• Title, Summary, Keyword: modulus

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Effect of Weld Elastic Modulus on Simulation of Stress Concentration and Fatigue Life for Boiler Vessel (ADINA & WINLIFE 활용한 압력용기 용접부 피로파괴 해석)

  • Choe, Byung Hak;Lee, Bum Gyu;Shim, Jong Heon;Park, Chan Sung;Kim, Jin Pyo;Park, Nam Gyu
    • Journal of Welding and Joining
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    • v.34 no.5
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    • pp.47-53
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    • 2016
  • The aim of this study is to consider effect of weld elastic modulus on simulations of stress concentration and fatigue life for pressure vessel. The investigations include analysis with ADINA and WINLIFE softwares for whole body model about using condition of the boiler vessel. Values of weld elastic modulus were divided by 5 steps in butt weld area of the boiler vessel body. The stress concentration of the butt weld more was increased in case of higher elastic modulus of weld area because of higher difference of material properties between matrix and weld. It was concluded that the fatigue lives were decreased along increasing stress concentration due to high elastic modulus of weld. The matrix microstructure was estimated as pearlitic structure of ${\alpha}$ ferrite and pearlite. And the microstructures of welds along 5 steps of elastic modulus were estimated as bainitic fine pearlite and martensite as increasing elastic modulus.

Prediction models of the shear modulus of normal or frozen soil-rock mixtures

  • Zhou, Zhong;Yang, Hao;Xing, Kai;Gao, Wenyuan
    • Geomechanics and Engineering
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    • v.15 no.2
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    • pp.783-791
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    • 2018
  • In consideration of the mesoscopic structure of soil-rock mixtures in which the rock aggregates are wrapped by soil at normal temperatures, a two-layer embedded model of single-inclusion composite material was built to calculate the shear modulus of soil-rock mixtures. At a freezing temperature, an interface ice interlayer was placed between the soil and rock interface in the mesoscopic structure of the soil-rock mixtures. Considering that, a three-layer embedded model of double-inclusion composite materials and a multi-step multiphase micromechanics model were then built to calculate the shear modulus of the frozen soil-rock mixtures. Given the effect of pore structure of soil-rock mixtures at normal temperatures, its shear modulus was also calculated by using of the three-layer embedded model. Experimental comparison showed that compared with the two-layer embedded model, the effect predicted by the three-layer embedded model of the soil-rock mixtures was better. The shear modulus of the soil-rock mixtures gradually increased with the increase in rock regardless of temperature, and the increment rate of the shear modulus increased rapidly particularly when the rock content ranged from 50% to 70%. The shear modulus of the frozen soil-rock mixtures was nearly 3.7 times higher than that of the soil-rock mixtures at a normal temperature.

Stability of a slender beam-column with locally varying Young's modulus

  • Kutis, Vladimir;Murin, Justin
    • Structural Engineering and Mechanics
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    • v.23 no.1
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    • pp.15-27
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    • 2006
  • A locally varying temperature field or a mixture of two or more different materials can cause local variation of elasticity properties of a beam. In this paper, a new Euler-Bernoulli beam element with varying Young's modulus along its longitudinal axis is presented. The influence of axial forces according to the linearized 2nd order beam theory is considered, as well. The stiffness matrix of this element contains the transfer constants which depend on Young's modulus variation and on axial forces. Occurrence of the polynomial variation of Young's modulus has been assumed. Such approach can be also used for smooth local variation of Young's modulus. The critical loads of the straight slender columns were studied using the new beam element. The influence of position of the local Young's modulus variation and its type (such as linear, quadratic, etc.) on the critical load value and rate of convergence was investigated. The obtained results based on the new beam element were compared with ANSYS solutions, where the number of elements gradually increased. Our results show significant influence of the locally varying Young's modulus on the critical load value and the convergence rate.

A NOR-type High-Speed Dual-Modulus Prescaler (NOR 형태의 고속 dual-modulus 프리스케일러)

  • Seong, Gi-Hyeok;Kim, Lee-Seop
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.37 no.2
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    • pp.69-76
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    • 2000
  • A dual-modulus prescaler divides the input signal by one of the moduli according to the control signal. In this paper, a new fast dual-modulus prescaler is proposed. The proposed prescaler has a ratioed-NOR structure different from a conventional ratioed-NAND structure. The proposed one can operate at a higher speed by using parallely connected NMOSs instead of using series-connected ones. HSPICE simulation results using HYUNDAI 0.65(m 2-poly 2-metal CMOS process parameters show that the maximum operating frequency of the proposed dual-modulus prescaler is 2.8㎓ with power consumption of 40.7㎽ at 5V supply voltage at $25^{\circ}C$. The proposed dual-modulus prescaler can be utilized for the frequency-synthesis in cellular radio front-ends.

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A Performance Improvement of CR-MMA Adaptive Equalization Algorithm using Adaptive Modulus and Adaptive Stepsize (Adaptive Modulus와 Adaptive Stepsize를 이용한 CR-MMA 적응 등화 알고리즘의 성능 개선)

  • Lim, Seung-Gag
    • The Journal of The Institute of Internet, Broadcasting and Communication
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    • v.19 no.5
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    • pp.107-113
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    • 2019
  • This paper proposes the Hybrid-CRMMA adaptive equalization algorithm that is possible to improves the performance of CR-MMA based on adaptive modulus and adaptive stepsize. The 16-QAM nonconstant modulus signal is reduced to 4-QAM constant modulus signal, and the error signal were obtained based on the fixed statistic modulus of transmitted signal. It is possible to improving the currently MMA adaptive equalization performance. The proposed Hybrid-CRMMA composed of adaptive modulus which is propotional to the power of equalizer output and adaptive stepsize which is function of the nonlinearties of error signal, and its improved equalization performance were confirmed by computer simulation. For this purpose, the output signal constellation, the residual isi and maximum distortion and MSE that is for the convergence characteristics, the SER that is meaning the robustness of external noise of algorithm were used. As a result of computer simulation, it was confirmed that the proposed Hybrid-CRMMA has more superior performance in every index compared to currently CR-MMA.

An Experimental Study of Mechanical Properties of High-strength Concrete (고강도 콘크리트의 역학적 특성에 대한 실험 연구)

  • Yang, In-Hwan;Hwang, Chul-Sung
    • 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.

A Study on Establishing the Subbase Compaction Control Method based on the In-situ Elastic modulus (현장탄성계수에 근거한 보조기층 다짐관리방안 연구)

  • Choi, Jun-Seong;Kim, Jong-Min;Han, Jin-Seok;Kim, Bu-Il
    • International Journal of Highway Engineering
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    • v.13 no.1
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    • pp.33-40
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    • 2011
  • The resilient modulus which is presented mechanical properties of compacted subbase material is the design parameter on the Mechanistic - Empirical pavement design guide. The compaction control method on the Mechanistic - Empirical pavement design guide will be the way to confirm whether the in-situ elastic modulus measured after the compaction meets the resilient modulus which is applied the design. The resilient modulus in this study is calculated by the neural network suggested by Korea Pavement Research Program, and degree of compaction as the existing compaction control test and plate bearing capacity test(PBT) was performed to confirm whether the in-situ elastic modulus is measured. The Light Falling Weight Deflectometer(LFWD) is additionally tested for correlation analysis between each in-situ elastic modulus and resilient modulus, and is proposed correlation equation and test interval which can reduced overall testing cost. Also, the subbase compaction control procedure based on the in-situ elastic modulus is proposed using the in-situ PBT and LFWD test result.

Evaluation of the Resilient and Permanent Behaviors of Cohesive Soils (점성토의 회복 및 영구변형 특성 평가)

  • SaGong, Myung;Kim, Dae-Hyeon;Choi, Chan-Yong
    • Journal of the Korean Society for Railway
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    • v.11 no.1
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    • pp.61-68
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    • 2008
  • Resilient modulus has been used for characterizing the stress-strain behavior of subgrade soils subjected to traffic loadings. With the recent release of the M-E Design Guide, highway agencies are further encouraged to implement the resilient modulus test to improve subgrade design. The subgrade design for the trackbed, however, is primarily relying on the static test results such as $K_{30}$ and deformation modulus, Ev. Therefore applicability of the resilient modulus for the design of trackbed needs to be evaluated. In this study, physical property tests, unconfined compressive tests and resilient modulus tests were conducted to assess the resilient and permanent strain behavior of 14 cohesive subgrade soils. A predictive model for estimating the resilient modulus is proposed based on the results of unconfined compressive tests and tangent elastic modulus, unconfined compressive strength, failure strain, secant modulus at peak, and yield strain. The predicted resilient moduli using the predictive models compared satisfactorily with measured ones. Although the permanent strain occurs during the resilient modulus test, the permanent behavior of subgrade soils is currently not taken into consideration.

Effect of Temperature and Aging on the Relationship Between Dynamic and Static Elastic Modulus of Concrete (온도와 재령이 콘크리트의 동탄성계수와 정 탄성계수의 상관관계에 미치는 영향)

  • 한상훈;김진근;박우선;김동현
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.610-618
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    • 2001
  • This paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model of the relationships we proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperatures of 10, 23, and 50$\^{C}$ Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus according to cement type, temperature and aging. The proposcd relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type md temperature.

Evaluation of Correlation between Subgrade Reaction Modulus and Strain Modulus Using Plate Loading Test (평판재하시험을 이용한 지반반력계수와 변형률계수의 상관관계 평가)

  • Kim, Dae-Sang;Park, Seong-Yong;Kim, Soo-Il
    • Journal of the Korean Geotechnical Society
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    • v.24 no.6
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    • pp.57-67
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    • 2008
  • Two test methods, nonrepetitive plate loading test (NPLT) and repetitive plate loading test (RPLT) are being used to control the quality of compaction through the evaluation of the stiffness of subgrade soils in the Korea railway industry. Subgrade reaction modulus ($k_{30}$) from the NPLT and strain modulus ($E_v$) from the RPLT are the index values to check them. The methods have similar aspects, but they differ in the modulus evaluation method, the numbers of loading stage, termination procedures, etc. This paper analyses the differences of the two test methods and evaluates the relationship between subgrade reaction modulus and strain modulus. In order to develop the relationship, total 22 tests were performed including the NPLT and the RPLT at the 6 original grounds, and 5 upper or lower subgrades in Kyungbu High Speed Railway II stage construction sites. According to the soil conditions, the relationship between subgrade reaction modulus and strain modulus was proposed with corrections by considering strain states, mean confining pressures, and Poisson's ratio.