• Title, Summary, Keyword: Modulus Ratio

Search Result 1,197, Processing Time 0.061 seconds

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
    • /
    • v.43 no.2
    • /
    • pp.177-185
    • /
    • 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 Study on the Prediction of Elastic Modulus in Short Fiber Composite Materials (단섬유 복합재료의 탄성계수 예측에 관한 연구)

  • Kim Hong Gun
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.29 no.2
    • /
    • pp.318-324
    • /
    • 2005
  • Theoretical efforts are performed to extend the formulation of NSLT(New Shear Lag Theory) for the prediction of the elastic modulus in short fiber composite. The formulation is based on the elastic stress transfer considering the stress concentration effects influenced by elastic modulus ratio between fiber and matrix. The composite modulus, thus far, is calculated by changing the fiber aspect ratio and volume fraction. It is found that the comparison with FEA(Finite Element Analysis) results gives a good agreement with the present theory (NSLT). It is also found that the NSLT is more accurate than the SLT(Shear Lag Theory) in short fiber regime when compared by FEA results. However, The modulus predicted by NSLT becomes similar values that of SLT when the fiber aspect ratio increases. Finally, It is shown that the present model has the capability to predict the composite modulus correctly in elastic regime.

A Study on Prediction of Young's Modulus of Composite with Aspect Ratio Distribution of Short Fiber (장단비 분포를 갖는 단섬유 복합재의 영계수 예측에 대한 연구)

  • Lee, J.K.
    • Journal of Power System Engineering
    • /
    • v.10 no.4
    • /
    • pp.99-104
    • /
    • 2006
  • Young's modulus of composite has been predicted by Eshelby's equivalent inclusion method modified with Mori-Tanaka's mean field theory, where short fibers of aspect ratio distribution are assumed to be aligned. Young's modulus of the composite is predicted with the smallest class interval for simulating the actual distribution of fiber aspect ratio, which is compared with that computed using different class intervals. Young's modulus of the composite predicted with mean aspect ratio or the largest class interval is overestimated by the maximum 10%. As the class interval of short fibers for predicting Young's modulus decreases, the predicted results show good agreements with those obtained using the actual distribution of fiber aspect ratio. It can be finally concluded from the study that if and only if the class interval of short fiber normalized by the maximum aspect ratio is smaller than 0.1, the predicted results are consistent with those obtained using the actual distribution of aspect ratio.

  • PDF

단위체 형상의 구조적 변화에 따른 오그제틱 회전 강체 구조의 기계적 특성에 대한 유한 요소 해석

  • Jo, Hyeon-Ho;Eom, Yun-Sik
    • Proceeding of EDISON Challenge
    • /
    • /
    • pp.317-323
    • /
    • 2017
  • Due to the unique characteristic of auxetic material, negative poisson's ratio, it has a variety of distinctive properties compared to conventional materials. Numerous researches have been conducted on the auxetic material in order to find out how to make auxetics. In this study, we analyzed triangular and rectangular patterned rotating rigid units using finite element method. Our purpose is to investigate the mechanical properties of the rotating rigid units and to show their auxetic behaviors. We studied the Poisson's ratio and the bulk modulus of the rotating rigid units depending on their unit cell sizes. The Poisson's ratio and the bulk modulus decreased as the number of unit cells increased. Also, when the geometry of the unit cell was changed, the tendency of the Poisson's ratio and the bulk modulus was also different from the previous case. The results of the Poisson's ratio and the bulk modulus referred that they were critically affected by the number of unit cells and the shape of unit cell.

  • PDF

Vibration Characteristics of Boxthorn(Lycium chinense Mill) (구기자 가지의 진동 특성)

  • 서정덕
    • Journal of Biosystems Engineering
    • /
    • v.26 no.2
    • /
    • pp.105-114
    • /
    • 2001
  • Modulus of elasticity, modulus of rigidity, damping ratio, and natural frequency of three varieties of boxthorn (Lycium chinense Mill) (Cheongyang #2, Cheongyang gugija, and Cheongyang native) branches were analyzed. Modulus of elasticity and modulus of elasticity and modulus of rigidity of the boxthorn branch was determined using standard formula after simple beam bending and torsion test, respectively, using an universal testing machine. Damping ratio and natural frequency of branches were determined using a system consisted of an accelerometer, a PC equipped with A/D converter, and a software for data analysis. Relationship between the elastic modulus and branch diameter in overall varieties and branch types showed a good correlation (r -0.81). There was, however, no correlation between torsional rigidity and branch diameter. The internal damping results were highly variable and the overall range of the damping ratio of the boxthorn branch was 0.014-0.087, which indicated that the branch was a lightly damped structure. The natural frequency of the boxthorn branch was in the range of 89-363 rad/s for the overall varieties and branch types. A good correlation (r 0.82) existed between the natural frequency and branch diameter in overall varieties and branch type.

  • PDF

Effects of silt contents on the static and dynamic properties of sand-silt mixtures

  • Hsiao, Darn H.;Phan, Vu T.A.
    • Geomechanics and Engineering
    • /
    • v.7 no.3
    • /
    • pp.297-316
    • /
    • 2014
  • This paper presents a detailed study focused on investigating the effects of silt content on the static and dynamic properties of sand-silt mixtures. Specimens with a low-plastic silt content of 0, 15, 30 and 50% by weight were tested in static triaxial, cyclic triaxial, and resonant columns in addition to consolidation tests to determine such parameters as compression index, internal friction angle, cohesion, cyclic stress ratio, maximum shear modulus, normalized shear modulus and damping ratio. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290 kPa; and constant relative density, $D_r$ = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as silt content increased, the internal friction angle, cyclic stress ratio and maximum shear modulus decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in silt content. In addition, as silt content increased, the maximum shear modulus increased. The cyclic stress ratio first decreased as silt content increased to reach the threshold silt content and increased thereafter with further increases in silt content. Furthermore, the damping ratio was investigated based on different silt contents in three types of specimens.

Effects of the Spinning Conditions on the Tangent Modulus-Strain Culves of Polypropylene Monofilaments (방사 조건이 폴리프로필렌 모노필라멘트의 탄젠트 탄성률-변형률 곡선에 미치는 영향)

  • Im, Jeong-Ryeol;Sim, Hyeon-Ju;Kim, Sang-Yong
    • Textile Science and Engineering
    • /
    • v.31 no.2
    • /
    • pp.129-142
    • /
    • 1994
  • The effects of spinning conditions on the tangent modulus-strain curves have been studied using isotactic polypropylene(iPP) mononlaments. The tangent modulus-strain curve, which is derived from the first derivative of the true stress-strain curve, showed three distinct peaks. The tangent modulus of the first and the second peak in the tangent modulus-strain curve were increased as the draw ratio and the spinning speed were increased. The tensile strain of the first peak had little dependence on the process conditions, however, that of the second peak decreased above the natural draw ratio. The spinning conditions had little effect on the tangent modulus of the third peak, while the tensile strain of the third peak decreased as the draw ratio was increased. The variation of the isotactic helix content in iPP monofilament, determined from the FIIR spectra, was in agreement with that of the tangent modulus-strain curve with the tensile strain.

  • PDF

Presumption of Optimum Concrete Elastic Modulus according to Content of Crushed Stone Powder (폐석분 함유율에 따른 최적의 콘크리트 탄성계수 추정)

  • Park Do-Kyong;Yang Keek-Young
    • Journal of the Korea Institute of Building Construction
    • /
    • v.6 no.1
    • /
    • pp.101-107
    • /
    • 2006
  • While a Study with regard to the measurement on Concrete Strength and the Change of Drying Shrinkage in accordace with Content Ratio of Crushed Stone Powder, it is being analyzed as the result that the strength according to Content Ratio of crushed Stone Powder is somewhat lowering. Accordingly, it is the real situation that the Concrete mixed with Crushed Stone Powder is utilized for non-structural material, not for the structural material. Therefore, this Research willing to furnish the suitable utilizing scheme for construction site as well as practical life by means of conduct the experiment on both Concrete Pressure Strength according to mixture with Crushed Stone Powder and Elastic Modulus, it also presumes the optimum Elastic Modulus Equation after analysis of comparison with common concrete strength. As the result of the experiment, in case of the Content Ratio of Crushed Stone Powder is less than 5%, it did not display a big difference in its both strength and matter-property compare with common concrete. In case of Elastic Modulus, when the Pressure Strength is 50% and 40% respectively, the Elastic Modulus Equation accords very well with the provided condition of Quadratic function, and as the result of the Presumption on Elastic Modulus according to Content of Crushed Stone Powder, in case the Pressure Strength is 50%, Elastic Modulus Equation showed that Error Ratio of Cubic function is at degree of 0.0005%, in case the Pressure Strength is 40%, Elastic Modulus Equation was accorded well with the value of the experimental data likely as the Error Ratio of Cubic function is at the degree around 0.0034%, respectively.

Complex Modulus of Alumina Green Tapes Measured by Micro Fourier Rheometer (Micro Fourier Rheometer에 의한 알루미나 그린 테이프의 Complex Modulus 측정)

  • ;;;;Michael V. Swain;Bruno Pfister
    • Journal of the Korean Ceramic Society
    • /
    • v.36 no.2
    • /
    • pp.122-129
    • /
    • 1999
  • Alumina tapes, having various weight ratios of alumina powder/(alumina+binder+plasticizer), X, and binder / (binder+plsticizer), Y, were prepared and their complex modulus was measured using Micro Fourier Rheometer. As the X and Y ratios increased, Transfer function(TF) magnitude and Transfer function (TF) phase increased and decreased, respectively, indicating that the elastic modulus of the tapes depends on the weight ratios. The temperature dependence of the viscosity of the tapes was visualized by the decreased TF magnitude and the increased TF phase. The Y ratio dependence of the complex modulus related to the glass transition temperature of the tapes and the moduls change by the Y ratio was higher than that by the X ratio within the comperature of the tapes and the modulus changes by the Y ratio was higher than that by the X ratio within the composition range, investigated in the present study. The measurement of the complex modulus of the alumina tapes suggested that the TF phase should be higher that 17$^{\circ}$for the tapes to be utilized for 3-dimensional shaping.

  • PDF

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

  • Oh, Sei-Chang
    • Journal of the Korean Wood Science and Technology
    • /
    • v.41 no.5
    • /
    • pp.425-431
    • /
    • 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.