• Geomechanics and Engineering
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• v.5 no.1
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• pp.57-70
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• 2013

Constant rate of strain (CRS) consolidation tests were conducted for undisturbed Ariake clay samples from three boreholes in Saga Plain of Kyushu Island, Japan. The coefficients of consolidation ($c_{\nu}$) were interpreted from the CRS test results by small- and large-strain theory. Large-strain theory was found to interpret smaller $c_{\nu}$ values and less strain rate effect on $c_{\nu}$ than that by small-strain theory. Comparing the theoretical strain distributions within a soil specimen to those obtained by numerical simulation shows that the small-strain theory can be used only for the dimensionless parameter $c_{\nu}/\dot{\varepsilon}H_0^2{\geq}50$ (where $\dot{\varepsilon}$ is strain rate and $H_0$ is the specimen height), and the large-strain theory can be used for a larger range of strain rates. Applying the criterion to undisturbed Ariake clay with a $c_{\nu}$ value of about $1{\times}10^{-7}\;m^2/s$, it is suggested that the large-strain theory should be adopted for calculating the $c_{\nu}$ value when $\dot{\varepsilon}$ > 0.03%/min.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.146-151
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• 2013

Carbon nanofibers (CNFs) are electrically conductive. When CNFs are used as fillers in resin, this electrical conductivity can be yielded without adversely affecting the mechanical properties of the resin. When an elastomer is adopted as the resin, a conductive elastomer can then be produced. Due to its flexibility and conductive properties, a large strain sensor based on changes in resistivity may be produced, for strain sensing in flexible structures. In this study, a patch-type large strain sensor using resistivity change in a CNF/elastomer composite was proposed. The measurement limits of the sensor were investigated experimentally, and the limit was found to be 40%, which greatly exceeded the limits of conventional metal-foiled strain gages. Also, the proposed CNF/elastomer large strain sensor can be used to measure flexible materials, while conventional strain gages cannot be used to measure such strains.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.33-36
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• 2014

In this paper, a carbon strain gauge for large strain was developed. The carbon strain gauge was fabricated by forming PCB and antenna pattern using Cu/Ni/Au film and carbon resistor pattern using screen printing process on plastic film substrate. It was possible to develop low-cost disposable strain gauge since the carbon paste was cheap and the fabrication process was simple. The wireless communication type carbon strain gauge was fabricated by integrating signal processing circuit, antenna and power all together on the same substrate as a strain gauge. The wireless communication type carbon strain gauge has a merit of being available immediately at the spot without any particular system.

• Smart Structures and Systems
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• v.8 no.5
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• pp.471-486
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• 2011

Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite's strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.

• Macromolecular Research
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• v.8 no.6
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• pp.268-275
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• 2000

After imposing a large pre-strain, anisotropy increases with increasing residual extension ratio. Gums have very low residual extension ratio and exhibit little anisotropy, while black filled SBR and especially sulfur-cured carbon black filled NR have large set and anisotropy. For carbon black filled rubber, samples subjected to tensile loading in perpendicular to the pre-strain direction have the same stress-strain curves shape as the sample without pre-strain (=isotropic samples), but slightly lower modulus. However, compared to isotropic or perpendicular directional samples to pre-strain direction, samples subjected to tensile loading in parallel to the pre-strain direction show low stress at low deformation, but have high stiffness at high deformation. Normalized anisotropy changes with strain. The normalized anisotropy for various deformations is a linear function of residual extension ratio.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1004-1011
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• 2008

In this study, obtained large block sample and piston sample of marine clay in korea were performed unconfined compression and consolidation test. Soil properties of two type samples such as failure strain, between two parameter's ratio($E_{50}$ and $q_u$), and volumetric strain were used to evaluate sample disturbance. The result, large block samples show a low disturbance than piston samples. Therefore, we suggest new sample disturbance evaluated method through the relation of OCR and volumaric strain at shallow of marine clay in Korea and suggest new sample disturbance classified method by subdivided grade for failure strain of unconfined compression test.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.919-925
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• 2018

Stress-strain responses of weak-to-strong carbonate rocks used for tunnel construction were studied. The analysis of applicability of exponential stress-strain models based on Haldane's distribution function is presented. It is revealed that these exponential equations presented in transformed forms allow us to predict stress-strain relationships over the whole pre-failure strain range without mechanical testing of rock samples under compression using a press machine and to avoid measurements of axial failure strains for which relatively large values of compressive stress are required. In this study, only one point measurement (small strain at small stress) using indentation test and uniaxial compressive strength determined by a standard Schmidt hammer are considered as input parameters to predict stress-strain response from zero strain/zero stress up to failure. Observations show good predictive capabilities of transformed stress-stress models for weak-to-strong (${\sigma}_c$ <100 MPa) heterogeneous carbonate rocks exhibiting small (< 0.5 %), intermediate (< 1 %) and large (> 1 %) axial strains.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.206-214
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• 1996

Because of the wide variety of the composite materials, inherent variability in properties, and complex temperature and strain rate dependence, large strain behavior of these materials has not been well characterized. Large strain behavior under uniaxial tension is characterized over a range of temperatures and strain rates, and a modified simple linear viscoelastic model is fit to the observed data. Of particular importance is the strain rate and temperature dependence of these composites, and it is the primary focus of this study. The strain rate and temperature dependence is then used to predict limiting tensile strains, based on Marciniak imperfection theory. Excellent correlation was obtained between model and experiment and the results are summarized in maps of forming limit as a function of strain rate and temperature.

• Geotechnical Engineering
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• v.13 no.2
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• pp.29-38
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• 1997

Strain softening is observed for geomaterials such as rocks when they are sheared. The proper computational modelling for strain softening is very important because this behavior is closely related to failure in geotechnical problems. In this paper, we have investigated the proper FEM techniques for modelling strain softening in order to simulate failure behavior numerically. In showing numerical examples, the effects of element shape, mesh pattern and of imperfection and the difference between small and large deformation theories, of displacement control and pressure control after peak have been discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.64-70
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• 2009

This study is to analyze the impact of automotive body with computer simulation. The total deformation, equivalent strain and strain and principal stress are analyzed respectively in case of front, rear and side impacts. The maximum total deformation of side impact is more than 6 times as large as that of rear impact. The maximum equivalent strain or stress of side impact is more than 4 times as large as that of rear impact. These deformation, strain and stress of front impact are a little more than those of rear impact. The maximum principal stress of side impact is more than 4.5 times as large as that of rear impact. This stress of front impact is a little more than that of rear impact.