• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.11-19
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• 2022

본 연구에서는 기계식 커플러의 이음성능을 향상시키기 위해 다른 접합방식을 가진 두 가지의 새로운 커플러를 개발하였다. 두 가지 방식의 기계식 이음장치에 대하여 응력 해석을 수행하였다. 커플러의 재료특성, 접합방식, 내부 조임쇠의 경사길이를 변수로 최대 인장강도의 영향성을 분석하기 위해 일축인장시험을 수행하였다. 일축인장시험결과를 만족하는 시험체를 대상으로 KS D 0249에 의거하여 정적내력시험 및 반복하중 시험을 수행하였다. 이에 대한 연구결과는 다음과 같다. (1) 커플러의 인장강도와 내부 조임쇠의 경사길이는 최대 인장강도에 영향을 끼친다. (2) 연결 방식에 따라 접합된 철근의 강성, 슬립량, 강성감소율에 영향이 있다. 연구결과는 새롭게 제안된 향상된 기계식 이음장치의 현장 적용에 대한 가능성을 검증하였다.

• 소성∙가공
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• 제29권4호
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• pp.179-187
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• 2020

Existing composite forming processes such as the autoclave, prepreg compression forming (PCF), RTM, etc. require high production costs because of their long processing time. On the other hand, microwave heating process (MHP) can reduce the production costs since both mold and composite material can be heated directly. The aim of this study is to manufacture a mold consisting of polytetrafluoroethylene (PTFE), quartz glass, stainless steel clamps, and polyether ether ketone (PEEK) bolts for fabricating FML based on self-reinforced polypropylene (SRPP) using the MHP. First, the flame test was carried out prior to the MHP to check the temperature on the mold and whether the spark occurred at the mold and the edge of the FML. Second, the uniaxial tensile test was then conducted to obtain the mechanical properties of the FML manufactured by the MHP. The mechanical properties were compared with those of the FML fabricated by the PCF. As a result, the MHP using the PTFE mold can manufacture the FML more rapidly than the PCF, and obtain acceptable mechanical properties.

• 터널과지하공간
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• 제7권3호
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• pp.221-229
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• 1997

Disc-type and ring-type specimens of four different materials were tested to investigate the tensile characteristics and their brief results are presented. Materials tested were marble, granite, cement mortar and plaster. Unizxial tensile strengths are compared with Brazilian and ring test strengths. It was found that Brazilian strengths were usually greater than uniaxial tensile strengths and affected by loading rates. In the ring tests, tensile strengths were generally found to be decreased as relative hole radius being increased. Ring test strengths, however, converged to some value in r$\geq$0.45 of marble, r$\geqq$0.29 of cement mortar and r$\leq$0.5 of plaster specimens. In such range of r, furthermore, transverse cracking of specimens were observed.

• 대한금속재료학회지
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• 제48권11호
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• pp.965-973
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• 2010

The small punch creep (SPC) test has recently received much attention as a new alternative to the conventional uniaxial creep test because it needs only a miniature-sized specimen directly detached from an operating system or component without any serious sampling damages. However, it is difficult to obtain the equivalent uniaxial creep data directly from the SPC data. As a specimen is deformed by a punch in the SPC test, the test result is sensitive to the friction between them. Finite element analyses with various friction coefficients was performed and showed a tendency of increased SPC life with an increased friction coefficient. The necking position predicted by the SPC simulation with a proper friction coefficient showed good agreement with that observed from the real SPC test. Finally, a noble method to convert the SPC load and displacement rate into the equivalent uniaxial creep stress and strain rate, respectively, was established in this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.45-48
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• 2008

The mechanical behavior of small-sized materials has been investigated for many industrial applications, including MEMS and semiconductors. It is challenging to obtain accurate mechanical properties measurements for thin films due to several technical difficulties, including measurement of strain, specimen alignment, and fabrication. In this work, we used the micro-tensile testing unit with the real-time DIC (Digital Image Correlation) strain measurement system. This system has advantages of real time strain monitoring up to 50 nm resolution during the micro-tensile test, and ability to measure the young's modulus and Poisson's ratio at the same time. The mechanical properties of SCS (Single Crystal Silicon) are measured by uniaxial tension test from freestanding SCS which are $2.5{\mu}m$ thick, $200-500{\mu}m$ wide specimens on the (100) plane. Young's modulus, Poisson's ratio and tensile strength in the <110> direction are measured by micro-tensile testing system.

• Smart Structures and Systems
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• 제23권5호
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• pp.479-493
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• 2019

In this paper, the interaction between notch and micro pore under uniaxial compression has been performed experimentally and numerically. Firstly calibration of PFC2D was performed using Brazilian tensile strength, uniaxial tensile strength and biaxial tensile strength. Secondly uniaxial compression test consisting internal notch and micro pore was performed experimentally and numerically. 9 models consisting notch and micro pore were built, experimentally and numerically. Dimension of these models are 10 cm*1 cm*5 cm. the length of joint is 2 cm. the angularities of joint are $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$. For each joint angularity, micro pore was situated 2 cm above the lower tip of the joint, 2 cm above the middle of the joint and 2 cm above the upper of the joint, separately. Dimension of numerical models are 5.4 cm*10.8 cm. The size of the cracks was 2 cm and its orientation was $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$. Diameter of pore was 1cm which situated at the upper of the notch i.e., 2 cm above the upper notch tip, 2 cm above the middle of the notch and 2 cm above the lower of the notch tip. The results show that failure pattern was affected by notch orientation and pore position while uniaxial compressive strength is affected by failure pattern.

• Advances in concrete construction
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• 제11권4호
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• pp.347-356
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• 2021

To address the limitation of the commonly used steam curing of reactive powder concrete (SC-RPC) in engineering, a preparation technology of normal curing reactive powder concrete (NC-RPC) is proposed. In this study, an experimental comparative research on the mechanical properties of NC-RPC and SC-RPC under uniaxial tension is conducted. Under the premise of giving full play to the ultra-high performance of RPC, the paper tries to explore whether normal curing can replace steam curing. The results show that various mechanical indexes of NC-RPC (e.g., tensile strength, ultimate tensile strain, elastic modulus and deformation performance) could basically reach the mechanical index values in steam curing at 28d age, some performance is even better at a longer age. So it affirms the feasibility of normal curing. In this paper, the influence of normal curing age on the tensile properties of RPC is discussed, and the relationship between each index and age is introduced in detail. Based on the experimental data, the tensile mechanism of RPC is analyzed theoretically, and two kinds of tensile constitutive models for RPC are proposed, one is curvilinear model, and another one is polygonal line model. The validity of the two models is further verified by the test results of others.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.23-26
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• 2004

The deformation behaviors of fully annealed or T6-treated 6061 and 7075 aluminum tubes are investigated at elevated temperature using uniaxial tensile test. Fully annealed 6061 and 7075 tube, and T6-treated 7075 tube do not show sharp local necking with an elongation of $50\%$ at tensile temperature of $300^{\circ}C$, accordingly, it is expected that warm hydroforming process can be applied. The increase of tensile temperature does not significantly affect the total elongation of T6-treated 6061 tube.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.258-263
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• 2004

Mechanical property evaluation of micrometer-sized structures is necessary to help design reliable microelectromechanical systems(MEMS) devices. Most material properties are known to exhibit dependence on specimen size and such properties of microscale structures are not well characterized. This paper describes techniques developed for tensile testing of materials used in MEMS. Epi-polycrystalline silicon is currently the most widely used material, and its tensile strength has been measured as 1.52GPa. We have developed an uniaxial testing machine for testing microscale specimen using electro-magnetic actuator. The field magnet and the moving coil taken from an audio-speaker were utilized as the components of the actuator. Structure of specimen was designed and manufactured for easy handling and alignment. In addition to the static tensile tests, new techniques and procedures for measuring strength are described.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.452-455
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• 2008

In the present study, blow forming characteristics of commercially roiled AZ31 alloy sheets were investigated. Two different kinds of AZ31 sheets were originally fabricated by using direct casting and strip casting methods respectively. Both sheets have similar grain sizes of about $7{\mu}m$ with a relatively equiaxed structure after rolling. A series of tensile tests were carried out to get flow behavior in terms of temperature and strain rate. Also, grain size effect was investigated by annealing as-received sheet at elevated temperatures. Elongation increased with temperature increment as well expected. However, the differences in tensile test condition did not give much difference in elongation even at the temperature range where a large elongation would be expected with such as fine grain of $7{\mu}m$. Blow forming experiments showed that forming condition did not result in higher difference in dome height. However, the interesting feature from this study was that formability of this AZ31 alloy got different with stress condition. Firstly, biaxial stress condition might result in lower temperature and strain rate dependencies compared to uniaxial tension results for both DC and SC sheets. Secondly, DC showed slower grain growth in uniaxial tension than in biaxial stress state while SC has much higher grain growth rage in uniaxial tension than in bulging.