• Title/Summary/Keyword: Strain Effects

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A Study on the Improvement of Accuracy and Precision in the Vision-Based Surface-Strain Measurement (비전을 이용한 곡면변형률 측정의 정확도 및 정밀도 향상에 관한 연구)

  • 김두수;김형종
    • Transactions of Materials Processing
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    • v.8 no.3
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    • pp.294-305
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    • 1999
  • A vision-based surface-strain measurement system has been still improved since the authors devel-oped the first version of it. New algorithms for the subpixel measurement and surface smoothing are introduced to improve the accuracy and precision in the present study. The effects of these algorithms are investigated by error analysis. And the equations required to calculate 3D surface-strain of a shell element are derived from the shape function of a linear solid finite-element. The influences of external factors on the measurement error are also examined, and several trials are made to obtain possible optimal condition which may minimize the error.

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Analysis of static and dynamic characteristics of strain gradient shell structures made of porous nano-crystalline materials

  • Hamad, Luay Badr;Khalaf, Basima Salman;Faleh, Nadhim M.
    • Advances in materials Research
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    • v.8 no.3
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    • pp.179-196
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    • 2019
  • This paper researches static and dynamic bending behaviors of a crystalline nano-size shell having pores and grains in the framework of strain gradient elasticity. Thus, the nanoshell is made of a multi-phase porous material for which all material properties on dependent on the size of grains. Also, in order to take into account small size effects much accurately, the surface energies related to grains and pores have been considered. In order to take into account all aforementioned factors, a micro-mechanical procedure has been applied for describing material properties of the nanoshell. A numerical trend is implemented to solve the governing equations and derive static and dynamic deflections. It will be proved that the static and dynamic deflections of the crystalline nanoshell rely on pore size, grain size, pore percentage, load location and strain gradient coefficient.

Increasing the performance of energy harvesting in vibration mode shapes

  • Jabbari, Majid;Ghayour, Mostafa;Mirdamadi, Hamid Reza
    • Advances in Computational Design
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    • v.1 no.2
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    • pp.155-173
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    • 2016
  • This paper presents a method of design for the energy harvesting of a piezoelectric cantilever beam. Vibration modes have strain nodes where the strain distribution changes in the direction of the beam length. Covering the strain nodes of the vibration modes with continuous electrodes effects a cancellation of the voltages outputs. The use of segmented electrodes avoids cancellations of the voltage for multi-mode vibration. The resistive load affects the voltage and generated power. The optimum resistive load is considered for segmented and continuous electrodes, and then the power output is verified. One of the effective parameters on energy harvesting performance is the existence of concentrated mass. This topic is studied in this paper. Resonance and off-resonance cases are considered for the harvester. In this paper, both theoretical and experimental methods are used for satisfactory results.

Effects of Process Variables on Static and Metadynamic Sofetning of SCM 440 (SCM 440 강재의 정적 및 준동적 연화에 미치는 공정변수의 영향)

  • 한형기;김성일;정태성;유연철
    • Transactions of Materials Processing
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    • v.9 no.1
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    • pp.80-87
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    • 2000
  • The static softening behavior of SCM 440 could be characterized by the hot torsion test in the temperature ranges of 90$0^{\circ}C$~110$0^{\circ}C$and strain rate ranges of 0.05/sec~5/sec. Interrupted deformation was performed with 2 pass deformation in the pass strain ranges of 0.25$\varepsilon$p~3$\varepsilon$p and interrupted time ranges of 0.5~100sec. The dependences of process variables, pass strain ($\varepsilon$i), stain rate ($\varepsilon$), temperature (T) and interpass time (ti), on static recrystallization (SRX) and metadynamic recrystallization (MDRX)were individually predicted from the modified Avrami's equations, The dependence of pass strain on MDRX was neglectable. Comparison of the softening kinetics between MDRX and SRX showed that the rate of MDRX was more rapid than that of SRX for the same deformation variables. Controlled multipass deformations were performed using static and metadynamic recrystallization of SCM 440.

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Cracking behavior of RC shear walls subject to cyclic loadings

  • Kwak, Hyo-Gyoung;Kim, Do-Yeon
    • Computers and Concrete
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    • v.1 no.1
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    • pp.77-98
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    • 2004
  • This paper presents a numerical model for simulating the nonlinear response of reinforced concrete (RC) shear walls subject to cyclic loadings. The material behavior of cracked concrete is described by an orthotropic constitutive relation with tension-stiffening and compression softening effects defining equivalent uniaxial stress-strain relation in the axes of orthotropy. Especially in making analytical predictions for inelastic behaviors of RC walls under reversed cyclic loading, some influencing factors inducing the material nonlinearities have been considered. A simple hysteretic stress-strain relation of concrete, which crosses the tension-compression region, is defined. Modification of the hysteretic stress-strain relation of steel is also introduced to reflect a pinching effect depending on the shear span ratio and to represent an average stress distribution in a cracked RC element, respectively. To assess the applicability of the constitutive model for RC element, analytical results are compared with idealized shear panel and shear wall test results under monotonic and cyclic shear loadings.

Effect of Aqueous Solutions of Pesticides on Survival of Entomopathogenic Nematodes (농약이 곤충병원성 선충의 생존에 미치는 영향)

  • 이동운;추호렬;최은정
    • Asian Journal of Turfgrass Science
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    • v.13 no.4
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    • pp.213-222
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    • 1999
  • The toxic effects of four pesticides on the entomopathogenic nematodes. Heterorhabditis bacteriophora NC strain, Steinernema glaseri NC and Dongrae strain were tested by checking the mortality of infective juveniles(Ijs) in aqueous solution of pesticide. Mortality of Ijs was influenced by pesticide and concentration and soaking time. The herbicide alachlor and insecticide fenitrothion were toxic to Ijc of three entomopathogenic nematodes. But, the fungicides mepronil and tolclofos-methyl were nontoxic to Ijs. Tolclofos-methyl showed significantly very week toxicity at 28 days after soaking for S. glaseri NC strain. H. bacteriophora NC strain was more highly sensitive to high temperature condition then were the other nematodes.

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Prediction of Soil Deformation with Nonlinear-Anisotropic Model (비선형 이방성 모델을 이용한 흙의 변형 거동 예측)

  • 윤충구;정영훈;정충기
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.03a
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    • pp.41-48
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    • 2002
  • The fact that nonlinearity and anisotropy of soil should be considered for the proper estimation of soil deformation has been recongnized for a long time. In this study, a new stiffness model which can reflect both nonlinearity and anisotropy is proposed. Nonlinearity is simulated by Ramberg-Osgood model and anisotropy is modeled with the cross-anisotropic elasticity. Analysis results with the developed model compared with those from analyses using linear isotropic model, linear anisotropic model, and nonlinear isotropic model. In the triaxial compression like condition, the effects of nonlinearity on the vertical strain are significant, but soil anisotropy does not affect the vertical strain. In 1-dimensional deformation condition, however, both nonlinearity and anisotropy of soil influence the final magnitude of the vertical strain. Also the increase of poisson's ratio magnifies the effect of anisotropy on the vertical strain in this condition.

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Flexural Performance of RC Beams Strengthened with Diffrent Amount of CFRP Composite (탄소섬유복합체로 보강된 RC부재의 보강재 강성에 따른 휨 보강성능)

  • You, Young-Chan;Choi, Ki-Sun;Kim, Keung-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.129-132
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    • 2006
  • It is generally reported that most of RC beams strengthened with simply bonded FRP composite is failed by FRP debonding. Also, the flexural performance of RC member strengthened with FRP composite can be calculated using the effective strain of FRP. The effective strain as a result of the debonding failure depends on many variables, such as FRP stiffness including the thickness($t_f$) and modulus of elasticity($E_f$), the amount of FRP but the FRP stiffness is reportedly the most influential. The purpose of this paper, therefore, is to examine effects of FRP stiffness on the flexural strengthening of RC beams. 4 different stiffness of CFRP composite including CFRP sheet and laminae were selected. From the tests, it was found that the flexural performance of RC beams strengthened with CFRP composite can be calculated based on the effective strain of the CFRP composite and the effective strain is inversely proportional to the CFRP stiffness.

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Wireless health monitoring of stay cable using piezoelectric strain response and smart skin technique

  • Kim, Jeong-Tae;Nguyen, Khac-Duy;Huynh, Thanh-Canh
    • Smart Structures and Systems
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    • v.12 no.3_4
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    • pp.381-397
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    • 2013
  • In this paper, wireless health monitoring of stay cables using piezoelectric strain sensors and a smart skin technique is presented. For the cables, tension forces are estimated to examine their health status from vibration features with consideration of temperature effects. The following approaches are implemented to achieve the objective. Firstly, the tension force estimation utilizing the piezoelectric sensor-embedded smart skin is presented. A temperature correlation model to recalculate the tension force at a temperature of interest is designed by correlating the change in cable's dynamic features and temperature variation. Secondly, the wireless health monitoring system for stay cables is described. A piezoelectric strain sensor node and a tension force monitoring software which is embedded in the sensor are designed. Finally, the feasibility of the proposed monitoring technique is evaluated on stay cables of the Hwamyung Grand Bridge in Busan, Korea.

Wave propagation analysis of carbon nanotubes reinforced composite plates

  • Mohammad Hosseini;Parisa Chahargonbadizade;Mohammadreza Mofidi
    • Structural Engineering and Mechanics
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    • v.88 no.4
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    • pp.335-354
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    • 2023
  • In this study, analysis of wave propagation characteristics for functionally graded carbon nanotube-reinforced composite (FG-CNTRC) nanoplates is performed using first-order shear deformation theory (FSDT) and nonlocal strain gradient theory. Uniform distribution (UD) and three types of functionally graded distributions of carbon nanotubes (CNTs) are assumed. The effective mechanical properties of the FG-CNTRC nanoplate are assumed to vary continuously in the thickness direction and are approximated based on the rule of mixture. Also, the governing equations of motion are derived via the extended Hamilton's principle. In numerical examples, the effects of nonlocal parameter, wavenumber, angle of wave propagation, volume fractions, and carbon nanotube distributions on the wave propagation characteristics of the FG-CNTRC nanoplate are studied. As represented in the results, it is clear that the internal length-scale parameter has a remarkable effect on the wave propagation characteristics resulting in significant changes in phase velocity and natural frequency. Furthermore, it is observed that the strain gradient theory yields a higher phase velocity and frequency compared to those obtained by the nonlocal strain gradient theory and classic theory.