• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.1
• /
• pp.150-157
• /
• 2008

Bellows are commonly used in piping systems to absorb expansion and contraction in order to reduce stress. Unlike most piping components, bellows consist of a thin-walled shell of revolution with a corrugated meridian, in order to provide the flexibility needed to absorb mechanical movements. It is a composite shell structure consisting of at least one toroidal shell, an annular plate or conical shell. It is difficult to analyze the behavior of bellows because of its complex geometry. Simplified formulas for variable mechanical behaviors of bellows are provided by a standard called EJMA. An automatic design software for bellows is programming by using VBA(Visual Basic for Application) based on EJMA. Bellows engineers can effectively make a decision for bellows geometries because this software provides graphically design results in its post-processor. Bellows design software is expected to give quite a good guidance to practical design. The characteristics of bellows are also investigated through the automatic design process in bellows design software.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.344-349
• /
• 2005

The axially moving thin beam-plates exposed to sudden thermal loadings may experience severe vibrations through the thermal shock process. For accurate prediction of the thermal shock-induced vibrations, this paper develops a spectral element model for axially moving thermoelastic beam-plates. The spectral element model which is represented by spectral element matrix is formulated from the frequency-dependent dynamic shape functions which satisfy the governing equations in the frequency-domain. Thus, when compared with the classical finite element model in which simple polynomial functions are used as the shape functions, the spectral element model can provide exact solution by treating a whole uniform structure member as a single finite element, regardless of its length.

• Nuclear Engineering and Technology
• /
• v.53 no.8
• /
• pp.2682-2695
• /
• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• Smart Structures and Systems
• /
• v.28 no.6
• /
• pp.745-760
• /
• 2021

Dynamic buckling of structure is one of the failure modes that needs to be considered since it may result in catastrophic failure of the structure in a short period of time. For a thin fiber-reinforced polymer (FRP) plate under compression, buckling is an inherent hazard which will be intensified by the existence of defects like holes, cracks, and delamination. On the other hand, the growth of the delamination is another prime concern for thin FRP plates. In the current paper, reinforcing the plates against buckling is realized by using SMA wires in the form of stitches. A numerical framework is proposed to simulate the dynamic instability emphasizing the effect of the SMA stitches in suppressing delamination growth. The suggested algorithm is more accurate than the other methods when considering the transformation point of the SMA wires and the modeling of the cohesive zone using simple and yet reliable technique. The computational design of the method by producing the line by line orders leads to a simple algorithm for simulating the super-elastic behavior. The Lagoudas constitutive model of the SMA material is implemented in the form of user material subroutines (VUMAT). The normal bilinear spring model is used to reproduce the cohesive zone behavior. The nonlinear finite element formulation is programmed into FORTRAN using the Newmark-beta numerical time-integration approach. The obtained results are compared with the results obtained by the finite element method using ABAQUS/Explicit solver. The obtained results by the proposed algorithm and those by ABAQUS are in good agreement.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.1
• /
• pp.233-241
• /
• 2005

The paper is presented experimental study results on bond stress between profiled steel and concrete in Profiled SPC(Profiled Steel Plate Concrete) rectangular steel tubes through an experimental program in which 13 pull-out specimens were tested. Advantages and class of composite members and current problems of construction work are noted, past research of PSSC is described. An experimental study is described and evaluated. The bond capacity is interrelated with slip at the steel concrete interface. The factors influencing the mechanism of bond stress transfer were the cross section shape, length/diameter, diameter/thickness and environmental parameters (temperature, moisture). The results of experimental program indicated that the force transfer could be characterized into two regions The first region was governed by bond with no relative slip between the profiled steel and concrete. The second region occurs after the chemical debonding. Bond stress transfer in this region was governed by frictional resistance between profiled steel and concrete and cross section shapes. The important factors influencing the magnitude of frictional resistance are the profiled steel shapes, length/diameter and environmental parameters. (temperature, moisture)

• Steel and Composite Structures
• /
• v.33 no.5
• /
• pp.717-727
• /
• 2019

This paper is motivated by the lack of studies in the technical literature concerning to vibration analysis of a single-layered graphene sheet (SLGS) with corner cutout based on the nonlocal elasticity model framework of classical Kirchhoff thin plate. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of the L-shape SLGS deflection field. Trimming technique is employed to create the cutout in geometry of L-shape plate. The L-shape plate is assumed to be Free (F) in the straight edges of cutout while any arbitrary boundary conditions are applied to the other four straight edges including Simply supported (S), Clamped (C) and Free (F). The Numerical studies are carried out to express the influences of the nonlocal parameter, cutout dimensions, boundary conditions and mode numbers on the variations of the natural frequencies of SLGS. It is precisely shown that these parameters have considerable effects on the free vibration behavior of the system. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems. This study serves as a benchmark for assessing the validity of numerical methods used to analyze the single-layered graphene sheet with corner cutout.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.1
• /
• pp.36-40
• /
• 2003

The diamond-like nanocomposite (DLN) thin films were deposited on Si substrates using $CH_4/(C_2H_5O)_4Si/H_2$/Ar gas mixtures as source gases by the plasma enhanced chemical vapor deposition (PECVD). The chemical structure and microstructure of grown films were investigated and their tribological properties were evaluated by a ball-on-plate type tribometer. The deposited DLN films mainly consisted of diamond-like a-C:H and quartz-like a-Si:O networks. The DLN films had a good agreement with tribological coating applications due to their extremely low friction coefficients and low wear rates.

• Animal Systematics, Evolution and Diversity
• /
• v.36 no.2
• /
• pp.143-153
• /
• 2020

Six new species of two genera Dysidea and Pleraplysilla (Demospongiae: Dictyoceratida: Dysideidae) are described from Jejudo Island, Dokdo Island and Guryongpo, Korea. Among them, five new species of the genus Dysidea are compared with other reported species in fibres structure, cored detritus and fibres arrangement. Dysidea niveus n. sp. is characterized by thin collagenous plate-like fibres. Dysidea dokdoensis n. sp. is similar to D. geomunensis Kim et al., 2020 in skeletal structure, but differs in length of surface conules. Dysidea hydra n. sp. is similar to D. mureungensis Kim et al., 2020 at the surface, but differs in fibres cored with spicules. Dysidea sabulum n. sp. is similar to D. glavea Kim et al., 2020 in cored large sands in fibres, but differs in having numerous large sands cored in fibres throughout the sponge. Dysidea hirsuta n. sp. is unique, only surface fibres cored with large sands but not in choanosome. A new species of genus Pleraplysilla, P. flabellum n. sp. is compared with seven other reported species. This new species is not encrusting but has a thick flabellate shape.

• Journal of computational fluids engineering
• /
• v.12 no.2
• /
• pp.37-45
• /
• 2007

The hybrid Cartesian/immersed boundary method is applied to simulate fluid-structure interaction of a two-dimensional orbiting flexible foil. The elastic deformation of the flexible foil is modelled based on the dynamic equation of a thin-plate. At each time step, the locations and velocities of the Lagrangian control points on the flexible foil are used to reconstruct the boundary conditions for the flow solver based on the hybrid staggered/non-staggered grid. To test the developed code, the flow fields around a flapping elliptical wing are calculated. The time history of the vertical force component and the evolution of the vorticity fields are compared with recent other computations and good agreement is achieved. For the orbiting flexible foil, the vorticity fields are compared with those of the case without the deformation. The combined effects of the angle of attack and the orbit on the deformation are investigated. The grid independency study is carried out for the computed time history of the deformation at the tip.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.189-190
• /
• 2006

A patient table considering x-ray transparency, mechanical safety and compact multi-axis moving mechanism has been developed. The goal of medical imaging technology is to keep radiation exposure of patients during x-raying to a minimum. In order to obtain clear pictures at low dose, however, the x-ray table which supports the patient must be sufficiently permeable to radiation to allow good image resolution. The table top is made of low density foam for x-ray transparent effective area and structural aluminum plate to connect moving mechanism under the table, covered with thin carbon fiber. This sandwich construction is very rigid and lightweight, so the table top can handle relatively heavy load comparing to its cantilevered structure which is unavoidable as long as cooperate with C-arm radiography. To verify the design results finite element static analysis and experimental tests have been done. According to the verification the results well satisfy certification guide lines as a medical device.