• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1638-1645
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• 2006

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of $1{\sim}2mm/sec$ and frequency of 132 mm. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.147-153
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• 2004

This paper presents an analytical modeling technique fer representing a hysteretic behavior of a multi-leaf spring used for a large truck. It divides a nonlinear hysteretic curve of the multi-leaf spring into four parts; loading part, unloading part and two transition parts. It provides conditions fur branching to a part of the curve corresponding to a current multi-leaf spring status. This paper also presents a computational modeling technique of the multi-leaf spring. It models the multi-leaf spring with three links and a shackle. It assumes those components as rigid bodies. The links are connected by rotational joints, and have rotational springs at the joints. The spring constants of the rotational springs are computed with a force from the analytical model of the hysteretic curve of the multi-leaf spring. Static and dynamic tests are performed to verify the reliability of the presented techniques. The tests are performed with various amplitudes and excitation frequencies. The hysteretic curves from the tests are compared with those from the simulations. Since th e presented techniques reproduce the hysteretic characteristic of the multi -leaf spring faithfully, they contribute on improving the reliability of the computational model of a large truck.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.270-276
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• 2005

This paper develops the flexible computational model of a heavy truck by interfacing the frame modeled as a flexible body to the heavy truck's computational model composed of rigid bodies. The frame is modeled by the finite element method. Three torsional modes and three bending modes of the frame are considered for the interface of the heavy truck's computational model. The actual vehicle test is conducted off road with a velocity of 20km/h. The vertical accelerations at the cab and front axle are measured in the test. For the verification of the developed computational model, the measured vertical acceleration profiles are compared with the simulation results of the heavy truck's flexible computational model. E grade irregular road profile of ISO is used as an excitation input in the simulation. The verified flexible computational model is used to compare the vibration characteristics of a front suspension system having a multi-leaf spring and that having a tapered leaf spring. The comparison results show that the front suspension having a tapered leaf spring has a higher vertical acceleration at the front axle but a lower vertical acceleration at the cab than the suspension system having a multi-leaf spring.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.413-419
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• 2000

An efficient method for calculating the nonlinear stiffness of the Progressive Multi-Leaf Spring is developed and evaluated. It utilizes the interaction between the main and help spring that induces the nonlinearity. The main and the help springs are modeled as multi-leaf cantilever beams, and, then, they are integrated as one by connecting the two models for each side of the Progressive Multi-Leaf Spring at the center-bolt. The results from the developed model are evaluated by use of the commercial FEA program, ABAQUS. The nonlinear spring coefficients calculated by FEM analysis yield the numbers very close to the numbers calculated for the spring coefficients by used of the developed method. From the comparative evaluations, the developed method is accurate enough and very efficient in calculation time for evaluating the nonlinear spring property of the Progressive Multi-Leaf Spring.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.67-72
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• 2010

In this study, performance analysis and design optimization is carried out for a multi-rate spring brake system, which is used in a cable ride to stop the arriving passengers in safe and comfortable manner. Mathematical model for the spring is developed toward the objective of minimizing the impact at the arrival while satisfying the constraint of limited distance at the stop. Matlab code is utilized to examine parameters affecting the performance of the brake system. The results are validated by a commercial software RecurDyn. Kriging meta model is used to reduce the computational cost of the analysis. Optimization is conducted by RecurDyn, from which the design parameters are determined that minimizes the impact at the stop.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.17-30
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• 1993

A practical multi-spring model is proposed for a nonlinear analysis of reinforced concrete members, especially columns, taking into account the interaction of axial load and bi-directional bending moment. The parameters of the model are determined on the basis of material properties and section geometry. The axial force-moment interaction curve of reinforced concrete sections predicted by the model was shown to agree well with those obtained by the flexural analysis utilizing realistic stress-strain relations of materials. The reliability of the model was also examined with respect to the test of reinforced concrete columns subjected to varying axial load and bi-directional lateral load reversals. The analytical results agreed well with the experiment.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.107-113
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• 2006

This paper presents an efficient dynamic modeling method for multi-stepped rotor system using effective spring elements to take into account the structural weakening effect due to the steps. This paper demonstrates that the Timoshenko shaft model give rise to a significant error in the case of multi-stepped rotors. An effective bending spring model is introduced to represent the structural weakening effect in the presence of steps. The proposed modeling method is validated through a series of simulations and experiments. Finally, a spindle is dealt with as an analysis example.

• Journal of the Society of Disaster Information
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• v.3 no.2
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• pp.147-169
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• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.199-207
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• 2003

The Timoshenko beam model has been known as the most accurate model for representing beam structures. However, the Timoshenko beam model may give rise to a significant error when it is applied to multi-stepped beam structures. This paper is intended to demonstrate the modeling error of Timoshenko beam based finite element model for multi-stepped beam structures and to suggest a new modeling method to improve the accuracy. A tentative bending spring is introduced into the stepped section to represent the softening effect due to the presence of step. This paper also proposes a finite element modeling method in the light with the tentative bending spring model for the step softening effect. The proposed method rigorously adapts computation results from a commercial finite element code. The validity of the proposed method is demonstrated through a series of simulation and experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.788-791
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• 2002

The Timoshenko beam model has been acknowledged as the most accurate model for representing beam structures. However, the Timoshenko beam model may give rise to significant error when it is applied to multi-stepped beam structures. This paper is intended to demonstrate and improve the modeling error of Timoshenko beam theory for multi-stepped team structures. A tentative bending spring is introduced to represent the stiffness change around a step in beams. This paper proposes a finite element modeling method in the light with the bending spring. The proposed method is rigorously compared with commercial finite element codes. The validity of the proposed method is also demonstrated through an experiment..