• Title, Summary, Keyword: Shear modulus

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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.

A Suggestion of an Empirical Equation for Shear Modulus Reduction Curve Estimation of Sandy Soils (사질토 전단탄성계수 감소곡선 산정을 위한 경험식 제안)

  • Park, Dug-Keun
    • Journal of the Korean Geotechnical Society
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    • v.18 no.3
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    • pp.127-138
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    • 2002
  • In dynamic analyses such as seismic ground response and soil-structure interaction problems, it is very crucial to obtain accurate dynamic shear modulus of soil deposit. In this study, an extensive data base of available experimental data is compiled and reanalyzed to establish a simple empirical formula for the dynamic shear modulus reduction curve to cover wide range of strain for sandy soils. The proposed empirical equation is to represent the dynamic shear modulus degradation with strain in terms of low-amplitude dynamic shear modulus and effective mean confining Pressure, since those factors have the most significant effect on the Position and shape of the shear modulus reduction curve for nonelastic soils. If low-amplitude shear modulus is measured, degraded modulus at any shear strain amplitude can be calculated using the proposed equation.

Measurement of the Shear Modulus of an Ultrasound Tissue Phantom (초음파 연조직 팬텀에서 횡탄성의 측정)

  • Park, Jeong-Man;Choi, Seung-Min;Kwon, Sung-Jae;Jeong, Mok-Kun
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.6
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    • pp.399-409
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    • 2012
  • In this paper we propose a method for measuring the shear modulus of an ultrasound soft tissue phantom using an acoustic radiation force. The proposed method quantitatively determines the shear modulus based on the rise time of a displacement induced by an acoustic radiation force at the focal point of a focused ultrasound beam. The shear wave speed and shear modulus obtained from the proposed method and a shear wave propagation method were compared to verify the validity of the proposed method. In the shear wave propagation method, the shear modulus is first computed by measuring the propagating speed of a shear wave induced in a phantom by a limited-diffraction transmit field, and then was compared to that obtained with the proposed method in an ultrasound data acquisition system calibrated based on the first computed shear modulus. The relative errors between the two methods were found to be 4% for shear wave speed and less than 9% for shear modulus, confirming the usefulness of the proposed method.

The Variation Rate of Shear Modulus for Anisotropic Magneto-rheological Elastomer due to Volume Fraction of CIP (CIP 부피비에 따른 이방성 MRE의 전단계수 변화율)

  • Jeong, Un-Chang;Yoon, Ji-Hyun;Yang, In-Hyung;Lee, You-Yub;Oh, Jae-Eung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1132-1137
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    • 2011
  • MRE(magneto-rheological elastomers) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb vibration of broader frequency range. These characteristic phenomena result from the orientation of magnetic particles named carbonyl iron powder(CIP) in rubber matrix. In this paper, simulation on variation rate of shear modulus for anisotropic MRE due to volume fraction of CIP and an effective permeability model was applied to predict the field-induced shear modulus of MREs. Also, the variation rate of shear modulus for anisotropic MRE was derived using magneto-mechanical theory. Based on Maxwell-Garnett mixing rule, the increment of shear modulus was calculated to evaluate the shear modulus of MREs with column structure of CIP due to induced current. The simulation results on variation rate of shear modulus can be applied to the variable mechanical system of MRE such as tunable vibration absorber, stiffness variable bush and mount.

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.

Prediction models of the shear modulus of normal or frozen soil-rock mixtures

  • Zhou, Zhong;Yang, Hao;Xing, Kai;Gao, Wenyuan
    • Geomechanics and Engineering
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    • v.15 no.2
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    • pp.783-791
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    • 2018
  • In consideration of the mesoscopic structure of soil-rock mixtures in which the rock aggregates are wrapped by soil at normal temperatures, a two-layer embedded model of single-inclusion composite material was built to calculate the shear modulus of soil-rock mixtures. At a freezing temperature, an interface ice interlayer was placed between the soil and rock interface in the mesoscopic structure of the soil-rock mixtures. Considering that, a three-layer embedded model of double-inclusion composite materials and a multi-step multiphase micromechanics model were then built to calculate the shear modulus of the frozen soil-rock mixtures. Given the effect of pore structure of soil-rock mixtures at normal temperatures, its shear modulus was also calculated by using of the three-layer embedded model. Experimental comparison showed that compared with the two-layer embedded model, the effect predicted by the three-layer embedded model of the soil-rock mixtures was better. The shear modulus of the soil-rock mixtures gradually increased with the increase in rock regardless of temperature, and the increment rate of the shear modulus increased rapidly particularly when the rock content ranged from 50% to 70%. The shear modulus of the frozen soil-rock mixtures was nearly 3.7 times higher than that of the soil-rock mixtures at a normal temperature.

Characteristics of Dynamic Shear Modulus Mastercurve of Aged or Unaged Asphalt Binders (동전단 마스터곡선을 이용한 아스팔트 바인더의 노화 특성 평가)

  • Yun, Tae Young;Ham, Sang Min;Yoo, Pyeong Jun
    • International Journal of Highway Engineering
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    • v.15 no.1
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    • pp.87-94
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    • 2013
  • PURPOSES: To characterize the aging effect on asphalt binder, dynamic shear modulus mastercurve of two typical asphalt binders are developed. METHODS: To develop dynamic shear modulus mastercurve, dynamic shear modulus at high temperature and creep stiffness at low temperature are measured by temperature sweep test and bending beam rheometer test, respectively. RESULTS: It is observed that the aging effect on asphalt binder can be clearly observed from dynamic shear modulus mastercurve and the mastercurve can be utilized to predict behavior of asphalt binder at wide range of temperature. CONCLUSIONS: It is confirmed that SBS 5% modified binder has more desirable mechanical property at low and high temperature as a pavement material comparing to PG64-22 binder and the mastercurve is an effective tool to evaluate the property of asphalt binder.

Experimental Investigation of Shear Modulus of a Core in a Metallic Sandwich Plate with a Truss Core (트러스형 금속 샌드위치 판재에서 심재의 전단특성계수의 실험적 결정)

  • Jung, Chang-Gyun;Seong, Dae-Young;Yang, Dong-Yol;Moon, Kyung-Je;Ahn, Dong-Gyu
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.8
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    • pp.67-73
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    • 2007
  • A sandwich plate with a truss core is composed of two face sheets and a pyramidal truss core between face sheets. This paper shows how to estimate the shear modulus of a truss core, experimentally. To determine the shear modulus of truss cores, 3-point bending tests are performed. For tests, metallic sandwich beams with truss cores are fabricated. Two kinds of truss cores are tested to investigate the shear modulus. Each test is repeated under different widths in order to increase accuracy. As a result, the shear modulus of sandwich beam is properly calculated. The deflection of a sandwich beam with a truss core by shear deformation takes the major contribution of the total deflection and the shear modulus of sandwich beam should be considered whenever it is designed.

Effective Longitudinal Shear Modulus of Polymeric Composite Using Iosipescu Shear Test (Iosipescu Shear Test를 이용한 고분자 복합재료의 종방향 전단계수 연구)

  • Jeong, Tae-Heon;Kwon, Yong-Su;Lee, You-Tae;Lee, Dong-Joo
    • Journal of the Korean Society of Industry Convergence
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    • v.3 no.1
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    • pp.61-67
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    • 2000
  • Effective shear modulus of continuous fiber reinforced polymeric composites is measured using a modified Iosipescu Shear Test(IST) and compared with data obtained by finite element analyses that a concept of unit cell is. It is found that the numerical results of the longitudinal shear modulus give a good agreement with experimental data at lower fiber volume fraction. In this paper, both the distance and stress transfer between the fibers are discussed as the major factors.

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Dynamic Deformation Characteristics of Fiber Mixed Silty Sand (섬유보강 실트질 모래의 동적 변형특성)

  • Heo, Joon;Chang, Pyoung-Wuck
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.6
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    • pp.59-70
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    • 2005
  • A series of resonant column test was performed to investigate the dynamic deformation characteristics of silty sand soils mixed with polypropylene fibrillated type fiber. Results show that optimum mixing ratios were $0.2\%$ for 19mm of cut fiber for shear modulus and $0.1\%$ for 60mm cut fiber fur damping ratio. As shear strain was increased, normalized values of shear modulus (G(Reinforced)/ G(Unreinforced)) of fiber reinforced soil were increased up to $10^{-3}\%\~10^{-1}\%$ ranges. However, normalized damping ratio (D(Reinforced/D(Unreinforced)) was diminished with an increase in strain beyond $10^{-3}\%\~10^{-1}\%$ for the damping capacity of soils mixed with fiber. Normalized shear modulus $(G/G_{max})$ obtained from the test was plotted in the chart suggested by Seed and Idriss. The shear modulus of silty sand was located between sand and gravel curves.