• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.194-197
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• 2007

액체로켓 연소기 재생냉각 챔버의 제작에 사용되는 구리합금의 성형한계 곡선을 얻기 위하여 돔 장출 시험과 인장시험을 수행하였다. 성형한계 곡선에 대한 실험적인 연구를 위하여 인장시편을 사용하여 인장-압축 변형률 상태의 데이터를 얻었으며, 인장-인장의 변형률 상태를 얻기 위하여 돔 장출 시험용 시편을 사용한 돔 장출 시험 또한 수행하였다. 시험에 사용한 모든 시편은 제작방법에 따라 종 방향과 횡 방향시편으로 구분하였다. 시험 결과 인장-인장 변형률 상태에서 최대 주 변형률과 부 변형률은 62.3%와 58.6%이며 인장-압축 상태에서는 60.5%와 25.8%로 나타났다.

• Steel and Composite Structures
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• 제28권1호
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• pp.13-24
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• 2018

A size-dependent novel hyperbolic shear deformation theory of simply supported functionally graded beams is presented in the frame work of the non-local strain gradient theory, in which the stress accounts for only the nonlocal strain gradients stress field. The thickness stretching effect (${\varepsilon}_z{\neq}0$) is also considered here. Elastic coefficients and length scale parameter are assumed to vary in the thickness direction of functionally graded beams according to power-law form. The governing equations are derived using the Hamilton principle. The closed-form solutions for exact critical buckling loads of nonlocal strain gradient functionally graded beams are obtained using Navier's method. The derived results are compared with those of strain gradient theory.

• 한국구조물진단유지관리공학회 논문집
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• 제5권3호
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• pp.233-244
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• 2001

Stress-strain behaviour of soil varies based on stress path and stress history. There has been few study on the characteristics of yielding curve which has anisotropic compression stress history in decomposed granite soil. During this study, various stress path tests in previous anisotropic compression stress history are performed on compacted decomposed granite soil sampled at Iksan, Chonbuk. Yielding points are determined from various stress-strain curves (${\eta}-{\varepsilon}$, ${\eta}$-v, and ${\eta}$-k, ${\eta}$-W curves). Stress-strain curve is certified which shows yielding point very clearly. The shape and characteristics of anisotropic compression yielding curves are examined. The main results are summarized as follows : 1) p' constant and compressive direction in stress paths, which has experienced previous anisotropic compression stress history, shows relatively dear yielding points. 2) Yielding curves defined from ${\eta}$-k and ${\eta}$-W curve show almost perfect ellipse. 3) Directions of plastic strain incremental vector($dv^p/d{\varepsilon}^p$) are not perpendicular to yielding curve.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.329-332
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• 2008

This study presents a viscoelastic characterization of flexible pavement subjected to moving loads. A series of field tests have been conducted on three pavement sections (A2, A5, and A8) at the Korea Expressway Corporation (KEC) test road. The effect of vehicle speed on the responses of each test section was investigated at three speeds: 25km/hr, 50km/hr, and 80km/hr. During the test, both longitudinal and lateral strains were measured at the bottom of asphalt layers and in-situ measurements were compared with the results of finite element (FE) analyses. A commercial FE package was used to model each test section and a step loading approximation has been adopted to simulate the effect a moving vehicle. Field responses reveal the strain anisotropy (i.e., discrepancy between longitudinal and lateral strains) and the amplitude of strain normally decreases as the vehicle speed increases. In most cases, lateral strain was smaller than the longitudinal strain, and strain reduction was more significant in lateral direction.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4030-4048
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• 2022

In this study, road transportation tests were conducted with surrogate fuel assemblies under normal conditions of transport to evaluate the vibration and shock load characteristics of spent nuclear fuel (SNF). The overall test data analysis was conducted based on the measured acceleration and strain data obtained from the speed bump, lane-change, deceleration, obstacle avoidance, and circular tests. Furthermore, representative shock response spectrums and power spectral densities of each test mode were acquired. Amplification or attenuation characteristics were investigated according to the load transfer path. The load attenuated significantly as it transferred from the trailer to the cask. By contrast, the load amplified as it transferred from the cask to the surrogate SNF assembly. The fuel loading location on the cask disk assembly did not exhibit a significant influence on the strain measured from the fuel rods. The principal strain was in the vertical direction, and relatively large strain values were obtained in spans with large spacing between spacer grids. The influence of the lateral location of fuel rods was also investigated. The fuel rods located at the side exhibited relatively large strain values than those located at the center. Based on the strain data obtained from the test results, a hypothetical road transportation scenario was established. A fatigue evaluation of the SNF rod was performed based on this scenario. The evaluation results indicate that no fatigue damage occurred on the fuel rods.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.77-80
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• 2008

Low-cycle fatigue (LCF) tests were carried out to investigate the effect of loading direction on the cyclic deformation behavior and fatigue resistance of rolled AZ31 magnesium alloy. The as-received alloy showed a strong basal texture indicating that the most of basal planes of hexagonal close-packed structure were located parallel to the rolling direction. Two types of specimens whose loading directions were oriented parallel (RD) and vertical (ND) to the rolling direction. respectively, were used for the comparison. It was found that RD specimens yielded at much lower stresses during compression, while vice versa for the ND specimens, which was mainly attributed to the formation of primary twins. This anisotropic deformation behavior resulted in the different mean stresses during the cycling of RD and ND specimens, affecting the fatigue resistance of two specimens. The ND specimen showed a superior fatigue resistance as compared to the RD specimen under strain-controlled condition.

• 한국생산제조학회지
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• 제7권4호
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• pp.21-27
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• 1998

In the case of existing in free-edge delaminations of composite laminates which are symmetry with respect to mid-plane in laminates also, in the case of asymmetry and anti-symmetry, the generalized quasi-three dimensional displacement field equations developed from quasi-three dimensional displacement field equations can be applied to solve above cases. We introduce three paramenters in this paper, which have not been used in quasi-three dimensional displacement field equations until now. To the laminate subjected to the axial extension strain $\varepsilon$0(C1) in $\chi$-direction, the bending deformation $\chi$$\chi$(C$_2$) around у-direction, the bending deformation w$\chi$(C$_4$) around z-direction and the twisting deformation $\chi$$\chi$y(C$_3$) around $\chi$-direction .The generalized quasi-three dimensional displacement field equations are able to be analyzed efectively.

• 복합신소재구조학회 논문집
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• 제4권1호
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• pp.1-8
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• 2013

The finite element analysis (FEA) is a numerical technique to find solutions of field problems. A field problem is approximated by differential equations or integral expressions. In a finite element, the field quantity is allowed to have a simple spatial variation in terms of linear or polynomial functions. This paper represents a review and an accuracy-study of the finite element method comparing the FEA results with the exact solution. The exact solutions were calculated by solid mechanics and FEA using matrix stiffness method. For this study, simple bar and cantilever models were considered to evaluate four types of basic elements - constant strain triangle (CST), linear strain triangle (LST), bi-linear-rectangle(Q4),and quadratic-rectangle(Q8). The bar model was subjected to uniaxial loading whereas in case of the cantilever model moment loading was used. In the uniaxial loading case, all basic element results of the displacement and stress in x-direction agreed well with the exact solutions. In the moment loading case, the displacement in y-direction using LST and Q8 elements were acceptable compared to the exact solution, but CST and Q4 elements had to be improved by the mesh refinement.

• 대한치과교정학회지
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• 제17권2호
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• pp.185-200
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• 1987

This paper was undertaken to observe the displacement of craniofacial complex with cervical headgear and to compare narrowing or widening effect of palate by use of contraction or expansion face-bow, respectively. The 3-dimensional finite element method(FEM) was used for a mathematical model composed of 597 nodes and 790 elements and an electrical resistance strain gauge investigation was performed to validate the finite element model. The outer bow of cervical headgear was adjusted to be placed below the occlusal plane by $25^{\circ}$ and met the midsagittal plane by $40^{\circ}$, and was loaded 1kg on each right and left hook toward posterior direction. The results were as follows 1. Generally, the maxillary teeth and facial bone were displaced in posterior, medial and downward direction. 2. It was the maxillary 2nd bicuspid that moved bodily. 3. The craniofacial complex rotated in a clockwise direction around the rotating axis which lay from the most posterior and lowest point connecting nasal crest of maxillary bone and vomer, progressively toward a more posterior, lateral and upward direction, anterior and upper area of pterygomaxillary fissure, base of medial pterygoid plate and laterally to the contact area of zygomatic arch with squamous part of temporal bone. 4. No contraction effect was observed by contraction face-bow when compared to the standard face-bow. 5. In case of expansion face-bow, the areas of maxillary 2nd bicuspid, molars and palate were expanded remarkably.

• 한국압력기기공학회 논문집
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• 제18권1호
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• pp.26-35
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• 2022

When piping system in a nuclear power plant is subjected to a beyond design seismic condition, it is important to accurately determine possibility of crack initiation and, if initiation occurs, its location and time. From recent experimental works on elbow pipes, it was found that the crack initiation location and crack propagation direction of the SA403 WP316 stainless steel elbow pipe were affected by the pipe thickness. In this paper, the crack initiation location and crack propagation direction for SA403 WP316 stainless steel elbow pipes with different thickness were analyzed via elastic-plastic finite element analysis. Based on FE results, the effect of the pipe thickness on different crack initiation location and crack propagation direction was analyzed using ovality, stress and strain components. It was also confirmed that the presence of internal pressure had no effect on the crack initiation location and crack propagation direction.