• 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.

• Design & Manufacturing
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• v.18 no.2
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• pp.57-63
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• 2024

In this study, the recyclability of commonly used PP (polypropylene) and ABS (acrylonitrile butadiene styrene) was evaluated by molding test specimens from mixture of virgin and shredded material, followed by measuring their strength properties, Experiments were conducted o two type of PP (transparent and non-transparent) and two types of ABS (white and yellow). Test specimens for each resin were prepared with shredded material ratios ranging from 10% to 50% in 10% increments. Changes in tensile strength, elastic modulus, and elastic limit were analyzed based on the mixing ratio of the shredded material. The experimental results demonstrated that the strength properties of all the resins remained consistent within a certain range, even with increasing proportions of shredded material. For transparent PP, the tensile strength ranged from 30.87± MPa, the elastic modulus from 1.23±0.04 GPa, and the elastic limit from 19.17±0.44%. Non-transparent PP exhibited a tensile strength ranging from 27.71±0.58 MPa, an elastic modulus from 1.03±0.06 GPa, and an elastic limit from 17.35±0.41%. For ABS, white ABS had a tensile strength of 39.42±0.28 MPa, an elastic modulus of 1.94±0.01 GPa, and an elastic limit of 36.76±0.25%. Yellow ABS showed a tensile strength of 39.25±0.78 MPa, an elastic modulus of 1.94±0.01 GPa, and an elastic limit of 37.14±0.23%, with values remaining consistent within this range. Based on these results, it was confirmed that the mechanical properties of the resins used in this study do not change significantly when mixed with recycled shredded material, indicating excellent mechanical recyclability.

• International Journal of Safety
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• v.11 no.1
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• pp.19-21
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• 2012

In this thesis, fracture test was performed in order to investigate the fracture strength of SFRC(steel fiber reinforced concrete) structures. The relationship between the compressive force and strain value of SFRC specimens were observed under the compressive strength test. From the fracture test results, the relationship between percentage of fiber by volume, compressive strength, elastic modulus, and tensile strength of SFRC beams were studied, and the measured elastic modulus of SFRC were compared with the calculated elastic modulus by ACI committee 544.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.163-170
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• 2005

In this paper, the rock bolts, soil nails with filling grout and the micro-piling with injecting grout by pressure were applied for the stabilization of the cut slopes consisting of sedimentary rocks, igneous rocks and metamorphic rocks respectively. The field measurements and 3-D FEM analyses to find out mobilized tensile stresses of the grouted-reinforcing members installed in the drilled holes were executed on each site. With assuming the increments of the cohesive strength in the improved ground, the back analysis using direct calibration approach of changing the elastic modulus of the ground was used to find out the improved elastic modulus which yields the same tensile stresses from field measurements. The results of back analysis show that the elastic modulus of the improved ground were 4 to 6 times as large as the elastic modulus of original ground. Consequently, the design for slope reinforcement to be more rational, it is proposed that not only the improved cohesive strength is to be used in the incremental ranges on well-known previous proposed data, but also the increased elastic modulus which is about 5 times as large as the original elastic modulus is to be considered in design.

• Geomechanics and Engineering
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• v.19 no.4
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• pp.353-360
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• 2019

The elastic modulus is an important parameter to characterize the property of rock. It is common knowledge that the strengths of rocks are significantly different under tension and compression. However, little attention has been paid to the bi-modularity of rock. To validate whether the rock elastic moduli in tension and compression are the same, Brazilian disc, direct tension and compression tests were conducted. A horizontal laser displacement meter and a pair of vertical and transverse strain gauges were applied. Four types of materials were tested, including three types of rock materials and one type of steel material. A comprehensive comparison of the elastic moduli based on different experimental results was presented, and a tension-compression anisotropy model was proposed to explain the experimental results. The results from this study indicate that the rock elastic modulus is different under tension and compression. The ratio of the rock elastic moduli under compression and tension ranges from 2 to 4. The rock tensile moduli from the strain data and displacement data are approximate. The elastic moduli from the Brazilian disc test are consistent with those from the uniaxial tension and compression tests. The Brazilian disc test is a convenient method for estimating the tensile and compressive moduli of rock materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.206-215
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• 2017

An experimental program was carried out to investigate the mechanical properties of high-strength concrete. High-strength concrete with compressive strengths of 80 to 120 MPa was tested. Test results are presented regarding effect of water-binder ratio on compressive strength and compressive strength gain. In addition, the effect of curing methods on compressive strength, elastic modulus, splitting tensile strength, and modulus of rupture is investigated. Test results of elastic modulus, splitting tensile strength, and modulus of rupture are compared with predictions from the current design recommendations. Predictions of elastic modulus by using KCI recommendation has good agreement with test results. However, predictions of modulus of rupture by using KCI recommendation underestimate the test results. ACI 363R recommendations predict well test results of splitting tensile strength and modulus of rupture. ACI 363R recommendations for predicting splitting tensile strength and modulus of rupture can be used for high-strength concrete with compressive strengths up to 120 MPa.

• Transactions of Materials Processing
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• v.13 no.5
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• pp.409-414
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• 2004

TRIP steel has got attention in automobile industry because of its high strength and high formability. However, the information on deformation behavior of TRIP steel, including bending and springback, is not enough until now. In this research, the V-die bending experiment and analysis have been done to obtain the information of springback of TRIP steel. And a new numerical method, where elastic modulus is varied with the change of the strain, was suggested. Tensile test for TRIP steel was done to get tensile properties as well as strain dependency of elastic modulus of the material. Strain-dependency of elastic modulus was used the numerical analysis of V-die bending and unbending process to predict springback amount. The results were compared with experiment, showing reasonable agreement. Through the analysis of V-die bending as well as draw bending of TRIP steel, the proposed scheme with variable elastic modulus was proven to well predict the deformation behavior of TRIP steel during bending and springback.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.349-358
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• 2021

The Brazilian test has been widely used to determine the indirect tensile strength of rock, concrete and other brittle materials. The basic assumption for the calculation formula of Brazilian tensile strength is that the elastic moduli of rock are the same both in tension and compression. However, the fact is that the elastic moduli in tension and compression of most rocks are different. Thus, the formula of Brazilian tensile strength under the assumption of isotropy is unreasonable. In the present study, we conducted Brazilian tests on flat disk-shaped rock specimens and attached strain gauges at the center of the disc to measure the strains of rock. A tension-compression bi-modular model is proposed to interpret the data of the Brazilian test. The relations between the principal strains, principal stresses and the ratio of the compressive modulus to tensile modulus at the disc center are established. Thus, the tensile and compressive moduli as well as the correct tensile strength can be estimated simultaneously by the new formulas. It is found that the tensile and compressive moduli obtained using these formulas were in well agreement with the values obtained from the direct tension and compression tests. The formulas deduced from the Brazilian test based on the assumption of isotropy overestimated the tensile strength and tensile modulus and underestimated the compressive modulus. This work provides a new methodology to estimate tensile strength and moduli of rock simultaneously considering tension-compression bi-modularity.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.343-348
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• 2018

This paper reports mechanical behavior of recycled fine aggregate concretes after high temperatures. It is found that compressive strength of recycled fine aggregate concretes decline significantly as the temperature rises. The elastic modulus of recycled fine aggregate concretes decreases with the increase in temperature, and the decrease is much quicker than the decrease in compressive strength. The split tensile strength of recycled fine aggregate concrete decrease as the temperature rises. Through the regression analysis, the relationship of the mechanical behavior with temperature are proposed, including the compressive behavior, elastic modulus and split tensile strength, which are fitting the test data.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.89-96
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• 2004

Micro-tensile testing system, consisting of a micro tensile loading system and micro-ESPI(Electronic Speckle Pattern Interferometry) system, has been developed for measurement of micro-tensile properties of thin micro-materials. Micro-tensile loading system had a load cell with the maximum capacity of 50N and micro actuator with resolution of 4.5nm in stroke. The system was used to apply a tensile load to the micro-sized specimen. During tensile loading, the micro-ESPI system acquired interferornetric speckle patterns in the deformed specimen and measured the in-plane tensile strain. The ESPI system consisted of a CCD-camera with a lens and the window-based program developed for this experiment. Using this system, stress-strain curves for 4 kinds of electrolytic copper foil 18$\square$m thick were obtained. From these curves, tensile properties, including the elastic modulus. yielding strength and tensile strength, were determined and also values of the plastic exponent and coefficient based on Ramberg-Osgood relationship were evaluated.