• 대한수학회논문집
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• 제21권1호
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• pp.145-149
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• 2006

We demonstrate a novel almost Kahler deformation on $\mathbb{R}^4$ which diffuses the scalar curvature.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1540-1555
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• 2021

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect its stress conditions, mechanical behavior and thermal-hydraulic performance. A reliable numerical method is of great importance to reveal the complex evolution of mechanical deformation, flow redistribution and temperature field for the plate-type fuel assembly under non-uniform irradiation. This paper is the first part of a two-part study developing the numerical methodology for the thermal-fluid-structure coupling behaviors of plate-type fuel assembly under irradiation. In this paper, the thermal-fluid-structure coupling methodology has been developed for plate-type fuel assembly under non-uniform irradiation condition by exchanging thermal-hydraulic and mechanical deformation parameters between Finite Element Model (FEM) software and Computational Fluid Dynamic (CFD) software with Mesh-based parallel Code Coupling Interface (MpCCI), which has been validated with experimental results. Based on the established methodology, the effects of non-uniform irradiation and fluid were discussed, which demonstrated that the maximum mechanical deformation with irradiation was dozens of times larger than that without irradiation and the hydraulic load on fuel plates due to differential pressure played a dominant role in the mechanical deformation.

• Journal of Mechanical Science and Technology
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• 제17권3호
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• pp.400-408
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• 2003

A study on the progressive inelastic deformation behavior of the 316 L stainless steel cylindrical structure with plate-to-shell junction under moving temperature front was carried out by structural test and analysis. The structural test intends to simulate the thermal ratcheting behavior occurring at the reactor baffle of the liquid metal reactor as free surface of hot sodium pool moves up and down under plant transients. The thermal ratchet load that heats the specimen up to 550$^{\circ}C$ was applied repeatedly and residual deformation was measured. The thermal ratcheting test was carried out with two types of cylindrical structures, one with plate to-shell junction and the other without the junction to investigate the effects of the geometric discontinuities on the global ratcheting deformation. The temperature distributions of the test specimens were measured and were used for the ratcheting analysis. The ratchet deformations were analyzed with the constitutive equation of the non-linear combined hardening model. The analysis results were in good agreement with those of the structural tests.

• 한국공간구조학회논문집
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• 제20권2호
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• pp.87-94
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• 2020

The present study is aimed to calculate the optimal damping according to the seismic load on the structure with a non-seismic design to perform structure analysis considering the deformation of structural joint connection and panel zone; to develop design program equipped with structural stability of the steel frame structures reinforced with the panel zone and viscous dampers, using the results of the analysis, in order to systematically integrate the seismic reinforcement of the non-seismic structures and the analysis and design of steel frame structures. The study results are as follows: When considering the deformation of the panel zone, the deformation has been reduced up to thickness of the panel double plate below twice the flange thickness, which indicates the effect of the double plate thickness on the panel zone, but the deformation showed uniform convergence when the ration is more than twice. The SMRPF system that was applied to this study determines the damping force and displacement by considering the panel zone to the joint connection and calculating the shear each floor for the seismic load at the same time. The result indicates that the competence of the damper is predictable that can secure seismic performance for the structures with non-seismic design without changing the cross-section of the members.

• 대한기계학회논문집A
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• 제27권1호
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• pp.109-118
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• 2003

The recent trend towards miniaturization causes an increased demand for parts with very small dimensions. Milli-structure components are classified as a component group whose size is between macro- and micro-scale. The manufacturing process of these components of thin sheet metal forming has a microscopic properties in addition to a typical phenomenon of bulk deformation because of the forming size. Also, the material properties and the deformation behavior change with miniaturization, which means that, a coarse grained materials show a higher resistance against deformation, when the grain size is in the range of the sheet thickness. In this study, a new numerical approach is proposed to simulate intergranular milli-structure in forming by the finite element method. The grain element and grain boundary element are introduced to simulate the milli-structure in the bending. The grain element is used to analyze the deformation of individual grain while the grain boundary element is for the investigation on the movement of the grain boundary. Also, the result of the finite element analysis is confirmed by a series of milli-sized forming experiments.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.64-71
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• 2009

The stresses acting on shotcrete lining of tunnel have been measured virtually by monitoring instruments installed during construction. However, the malfunction of instrument and the lack of consistency of signal have always been controversial, but re-installation of instrument after construction of tunnel lining is practically impossible. Therefore, authors have carried out the study to develop a new technique for estimating the stress acting on shotcrete lining during and after construction. In the technique, stresses of shotcrete lining can be estimate by the measurement of deformation of free face. Therefore, the relationships between the stresses of shotcrete lining and deformation of free surface are indispensable factor. In this paper, the parametric study using 2D FEM analysis was carried out to estimate the relationships between the stress level acting on the tunnel shotcrete lining and the deformation near the free face (e.g. artificial crack in this study). The distribution of stresses of shotcrete lining is also investigated in this study as the preliminary investigation for the large-scale tunnel lining test and detailed 3D FEM analysis.

• 소성∙가공
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• 제19권6호
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• pp.357-362
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• 2010

Dry sliding wear behavior of pure Fe and Cu which have BCC and FCC crystal structure, respectively, was investigated. The wear characteristics of the pure metals with different crystal structure were compared. Dry sliding wear tests were carried out using a pin-on-disk wear tester at various loads under the constant sliding speed condition of 0.15 m/s against a silica ball at room temperature. Sliding distance was fixed as 600 m for all wear tests. Wear rate of a specimen was calculated by dividing the weight loss of the specimen after the test by the specific gravity and sliding distance. Worn surfaces and wear debris were analyzed by SEM. The wear of both pure Fe and Cu proceeded with surface deformation, resulting in similar wear rates despite of their structure difference under the current test conditions. Wear rates of both metals were low if the surface deformation due to wear forms thick surface-deformation layer that is strain hardened beneath the wearing surface. The pure Cu specimens showed a lot of oxides on the worn surface when tested at low loads less than 5 N, which resulted in very low wear rate.

• 대한조선학회논문집
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• 제55권5호
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• pp.421-430
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• 2018

The shape of a yacht sail made of thin fabric materials is easily deformed by wind speed and direction and it is affected by the deformation of the standing rig such as mast, boom, shrouds, stays and spreaders. This deformed sail shape changes the air flow over the sail, it makes the deformation of the sail and the rig again. To get a sail performance accurately these interactive behavior of sail system should be studied in aspects of the aerodynamics and the fluid-structure interaction. In this study aerodynamic analysis for the sail system of a 30 feet sloop is carried out and the obtained dynamic pressure on the sail surface is applied as the loading condition of the calculation to get the deformations of the sail shape and the rig. Supporting forces by rig are applied as boundary condition of the structure deformation calculations. And the characteristics of the air flow and the dynamic pressure over the deformed sail shape is investigated repeatedly including the lift force and the location of CE.

• International Journal of Korean Welding Society
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• 제3권2호
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• pp.7-14
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• 2003

During the manufacture of a ship, longitudinal deformation is produced by fillet welding on the Built­Up beam used to improve the longitudinal strength of a ship. This deformation needs a correcting process separate from a manufacture process and decreases productivity and quality. This deformation is caused by welding moment, which is the value multiplied the shrinking force due to welding by the distance from the neutral axis on a cross section of Built­Up beam. This deformation can be offset by generating a moment which is the same magnitude with and is located in an opposite direction to the welding moment on web plate by induction heating. Accordingly, this study clarifies the creation mechanism of the longitudinal deformation on Built­Up beam with FEM analysis and presents the preventative method of this deformation by induction heating basing the mechanism and verifies its validity through analysis and experiments. The induction heating used here is performed by deciding its location and quantity with experiments and simple equations and by applying them to a real structure.

• 대한수학회지
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• 제53권3호
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• pp.489-501
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• 2016

In this paper, we study the rigidity under $K{\ddot{a}}hler$ deformation of the complex structure of odd Lagrangian Grassmannians, i.e., the Lagrangian case $Gr_{\omega}$(n, 2n+1) of odd symplectic Grassmannians. To obtain the global deformation rigidity of the odd Lagrangian Grassmannian, we use results about the automorphism group of this manifold, the Lie algebra of infinitesimal automorphisms of the affine cone of the variety of minimal rational tangents and its prolongations.