• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.60-68
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• 2004

High velocity impacts are accompanied with large deformations, which generate a large amount of heat due to plastic works, resulting in a significant temperature rise of the material. Because the elevated temperature affects the dynamic properties of materials, it is important to predict the temperature rise during high-stram-rate deformations. Both existing vacancies and excess vacancies are credited to the stored energy, yet it is difficult to distinguish one from another in contribution to the stored energy using macroscopic level materials models. In this study, an atomistic material model for fee materials such as copper is set up to calculate the stored energy using molecular dynamics (MD) simulations. It is concluded that excess vacancies play an important role for the stored energy during a high-strain-rate deformation.

• Nuclear Engineering and Technology
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• v.35 no.4
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• pp.356-368
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• 2003

Material properties such as coolant specific heat, film heat transfer coefficient, cladding thermal conductivity, surface diffusion coefficient of the multi-bubble are improved in MACSIS-Mod1. The axial power and flux profile module was also incorporated with irradiation history. The performance and feasibility of the updated driver fuel pin have been analyzed for nominal parameters based on the conceptual design for the KALIMER breakeven core by MACSIS-MOD1 code. The fuel slug centerline temperature takes the maximum at 700mm from the bottom of the slug in spite of the nearly symmetric axial power distribution. The cladding mid-wall and coolant temperatures take the maximum at the top of the pin. Temperature of the fuel slug surface over the entire irradiation life is much lower than the fuel-clad eutectic reaction temperature. The fission gas release of the driver fuel pin at the end of life is predicted to be $68.61\%$ and plenum pressure is too low to cause cladding yielding. The probability that the fuel pin would fail is estimated to be much less than that allowed in the design criteria. The maximum radial deformation of the fuel pin is $1.93\%$, satisfying the preliminary design criterion ($3\%$) for fuel pin deformation. Therefore the conceptual design parameters of the driver fuel pin for the KALIMER breakeven core are expected to satisfy the preliminary criteria on temperature, fluence limit, deformation limit etc.

• Journal of Korean Association for Spatial Structures
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• v.21 no.3
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• pp.61-68
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• 2021

In this study, a rocking behavior experiment using a guide plate and a guide channel to prevent lateral deformation of a steel damper was planned. For this purpose, strut I-type specimen I-1 and strut S-type specimen S-1 were prepared. The experimental results were compared with the existing experimental results of SI-260 and SS-260 under the same conditions without the details of lateral deformation prevention in order to evaluate the effect of preventing lateral deformation. The damper with lateral deformation prevention detail was evaluated to have superior strength capacity, deformation capacity, and energy dissipation capacity than the damper without it. Therefore, the lateral deformation prevention detail was evaluated to have a good effect in improving the design capability of the steel damper.

• Journal of Hydrogen and New Energy
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• v.26 no.6
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• pp.652-658
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• 2015

The purpose of this study is to investigate the effects of changing dimension of a soft tube in a peristaltic pump on deformation, stress and fluid flow rate of the peristaltic pump. Geometries of the peristaltic pump is created in a Catia drawing software based on specifications of a real peristaltic pump. Afterwards, the geometries of this pump is imported into a commercial Ansys software to calculate deformation, stress, and fluid flow rate of this pump. The simulation results showed that the deformation and stress of the soft tube is increased by increasing soft tube diameter from 2 mm to 4 mm. When the tube diameter is increased to 5 mm and tube thickness is reduced to 0.5 mm, the soft tube is damaged. The highest fluid flow rate could be found at the tube thickness and diameter of 1 mm and 4 mm, respectively.

• Journal of Hydrogen and New Energy
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• v.12 no.4
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• pp.247-255
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• 2001

The relation between the deformation and the geometrical shape, and the effect of cold work on the hydrogen absorption behavior in palladium were investigated. The Pd specimens used were plates and wires as cold worked and annealed states. The palladium plates and wires were loaded with hydrogen by electrochemical method. Experimental analyses were carried out through X -ray diffraction, micrometer measurement and decimal balance measurement. As the results, it is found that the effect of cold work on hydrogen absorption capacity was relatively small. The deformation of the palladium plates in thickness direction is larger than in other lateral directions whereas the palladium wires showed the same deformation ratio in all radius directions because of the circular distribution of coexisting $\alpha$ and $\beta$ phases. The products of plastic deformation such as slip lines and voids etc. were observed abundantly in all specimens although the specimens had undergone only once of a hydrogen absorption and desorption.

• Design & Manufacturing
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• v.2 no.6
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• pp.43-48
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• 2008

Magnesium alloys have given high attention to the industry of light-weigh as automobile and electronics with aluminium, titanium and composite alloys due to their high strength, low specific density and good damping characteristics. But the magnesium contained structures under high temperature have the problems related to creep deformation and rupture life, which is a reason of developing the new material against creep deformation to use them safely. The purpose of this study is to predict the creep deformation mechanism and rupture time of AZ31 magnesium alloy. For this, creep tests of AZ31 magnesium alloy were done under constant creep load and temperature with the equipment including automatic temperature controller with acquisition computer. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined over the temperature range below 0.5Tm and stress range of 109~187MPa, respectively, in order to investigate the creep behavior. AZ31 Magnesium alloy identify the activation energy for creep deformation and the stress dependence to creep rate at below 0.5Tm, and then investigate the mechanism for creep deformation and creep rupture life of AZ31 Magnesium alloy.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.953-960
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• 2012

This paper reports the irradiation effect on the deformation behavior and tensile fracture properties of A533B RPV steel. An inverse identification technique using iterative finite element (FE) simulation was used to determine those properties from tensile data for the A533B RPV steel irradiated at 65 to $100^{\circ}C$ and deformed at room temperature. FE simulation revealed that the plastic instability at yield followed by softening for higher doses was related to the occurrence of localized necking immediately after yielding. The strain-hardening rate in the equivalent true stress-true strain relationship was still positive during the necking deformation. The tensile fracture stress was less dependent on the irradiation dose, whereas the tensile fracture strain and fracture energy decreased with increasing dose level up to 0.1 dpa and then became saturated. However, the tensile fracture strain and fracture energy still remained high after high-dose irradiation, which is associated with a large amount of ductility during the necking deformation for irradiated A533B RPV steel.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.287-292
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• 2011

To evaluate the pressure-resistant performance of underwater equipment, hyperbaric chamber test facility which can make the hydrostatic pressure is used. In this test, strain gage is generally applied to measure the strain of object under test is suitable for measuring a tiny deformation, but it can not measure a large deformation. Thus this paper suggests a method to estimate the over -order deformation of object under test by the image processing with the image acquired from underwater camera in the hydrostatic test. The main procedure of suggested method comprises the first step to find significant points by processing the image two dimensionally and the second step to estimate a deformation of object under test by tracking the motion of these points. If completing the remained research which is estimating the deformation and comparing it with a real one, it can be a method to measure the over -order deformation of object under test.

• Tribology and Lubricants
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• v.32 no.1
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• pp.1-8
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• 2016

This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.121-128
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• 2007

Enhanced lower order shear deformation theory is developed in this study. Generally, lower order theories are not adequate to predict accurate deformation and stress distribution through the thickness of laminated plate. For the accurate prediction of detailed stress and deformation distributions through the thickness, higher order zigzag theories have been proposed. However, in most cases, simplified zigzag higher order theory requires $C_1$, shape functions in finite element implementation. In commercial FE softwares, $C_1$, shape functions are not so common in plate and shell analysis. Thus zigzag theories are useful for the highly accurate prediction of thick composite behaviors but they are not practical in the sense that they cannot be used conveniently in the commercial package. In practice, iso-parametric $C_0$ plate model is the standard model for the analysis and design of composite laminated plates and shells. Thus in the present study, an enhanced lower order shear deformation theory is developed. The proposed theory requires only $C_0$ shape function in FE implementation. The least-squared energy error between the lower order theory and higher order theory is minimized. An enhanced lower order shear deformation theory(ELSDT) in this paper is proposed for smart structure under complex loadings. The ELSDT is constructed by the strain energy transformation and fully coupled mechanical, electric loading cases are studied. In order to obtain accurate prediction, zigzag in-plane displacement and transverse normal deformation are considered in the deformation Held. In the electric behavior, open-circuit condition as well as closed-circuit condition is considered. Through the numerous examples, the accuracy and robustness of present theory are demonstrated.