• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.625-636
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• 2017

This study looked into the behavior of precast concrete track due to temperature variation and initial track deformation and examined the effect of initial deformation and deformation caused by temperature gradient on the stress distribution of slab under train load. In this paper, one of two papers in a series, a finite element analysis model for calculating deformation and stress of precast concrete track was proposed; the temperature distribution and displacements measured at the precast concrete track in the field were compared with the analytical results. The results show that the slab always curled up due to initial deformation; by comparing the measured displacements with the displacements calculated by taking measured temperatures at each depth as input, the effective built-in temperature (EBITD), the temperature difference between the top and bottom of the slab corresponding to the initial deformation, can be estimated. If EBITD is relevantly assumed, the calculated displacements correlate well with the measured ones.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.129-136
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• 2004

Almost the steel bridges are manufactured and constructed by using weld process. The welding is necessary for connecting the flange, web and stiffener of steel bridges. However, residual stress and welding deformation producted by welding is a causes of decreasing the load carrying capacity of steel bridges. therefore, it is need to consider the initial stresses by welding when design the steel bridge. However, the influence of initial stress producted by welding on load carrying capacity of steel bridges is not elucidated. In this paper, the initial stress state on the flange, web and stiffener of steel bridges are clarified by carrying out 3-dimensional non-steady heat conduction analysis and 3-dimensional thermal elastic-plastic analysis. The influence of initial stress by welding on load carrying capacity of steel bridges is clarified by carrying out 3-dimensional elastic-plastic finite element analysis using finite deformation theory.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.539-547
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• 2002

The study proposed the initial equilibrium state analysis method that considers axial deformation, in order to accurately determine the initial shape of a cable-stayed bridge. Sepecifically, the proposed method adopted the successive iteration method. In order to evaluate appropriate initial cable force introduced in the initial equilibrium state analysis, parametric studies were performed and a useful linear analysis method proposed. The geometrically nonlinear static behaviors of cable-stayed bridges were considered, using three-dimensional frame element and elastic catenary cable element. The usefulness and applicability of the analytic method proposed in this study were demonstrated using numerical examples, including a real cable-stayed bridge. The algorithm, is applicable in cases wherein axial deformation is not adopted in the fabrication camber, or final cable force is adjusted to eliminate construction and fabrication errors occurring during construction.

• Structural Engineering and Mechanics
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• v.19 no.1
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• pp.73-96
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• 2005

For the spatially coupled free vibration analysis of shear deformable thin-walled non-symmetric curved beam subjected to initial axial force, an exact dynamic element stiffness matrix of curved beam is evaluated. Firstly equations of motion and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next a system of linear algebraic equations are constructed by introducing 14 displacement parameters and transforming the second order simultaneous differential equations into the first order simultaneous differential equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact $14{\times}14$ dynamic element stiffness matrix is determined using force-deformation relations. To demonstrate the accuracy and the reliability of this study, the spatially coupled natural frequencies of shear deformable thin-walled non-symmetric curved beams subjected to initial axial forces are evaluated and compared with analytical and FE solutions using isoparametric and Hermitian curved beam elements and results by ABAQUS's shell elements.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.214-223
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• 2006

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and happen large deformation phenomenon. Therefore, in this study, to find the structural shape after large deformation caused by initial stress, we need the shape analysis considering geometric nonlinear term. And we investigate the evaluation of shape analysis technique's convergence and efficiency according to the control method

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.637-648
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• 2017

In this paper, the effects of initial built-in deformation and temperature deformation on the stress distribution of discontinuous precast concrete track slab under train load were examined. According to the results, when train load is put on a precast concrete slab with initial built-in deformation and deformation due to temperature gradient, the maximum tensile stresses develop at the upper side of slab in the slab center, edge center and corner of shear pocket; the stress distribution is different from that of the case under train load only. Therefore, to accurately predict the actual weak points and failure modes, one should calculate the stress under train load considering the initial built-in and temperature deformation of the slab.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.21-28
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• 1999

In this paper, a finite element method for the determination of initial blank shape in sheet metal forming process will be introduced. The initial blank shape is determined by the only one step from the final to the initial blank. The used finite element inverse method adopted Henky's deformation theory, Hill's anisotropic yield criterion and simplified boundary conditions. Based on this theory. a three-dimensional membrane finite element code was developed. The developed code will be applied to several sheet metal forming examples for the demonstration of its validity.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.1
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• pp.1-12
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• 2020

In this study, thin foil fabrication using Ni/Ni₃Al single crystal was performed by cold-rolling. It was found that the cold-rolling behavior was strongly dependent on the initial crystallographic orientation rather than morphology of Ni₃Al precipitates. The deformation banding was formed in the case of (100)[001]- and (210)[001]-oriented specimens at 83% reduction in thickness. However, the effects of Ni₃Al precipitates morphology on the microstructure evolution of Ni/Ni₃Al single crystals during cold-rolling were not so serious comparing with the effects of initial crystallographic orientation. Therefore, it could be concluded that the deformation behavior of Ni/Ni₃Al single crystals at serious strain level was strongly dependent on the initial crystallographic orientation rather than the morphology of Ni₃Al precipitates, whereas the initial deformation behavior was related to both crystallographic orientation and the morphology of Ni₃Al precipitates.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.16-21
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• 2022

This study investigates the effect of the deformation on the sensitivity of a flexible polydimethylsiloxane (PDMS) membrane sensor. A PDMS membrane sensor was developed to measure the impact force of a water droplet using a silver nanowire (AgNW). The initial deformation of the membrane was confirmed with the application of a tensile force (i.e., tension) and fixing force (i.e., compressive force) at the gripers, which affects the sensitivity. The experimental results show that as the tension applied to the membrane increased, the sensitivity of the sensor decreased. The initial electrical resistance increased as the fixing force increased, while the sensitivity of the sensor decreased as the initial resistance increased. The movement of the membrane due to the impact force of the water droplet was observed with a high-speed camera, and was correlated with the measured sensor signal. The analysis of the motion of the membrane and droplets after collision confirmed the periodic movement of not only the membrane but also the change in the height of the droplet.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.467-472
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• 2007

In this study, the effects of initial texture on the twinning formation of AZ31 Mg rolled sheet was investigated. Uniaxial compression tests were carried out on samples cut along the normal direction(ND) and roiling direction(RD), respectively, of rolled AZ31 Mg alloy sheet at various temperatures (RT, 200, 250, 300, 350, $400^{\circ}C$) with the fixed strain rate($10^{-2}/s$). The results showed that deformation twining occurred actively only in the RD specimens, which promoted homogeneous deformation as compared to the ND specimens. The effect of temperature on the formation of deformation twins was also investigated, and the slip/twin transition temperature was found to be approximately $250^{\circ}C$.