parametrically investigated with respect to the orifice diameter and the wheel motion frequency.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.2
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• pp.196-209
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• 2022

Driving dynamic characteristics of semi-trailer loaded with precise equipments are very important to protect them from vibration, impact or other disturbances. In this paper, in order to identify the driving dynamic characteristics of the large scale semi-trailer equipped with swivel axle and hydropneumatic suspension unit, Dynamics Modeling & Simulation(M&S) were performed using general Dynamics Analysis Program(RecurDyn V9R2). The semi-trailer was modeled as two types - one is Multi Rigid Body Dynamics(MRBD) model, and the other Rigid-Flexible Body Dynamics(RFlex) one. The natural vibration mode and frequencies of semi-trailer body, acceleration of dummy-weight, pitch, roll and yaw of dummy-weight, swivel axle and hydropneumatic suspension cylinder support structure, and acting force of hydropneumatic suspensions etc. were obtained from the M&S. Additionally frequency analysis were performed using the data of behavior obtained from above M&S. Generally the quantitative results of RFlex are larger than them of MRBD in view of magnitude of the comparable parametric values.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.519-524
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• 2003

In this paper we discuss the dynamic characteristics of the in-arm type hydropneumatic suspension unit(ISU). For this, two accurate models are introduced. The first one is the Benedict-Webb-Rubin equation which is adopted for the spring behavior of a real gas. This equation is applicable for the high pressure of the nitrogen gas which acts as a spring in ISU system. The second one describes the behavior of a damper, which is divided into four parts - jounce-loading, jounce-unloading, rebound-loading and rebound-unloading. This approach gives a good approximation of the real damper system. For the comparison purpose, the numerical results of the dynamic behavior of ISU system using a real gas and an ideal gas are given in the paper.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.16-29
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• 1995

In this study a tracked vehicle is idealized as a 2-dimensional 9-degrees-of-freedom model which takes into account the effects of HSU units, torsion bars, and track. For the model equations of motion are derived using Kane's method. By using the equations of motion, a numerical example is solved and results are compared to those obtained by using a general purpose multi body dynamic analysis program. The comparison study shows the reasonable coherence between the two results. which confirms the effectiveness of the model. With the model, dynamic response optimization is carried out. The objective function is the peak value of the vertical acceleration of the vehicle at the driver's seat, and the constraints are the wheel travel limits, the ground clearance. and the limits of other design variables. Three different sets of design variables are chosen and used for the optimization. The results show the attenuation of the acceleration peak value. Thus the procedure presented in this study can be utilized for the design improvement of the real system.