• Title, Summary, Keyword: modulus

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Analytical Interpretation on the Uniaxial Tensile Properties of Geomembranes (지오멤브레인의 일축 인장성질에 대한 해석학적 고찰)

  • 전한용;유중조
    • Textile Science and Engineering
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    • v.34 no.8
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    • pp.561-568
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    • 1997
  • From the stress-strain curves of geomembranes, initial modulus, yield point, tensile strength and breaking elongation were obtained. It was derived from a relationship between the initial modulus and yield point by using the mathematical model. The order (n) of parabolic equation, $\sigma$=$\sigma$${\gamma}$(1-(($\varepsilon$${\gamma}$-$\varepsilon$)/$\varepsilon$${\gamma}$)"), is established to represent theoretically the uniaxial tensile behavior of geomembranes. The mechanical properties of HDPE, ECB and EVA geomembranes were examined according to ASTM D638 and substituted the experimental data for theoretical parameters. After determining (n), 2% secant modulus as an elastic modulus is considered to obtain the index value. It is proved that the initial modulus is equal to n times of secant modulus at yield point. When n is 4 (HDPE) and 7 (ECB, EVA), respectively, the theoretical values of mathematical model are located within the deflection of expermental data. And it is thought that 2% secant modulus, as an index modulus, is more appropriate than the initial modulus(tangent modulus at origin), because the 2% secant modulus has narrower error range than the initial modulus.ulus.

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Long-term development of compressive strength and elastic modulus of concrete

  • Yang, Shuzhen;Liu, Baodong;Yang, Mingzhe;Li, Yuzhong
    • Structural Engineering and Mechanics
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    • v.66 no.2
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    • pp.263-271
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    • 2018
  • Compressive strength and elastic modulus of concrete are constantly changing with age. In order to determine long-term development of compressive strength and elastic modulus of concrete, an investigation of C30 concrete cured in air conditions was carried out. Changes of compressive strength and elastic modulus up to 975 days were given. The results indicated that compressive strength and elastic modulus of concrete rapidly increased with age during the initial 150 days and then increased slowly. The gain in elastic modulus was slower than that of compressive strength. Then relationships of time-compressive strength, time-elastic modulus and compressive strength-elastic modulus were proposed by regression analysis and compared with other investigations. The trends of time-compressive strength and time-elastic modulus with age agreed best with ACI 209R-92. Finally, factors contributed to long-term development of compressive strength and elastic modulus of concrete were proposed and briefly analyzed.

Effects of Span-to-depth Ratio and Poisson's Ratio on Elastic Constants from Bending and Plate Tests

  • Jeong, Gi Young;Kong, Jin Hyuk
    • Journal of the Korean Wood Science and Technology
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    • v.43 no.2
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    • pp.177-185
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    • 2015
  • The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determination of elastic modulus and shear modulus. Different material properties and span to depth ratios were used to analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparent elastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulus evaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson's ratio influenced shear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Different shearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D 198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials could be obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending and correction factor for ASTM D 3044.

Evaluation of Modulus of Soils Using Various Laboratory Tests (다양한 실내시험을 이용한 지반의 탄성계수 평가)

  • 권기철;김동수
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.345-352
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    • 2000
  • It is very important to evaluate the reliable nonlinear modulus characteristics of soils not only in the analysis of geotechnical structures under working stress conditions but also for the soil dynamic problems. For the evaluation of modulus characteristics of soils, various tests have been mostly employed in laboratory. However, different testing techniques are likely to have different ranges of reliable strain measurements, different applied stress level, and different loading frequencies, and the modulus of soils can be affected by these variables. For reliable evaluation, therefore, those effects on the modulus need to be considered, and measured values should be effectively adjusted to actual conditions where the soil is working. In this paper, to evaluate the modulus characteristics of soils, laboratory testing such as free-free resonant column (FF-RC), resonant column (RC), torsional shear (TS), static TX, and cyclic M/sub R/ tests were performed. The effects of strain amplitude, loading frequency, loading cycles, confining pressure, density, and water content on modulus were investigated. It is shown that the FF-RC test, which is simple and inexpensive testing technique, can provide a reliable estimation of small strain Young's modulus (E/sub max/), and the modulus evaluated by various laboratory tests are comparable to each other fairly well when the effects of these factors are properly taken into account.

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Effect of Temperature and Aging on the Relationship between Dynamic and Static Elastic Modulus of Concrete (온도와 재령이 콘크리트의 동탄성계수와 정탄성계수의 상관관계에 미치는 영향)

  • 한상훈;김진근
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.445-450
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    • 2001
  • The paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model equations are proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperature of 10, 23, and 50 $^{\circ}C$. Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus, which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus. The proposed relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type, temperature, and aging.

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Theoretical Tensile Modulus of Multi-filament Yarns (멀티 필라멘트사의 이론적 인장 탄성률)

  • 박정환;오애경
    • Textile Science and Engineering
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    • v.39 no.5
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    • pp.598-605
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    • 2002
  • The theoretical tensile modulus of an ideal twisted yam was derived in the terms of mechanical values of its constituent fibers and yarn structural parameters by energy method. According to the theoretical results, the relative tensile modulus of yarn decreased with the increase of yarn's surface helix angle and the ratio of the fiber shear modulus to tensile modulus. Experimental data on twisted multi-filament yarns agree better with the predictions of this formula than those reported earlier in the literature.

Complex Modulus of Rough Rice Kernel under Cyclic Loading (주기적(週期的) 반복하중(反復荷重)을 받는 벼의 복소탄성율(複素彈性率))

  • Kim, M.S.;Park, J.M.
    • Journal of Biosystems Engineering
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    • v.16 no.3
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    • pp.263-271
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    • 1991
  • When grains is subjected to oscillating load, the dynamic viscoelastic behavior of the material will be describe the complex modulus of the material. The complex modulus and therefore the storage modulus, the loss modulus, and the phase angle for the sample should be obtainable with a given static viscoelastic property of the material under static load. The complex relaxation moduli of the rough rice kernel were computed from the Burger's model describing creep behavior of the material which were obtained in the previous study. Also, the effects of cyclic load and moisture content of grain on the dynamic viscoelastic behavior of the samples were analized. The storage modulus of the rough rice kernel slightly increased with the frequency applied but at above the frequency of 0.1 Hz it was nearly constant with the frequency, and the loss modulus of the sample very rapidly decreased with increase in the frequency on those frequency ranges. It was shown that the storage modulus and the loss modulus of the sample increased with decrease in grain moisture content. Effect of grain moisture content on the storage modulus of the sample was highly significant than effect of the frequency applied, but effect of the frequency on the loss modulus of the sample was more significant than effect of grain moisture content.

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Analytical and numerical study of temperature stress in the bi-modulus thick cylinder

  • Gao, Jinling;Huang, Peikui;Yao, Wenjuan
    • Structural Engineering and Mechanics
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    • v.64 no.1
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    • pp.81-92
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    • 2017
  • Many materials in engineering exhibit different modulus in tension and compression, which are known as bi-modulus materials. Based on the bi-modulus elastic theory, a modified semi-analytical model, by introducing a stress function, is established in this paper to study the mechanical response of a bi-modulus cylinder placed in an axisymmetric temperature field. Meanwhile, a numerical procedure to calculate the temperature stresses in bi-modulus structures is developed. It is proved that the bi-modulus solution can be degenerated to the classical same modulus solution, and is in great accordance with the solutions calculated by the semi-analytical model proposed by Kamiya (1977) and the numerical solutions calculated both by the procedure complied in this paper and by the finite element software ABAQUS, which demonstrates that the semi-analytical model and the numerical procedure are accurate and reliable. The result shows that the modified semi-analytical model simplifies the calculation process and improves the speed of computation. And the numerical procedure simplifies the modeling process and can be extended to study the stress field of bi-modulus structures with complex geometry and boundary conditions. Besides, the necessity to introduce the bi-modulus theory is discussed and some suggestions for the qualitative analysis and the quantitative calculation of such structure are proposed.

A Study on The Estimation of Effective Bulk Modulus of Hydraulic Oil With Pressure Variation (압력변동에 따른 유압유의 유효체적탄성계수 측정에 대한 연구)

  • 이재천;정용승
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.1
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    • pp.179-184
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    • 2003
  • It has been recognized that the compressibility of hydraulic fluid, which is characterized by the value of its bulk modulus, heavily affects on the system behavior and performance. In practice, the value of the oil bulk modulus varies by the operational and structural characteristics of the hydraulic system. This study presents the theoretical derivation of the effective bulk modulus and describes an experimental impulse technique that allows accurate measurement of oil effective bulk modulus with pressure variation in a hydraulic system. Experimental and analytical results show that the value of the effective bulk modulus varies a lot in low pressure region by the effect of entrained air, while the effective bulk modulus can be estimated just using the oil and container bulk modulus on the other high pressure region.

Determining Shear Modulus of 3-ply Laminated Veneer Lumber by Uniaxial Tension Test

  • Oh, Sei-Chang
    • Journal of the Korean Wood Science and Technology
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    • v.41 no.5
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    • pp.425-431
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    • 2013
  • Estimation equations of shear modulus in the plane of laminated veneer lumber (LVL) were compared each other through uniaxial tension test results. The equations - basic elastic equation in the dimensional orthotropic case, Hankinson's formula and empirical equation proposed by Salikis and Falk, were applied to determine the elastic constants at various angles to the grain, which were needed for determination of shear modulus. Tensile elastic modulus of LVL predicted from these equations were compared with test data to evaluate the accuracy of the equation. Tensile elastic modulus rapidly decreased at orientations between 0 and 15 degrees and elastic modulus at grain angles of 15, 30, and 45 degrees overestimated in the presented equations. But the proposed equation by Salikis and Falk showed better prediction, especially at 30, and 45 degrees. This proposed formula would be more useful and practical for estimating of shear modulus of wood composites like LVL to minimize the effect of Poisson's ratio term.