• Title/Summary/Keyword: tensile modulus

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Development of Eco-friendly Pavement Material using Polyurethane Binder (폴리우레탄 바인더를 활용한 친환경 도로포장용 혼합물 개발)

  • Choi, Ji Young;An, Young Jun;Park, Hee Mun;Kim, Tae Woo
    • International Journal of Highway Engineering
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    • v.15 no.2
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    • pp.113-119
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    • 2013
  • PURPOSES : The objectives of this study are to develop the eco-friendly pavement material using polyurethane binder and evaluate mechanical properties of the developed binder and concrete. METHODS : The bending beam test was conducted to select the sample candidates of polyurethane binder based on the bending strength. The characteristics of viscosity, curing time, and temperature change of sample binder was examined on different temperature conditions. The mechanical properties of polyurethane binder was estimated using the dynamic modulus testing. The indirect tensile strength test was conducted on polyurethane binder concrete with different gradation and binder content for evaluating the mechanical properties of concretes. RESULTS : Based on the beading beam test, four different binder samples were prepared for estimate the mechanical properties. The viscosity of polyurethane binder tends to increase with increase of liquid temperature and the hardening phenomenon begins 10 to 15 minutes at room temperature after mixing the resin and hardener. It is observed that the dynamic modulus of binder increases as loading frequency increases and change of modulus is found to be the highest in the PU-2I binder type. The PU-2I binder concretes shows the largest value of indirect tensile strength and indirect tensile energy. CONCLUSIONS : The use of polyurethane binder as pavement materials is capable of increasing the pavement performance and reducing the detrimental environmental effect during the highway construction.

Experimental Study on Unconfined Compression Strength and Split Tensile Strength Properties in relation to Freezing Temperature and Loading Rate of Frozen Soil (동결 온도와 재하속도에 따른 동결토의 일축압축 및 쪼갬인장 강도특성)

  • Seo, Young-Kyo;Choi, Heon-Woo
    • Journal of Ocean Engineering and Technology
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    • v.26 no.6
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    • pp.19-26
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    • 2012
  • Recently the world has been suffering from difficulties related to the demand and supply of energy due to the democratic movements sweeping across the Middle East. Consequently, many have turned their attention to never-developed extreme regions such as the polar lands or deep sea, which contain many underground resources. This research investigated the strength and initial elastic modulus values of eternally frozen ground through a uniaxial compression test and indirect tensile test using frozen artificial soil specimens. To ensure accurate test results, a sandymud mixture of standard Jumunjin sand and kaolinite (20% in weight) was used for the specimens in these laboratory tests. Specimen were prepared by varying the water content ratio (7%, 15%, and 20%). Then, the variation in the strength value, depending on the water content, was observed. This research also established three kinds of environments under freezing temperatures of $-5^{\circ}C$, $-10^{\circ}C$, and $-15^{\circ}C$. Then, the variation in the strength value was observed, depending on the freezing environment. In addition, the tests divided the loading rate into 6 phases and observed the variation in the stress-strain ratio, depending on the loading rate. The test data showed that a lower freezing temperature resulted in a larger strength value. An increase in the ice content in the specimen with the increase in the water content ratio influenced the strength value of the specimen. A faster load rate had a greater influence on the uniaxial compression and indirect tensile strengths of a frozen specimen and produced a different strength engineering property through the initial tangential modulus of elasticity. Finally, the long-term strength under a constant water content ratio and freezing temperature was checked by producing stress-strain ratio curves depending on the loading rate.

Effect of NR/BR Blends ratio and Oil Content on the Mechanical Properties of Rubber Isolator at Low Temperature (저온환경에서 NR/BR 블렌드 조성비 및 오일함량이 방진고무재료의 기계적 특성에 미치는 영향)

  • Kim, Wan-Doo;Kim, Wan-Soo;Woo, Chang-Soo;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.39 no.2
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    • pp.95-104
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    • 2004
  • New compounds were made using various NR/BR blend ratio and oil content to improve mechanical properties of rubber isolator at low temperature. Mechanical properties were investigated as a function of NR/BR blend ratio and oil content. Hardness and tensile modulus generally increased, but tensile strength and elongation at break decreased with increasing BR content. Hardness, tensile modulus and tensile strength decreased, but elongation at break were nearly the same with increasing oil content. The glass transition temperature of NR and BR were found to be $-50^{\circ}C$ and $-90^{\circ}C$ respectively based on the abrupt drops in storage elastic modulus and peak of loss factor. Two distinct transition temperature were observed in NR/BR blend compounds and each transition point was not affected by blend level indicating incompatible nature of NR/BR blend.

Experimental Study on the Hygrothermal Ageing Effect to the Strength of CFRP Materials for Marine Leisure Boat (열수노화 조건에서 레저선박용 탄소섬유강화플라스틱의 강도변화에 관한 실험적 연구)

  • Jeong, Han Koo;Noh, Jackyou
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.3
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    • pp.205-214
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    • 2018
  • This paper deals with the experimental study on the hygrothermal ageing effect to the strength of Carbon Fiber Reinforced Plastics (CFRP) materials for marine leisure boat manufactured by vacuum assisted resin infusion method. The experiments performed consist of tensile, flexural and shear tests according to American Society for Testing and Materials (ASTM) and Korean Industrial Standards (KS) test methods. Test coupons are varied from uni-directional(UD, $0^{\circ}$, $90^{\circ}$), Bi-Directional (BD), and Double-Bias (DB) carbon fiber fabrics in conjunction with epoxy resin. The results of tensile test show that tensile strength reduces significantly while not the same degree of reduction is observed for elasticity modulus with respect to the existence of hygrothermal ageing effect. This implies that the tensile strain induced from external load holds steady values but ultimate strength values change widely under hygrothermal ageing effect. In case of the flexural test, $0^{\circ}$ UD shows more strength reduction than $90^{\circ}$ UD while BD has reduced values in both flexural strength and elasticity modulus under hygrothermal ageing effect. It is learned that the bending strain induced from external load and ultimate strength values are reduced with respect to hygrothermal ageing effect. Shear test performed only on DB materials, and the results show marginal reduction in ultimate strength and moderate reduction in elasticity modulus. This means that the shear strain varies more than ultimate shear strength with respect to hygrothermal ageing effect. The experiment conducted in this paper clearly demonstrates the differences in material properties of the CFRP for the consideration of hygrothermal ageing effect. Findings obtained from this experimental study can serve as a fundamental input data for the realistic structural responses of marine leisure boat built in CFRP materials.

Measurement of Tensile Properties of Copper foil using ESPI technique (ESPI 기법을 이용한 동 박막의 인장 특성 측정)

  • 권동일;허용학;김동진;박준협;기창두
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1059-1062
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    • 2003
  • Micro-tensile testing system has been developed and micro-tensile tests for copper foil have been carried out. The system consisted of a micro tensile loading system and a micro-ESPI system for measuring strain. The loading system has a maximum loading capacity of 50N and a stroke resolution of 4.5nm. Stress-strain curves for the electro-deposited copper foil with the thickness of 18$\mu\textrm{m}$ were obtained, and tensile properties, including elastic modulus, yielding strength and tensile strength, were determined. The tensile properties obtained under three different conditions of testing speed showed a dependency on the speed.

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A Study on the Tensile Properties of Polyester Warp Knitted Fabrics (폴리에스테르 경편포의 신장특성에 관한 연구)

  • 김석근;최재우;남은우
    • Textile Coloration and Finishing
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    • v.12 no.1
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    • pp.17-24
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    • 2000
  • The tensile properties of polyester warp knitted fabrics of satin and reverse satin structure with various lengths of underlap were studied. In the range of low tension, the satin warp knitted fabric showed larger tensile energy and elongation in the direction of $0^\circ$ and larger tensile linearity, tensile resilience and initial modulus in $90^\circ$. Meanwhile, reverse satin one showed larger initial moduli in 0$^{\circ}$ and larger the others in $90^\circ$. In the range of high tension, the tendencies of both fabrics in $0^\circ$ direction were almost the same as those in all direction. As the under laps were shorter for both fabrics, tensile linearity, tensile energy and elongation increased, but tensile resilience decreased in all directions. However initial moduli were changed little.

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Temperature-Dependency of Tensile Properties of GFRP Composite for Wind Turbine Blades (풍력 발전 블레이드 복합재 GFRP의 인장 특성의 온도 의존성)

  • Huh, Yong-Hak;Kim, Jong-Il;Kim, Dong-Jin;Lee, Gun-Chang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.9
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    • pp.1053-1057
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    • 2012
  • In this study, the temperature-dependency of the tensile properties of a glass fiber reinforced plastic (GFRP) used in wind turbine blades was examined. The tensile strength, elastic modulus, and Poisson's ratio of the tensile specimen manufactured from uniaxial ($0^{\circ}$) and triaxial ($0/{\pm}45^{\circ}$) laminate composite plates were measured at four different testing temperatures-room temperature, $-30^{\circ}C$, $-50^{\circ}C$, and $60^{\circ}C$. It was found that the tensile strengths and elastic moduli of the uniaxial laminates were greater than those of the triaxial laminates over the testing temperature range. The tensile strength of the two laminates was significantly dependent on the testing temperature, while the dependency of the elastic modulus on the temperature was insignificant. Furthermore, it could be considered that the Poisson's ratio changed slightly with a change in the testing temperature.

Measuring Young's Modulus of Materials by Using Accelerometer (가속도계를 이용한 재료의 영계수 측정방법)

  • Sohn, Chang-Ho;Park, Jin-Ho;Yoon, Doo-Byung;Chong, Ui-Pil;Choi, Young-Chul
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.11 s.116
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    • pp.1158-1164
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    • 2006
  • For the description of the elastic properties of linear objects a convenient parameter is the ratio of the stress to the strain, a parameter called the Young's modulus of the material. Young's modulus can be used to predict the elongation or compression of an object as long as the stress is less than the yield strength of the material. Conventional method for estimating Young's modulus measured the ratio of stress to corresponding strain below the proportional limit of a material using a tensile testing machine. But the method needs precision specimens and expensive equipment. In this paper, we proposed method for estimating Young's modulus using accelerometer. The basic idea comes from that the wave velocity is different as the Young's modulus. To obtain Young's modulus, a group velocity is obtained. It is difficult to measure group velocity. This is because plate medium has a dispersive characteristics which has different wave speed as frequency. In this paper, we used Wigner-Ville distribution to measure group velocity. To verify the proposed method, steel and acryl plate experiments have been performed. Experimental results show that the proposed method is powerful for estimating Young's modulus.

Measuring Young's Modulus of Materials by using Accelerometer (가속도계를 이용한 재료의 영계수 측정방법)

  • Choi, Young-Chul;Park, Jin-Ho;Yoon, Doo-Byung;Sohn, Chang-Ho;Hwang, Il-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.1027-1032
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    • 2007
  • For the description of the elastic properties of linear objects a convenient parameter is the ratio of the stress to the strain, a parameter called the Young's modulus of the material. Young's modulus can be used to predict the elongation or compression of an object as long as the stress is less than the yield strength of the material. Conventional method for estimating Young's modulus measured the ratio of stress to corresponding strain below the proportional limit of a material using a tensile testing machine. But the method needs precision specimens and expensive equipment. In this paper, we proposed method for estimating Young's modulus using accelerometer. The basic idea comes from that the wave velocity is different as the Young's modulus. To obtain Young's modulus, a group velocity is obtained. It is difficult to measure group velocity. This is because plate medium has a dispersive characteristics which has different wave speed as frequency. In this paper, we used Wigner-Ville distribution to measure group velocity. To verify the proposed method, steel and acryl plate experiments have been performed. Experimental results show that the proposed method is powerful for estimating Young's modulus.

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Experimental Study on Tensile Creep of Coarse Recycled Aggregate Concrete

  • Seo, Tae-Seok;Lee, Moon-Sung
    • International Journal of Concrete Structures and Materials
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    • v.9 no.3
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    • pp.337-343
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    • 2015
  • Previous studies have shown that the drying shrinkage of recycled aggregate concrete (RAC) is greater than that of natural aggregate concrete (NAC). Drying shrinkage is the fundamental reason for the cracking of concrete, and tensile creep caused by the restraint of drying shrinkage plays a significant role in the cracking because it can relieve the tensile stress and results in the delay of cracking occurrence. However, up till now, all research has been focusing on the compressive creep of RAC. Therefore, in this study, a uniaxial restrained shrinkage cracking test was executed to investigate the tensile creep properties caused by the restraint of drying shrinkage of RAC. The mechanical properties, such as compressive strength, tensile splitting strength, and Young's modulus of RAC were also investigated in this study. The results confirmed that the tensile creep of RAC caused by the restraint of shrinkage was about 20-30 % larger than that of NAC.