• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.775-784
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• 2017

This study is devoted to developing many new substructure models for ballasted railway track by using the pyramid model philosophy. As the effect of railway embankment has been less considered in the previous studies in the field of vehicle/track interaction, so the present study develops the pyramid models in the presence of railway embankment and implements them in vehicle/track interaction dynamic analyses. Considering a moving car body as multi bodies with 10 degrees of freedom and the ballasted track including rail, sleeper, ballast, subgrade and embankment, two categories of numerical analyses are performed by considering the new substructure systems including type A (initiation of stress overlap areas in adjacent sleepers from the ballast layer) or type B (initiation of stress overlap areas in adjacent sleepers from the subgrade layer). A comprehensive sensitivity analyses are performed on effective parameters such as ballast height, sleepers spacing and sleeper width. The results indicate that the stiffness of subgrade, embankment and foundation increased by increasing the ballast height. Also, by increasing the ballast height, rail and ballast vertical displacement decreased.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.266-267
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• 2007

Sandwich sheet with inner structure is expected to find many applications because of high stiffness to mass ratio. In order to simulate forming of sandwich sheet with pyramid core, an effective simulation method is required. Compared to the expensive model using solid elements, cost effective model using simplified elements such as shells and beams is developed. By comparing two models in terms of the cost and accuracy for unit cell deformation, a developed model shows some advantages over the model using solid elements. Evolution of two kind of forming limits, face buckling and core buckling are successfully expressed by developed model. Developed model is also applied in the simulation of square cup drawing and L-type bending. The corresponding experiments are carried out. Deformation shape and wrinkling behavior are compared and discussed. It is found that simulation results using a developed model are in good agreement with experiments.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.55-59
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• 2012

Reverse Design(RD) plays an important role in simulation engineering, such as CFD (Computational Fluid Dynamics) and Virtual Engineering and Design. RD becomes much more valuable when there is no shape data of the practical models for CFD grid generations. In this study, two-camera based rapid prototyping(RP) system is proposed. 3D-PTV based measurement algorithm was adopted. The developed system was applied to reconstruct three-dimensional data of a human face, a motorcycle model, a cylindrical body and a triangular pyramid.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1405-1415
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• 1994

The soil on the behavior of the nonlinear elastic work-hardening plasticity has a variety of stress paths due to the state of soil and the test conditions. The soil with a specific volume ${\upsilon}$ in principal stress space (${\sigma}_1$, ${\sigma}_2$, ${\sigma}_3$, and ${\upsilon}$v) displays the shape of an irregular hexagonal pyramid with an end cap. With variations of ${\upsilon}$ the size of the cap is changed but its shape remains unchanged and the movement of the cap is controlled by the increase or decrease of the plastic volumetric strain. By reflecting such a property of soil various cap models have been developed by researchers. In this thesis, a constitutive model of soil with a combination of the nonlinear elastic work-hardening plastic cap and the failure surfaces of Mohr-Coulomb (M-C cap model) has been developed. According to the the results of analyses using the work-hardening plastic cap model, the normally consolidated soil under shearing has experienced the work-hardening and plastic flow (movement of the cap). But in the shearing of the overconsolidated soil the elastic behavior is shown until the stress path has reached the failure surface and the cap does not move.