• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.9
• /
• pp.1352-1358
• /
• 2004

The mechanical spring is one of widely used machine elements. Among various kinds, flat-type spring loaded by a rotating pin was studied. A flat spring was simplified to a cantilever beam, and numerical analysis was attempted. Since the loading pin rotates about a separate axis from the fixed spring or vice versa, the location, direction, and magnitude of the contact force including normal contact and friction loads vary accordingly. Meanwhile, the spring is deformed substantially as the relative motion progresses. Therefore, this problem needs to be formulated taking the follower loading characteristics and geometrical non-linearity into account. Derived nonlinear differential equation was solved to yield the spring deflection, contact force and the torque to rotate the pin, and the result was compared with a finite element solution. Also, the influences of principal design parameters were studied. The proposed methodology is expected to be useful for the design of pin-loaded flat spring and the prevention of mechanical failures in the form of yielding or fatigue failure of spring or severe wear of the components.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.4 s.22
• /
• pp.63-72
• /
• 2006

Fundamental equations of a member to analysis the elasto-plastic buckling analysis based on the deflection method are derived in this paper, and its validity and accuracy are shown by the numerical examples. The model discussing in the present paper has three elasto-plastic springs which are located at the both ends and center of a member and two elastic beam elements between them. The elasto-plastic springs represent the elasto-plastic behavior of the member and elastic beam element represents buckling behavior of the member. Numerical example shows the validity of this formulation.

• Journal of Drive and Control
• /
• v.18 no.2
• /
• pp.38-45
• /
• 2021

In recent years, the demand for an onboard scale system which can directly monitor load distribution and overload of vehicles has increased. Depending on the suspension type of the vehicle, the onboard scale system could use different types of sensors, such as, angle sensors, pressure sensors, load cells, etc. In the case of a vehicle equipped with leaf spring suspension system, the load of the vehicle is measured by using the deflection or displacement of the leaf spring. Leaf springs have hysteresis characteristics that vary in displacement depending on the load state. These characteristics cause load measurement errors when moving or removing cargoes. Therefore, this study aimed at developing an onboard scale device for cargo vehicles equipped with leaf springs. A sectional modeling method which can reduce measurement errors caused by hysteresis characteristics was also proposed.

• International Journal of Highway Engineering
• /
• v.10 no.3
• /
• pp.209-220
• /
• 2008

This paper presents the differences in the analysis results according to the underlying layer modeling methods when analyzing the curling behaviors of the concrete slabs on grade under environmental loads. The models of the slab on grade system considered in this study included a three-dimensional(3D) model, a model composed of 3D slab and springs for underlying layers, and a model composed of 2D slab and springs for underlying layers. First, when the underlying layer consisted of one layer, the curling behaviors according to the different models were compared. Then, the underlying layers that consisted of two different materials and thicknesses were considered. The results of this study showed that the tensionless spring model for the underlying layer gave very accurate results when the underlying layer consisted of one layer. However, when the underlying layers consisted of two layers, the spring model for the underlying layers could overestimate the displacements and underestimate the maximum stress with a large elastic modulus of upper underlying layer, a small elastic modulus of under underlying layer, and thick underlying layers.

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.6
• /
• pp.667-674
• /
• 2022

In this study, the correlation between the damage type and operating conditions of the sleepers was analyzed based on the design data and visual inspection results for the concrete sleepers of the sleeper floating track (STEDEF) that have been in operation for more than 20 years. It appeared in the form of cracks, breakages, and breaks in the concrete at the center and tie bar contact and buried areas. As a result of the numerical analysis, it was analyzed that the change in the left and right spring stiffness of the sleeper resilience pad increases the maximum stress, tensile stress, compressive stress, and displacement of the concrete sleeper, and stress concentration in the concrete at the tie bar contact area. It was proved analytically that the sleeper resilience pad can affect the damage of the concrete sleeper. Therefore, damage of concrete sleepers in the sleeper floating track in urban transit could be caused by changes in spring stiffness of sleeper resilience pads. It was reviewed that preventive maintenance such as improvement and timely replacement of sleeper resilience pads was necessary.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.8
• /
• pp.3638-3643
• /
• 2013

These days, workers in a construction site conduct a rebar bending process with a machine. This bending process has some problems such as long processing time and bad quality of the rebar. In order to manufacture a rebar having precision and machinability, we should study on Spring-back phenomenon. This phenomenon affects a shape of rebar after unloading due to restoration ability of material and it is influenced by bending angle, bending radius and a rebar diameter. The change of spring-back ratio according to the change of the parameters are analyzed by FEM. Consequently, Spring-back increases around $0.1^{\circ}$ as bending angle increases $10^{\circ}$. and it also increases around $0.6^{\circ}$ as diameter of rebar increases from ${\varphi}$ 10mm to ${\varphi}$ 16mm. while we can confirm that it decreases around $0.2^{\circ}$ as bending angle increases $10^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.5
• /
• pp.606-612
• /
• 1985

On the stability of the Beck's column with a tip mass, the influence of the characteristics of the springs at the fixed end of the column are studied. The equations of motion and boundary conditions of this system are established by using the Hamiton's principle. On the evaluation of the stability of the column, t he effect of the shear deformation and rotatory inertial is considered in calculation. For the maintenance of the stability of the column, it is proved that the constant of the translational spring at the fixed end must be very large while th magnitude of the constant of the rotational spring at the fixed end has no effect. When the constants of the springs at the fixed end are small, it is also proved that the influence of the moment of inertial of the tip mass on the stability of the column are decreased and for the translational spring the degree of the decrease is more and more. Therefore it is found that the characteristics of the springs at the fixed end are very effective elements for the stability of the column when the columns subjected to a compressive follower force are designed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.185-190
• /
• 2007

In recent days, vibration isolation system is mostly required in precise measurement and manufacturing system to reduce vibration due to external disturbances and internal actuators. Among all the vibration isolation systems, air spring is widely used because of its low resonant frequency and high damping ratio. In this study, we first analyze the passive air-spring system using leveling valve, and then design the active vibration isolation system. Because the non-linearity of pneumatic characteristics, we try to design the fuzzy controller which is better than PID controller at complex and non-linear system, and then compare them both in experiment and simulation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.221-224
• /
• 2008

A secant stiffness linear analysis method was developed for moment redistribution of moment-resisting frames. In the proposed method, rotational spring models are used for plastic hinges of the members whose flexural moments are needed to be redistributed. At the plastic hinges, secant stiffness is used to address the effect of the flexural stiffness reduced by inelastic deformation. Linear analysis is repeated with adjusted secant stiffness until the flexural equilibrium is satisfied in the structure and members. By using the secant stiffness analysis, the effect of the inelastic deformation on the moment redistribution can be considered. Further, the safety of plastic hinges can be evaluated by comparing the inelastic rotation resulting from the secant stiffness analysis with the rotational capacity of the plastic hinges. For verification, the proposed method was applied to a continuous beam tested in previous study. A application example for a multiple story moment-resisting frame was presented.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.19 no.3
• /
• pp.10-15
• /
• 2011

The separation actuator for the small satellite should fix satellite appendages with high clamping force. After operation, it has to be separated from the satellite body without any damage on satellite system and release the appendages such as a solar panel and an antenna successfully. Therefore, we invent a non-explosive separation actuator for the small satellite which generates low shock and is resettable. In order to confirm performance of the proposed separation actuator, we carried out experiments for separation time, maximum preload for activation, and shock level.