• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.422-427
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• 2002

This paper focuses on the formulation and validation of an automatic strategy for the selection of the locations and directions of strain gauges to capture at best the modal response of a blade in a series of modes. These locations and directions are selected to render the strain measurements as robust as possible with respect to random mispositioning of the gauges and gauge failures. The approach relies on the evaluation of the signal-to-noise ratios of the gauge measurements from finite element strain data and includes the effects of gauge size. A genetic algorithm is used to find the strain gauge locations-directions that lead to the largest possible value of the smallest modal strain signal-to-noise ratio, in the absence of gauge failure, or of its expected value when gauge failure is possible. A fan blade is used to exemplify the applicability of the proposed methodology and to demonstrate the effects of the essential parameters of the problem, i.e. the mispositioning level, the probability of gauge failure, and the number of gauges.

• Geotechnical Engineering
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• v.10 no.1
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• pp.27-46
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• 1994

It has been demonstrated in plane strain compression tests performed on dense Toyoura sand and Silver Leighton Buzzard sand, that the newly developed instrumentation for small strain measurements was capable of measuring the altering stiffness of sands for a wide range of shear strain from ($10^{-6}$to $10^{-2}$. It was found that for the range of shear strain($\gamma$) from $10^{-5}$ to those at peak, the Rowe's stressiilatancy relation seemed to be a good approximation for Toyoura sand and Silver Leighton Buzzard sand. However, the value of K and Poisson's ratio(at elastic range:${\nu}_{psc}^e$) varied with sand types. It was also found that the value of ${\nu}_{psc}^e$ and stress -dilatancy relation was irrespective of overconsolidation ratio(OCR).

• The Korean Journal of Ceramics
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• v.7 no.1
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• pp.30-35
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• 2001

The contribution of the non-$180^{\circ}C$ domains to the electric-field-induced strains (EFI-strains) of PZT ceramics was evaluated by an XRD method and by an interferometric method. The XRD intensity ratio of 200 and 002 diffraction peaks of tetragonal PZT was measured under strong electric fields. The amount of the $90^{\circ}$ domain reorientation was evaluated and the strain due to the domain reorientation was calculated. It was confirmed that the EFI-strain of PZT ceramics was equal to the sum of the strain calculated from the d$_33$ constant determined by the resonance-antiresonance method and the strain due to the $90^{\circ}$ domain reorientation. The amount of the $90^{\circ}$domain reorientation has a linear relation with the c/a ratio in the "soft" PZT ceramics. A Mech-Zehnder interferometer was constructed to measure the EFI-strains vs. electric-field curves of PZT ceramics as a function of frequency. The EFI-strain vs. electric-field curve showed a hysteresis due to the effect of the non-$180^{\circ}$ domain reorientation when the applied voltage was high and its frequency was low. The apparent piezoelectric constant increased from the d$_33$ value determined by the resonance-antiresonance method with decreasing frequency. This deviation was attributed to the non-$180^{\circ}$ domain contribution.tribution.

• Computers and Concrete
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• v.26 no.1
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• pp.31-52
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• 2020

This paper investigates the size dependent effect on the vibration analysis of a porous nanocomposite viscoelastic plate reinforced by functionally graded-single walled carbon nanotubes (FG-SWCNTs) by considering nonlocal strain gradient theory. Therefore, using energy method and Hamilton's principle, the equations of motion are derived. In this article, the effects of nonlocal parameter, aspect ratio, strain gradient parameter, volume fraction of carbon nanotubes (CNTs), damping coefficient, porosity coefficient, and temperature change on the natural frequency are perused. The innovation of this paper is to compare the effectiveness of each mentioned parameters individually on the free vibrations of this plate and to represent the appropriate value for each parameter to achieve an ideal nanocomposite plate that minimizes vibration. The results are verified with those referenced in the paper. The results illustrate that the effect of damping coefficient on the increase of natural frequency is significantly higher than the other parameters effect, and the effects of the strain gradient parameter and nonlocal parameter on the natural frequency increase are less than damping coefficient effect, respectively. Furthermore, the results indicate that the natural frequency decreases with a rise in the nonlocal parameter, aspect ratio and temperature change. Also, the natural frequency increases with a rise in the strain gradient parameter and CNTs volume fraction. This study can be used for optimizing the industrial and medical designs, such as automotive industry, aerospace engineering and water purification system, by considering ideal properties for the nanocomposite plate.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.263-271
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• 2010

The purposes of this study is to verify the fracture characteristic of steel which is manufactured in Korea, subjected to cyclic loading. This investigation deals with the low cycle fatigue behavior of longitudinal reinforcement in reinforced concrete bridge substructure (piles and columns of piers). Eighty-one specimens of longitudinal reinforcement were tested under axial strain controlled reversed cyclic tests with strain amplitudes. The selected test variables are ratio of tension strain to compression strain, yield stress of longitudinal reinforcement, ratio of diameter of longitudinal steel to clear length of longitudinal steel, size of longitudinal steel and strain amplitudes. Low cycle fatigue behavior and low-cycle fatigue life are investigated and discussed in this paper.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.12-17
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• 2010

Numerical simulations were performed for the prediction of the flame structure during the interaction between hydrogen and hydrocarbon flames. A counterflow flow geometry was introduced to establish the interacting two flames. Methane was used as a representative hydrocarbon fuel in this study. A well-known numerical code for the counterflow flame, OPPDIF, was used for the simulations. The detailed chemistry was adopted to predict the flame structure reasonably. The interaction of two one-dimensional premixed flames established in counterflow burner was investigated with the global strain rate and velocity ratio. It was found that the maximum temperature located near the methane flame surface while the heat release rate of methane was lower than hydrogen flame. The flame thickness become narrow with increasing the velocity ratio while the global strain rate was fixed. The local strain rate and heat release rate at the methane flame surface were correlated with the global strain rate, while those at the hydrogen flame were not correlated with the global strain rate. However, the maximum temperature of the interacting flames was correlated with the global strain rate.

• Physical Therapy Korea
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• v.18 no.2
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• pp.76-83
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• 2011

The aim of this study was to determine the immediate effects of single treatment of strain-counter strain (SCS) on pressure pain threshold (PPT) and muscle activity during scapular plane abduction with 3% body weight load. Fifteen asymptomatic male adults with upper trapezius latent trigger point (LTrP) (PPT<2.9 $kg/cm^2$) participated in this study. Pressure algometer was used to measure PPT and surface electromyography was used to record upper, middle arid lower trapezius, serratus anterior, infraspinatus and middle deltoid muscle activity and relative ratio during scapular plane abduction between pre- and post-intervention. There was a significant increase in upper trapezius PPT after a 90-second SCS (p<.05). The activity of the upper trapezius and middle deltoid was significantly decreased (p=.014, p=.001), coupled with a decreased muscle activity ratio between the upper and lower trapezius (p<.05). These results indicate that the SCS may effectively deactivate upper trapezius activity, thereby alleviating muscle balance and reducing pain sensitivity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.369-372
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• 2005

A study on the microstructure, the texture and the formability of the samples after ECAPed and subsequent heat-treated AA 1050 aluminum alloy sheet have been carried out. The specimens after the ECAP showed a very fine grain size, a decrease of <100> // ND. The <110>// ND textures appears in the specimens after the ECAP and subsequent heat-treatment at $400^{\circ}C$ for 1 hour. One of the most important properties in sheet metals is formability. The r-value or plastic strain ratio has was as a parameter that expressed the formability of sheet metals. The change of the plastic Strain ratios after the ECAP and subsequent heat-treatment conditions were investigated and it was found that they were two times higher than those of the initial Al sheets. This could be attributed to the formation above texture components through the ECAP and subsequent heat-treatment of AA 1050 Aluminum alloy sheet.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.1
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• pp.51-59
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which that can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the unconfined compressive strength properties and freezing and thawing resistance of CSG materials with unit cement content. The three types of CSG-80, CSG-100 and CSG-120 with cement content were designed to evaluate the optimum water content, dry density, strength, stress-strain, micro structure and durability factor. As the results, the optimum water content ratio with cement content showed almost similar tendency, and the unconfined compressive strength and dry density increased as cement content increases. The strength ratio of 7 days for 28 days were in the range of 55~61 % and the strain ratio in stress-strain curve were in the range of 0.8~1.6 % nearby maximum strength in 28 days. It is expected that this study will contribute to increasing application of CSG method as well as to increasing the utilizing of CSG materials as a environmentally friendly CSG method.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.553-558
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• 2005

A study on the microstructure, the texture and the formability of the samples after ECAPed and subsequent heat-treated AA 1050 aluminum alloy sheet have been carried out. The specimens after the ECAP showed a very fine grain size, a decrease of <100> // ND, and an increase of <111> // ND textures. The $\{111\}<112>,\;\{123\}<634>,\;\{110\}<001>,\;\{112\}<111>,\;\{110\}<111>,\;and\;\{013\}<231>$ texture components were increased in the specimens after the ECAP and subsequent heat-treatment at $400^{\circ}C$ for 1 hour. One of the most important properties in sheet metals is formability. The r-value or plastic strain ratio has was as a parameter that expressed the formability of sheet metals. The change of the plastic strain ratios after the ECAP and subsequent heat-treatment conditions were investigated and it was found that they were two times higher than those of the initial Al sheets. This could be attributed to the formation above texture components through the ECAP and subsequent heat-treatment of AA 1050 Aluminum alloy sheet.