• Nuclear Engineering and Technology
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• 제52권4호
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• pp.802-810
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• 2020

Three-dimensional finite element simulations are implemented for the in-pile thermo-mechanical behavior in U-Mo/Al monolithic fuel plates with different thermal creep rates of cladding involved. The numerical results indicate that the thickness increment of fuel foil rises with the thermal creep coefficient of cladding. The maximum Mises stress of cladding is reduced by ~85% from 344 MPa on the 98.0^th day when the creep coefficient of cladding increases from 0.01 to 10.0, due to its equivalent thermal creep strain enlarged by 3.5 times. When the thermal creep coefficient of Aluminum cladding increases from 0 to 1.0, the maximum mesoscale stress of fuel foil varies slightly. At the same time, the peak mesoscale normal stress of fuel foil can reach 51 MPa on the 98.0^th day for the thermal creep coefficient of 10, which increases by 60.3% of that with the thermal creep un-occurred in the cladding. The maximum through-thickness creep strain components of fuel foil differ slightly for different thermal creep coefficients of cladding. The dangerous region of fuel foil becomes much closer to the heavily irradiated side when the creep coefficient of cladding becomes 10.0. The creep performance of Aluminum cladding should be optimized for the integrity of monolithic fuel plates.

• 터널과지하공간
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• 제25권2호
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• pp.155-167
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• 2015

본 연구에서는 TOUGH2-FLAC3D 연계해석기법을 이용하여 암반공동에 고온의 열에너지를 30년간 저장하는 경우 주변 암반에 야기되는 열-수리-역학적 연계거동을 살펴보았다. 열에너지저장에 따른 암반의 거동 특성 및 환경 영향을 예측하고 이에 대한 제어기준을 수립하기 위한 기초 연구로서, 저장소 주변 암반에서 발생하는 열-수리 흐름과 역학적 거동의 상호작용에 대하여 검토하였다. 기본해석으로서 결정질 암반 내 원통형 공동에$350^{\circ}C$의 대용량 열에너지를 저장하는 경우를 모델링하였으며, 열에너지저장소의 단열성능은 고려하지 않았다. 암반 내 열전달의 주요 메카니즘은 암반의 전도에 의한 것으로 판단되며, 암반의 역학적 거동은 수리적 요소보다는 열적 요소에 지배적인 영향을 받는 것으로 나타났다. 암반과 지하수 가열에 따른 유효응력 재분포 양상과 열팽창으로 인한 암반 변위 및 지표 융기를 검토하였으며, 주변 암반에서의 전단파괴 위험도를 정량적인 수치를 통해 제시하였다. 암반 가열에 따른 열팽창으로 인하여 지표면에서 수 cm의 융기가 발생하였으며, 저장공동 상부에 인장응력이 크게 발달하면서 전단파괴의 위험도가 증가하는 것으로 나타났다.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1461-1471
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• 2002

Linear motor has a lot of advantages in comparison with conventional feed mechanisms: high velocity, high acceleration, good positioning accuracy and a long lifetime. An important disadvantage of linear motor is its high power loss and heating up of motor and neighboring machine components in operation. For the application of the linear motors to precision machine tools an effective cooling method and thermal optimizing measures are required. In this paper Finite-Element-Method for the thermal behavior of synchronous linear motor is introduced, which is useful for the design and manufacturing of linear motors. By modeling the linear motor the orthotropic physical properties of the sheet metal and windings were considered and convective coefficient in the water cooler and to the surroundings was defined by analytical and experimental method. The calculated isothermal lines could analyze the heat flow in the linear motor.

• 한국세라믹학회지
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• 제56권1호
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• pp.77-83
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• 2019

MgO-C refractories are used in basic furnaces and steel ladles due to their many desirable properties, such as excellent thermal shock resistance via low thermal expansion, and high thermal conductivity. However, the mechanical and thermal properties of the refractory continuously deteriorate by spalling phenomena and pore generation due to the oxidation of graphite, used as a carbon source, indicating that the characteristics and performance of MgO-C refractories need to be improved by using a new material or composition. In this study, the use of a Hertzian indentation test as a method for determining the damage and fracture behavior of an MgO-C refractory is described. The results highlight that Hertzain indentation tests can be one of the important evaluation tools for quasi-plastic damage accumulation of MgO-C refractories during falling process of scrap metal.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2069-2087
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• 2023

In nuclear power plant (NPP) accidents, the containment is subject to high temperatures and high internal pressures, which may further trigger serious chain accidents such as core meltdown and hydrogen explosion, resulting in a significantly higher accident level. Therefore, studying the mechanical performance of a containment under high temperature and high internal pressure is relevant to the safety of NPPs. Based on similarity principles, the 1:3.2 scale model of a prestressed concrete containment vessel (PCCV) of a NPP was designed. The loading method, which considers the thermal-pressure coupling conditions, was used. The mechanical response of the PCCV was investigated with a simultaneous increase in internal pressure and temperature, and the failure mechanism of the PCCV under thermal-pressure coupling conditions was revealed.

• Design & Manufacturing
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• 제17권2호
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• pp.27-32
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• 2023

Liquid silicon rubber (LSR) has fine thermal compatibility and is widely used in various fields such as medical care and automobiles because it is easy to implement products with good fluidity. With the recent development of flexible sensors, the focus has been on manufacturing conductive elastomers, such as silicone as elastic materials, and carbon black, CNT, and graphene are mainly used as nanomaterials that impart conductive phases. In this study, mechanical behavior and curing behavior were measured and analyzed to manufacture a CB-LSR complex by adding Carbon Black to LSR and to identify properties. As a result of the compression test, the elastic modulus tended to increase as carbon black was added. When the swelling test and the compression set test were conducted, the swelling rate tended to decrease as the content of carbon black increased, and the compression set tended to increase. In addition, DSC measurements showed that the total amount of reaction heat increased slightly as the carbon black content increased. It is considered that carbon black was involved in the crosslinking of LSR to increase the crosslinking density and have a positive effect on oil resistance reinforcement.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.41-52
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• 2013

Adequate design of engineered barriers, including canister, buffer and backfill, is important for the safe disposal of high-level radioactive waste. Three-dimensional computer simulations were carried out under different condition to examine the thermal and mechanical behavior of engineered barriers and rock mass. The research looked at five areas of importance, the effect of the swelling pressure, water content of buffer, density of compacted bentonite, emplacement type and the selection of failure criteria. The results highlighted the need to consider tensile stress in the outer shell of a canister due to thermal expansion of the canister and the swelling pressure from the buffer for a more reliable design of an underground repository system. In addition, an adequate failure criterion should be used for the buffer and backfill.

• 한국표면공학회지
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• 제47권6호
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• pp.293-296
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• 2014

Fe-Ni has been of great interest because it is known as one of low thermal expansion alloys as various application areas. This alloy was fabricated by electroforming process, and effect of heat treatment on thermal expansion and hardness was investigated. Nano-crystalline structure of 13.3 - 63.5 nm in size was observed in the as-deposited alloy. To investigate the effect of heat treatment on grain growth and mechanical/thermal properties, we conducted hardness and coefficient of thermal expansion (CTE). From this, we confirmed these properties were varied by heat treatment. In this nano-crystalline alloy, we could observe abnormal behavior in thermal expansion between $350-400^{\circ}C$. Additionally, an abrupt change in hardness has also been observed. However, once the grains grow up to micro-sized the mechanical and thermal properties mentioned above were stabilized similar to those of bulk alloys due to heat treatment.

• 방사성폐기물학회지
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• 제10권4호
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• pp.281-294
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• 2012

현재까지 개발된 고준위폐기물 심지층처분장의 열-수리-역학적 복합거동 해석을 위한 전산 코드의 현황을 조사하고, 문헌에 보고된 각 코드에 의한 계산치와 현장실험 측정치의 비교 결과를 이용하여, 기존 전산 코드들의 신뢰도를 분석하였다. 개발된 전산코드들은 완충재가 없는 처분장에서는 붕괴열에 따른 암반의 열-수리-역학적 거동을 비교적 잘 모사하였으나, 포화 경암층에 위치한 완충재가 존재하는 처분장의 공학적방벽시스템 내에서 일어나는 열-수리-역학적 복합거동의 예측은 만족스럽지 못하였다. 현재 제안된 열-수리-역학적 복합거동 해석모델을 고준위폐기물 처분장 공학적방벽시스템의 거동 해석에 적용하기 위해서는 완충재 내의 수분함량 및 전 압력 분포를 보다 정교하게 모사할 수 있도록 수학적 모델의 개선이 필요하다.

• Advances in materials Research
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• 제6권2호
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• pp.93-128
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• 2017

In this paper, thermal vibration behavior of nanoscale beams made of functionally graded (FG) materials subjected to various types of thermal loading are investigated. A Reddy shear deformation beam theory which captures both the microstructural and shear deformation effects without the need for any shear correction factors is employed. Material properties of FG nanobeam are assumed to be temperature-dependent and vary gradually along the thickness according to the power-law form. The influence of small scale is captured based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived through Hamilton's principle and they are solved applying analytical solution. The comparison of the obtained results is conducted with those of nonlocal Euler-Bernoulli beam theory and it is demonstrated that the proposed modeling predict correctly the vibration responses of FG nanobeams. The effects of nonlocal parameter, material graduation, mode number, slenderness ratio and thermal loading on vibration behavior of the nanobeams are studied in detail.