• 대한기계학회논문집A
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• 제21권8호
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• pp.1276-1290
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• 1997

The previous elastic stiffness formulas of leaf type holddown spring assemblies(HDSs) have been corrected and extended to be able to consider the point of taper runout for the TT-HDS and all the strain energies for both the TT-HDS and the TW-HDS based on Euler beam theory and Castigliano'stheorem. The elastic stiffness sensitivity of the leaf type holddown spring assemblies was analyzed using the derived elastic stiffness formulas and their gradient vectors obtained from the mid-point formula. As a result of the sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness. In addition, it was found that the sensitivity of the leaf type HDS's elastic stiffness is exponentially correlated to the leaf thickness.

• 한국기계가공학회지
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• 제18권5호
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• pp.103-109
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• 2019

The pressure reducing valve for water is controlled by the load of the compression spring and the force of the fluid acting on the diaphragm of the stem. Repeated upward and downward reciprocation of the pressure-reducing valve stem damages the diaphragm, resulting in leakage. In this study, we designed a stem without a diaphragm and adjusted the stiffness of the compressing spring. In order to select the spring stiffness, springs offering a stiffness of -20%, -10%, 0%, and 10% with respect to the stiffness of the compression spring attached to the existing pressure reducing valve stiffness. A prototype for the pressure reducing valve was fabricated and the pressure change was evaluated for the target static pressure (6 bar) by testing the pressure characteristics after mounting the modified stem and each compression spring. Evaluation of the pressure characteristics was carried out using ASSE 1003 and KS B 6153. In addition, the flow rates were compared by internal flow analysis of the conventional pressure reducing valve and the pressure reducing valve using the modified stems, and the flow analysis was performed using Solidworks flow simulation 2018. The spring stiffness was constantly discharged at the target static pressure of 3.793 kgf/mm, and the flow rate was increased by about 15% compared with the conventional pressure reducing valve.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.89-96
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• 1999

This paper presents the optimization design technique on the joint stiffness and section characteristic factors of chassis frame, by using beam and spring elements in a given design package. Two correction methods are used for the optimization design of chassis frame. First is the equivalent inertia of moment method in relation to the section characteristic factors of joint zones, which are thickness , width and height of frame channel section. Second is the rotational spring element with joint stiffness of joint zones. The CAE example shows that the relationship of section characteristic factors and joint stiffness can effectively be used in designing chassis frame. In this point, if static and dynamic targets are given, the joint-zone and section characteristic factors of chassis frame intended may be designed and defined by using beam and rotational spring elements.

• 유공압시스템학회논문집
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• 제8권2호
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• pp.17-22
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• 2011

The analysis of an air spring characteristics is necessary to design and control automotive air suspension system properly. A mathematical model of an air spring was derived in light of energy conservation first. Then static and dynamic experiments of the air spring have been fulfilled. The static stiffness with various initial pressures and effective areas were obtained from the static experimental results. Theoretical static stiffness obtained by using the mathematical model and effective area data is in close accordance with the experimental estimation. The dynamic experimental results show that the hysteresis in displacement-force cycle decreases when the frequency of the harmonic displacement excitation signal increases, but it does not change too much as the frequency is higher than 1Hz. And the dynamic stiffness goes up with increasing of the initial pressure and the excitation frequency.

• 한국소음진동공학회논문집
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• 제27권2호
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• pp.162-167
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• 2017

The chevron rubber spring is used for subway vehicle as a primary suspension. Generally, the primary suspension has an influence to the running performance and not so much effect on the ride comfort in railway vehicle. But the stiffness of chevron spring is harder and harder as time goes on because of rubber characteristics. Therefore the dynamic characteristics such as ride comfort and derailment coefficient should be reviewed according to the stiffness variation of chevron rubber spring. In this paper the effect of chevron rubber spring on dynamic characteristics was studied by considering multi-body dynamics of railway vehicle on one straight line and seven curved lines.

• 한국기계가공학회지
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• 제13권3호
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• pp.49-55
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• 2014

This paper examines the effects of spring characteristics and stiffness in relation to the characteristics of hydrodynamic force. Spring forces and stiffness determine the performance of this type of pan check valve and have an effect on the overall operation. The hydraulic efficiency of the pan check valve is relatively low compared to that of a common check valve. However, a pan check valve is structurally more stable than a common check valve. We implemented the optimum design to increase the flow rate and to resolve the suppression of the pressure drop according to the extent of the compression of the spring. From the results of a flow analysis, we demonstrate spring stiffness design criteria depending on the extent of the compression of the spring of pan check valve acting on the fluid at the inlet 1 MPa pressure.

• 융복합기술연구소 논문집
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• 제3권2호
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• pp.23-29
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• 2013

When a human operator interacts with a virtual wall that is modeled as a virtual spring model, the lager the stiffness of the virtual spring is, the more realistic the operator feels that the virtual wall is. In the previous studies, it is shown that the maximum available stiffness of a virtual spring to guarantee the stability can be increased when the first-order-hold method is applied, however the effects of a human impedance on the stability are not considered. This paper presents the effects of a human impedance on stability of haptic system with a virtual spring and a first-order-hold (FOH) method. The human impedance model is modeled as a linear second-order system model. The relations between the maximum available stiffness of a virtual spring and the human impedance such as a mass, a damping and a stiffness are analyzed through the MATLAB simulation. It is shown that the maximum available stiffness is proportional to the square root of the human mass or damping respectively.

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.293-304
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• 2021

Structural failure due to seismic pounding between two adjacent buildings is one of the major concerns in the context of structural damage. Pounding between adjacent structures is a commonly observed phenomenon during major earthquakes. When modelling the structural response, stiffness of impact spring elements is considered to be one of the most important parameters when the impact force during collision of adjacent buildings is calculated. Determining valid and realistic stiffness values is essential in numerical simulations of pounding forces between adjacent buildings in order to achieve reasonable results. Several impact model stiffness values have been presented by various researchers to simulate pounding forces between adjacent structures. These values were mathematically calculated or estimated. In this study, a linear spring impact element model is used to simulate the pounding forces between two adjacent structures. An experimental model reported in literature was adopted to investigate the effect of different impact element stiffness k on the force intensity and number of impacts simulated by Finite Element (FE) analysis. Several numerical analyses have been conducted using SAP2000 and the collected results were used for further mathematical evaluations. The results of this study concluded the major factors that may actualise the stiffness value for impact element models. The number of impacts and the maximum impact force were found to be the core concept for finding the optimal range of stiffness values. For the experimental model investigated, the range of optimal stiffness values has also been presented and discussed.

• 대한기계학회논문집
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• 제18권6호
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• pp.1496-1502
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• 1994

The influences of spring position and spring stiffness on the critical force of a cantilevered beam subjected to a follower force are investigated. The spring attatched to the beam is assumed to be a translational one and can be located at arbitrary positions of the beam as it has not been assumed so far. The effects of transeverse shear deformation and rotary intertia of the beam are also included in this analysis. The charateristic equation for the system is derived and a finite element model of the beam using local coordinates is formulated through extended Hamilton's principle. It is found that when the spring is located at position less than that of 0.5L, the flutter type instability only exists. It is shown that the spring position approaches to the free end of the beam from its midpoint, instability type is changed from flutter to divergence through the jump phenomina according to the increase of spring stiffness.

• 동력기계공학회지
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• 제18권2호
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• pp.77-82
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• 2014

The air spring is widely used in various fields such as a suspension system and an anti-vibration system because the natural frequency is kept constant regardless of the change in the load, spring constant is easy to change, and, vibration and shock isolation performance are excellent. The purpose of this study is to derive a nonlinear governing equation of an air spring, to analyze the effect of the various parameters on the dynamic stiffness of the air spring, and, to suggest a more efficient design method of an air spring system. In order to do so, this study investigates the impact of all the parameters that could affect the dynamic stiffness of the air spring while changing the excitation amplitude and the frequency with a developed governing equation.