• 한국지반공학회논문집
• /
• 제20권7호
• /
• pp.171-181
• /
• 2004

본 연구는 불포화 상태 전 범위에 대한 사질토의 인장강도 모델화 가능성을 조사하기 위해 실시 되었다. 새로 개발된 직접인장시험기법을 이용하여 인장시험이 실시되었다. 측정된 결과는 Rumpf 및 Schubert가 동일크기의 이상적인 구에 대해 개발한 이론적인 인장강도 모델들에 의한 예측 값과 비교 되었다. 이를 위해 석션-포화실험을 통해 얻어진 흙-수분특성곡선을 이용하여 이론모델에 있어 중요한 요소인 불포화상태(pendular, funicular, capillary) 구분 및 음의 간극수압 값을 산정하는데 사용하였다. Pendular 상태에서 불포화모래의 비선형 거동이 Rumpf의 모델에 의해 적절이 묘사되었다. Funicular 및 capillary상태의 경우, 함수비가 증가함에 따라 인장강도가 증가하다 최고 값이 도달한 후 다시 감소하는 실험 측정치의 경향도 Schubert의 모델에 의해 적절히 묘사되었다. 본 비교 연구는 이상적인 단일 크기의 입자에 대해 개발된 이론적인 모델이 다양한 크기를 갖는 불포화 사질토의 인장강도를 예측할 수 있다는 가능성을 뒷받침해준다.

• 한국재료학회지
• /
• 제12권10호
• /
• pp.820-824
• /
• 2002

It is of importance to know that the bonding strength and interfacial stress of SOI wafer pairs to meet with mechanical and thermal stresses during process. We fabricated Si/2000$\AA$-SiO$_2$ ∥ 2000$\AA$-SiO$_2$/Si SOI wafer pairs with electric furnace annealing, rapid thermal annealing (RTA), and fast linear annealing (FLA), respectively, by varying the annealing temperatures at a given annealing process. Bonding strength and interfacial stress were measured by a razor blade crack opening method and a laser curvature characterization method, respectively. All the annealing process induced the tensile thermal stresses. Electrical furnace annealing achieved the maximum bonding strength at $1000^{\circ}C$-2 hr anneal, while it produced constant thermal tensile stress by $1000^{\circ}C$. RTA showed very small bonding strength due to premating failure during annealing. FLA showed enough bonding strength at $500^{\circ}C$, however large thermal tensile stress were induced. We confirmed that premated wafer pairs should have appropriate compressive interfacial stress to compensate the thermal tensile stress during a given annealing process.

• Journal of Welding and Joining
• /
• 제28권2호
• /
• pp.91-95
• /
• 2010

Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curve were systematically rearranged in the $\Delta\sigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $\Delta\sigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.

• 한국안전학회지
• /
• 제29권3호
• /
• pp.1-7
• /
• 2014

In this study, for the evaluation of the static and fatigue joining strength of the joint, the geometry of the cross-tension specimen was adopted. The specimens were produced with optimal joining force and fatigue life of the clinch joint specimens was evaluated. The material selected for use in this study was cold rolled mild steel (SPCC) with a thickness of 0.8 mm. The maximum tensile load was 708 N for the specimen with single point. The fatigue endurance limit (=42.6 N) per point approached to 6% of the maximum tensile strength at a load ratio of 0.1, suggesting that the joints are vulnerable to cross-tension loading during fatigue. Compared to equivalent stress and maximum principal stress, the SWT fatigue parameter and equivalent strain can properly predict the current experimental fatigue life. The SWT parameter can be expressed as $SWT=2497.5N^{-0.552)_f$.

• 한국재료학회지
• /
• 제11권12호
• /
• pp.1057-1062
• /
• 2001

We investigated the change of mechanical properties for TiNi shape memory alloy by heat treatment. 6061Al matrix composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum casting. TiNi alloy has the maximum tensile strength at 673K treated and there is no change of tensile strength and hardness at 448K treated. The composites, prepared by vacuum casting, showed good interface bonding by vacuum casting. It was about 3$\mu\textrm{m}$ of thickness of the diffusion layer. Tensile strength of the composite was in higher than that of 6061Al alloy as increased value of about 70MPa at room temperature and about 110MPa at 363K. We thought that the increase of the tensile strength at 363K was due to reverse transformation of the TiNi shape memory alloy.

• 한국건축시공학회지
• /
• 제18권5호
• /
• pp.455-461
• /
• 2018

본 연구에서는 현재 국내에 일반적으로 적용되고 있는 폴리우레탄 도막방수재를 대상으로 12개월간의 장기 화학열화요인 작용 시 재료적 측면에서의 성능변화 특성을 인장성능 중심으로 평가하고, 도출된 데이터를 회귀분석기법을 적용하여 정량적 회귀식을 제시함에 따라 폴리우레탄 도막방수재의 장기내구성 확보여부에 대하여 대략적으로 성능예측 가능한 기초적 데이터 베이스를 구축하였다. 화학적 열화 환경에서 폴리우레탄 도막방수재는 약 23%~38%의 강도 저하를 나타냈다. 또한 신장률의 경우 약 15%~22%의 성능 저하를 나타내는 것을 확인할 수 있었으며, 제시한 회귀방정식은 화학적 열화조건에서 도막재의 성능 변화 정도를 예측하는데 활용 가능할 것으로 판단된다.

• 한국염색가공학회지
• /
• 제34권2호
• /
• pp.127-133
• /
• 2022

With the increasing interest in the expression of individuality and appearance of modern people, it is time to conduct research and development of novel hair coloring from various angles. Therefore, taking into account the order of discoloration of hair pigments, we selected a creative and novel emulsion as a novel material for hair coloring, rather than a cosmetic material such as hot water extract using natural products dealt with in previous studies, commercially available hair manicure, and oxidation hair dye for hair. Thus, the change in tensile strength and elongation of hair samples by color was studied. As a result of the study, hair with green emulsion paint had a significantly higher maximum load, maximum stress, maximum elongation and breaking load, breaking stress, breaking elongation values are shown. Maximum in terms of modulus, green emulsion applied hair and the control group were higher in the 0-15s strain and 15-145s sections, respectively, and the tangential modulus value was much higher in the control group than the experimental group hairs in all the 0-145s sections. This study, which analyzes the dynamic changes of hair samples that extend the daily color gamut, will greatly contribute to the development of innovative hair coloring materials in the research and production of hair beauty works, and it is judged that it will also contribute to the development of the beauty industry.

• 한국농공학회지
• /
• 제39권1호
• /
• pp.83-92
• /
• 1997

An experimental study of the application of Silica fume for the high strength concrete was conducted. Nine specimens with three different contents of silica fume, 0%, 10%, 20% and with three water-cement ratio 30%, 40%, 50% were tested. Results shows that 10% of silica fume and 30% of water-cement ratio has a maximum strength with 700kg/$cm^2$ of compressive strength and 64kg/$cm^2$ of splitting tensile strength and 100kg/$cm^2$ of flexural strength. Slump value of the tested samples decreases with increasing water-cement ratio and elapsed time of silica fume. Splitting tensile strength$({\sigma}_f)$ and flexural strength $({\sigma}_f)$ and static modulus of elasticity(E) can be correlated with compressive strength $({\sigma}_c)$ from a regression analysis.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.240-245
• /
• 2004

Tensile properties of hard coating material, TiN, were evaluated using micro-tensile testing system. TiN has been known as a hard coating material commonly used today. Micro-tensile testing system consisted of a micro tensile loading system and a micro-ESPI(Electronic Speckle Pattern Interferometry) system. Micro-tensile loading system had a maximum load capacity of 500mN and a resolution of 4.5 nm in stroke. TiN thin film $1{\mu}m$ thick was deposited on the Si wafer pre-deposited of $Si_3N_4$ film substrate by the closed field unbalanced magnetron sputtering (CFUBMS) process. Three kinds of micro-tensile specimen with the respective width of $50{\mu}m$, $100{\mu}m$ and $500{\mu}m$ were fabricated by MEMS process. The mechanical properties including tensile strength and elastic modulus were determined using the micro-tensile testing system and compared by those obtained by nano-indentation

• 한국건설순환자원학회논문집
• /
• 제8권4호
• /
• pp.458-466
• /
• 2020

이 연구의 목적은 비정질 강섬유와 폴리아미드 섬유를 이용한 고성능 하이브리드 섬유보강 콘크리트의 압축 및 인장 거동을 평가하는 것이다. 이를 위하여 목표 압축강도 40MPa 및 60MPa 각각에 대해서 비정질 강섬유와 폴리아미드 섬유를 총 부피비로 1.0% 혼입한 고성능 하이브리드 섬유보강 콘크리트를 제작한 후 압축강도, 압축인성, 직접인장강도 및 응력-변형률 특징 등의 압축 및 인장 거동을 평가하였다. 그 결과, 고성능 하이브리드 섬유보강 콘크리트의 압축강도는 플레인 콘크리크보다 다소 감소하였으나, 압축인성, 압축인성 비, 직접인장강도는 크게 증가하는 것으로 나타났다. 또한 압축 및 인장 시험시 플레인 콘크리트는 최대응력 이후 취성파괴를 나타냈으나, HPHFRC는 변형연화 현상을 나타내어, 압축 및 인장 거동이 크게 개선되는 것으로 나타났다.