심층혼합 시료의 탄성계수에 관한 실험적 연구

박춘식,박환기 한국지반공학회 2018 한국지반공학회논문집 Vol.34 No.10

In this study, aimed at determining the elastic modulus of deep mixed samples, 320 test specimens were developed by mixing 8%, 10%, 12%, and 14% of stabilizer mixture in the granular conditions of clay, sand and gravel. Uniaxial compression tests were carried out using these specimens, and the uniaxial compression strength and strain were analyzed to determine the secant elastic modulus and tangent elastic modulus. Laboratory test results showed that the uniaxial compression strength of all deep mixed samples increased with increasing curing time and stabilizer mixing ratio, and that the secant elastic modulus and the tangen elastic modulus also increased. The increase of the elastic modulus according to the curing period turned out greater in the tangent elastic modulus than in the secant elastic modulus. In order to measure elastic modulus with changes in stabilizer mixing ratio, the correlation coefficient between the elastic modulus for stabilizer mixing ratio of 8% and that of 10%, 12% and 14% was calculated respectively by the specimen condition. The elastic modulus tended to increase as the grain size in a deep mixed specimen increased. The distribution of grain size that had the greatest effect appeared when the composition ratio of sand was high. On the other hand, the increase in the elastic modulus was larger in the sand specimens than in the clay and gravel specimens. Based on these results, it is suggested that a pertinent soil parameter of the deep mixed ground in the field may be obtained by the particle size distribution and the mixing ratio of stabilizer of the deep mixed soil.

An experimental method to determine glass elastic modulus based on the fundamental frequency of the elastic support-free end beam

Kun Jiang,Danguang Pan 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.2

Silicate glass is usually a brittle and plate-like material, and it is difficult to measure the elastic modulus by the traditional method. This paper develops a test method for the glass elastic modulus based on the fundamental frequency of the cantilever beam with an elastic support and a free end. The method installs the beam-type specimen on a semi-rigid support to form an elastic support-free end beam. The analytic solution of the stiffness coefficients of the elastic support is developed by the fundamental frequency of the two specimens with known elastic modulus. Then, the glass elastic modulus is measured by the fundamental frequency of the specimens. The method significantly improves the measurement accuracy and is suitable for the elastic modulus with the beam-type specimen whether the glass is homogeneous or not. Several tests on the elastic modulus measurement are conducted to demonstrate the reliability and validity of the test method.

평판재하시험, 흙강성측정기 및 동적콘관입시험기를 이용한 노상토의 탄성계수 비교

김규선 한국지반공학회 2015 한국지반공학회논문집 Vol.31 No.3

This paper describes the correlation and relationship between elastic moduli measured by three stiffness measurementmethods with different mechanical characteristics to evaluate the compaction characteristics of subgrade soils. The SoilStiffness Gauge (SSG) with very small strain (≈ 0.001%) ranges, static Plate Loading Test (PLT) with mid-level strain(≈ 0.01~0.1%) ranges, and Dynamic Cone Penetrometer (DCP) using penetration resistance were implemented tomeasure the elastic modulus. To use the elastic modulus measured by different measurement methods with a wide rangeof strain in practice, it is required to identify the correlation and relationship of measured values in advance. Thecomparison results of the measured elastic moduli (ESSG, EPLT, EDCP) using the three measurement methods for domesticand overseas subgrade soils under various conditions indicate that the evaluated elastic modulus relies on the types ofsoils and the level of stress condition. The correlation analysis of the measured elastic moduli except the data of cementtreated soils indicates that the static elastic modulus (EPLT) is evaluated as about 60 to 80% of the dynamic elasticmodulus (ESSG). Unusual soils such as cement treated soils are required to be corrected by the stress correction duringthe correlation analysis with typical soils, because these types of soils are sensitive to the stress condition when measuringthe static elastic modulus (EPLT) of soils. In addition, when considering the use of DCP data for the evaluation of theelastic modulus (EDCP), the measured data of the elastic modulus less than 200 MPa show more reliable correlation.

암종별 P파 속도, 정탄성계수 및 동탄성계수의 상관관계 분석 연구

문성우,김형신,윤현석,서용석 대한지질공학회 2019 지질공학 Vol.29 No.3

The relationship between the P wave velocity, static elastic modulus, and dynamic elastic modulus of different rock types was investigated to identify the distributive characteristics of the dynamic elastic modulus. Laboratory and in situ test results from 1,646 rock specimens, which are obtained for design and construction of structure, were analyzed, and grouped into three key rock types: gneiss, granite, and sandstone. These relationships were verified by comparing them with the results from previous studies. The gneiss samples exhibit a linear P wave velocity-static elastic modulus relationship, whereas the granite and sandstone samples exhibit exponential relationships. Their coefficient of determination (R2) values are all in the 0.491-0.642 range, and are similar to those obtained in previous studies. The relationship between the static and dynamic elastic modulus exhibits a linear relationship for all rock types, yielding a coefficient of determination in the 0.543-0.676 range. The relationship between the P wave velocity and static elastic modulus follows an exponential regression for all rock types, with a high coefficient of determination that is in the 0.875-0.940 range. 국내 40개 구조물 설계 시 수행된 1,646개의 실내 및 현장시험 결과를 활용하여 국내 암종에 따른 동탄성계수의 분포특성을 파악하기 위하여 암종별 P파 속도, 정탄성계수, 동탄성계수 간의 상관식을 도출하고 기존 연구사례와 비교하여 검증하였다. P파 속도와 정탄성계수의 관계를 살펴보면 편마암에서는 선형, 화강암과 사암에서는 지수 함수의 관계를 보인다. 결정계수(R2)는 0.491~0.642로 높지 않지만, 결정계수를 0.836~0.990로 제시하고 있는 기존의 연구사례와 유사한 분포범위를 보인다. 정탄성계수와 동탄성계수의 상관식은 모든 암종에서 선형적인 관계를 보이며, 결정계수는 0.543~0.676이다. P파 속도와동탄성계수의 상관식은 지수함수의 관계를 보이며, 결정계수는 0.875~0.940으로 높게 나타난다.

서울⋅경기지역 화강암의 탄성파속도와 탄성계수에 의한 암석의 일축압축강도와의 상관성 연구

손인환,김병국,이벽규,장승진,이수곤 한국재난정보학회 2019 한국재난정보학회 논문집 Vol.15 No.2

연구목적: 본 연구에서는 서울 ․ 경기지역의 화강암을 대상으로 시추조사 시 채취된 암석 시료에서 측정된 물리적 특성 중 탄성파속도와 탄성계수로부터 암석의 일축압축강도와의 상관성을 분석하여 암석의 일축압축강도를 추정하는 것을 목 적으로 한다. 연구방법: 119개의 화강암 시추 코아 시료를 대상으로 탄성파 속도와 탄성계수 그리고 일축압축강도와의 상관관계를 도출하 기 위하여 실내 암석 실험을 실시하였다. 연구결과: 화강암에 대하여 탄성파속도와 일축압축강도 그리고 탄성계수와의 상호 관계를 단순회 귀와 다중회귀로 분석한 결과는 전반적으로 관계식에 나타난 것처럼 신뢰도가 낮음을 확인하였다. 이는 화강암의 구성 입자가 균질하지 못 하여 탄성파속도와 탄성계수를 이용한 압축강도 추정에 대한 활용성이 낮은 원인으로 사료된다. 결론: 본 연구에서 암석의 탄성파속도와 탄 성계수로부터 일축압축강도를 추정하기 위한 상관관계를 분석하기 위하여 단순회귀분석과 다중회귀분석 방법을 이용하였다. 단순회귀분 석은 결정계수(R2)가 0.61~0.67 이었으며 , 다중회귀분석은 0.71로 나타났다. 따라서 다중회귀분석을 이용하여 암석의 일축압축강도를 추 정할 때 다소 신뢰성이 높아질 수 있다. 또한, 향후 탄성파 속도와 탄성계수를 이용한 암석의 일축압축강도를 추정할 때 다양한 통계분석 기 법(회귀분석, 인공신경망, 빅데이터 분석 등)을 활용하면 보다 신뢰성이 높은 결과를 얻을 수 있을 것으로 본다. Purpose: The purpose of this study is to attain the correlation analysis and thereby to deduce the uniaxial compressive strength of rock specimens through the elastic wave velocity and the elastic modulus among the physical characteristics measured from the rock specimens collected during drilling investigations in Seoul and Gyeonggi region. Method: Experiments were conducted in the laboratory with 119 granite specimens in order to derive the correlation between the compressive strength of the rocks and elastic wave velocity and elastic modulus. Results: In the case of granite, the results of the analysis of the interaction between the compressive strength of a rock and the elastic wave velocity and elastic modulus were found to be less reliable in the relation equation as a whole. And it is believed that the estimation of the compressive strength by the elastic wave velocity and elastic modulus is less used because of the composition of non-homogeneous particles of granite. Conclusion: In this study, the analysis of correlation between the compressive strength of a rock and the elastic wave velocity and elastic modulus was performed with simple regression analysis and multiple regression analysis. The coefficient determination (R2) of simple regression analysis was shown between 0.61 and 0.67. Multiple regression analysis was 0.71. Thus, using multiple regression analysis when estimating compressive strength can increase the reliability of the correlation. Also, in the future, a variety of statistical analysis techniques such as recovery analysis, and artificial neural network analysis, and big data analysis can lead to more reliable results when estimating the compressive sterength of a rock based on the elastic wave velocity and elastic modulus.

Non-contact Measurement of Elastic Modulus by using Laser Ultrasound

김종범,장경영 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.5

Non-contact measurement of elastic modulus is necessary for the in-line assessment of material in harsh environments such as high temperature. In this paper, a fully non-contact method to measure elastic modulus is proposed based on the laser ultrasonic technique (LUT) that uses a short-pulsed laser to generate ultrasound and the other laser coupled to an interferometer using a photorefractive crystal to detect the ultrasonic wave displacement. Basically, this method measures velocities of shear wave and longitudinal wave to obtain the elastic modulus. The uniqueness is that the velocity of shear wave is measured in the thermo-elastic regime first and then the velocity of longitudinal wave is measured in the ablation regime. This is because the strong mode of generated ultrasound is the shear wave in the thermo-elastic regime while the longitudinal wave in the ablation regime. Regime change can be achieved simply by switching the laser power, with no change in the measurement setup. In order to demonstrate the usefulness of the proposed method, the elastic modulus of aluminum casting alloy has been measured and the results were compared with a conventional contact method and a destructive tensile test. They showed good agreement with each other, which verified the usefulness of the proposed noncontact elastic modulus measurement method.

A Study on the Effect of Young’s Modulus Modeling on the Energy Conservation in Elastic–Plastic Material Computation

Eun-Ho Lee 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.10

Young’s modulus has a strong effect on the mechanical behavior of elastic–plastic materials, such as elastic stiff ness, elastic recovery, and potential energy. Since springback prediction is important in the sheet metal forming process, many of Young’s modulus studies have been focused on capturing the amount of springback. This work investigated the effect of Young’s modulus modeling focusing on energy conservation point. For this study, three representative concepts of Young’s modulus modeling (fixed modulus, chord modulus, and nonlinear modulus models) were employed. The three modulus models were coupled with the Chaboche kinematic hardening, and implemented into the ABAQUS User-defined material subroutine. The models were used to simulate cyclic loading, monotonic loading conditions, and 2D-draw bending process including the springback prediction. The models showed good agreement with the measured data in the numerical studies. However, in the chord modulus model, a negative potential energy phenomenon was detected during the elastic recovery path, which is unrealistic, while the fixed and nonlinear modulus models keep the energy conservation law. This work discusses the reason for the negative potential energy computation based on the energy dissipation, and presents a numerical method to compensate the negative potential energy.

Application of an Image-Based Model of the Elastic Modulus of Porous Thermal Barrier Coatings

Moteb Alotaibi 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

The elastic modulus of plasma-sprayed thermal barrier coatings (TBCs), which have been utilized for gas turbine enginecomponents at elevated temperatures, has been investigated using a proposed model. The main purpose of this paper is toexplore the alterations in porous TBC microstructure that lead to alterations in its mechanical properties, including elasticmodulus. This paper investigates the effect of different types of defects, i.e., nonflat porosity, microcracks and interlamellarporosity, on the elastic modulus of porous TBC materials. The first part of this paper quantitively studies the microstructuralcharacterization of plasma-sprayed TBCs by means of an image analysis approach. The second part of this paper predictsthe elastic modulus of plasma-sprayed TBCs based on microstructural changes, i.e., defects. The volumetric fraction of differenttypes of defects and their shapes and orientations are also taken into account. It is found that both microcracks andinterlamellar porosity exhibit a crucial optimization on the elastic modulus of porous TBCs, while nonflat porosity showsa lesser effect on the elastic modulus. The predicted data of the proposed model show relatively good agreement with FEAmodel results and experimentally measured results. These simulation results could help to further the understanding of theimpact of porous TBC microstructural alterations on elastic modulus.

Preliminary Study on In-Situ Modulus Measurement Using Knocking Ball test; A Case Study on Setul Limestone

Mazlina Razali,Mohd Ashraf Mohamad Ismail,Andrew Lee Kwan Yee,Raja Asyraf Azizan Raja Adnan,Kenichi Kawano,Kensuke Date,Yasuhiro Yokota,Sharan Kumar Nagendran,Zuraini Zainal 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

The in-situ elastic modulus (E) is a vital parameter for describing rock strength in many engineering projects on rock slopes. The elastic modulus and uniaxial compressive strength (UCS) are typically investigated via laboratory tests using core samples. However, the direct determination of E is costly and time-consuming in preparing many intact samples from highly weathered Setul limestone. The knocking ball testing method is a non-destructive test that can quickly and easily obtain the elastic modulus of rock in-situ by striking the surface of a rock mass with a spherical steel hammer. This study presents the relationship between the elastic modulus of knocking ball (Ekb) and the uniaxial compressive strength of the Schmidt hammer (UCS-Schmidt). Results show that the regression coefficient correlation, R2 is 0.851, indicating a positive trend with a few outliers. The measured Ekb were also verified with mineral propertiesand correlated to differential weathering grades to confirm the accuracy of measurement results. The finding compared to previous similar studies tested on several types of rock show a statistically significant. This research highlights the effectiveness of the knocking ball method for determining the modulus of rock slope at different weathering grades. A high elastic modulus corresponds to a high uniaxial compressive strength, verified by the laboratory test. This study shows that the knocking ball can be useful for predicting in-situ elastic modulus.

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

Sei Chang Oh 한국목재공학회 2013 목재공학 Vol.41 No.5

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.