• Tunnel and Underground Space
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• v.6 no.1
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• pp.19-29
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• 1996

Back analysis model, capable of calculating the mechanical properties and the in-situ stresses of jointed rock mass, was developed based on the inverse method using a continuum theory. Constitutive equation for the behavior of jointed rock contains two unknown parameters, elastic modulus of intact rock and stiffness of joint, hence algorithm which determines both parameters simultaneously cannot be established. To avoid algebraic difficulties elastic modulus of intact rock was assumed to be known, since the representative value of which would be quite easily determined. Then, the ratio ($\beta$) of joint stiffness to elastic modulus of intact rock was assigned and back analysis for the behavior of jointed rock was carried-out. The value $\beta$ was repeatedly modified until the elastic modulus from back analysis became very comparable to the predetermined value. The joint stiffness could be calculated by multipling the ratio $\beta$ to the final result of elastic modulus. Accuracy and reliability of back analysis procedure was successfully testified using a sample model simulating the underground opening in the jointed rock mass. Applicability of back analysis model for the underground excavation in practice was also verified by analyzing the mechanical properties of jointed rock in which underground oil storage cavern were under construction.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.397-400
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• 2002

The mechanical properties of concrete such as modulus of elasticity, bond strength and shear strength are proportional to square root of compressive strength. And compressive strength of concrete is developed rapidly at early ages. Thus the relationship between compressive strength and its mechanical properties should be verified because the mechanical properties of early age concrete and hardened concrete are different. In this study, to predict the concrete slab deflection at early ages, modulus of elasticity and effective moment of inertia(Ie) are observed and compared with experimental results.

• Advances in biomechanics and applications
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• v.1 no.3
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• pp.187-210
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• 2014

With the goal of increasing the survivorship of the prosthesis and anticipating primary stability problems of new prosthetic implants, finite element evaluation of the micromotion, at an early stage of the development, is mandatory. This allows assessing and optimizing different designs without manufacturing prostheses. This study aimed at investigating, using finite element analysis (FEA), the difference in the prediction of the primary stability of cementless hip prostheses implanted into a $Sawbones^{(R)}$ 4th generation, using the manufacturer's mechanical properties and using mechanical properties close to that of human bone provided by the literature (39 papers). FEA was carried out on the composite $Sawbones^{(R)}$ implanted with a straight taper femoral stem subjected to a loading condition simulating normal walking. Our results show that micromotion increases with a reduction of the bone material properties and decreases with the augmentation of the bone material properties at the stem-bone interface. Indeed, a decrease of the cancellous Young modulus from 155MPa to 50MPa increased the average micromotion from $29{\mu}m$ up to $41{\mu}m$ (+42%), whereas an increase of the cancellous Young modulus from 155MPa to 1000MPa decreased the average micromotion from $29{\mu}m$ to $5{\mu}m$ (-83%). A decrease of cortical Young modulus from 16.7GPa to 9GPa increase the average global micromotion from $29{\mu}m$ to $35{\mu}m$ (+33%), whereas an increase of the cortical Young modulus from 16.7GPa to 21GPa decreased the average global micromotion from $29{\mu}m$ to $27{\mu}m$ (-7%). It can also be seen that the material properties of the cancellous structure had a greater influence on the micromotion than the material properties of the cortical structure. The present study shows that micromotion predicted at the stem-bone interface with material properties of the $Sawbones^{(R)}$ 4th generation is close to that predicted with mechanical properties of human femur.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.105-113
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• 2016

Most studies on mechanical properties of concrete with recycled aggregate was focused on the concrete with compressive strength of less than 40 MPa. Therefore, this paper concerns the compressive strength and mechanical properties of concrete with compressive strength of greater than 40 MPa containing recycled coarse aggregate (RCA). The experimental parameters were compressive strength level and replacement ratio of RCA. Compressive strength level was 45 and 60 MPa, and replacement ratio of RCA was 30, 50, 70 and 100%. The results of the test were discussed: compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. The design code predictions for elastic modulus overestimated the experimental results. However, the design code predictions for modulus of rupture were generally in agreement with the measured values.

• Earthquakes and Structures
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• v.26 no.2
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• pp.97-115
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• 2024

In this paper, a database consisting of the dynamic shear modulus ratio and damping ratio test data of clay obtained from 406 groups of triaxial tests is constructed with the starting area of Xiong'an New Area as the research background. The aim is to study the nonlinear dynamic properties of clay in this area under cyclic loading. The study found that the effective confining pressure and plasticity index have certain influences on the dynamic shear modulus ratio and damping ratio of clay in this area. Through data analysis, it was found that there was a certain correlation between effective confining pressure and plasticity index and dynamic shear modulus ratio and damping ratio, with fitting degree values greater than 0.1263 for both. However, other physical indices such as the void ratio, natural density, water content and specific gravity have only a small effect on the dynamic shear modulus ratio and the damping ratio, with fitting degree values of less than 0.1 for all of them. This indicates that it is important to consider the influence of effective confining pressure and plasticity index when studying the nonlinear dynamic properties of clays in this area. Based on the above, prediction models for the dynamic shear modulus ratio and damping ratio in this area were constructed separately. The results showed that the model that considered the combined effect of effective confining pressure and plasticity index performed best. The predicted dynamic shear modulus ratio and damping ratio closely matched the actual curves, with approximately 88% of the data falling within ±1.3 times the measured dynamic shear modulus ratio and approximately 85.1% of the data falling within ±1.3 times the measured damping ratio. In contrast, the prediction models that considered only a single influence deviated from the actual values, particularly the model that considered only the plasticity index, which predicted the dynamic shear modulus ratio and the damping ratio within a small distribution range close to the average of the test values. When compared with existing prediction models, it was found that the predicted dynamic shear modulus ratio in this paper was slightly higher, which was due to the overall hardness of the clay in this area, leading to a slightly higher determination of the dynamic shear modulus ratio by the prediction model. Finally, for the dynamic shear modulus ratio and damping ratio of the engineering site in the starting area of Xiong'an New Area, we confirm that the prediction formulas established in this paper have high reliability and provide the applicable range of the prediction model.

• Fibers and Polymers
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• v.3 no.4
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• pp.169-173
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• 2002

Fabric touch was evaluated psychophysically in order to determine the relationship between mechanical properties and subjective sensation. For subjective touch sensation, eight aspects such as hardness, smoothness, coarseness, coolness, pliability, crispness, heaviness and thickness were evaluated using free modulus magnitude estimation (FEME) technique. KES-FB was used to measure the mechanical properties of fabrics. Woolen fabric with the highest values of WC and weight was evaluated as the coarsest, heaviest and thickest. While silk crepe do chine with the lowest LT, G, 2HG, thickness and weight was rated as smoother and more pliable than any other fabrics. And flax with the highest values of LT and SMD was evaluated as hard, cool and crisp. Fabric touch and satisfaction were predicted well from the mechanical properties, especially from SMD, by regression analysis. Satisfaction for touch increased as smoothness increased.

• Korea-Australia Rheology Journal
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• v.15 no.1
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• pp.43-50
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• 2003

In this study, two types of biodegradable resins-based clay nanocomposites, in which organic montmorillonite clay was filled, were prepared by the direct melt blending method. In order to characterize the nanocomposite structure, wide-angle X-ray diffraction (WAXD) and TEM observation were performed. Characterization of the nanocomposites shows that intercalated and partially exfoliated structures were generated by the melt blending method. Mechanical and rheological properties of the nanocomposites were measured respectively. For the mechanical properties, there were improvements in tensile strength and Young's modulus of the nanocomposites due to the reinforcement of nanoparticles. The rheological behaviors of the nanocomposites were significantly affected by the degree of the dispersion of the organoclay. The storage modulus of the nanocomposites was measured and the degree of the dispersion of the organoclay was evaluated from the value of the terminal slope of the storage modulus. In addition, the quantity of the shear necessary for making the nanocomposite for melt intercalation method was estimated from the relationship between the value of the terminal slope of the storage modulus and the applied shear.

• Geomechanics and Engineering
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• v.12 no.5
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• pp.863-870
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• 2017

With the increasing interest in using bacterial biofilms in geo-engineering practices, such as soil improvement, sealing leakage in earth structures, and hydraulic barrier installation, understanding of the contribution of bacterial biofilm formation to mechanical and hydraulic behavior of soils is important. While mechanical properties of soft gel-like biofilms need to be identified for appropriate modeling and prediction of behaviors of biofilm-associated soils, elastic properties of biofilms remain poorly understood. Therefore, this study investigated the microscale Young's modulus of biofilms produced by Shewanella oneidensis MR-1 in a liquid phase. The indentation test was performed on a biofilm sample using the atomic force microscopy (AFM) with a spherical indentor, and the force-indentation responses were obtained during approach and retraction traces. Young's modulus of biofilms was estimated to be ~33-38 kPa from these force-indentation curves and Hertzian contact theory. It appears that the AFM indentation result captures the microscale local characteristics of biofilms and its stiffness is relatively large compared to the other methods, including rheometer and hydrodynamic shear tests, which reflect the average macro-scale behaviors. While modeling of mechanical behaviors of biofilm-associated soils requires the properties of each component, the obtained results provide information on the mechanical properties of biofilms that can be considered as cementing, gluing, or filling materials in soils.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.796-801
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• 2007

The optical performance of the mirror for satellite camera is highly dependent on the adhesive properties between the mirror and its support. In order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Shear moduli of the adhesives are determined by using single lap adhesively bonded joint. For the shear tests, several points have been selected from $-20^{\circ}C$ to $50^{\circ}C$ which is operating temperature range of the adhesive. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics of the adhesives are discussed regarding their temperature sensitivity. The analysis results of RMS wavefront error w.r.t shear modulus are presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.489-495
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• 2009

A novel technique to measuret of viscoelastic properties of polymers is proposed to investigate complex Poisson's ratio as a function of frequency. The forced vibration responses for the samples under the normal and the shear deformation are to be measured with varying load masses. The measured data were used to obtain the viscoelastic properties of the material based on an accurate 2D numerical deformation model of the sample. The 2D model enabled us to exclude data correction by the empirical form factor used in 1D model. Comprehensive measurements of viscoelastic properties of two slightly varied silicone RTV rubber ($Silastic^{(R)}$ S2) compositions were performed. Standard composition (90% PDMS polymer + 10% catalyst) and modified composition (92.5% polymer + 7.5% catalyst) were tested in temperature range from $30^{\circ}C$ to $70^{\circ}C$. Shear modulus, modulus of elasticity, loss factor, and both the real and the imaginary parts of the Poisson's ratio were determined for frequencies from 50 to 400Hz in the linear deformation regime (at relative deformations $10^{-4}{\sim}10^{-3}$).