• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.265-269
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• 2003

Sn(또는 SnAg)/Ni(P)와 Sn/Cu 계의 열사이클동안 형성되는 금속간화합물에 의해 유기되는 응력의 변화를 in-situ로 관찰하였다. Sn(또는 SnAg)/Ni(11.7P) 박막은 계면반응으로 인해 $Ni_3P$와 $Ni_3Sn_4$ 상이 형성되고 이때 인장응력이 발생하였으며, 한편, Sn(또는 SnAg)/Ni(3P) 박막의 계면반응에 의해서는 동일한 $Ni_3P$와 $Ni_3Sn_4$ 상이 형성됨에도 불구하고 압축응력이 발생하였다. SmAg를 사용할 때 형성되는 $Ag_3Sn$이 응력에 미치는 영향은 거의 없었다. Sn/Cu 박막의 경우는 계면반응 초기에는 인장응력이 발생하였고 어느 정도 이상 반응이 진전됨에 따라 압축응력이 발생하였고 최종적으로 $Cu_3Sn$ 상이 형성되었다. 초기의 인장응력은 계면에서 원자들의 intermixing 베 의한 것이고 압축응력은 Sn 방향으로 일방향 성장하는 금속간화합물 형성에 기인한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1243-1251
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• 2013

The purpose of this study is to investigate the influence of initial clamping force of tension clamp on the performance of an elastic rail fastening system used in sharp curve track. In this study, the initial clamping force and the increasing lateral wheel loads were conducted in the analytical and experimental study, i.e., finite element analysis, laboratory and field test. Using the analytical and experimental results, the performance of the tension clamp was investigated. It was found that the stress of tension clamp depends on the initial clamping force. Therefore the initial clamping force appeared to directly affect the compression stress of the tension clamp. It was found that the compression stress of tension clamp was transferred to the tensile stress by applied the lateral wheel load in service sharp curve track. Further, it was concluded that the initial clamping force was applied on the strengthening force for the tension clamp and then the appropriate initial clamping force was important to ensure a stable performance and long term endurance of tension clamp.

• The korean journal of orthodontics
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• v.32 no.5 s.94
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• pp.343-353
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• 2002

This study was designed to investigate the stress distribution of alveolar bone in case of on masse retraction with lingual K-loop archwire using the 3-dimensional photoelastic stress analysis followed by stress freezing process. Lingual K-loop archwire which had loop in 15mm height was used and activated by retraction force of 350gm per each side. The results were as follows 1. Central incisor : As the closer side to crown, the larger tensile stress was distributed at both mesial and labial surfaces and the larger compressive stress was distributed at distal surface. As the closer side to root apex, the larger compressive stress was distributed at lingual surface. The compressive stress was distributed at root apex. 2. Lateral incisor : The tensile stress was distributed at the coronal side of mesial surface. The compressive stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at labial surface. The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of lingual surface. The compressive stress was distributed at root apex. 3. Canine The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of mesial surface. The tensile stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. The compressive stress was distributed at root apex. 4. Second premolar : The tensile stress was distributed at mesial surface. The compressive stress was distributed at coronal side and the tensile stress was distributed at apical side of distal surface. The compressive stress was distributed at coronal side of buccal surface. As the closer side to crown, the larger tensile stress was distributed at lingual surface. The compressive stress was distributed at root apex. 5. First molar . As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. No stress was distributed at buccal surface and palatal root apex. As the closer side to crown, the larger tensile stress was distributed at both lingual surfaces. The compressive stress was distributed a4 buccal root apexes. 6. Second molar The compressive stress was distributed at all root apexes. As the closer side to crown, the larger compressive stress was distributed at both mesial and lingual surfaces, and the larger tensile stress at both distal and buccal surfaces. Transverse bowing effect was observed in on-masse retraction with lingual K-loop archwire, however vertical towing effect was not. Rather, reverse vortical bowing effect was developed.

• Journal of the Korean GEO-environmental Society
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• v.19 no.12
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• pp.47-58
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• 2018

Duncan & Chang(1970) proposed the Duncan-Chang model that a linear relation of transformed stress-strain plots was reconstituted from a nonlinear relation of stress-strain curve of triaxial compression test using hyperbolic theory so as to estimate an initial tangent modulus and ultimate deviator stress for the soil specimen. Although the transformed stress-strain plots show a linear relationship theoretically, they actually show a nonlinearity at both low and high values of strain of the test. This phenomenon indicates that the stress-strain curve is not a complete form of a hyperbola. So, if linear regression analyses for the transformed stress-strain plot are performed over a full range of strain of a test, error in the estimation of their linear equations is unavoidable depending on ranges of strain with non-linearity. In order to reduce such an error, a modified regression analysis method is proposed in this study, in which linear regression analyses for transformed stress-strain plots are performed over the entire range of strain except the range the non-linearity is shown around starting and ending of the test, and then the initial tangent modulus and ultimate deviator stresses are calculated. Isotropically consolidated-drained triaxial compression tests were performed on compacted weathered soil with a modified Proctor density to obtain their model parameters. The modified regression analyses for transformed stress-strain plots were performed and analyzed results are compared with results estimated by 2 points method (Duncan et al., 1980). As a result of analyses, initial tangent moduli are about 4.0% higher and ultimate deviator stresses are about 2.9% lower than those values estimated by Duncan's 2 points method.

• Geotechnical Engineering
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• v.14 no.5
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• pp.219-234
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• 1998

Modulus measurements in vertical boreholes under simulated horizontal in-situ stress conditions were performed on laboratory rock specimens. The experimental program was focused on the examination of modulus change with the variation of the orientation, magnitude and ratios of horizontal biaxial stresses. The experiment results show that the modulus increases when the magnitude of the horizontal stresses increases. The modulus measured in the minimum principal direction increased when the ratio between the horizontal principal stresses increased, while the modulus measured in the maximum principal direction decreased when the ratio of the horizontal principal stresses increased. These were caused by the tangential stresses that vary depending upon the magnitude of horizontal stresses, the applied pressure and the orientation of measurement. Also, the measured moduli were determined under tensile stress, compressive stress, or both stresses. Thus, the stress effect on deformation modulus should be considered, not only for the interpretation of the results of borehole deformability measurement, but also for the design of underground gas storage and pressure tunnel, and for the interpretation of tunnel monitoring.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.49.2-49.2
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• 2018

스퍼터링에 의해 증착된 박막 내 기계적 응력 발생 현상을 규명하기 위하여 활발한 이론적, 실험적 접근이 있었으나, 복잡한 플라즈마 증착환경 내에서 다양한 증착 파라미터로 인해 정확한 응력 발생 메커니즘에 대해 아직도 완벽한 규명이 되지 않은 상황이다. 본 연구에서는 몰리브데늄 (Mo)과 텅스텐 (W) 박막을 마그네트론 스퍼터링법을 이용하여 증착 시 발생하는 잔류응력 발생 현상에 대해 논의하겠다. Mo 박막의 경우 증착압력을 2.5 mTorr와 4.1 mTorr로 고정시킨 채 기판 바이어스를 0-250 V 간격으로 변화시킨 결과, 2.5 mTorr에서는 기판바이어스가 증가할수록 압축응력이 증가하는 반면 4.1 mTorr에서는 기판바이어스가 증가할수록 인장응력이 증가하는 것이 확인되었다. 이러한 반대 경향의 잔류응력을 발생시키는 기판 바이어스 효과를 확인하기 위하여 증착 파라미터 변경에 따른 박막 성장 거동 모델을 제시한다. W 박막은 준안정상인 ${\beta}$-상이 증착 초기(2.5 nm)에 형성이 되고, 증착 과정에서 열역학적 안정상인 ${\alpha}$-상으로 상변태 하였다. 상변태에 의한 부피 변화에 따른 잔류응력 발생의 분석을 위하여 X-ray 회절피크의 비대칭성을 분석한 결과 압축응력과 인장응력이 공존하고 있는 것으로 확인되었다. 본 연구결과는 스퍼터링 공정 시 높은 에너지를 가지는 중성화된 Ar과 스퍼터된 원자가 기판과 충돌 시 atomic peening effect에 의해 압축응력이 발생한다는 일반적인 이론과 상충되는 결과로서, Mo 및 W 박막 내 잔류응력 제어를 위한 방안을 제시한다.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.309-317
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• 2002

The mechanical characteristics of Light-Weighted Foam Soil(LWFS) are investigated in this research. LWFS is composed of the dredged soil from offshore, cement and foam to reduce the unit-weight and increase compressive strength. For this purpose, the unconfined compression tests and triaxial compression tests are carried out on the prepared specimens of LWFS with various conditions such as initial water contents, cement contents, curing conditions and confining stresses. The test results of LWFS indicated that the stress-strain relationship and the compressive strength are strongly influenced by the cement contents rather than the intial water contents of the dredged soils. On the other hand, the stress-strain relationship from triaxial compression test has shown strain-softening behavior regardless of curing conditions. The stress-strain behavior for the various confining stress exhibited remarkable change at the boundary where the confining stress approached to the unconfined compression strength of LWFS. In order to obtain the ground improvement of the compressive strength above 200kPa, the required LWFS mixing ratio is found to be 100%~160% of the initial water contents of dredged soil and 6.6% of cement contents.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.107-108
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• 2007

박막형태의 소재는 일반적으로 광 전자 및 소재가 공 관련 산업에서 특수한 기능이 요구되는 부품 제조에 광범위하게 응용되고 있다. 이러한 박막 소재는 물성 면에서 벌크물질일 때의 물성과 매우 다를 수 있는 것으로알려져 있다. 박막에 스트레인이 존재하면 전자의 이동도나 밴드갭 에너지를 변화시켜 줄 수 있으며, 계면의 전위는 소자를 열화 시키는 역할을 하기도 한다. 이러한 이유로 박막 성장 시 실시간으로 스트레인을 관찰하고 이 결과를 실제 제조공정에 피드백 하여, 소자의 신뢰성을 확보하는 노력이 행해지고 있다. 구리박막의 실시간 응력거동은 F.Spaepen에 의해 보고된 초기 압축응력, 인장응력, 2차적으로 나타나는 점진성의 압축응력의 독특한 3단계 응력거동으로 나타나는 것으로 알려져 있으며, 본 실험에서는 박막증착도중 단시간 증착을 중단한 이후 재 증착을 하여 응력거동을 관찰함으로써 독특한 3단계 응력거동의 메커니즘을 알고자 하였다.

• Journal of the Korean Geotechnical Society
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• v.27 no.8
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• pp.31-37
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• 2011

In order to evaluate the effect of matric suction on the strength and deformation characteristics, the unsaturated unconfined compression test is performed for the statical1y compacted silty sand. Specimens used were made under conditions with various initial degrees of saturation. The initial matric suction, matric suction at the peak shear strength and the volumetric deformation during the shear process were measured. From these results, it was found that the initial degree of saturation exerts the influence on the behaviors of suction, peak shear strength and the volumetric deformation. Furthermore, the suction stress($P_s$) which means the apparent cohesion due to matric suction in the unsaturated shear strength could be derived.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.113-120
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• 1995

여러가지 두꺼운 복합재료 구조물은 3차원 압축 부하 상태에 노출되는 경우가 발생한다. 이런 경우에 있어 서의 복합재료 압축 강도는 압축 평균 응력을 이용하면 예측이 가능할지도 모른다. 이번 연구 에서는 압축 평균 응력을 이용하여 탄소섬유 강화 복합재료들의 압축 강도를 예측하는 모델을 개발 하고자 한다. 이 모델은 압축강도에 영향을 주는 요소, 초기 misalignment를 고려하였고, 탄소섬유와 수지사이에 접합강도가 임계값을 초과할때 복합재료의 파괴가 일어난다고 가정한다. 또 여라가지 문헌들을 통하여 유압이 접합강도에 미치는 점들을 보여준다. 본 모델을 이용한 예측값들은 가해지는 유압에 따라 증가되며, 실험값들과 비교 분석될 것이다.