• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.166-173
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• 2007

Fatigue fracture behavior of a hybrid bolted joint was evaluated in comparison to the case of static fracture. Two kinds of specimens were fabricated for the mechanical tests; a hybrid bolted joint specimen for the shear test and a hybrid joint part specimen applied in the real tilting car body for the bending test. Characteristic fracture behaviors of those specimens under cyclic toads were obviously different from the case under static loads. For the hybrid bolted joint specimen, static shear loading caused the fracture of the bolt body itself in a pure shear mode, whereas cyclic shear loading brought about the fracture at the site of local tensile stress concentration. For the hybrid joint part specimen, static bend loading caused the shear deformation and fracture in the honeycomb core region, while cyclic bend loading did the delamination along the interface between composite skin and honeycomb core layers as well as the fracture of welded joint part. Experimental results obtained by static and fatigue tests were reflected in modifications of design parameters of the hybrid joint structure in the real tilting car body.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.245-252
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• 2007

Since the new millennium, truss PCMs(Periodic Cellular Metals) have drawn attention because of their superior specific stiffness, strength and multi-functionality. Prior studies have focused on the structural design and optimization. Kagome truss PCM has been proved to have the higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. In this study, we introduce a new idea to fabricate multi-layered Kagome truss PCM from continuous wires which can gain high strength as in piano wires and can be controlled to be defect free owing to drawing process. The relative density, the stiffness and the strength under bending and compressive load are estimated through elementary mechanics and compared with the results from experiments and FEA. The failure mechanisms are analyzed, and also mechanical performance and production are discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.19-26
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• 2002

In this paper, the nonlinear structural analysis for the composite structure of the spent nuclear fuel disposal container and the 50cm thick bentonite buffer is carried out to predict the collapse of the container while the sudden rock movement of 10cm is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Horizontal symmetric rock movement is assumed in this structural analysis. Elastoplastic material model is adopted. Drucker-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the container(cast iron insert, copper outer shell and lid and bottom). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffer, the container structure still endures elastic small strains and stresses below the yield strength. Hence, the 50cm thick bentonite buffer can protect the container safely against the 10cm sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the container structure due to the shear deformation of the bentonite buffer. The elastoplastic nonlinear structural analysis for the composite structure of the container and the bentonite buffer is performed using the finite element analysis code, NISA.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.349-359
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• 2001

An enhanced four-node plate element, which has been developed for explicit dynamic analysis of plate, is described in this paper. Reissner-Mind1in(RM) assumptions are adopted to consider transverse shear deformation effects in the present plate element. RM plate element produces a shear locking phenomena in thin plate so that the substitute natural strains based on assumed strain method are explicitly derived. The present plate element is applied into the explicit transient algorithm and the mass matrix of plate is formulated by using special lumping method proposed by Hinton et al. The performance of the element is verified with numerical examples.

• Steel and Composite Structures
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• v.20 no.2
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• pp.267-293
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• 2016

It is well known that, in order to accurately predict the behaviour of steel structures a requirement the definition of the mechanical behaviour of beam-to column joints is of primary importance. This goal can be achieved by means of the so-called component method, which, in order to obtain the whole behaviour of connections, provides to break up joints in basic components of deformability and resistance. One of the main joint components used to model bolted connections is the so-called equivalent T-stub in tension, which is normally used to predict the behaviour of bolted plates in bending starting from the behaviour of the single bolt rows. In past decades, significant research efforts have been devoted to the prediction of the behaviour of bolted T-stubs but, to date, no particular attention has been devoted to the characterization of their plastic deformation capacity. To this scope, the work presented in this paper, taking into account the existing technical literature, proposes a new theoretical model for predicting the whole behaviour up to failure of bolted T-stubs under monotonic loading conditions, including some complexities, such as the bolt/plate compatibility requirement and the bolt fracture, which are necessary to accurately evaluate the ultimate displacement. After presenting the advances of the proposed approach, a comparison between theoretical and experimental results is provided in order to verify its accuracy.

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.65-70
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• 2005

Fracture behavior and pipe strength are very important to the integrity of energy plants, ocean structures, and so forth. The pipes of energy plants and ocean structures are subject to local wall thinning, resulting from severe erosion-corrosion damage. Recently, the effects of local wall thinning on fracture strength and fracture behavior of piping systems have been the focus of many studies. In this paper, the elasto-plastic analysis is performed by FE code ANSYS on straight pipes with wall thinning. We evaluated the failure mode, fracture strength and fracture behavior, using FE analysis. Also, the effect of the axial strain on deformations and failure modes was estimated by FE analysis.

• Journal of the Korean Institute of Navigation
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• v.24 no.1
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• pp.85-95
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• 2000

In the country where the population concentrates in the metropolis with the narrow land, development of the ocean space is necessary. Recently, mega-float offshore structure has been studied as one of the effective utilization of the ocean space. And very large floating structures are now being considered for various applications such as floating airports, offshore cities and so on. This very large structure is relatively flexible compared with real floating structures like large ships. when we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compared with horizontal. And it is necessary to examine the effect of ocean wave external force received from the natural environment. In this study, the mat-type large floating structure is made to be analytical model. And the analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. The validity of analysis method is verified in comparison with the experimental result in the Japan Ministry of Transport Ship Research Institution. In order to know the characteristics of the dynamic response of the large floating structures, effects of wavelength, bending rigidity of the structure, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.413-413
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• 2007

In recent years, flexible display devices such as liquid crystal display (LCD), organic light emitting diode (OLED), etc. have attracted considerable interest in a wide variety of applications. Polymer substrate is absolutely necessary to realize this kind of flexible display devices. Using the polymer as a substrate, there are lots of advantages including not only mechanical flexibility such as rolling and bending characteristics but also light weights, low cost and so on. In detail, thickness and weights is only one forth and one second of glass substrate, respectively. However, it needs low temperature below $150^{\circ}C$ in the fabrication process comparing to conventional deposition process. The polymer substrate is not thermally stable as much as the glass substrate so that some deformation can be occurred according to variation of temperature. In particular, performance of devices can be easily deteriorated by shrinkage of substrate when heating it. In this paper, pre-annealing and deposition of buffer layer was introduced and studied to solve previously mentioned problems of the shrinkage and followed shear stress.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.479-486
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• 2003

This paper presents an elastoplastic analysis for spent nuclear fuel disposal container and its 50 cm thick bentonite buffer to predict the collapse of the container while the horizontal asymmetric sudden rock movement of 10 cm is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucker-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the container. Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffer, the container structure still endures elastic small strains and stresses below the yield strength. Hence, the asymmetric 50 cm thick bentonite buffer can protect the container safely against the 10 cm sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the container structure due to the shear deformation of the bentonite buffer. The finite element analysis code, NISA, is used for the analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1997-2007
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• 2002

Composite air spindles are appropriate for the high-speed and the high-precision machining as small hole drilling of printed circuit board (PCB) or wafer cutting for manufacturing semiconductors because of the low rotational inertia, the high damping ratio and the high fundamental natural frequency of composite shaft. The axial load and stiffness of composite air spindles fur drilling operation are determined by the thrust ben ring composed of the air supply part mounted on the housing and the rotating part mounted on the rotating shaft. At high-speed rotation, the rotating part of the thrust bearing should be designed considering the stresses induced by centrifugal force as well as the axial stiffness and the natural frequency of the rotating shaft to void the shaft from failure due to the centrifugal force and resonant vibration. In this work, the air supply part of the thrust bearing was designed considering the bending stiffness of the bearing and the applied load. The rotating part of the thrust bearing was designed through finite element analysis considering the cutting forces during manufacturing as well as the static and dynamic characteristics under both the axial and con trifugal forces during high-speed rotation.