• Title/Summary/Keyword: 변형률 진폭

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Low Cycle Fatigue Behavior of Longitudinal Reinforcement (축방향철근의 저주파 피로 거동)

  • Lee, Jae-Hoon;Ko, Seong-Hyun
    • 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.

Fatigue Life Prediction and Ratcheting behavior of the Elbrodur-NIB under Fatigue loading with mean stress (평균응력을 포함한 피로하중 하에서 Elbrodur-NIB의 피로수명예측 및 Ratcheting 거동)

  • Lim, Chang-Bum
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.7
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    • pp.612-617
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    • 2011
  • An experimental study was carried out for the Elbrodur-NIB(copper alloy) at room temperature under stress-controlled uniaxial fatigue loading with and without mean stress. As a result, the effects of stress amplitude, mean stress and stress rate on ratcheting behavior were investigated. The ratcheting strain increased with increasing stress amplitude for a given mean stress, and with mean stress for a given stress amplitude. But, the ratcheting strain decreased as the stress rate increased. The three mean stress models were investigated and the mean stress models of Smith-Watson-Topper and Walker yielded good correlation of fatigue lives in the life range of $10^2-10^5$cycles.

Fatigue Life Analysis and Prediction of 316L Stainless Steel Under Low Cycle Fatigue Loading (저사이클 피로하중을 받는 316L 스테인리스강의 피로수명 분석 및 예측)

  • Oh, Hyeong;Myung, NohJun;Choi, Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.12
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    • pp.1027-1035
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    • 2016
  • In this study, a strain-controlled fatigue test of widely-used 316L stainless steel with excellent corrosion resistance and mechanical properties was conducted, in order to assess its fatigue life. Low cycle fatigue behaviors were analyzed at room temperature, as a function of the strain amplitude and strain ratio. The material was hardened during the initial few cycles, and then was softened during the long post period, until failure occurred. The fatigue life decreased with increasing strain amplitude. Masing behavior in the hysteresis loop was shown under the low strain amplitude, whereas the high strain amplitude caused non-Masing behavior and reduced the mean stress. Low cycle fatigue life prediction based on the cyclic plastic energy dissipation theory, considering Masing and non-Masing effects, showed a good correlation with the experimental results.

Influence of strain rate on the acoustic emission signal characteristics in corrosive environment (부식환경하에서 음향방출신호 특성에 미치는 변형률속도의 영향)

  • Yu, Hyo-Seon;Jeong, Se-Hui
    • Korean Journal of Materials Research
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    • v.5 no.1
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    • pp.12-21
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    • 1995
  • The study was performed to study the effects of strain rate on acoustics emission( AE) during bulging test in corrosive environmentsynthetic sea water. The strain rates used were in the range $4 \times 10^{-6}S^{-1}$ to $1 \times 10^{-4} \times S^{-1}$ and the parameters used to evaluate AE signal characteristics were AE hit and amplitude. It can be observed that the cumulative AE hit and average amplitude during fracture process increase highly at decreasing strain rates while the equivalent fracture strain and the crack length of circumferencial direction become decrease. The peak point of AE signal characteristic parameters approach to the first half of test. When the average amplitude per unit equivalent fracture strain was above 20dB, it was definitly observed stress corrosion cracking phenomena. Additional, we knew that the AE test had the possibility to evaluate SCC susceptibility with various strain rates.

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Fatigue Life Prediction of Automotive Rubber Component Subjected to a Variable Amplitude Loading (가변진폭하중에서의 자동차 고무 부품의 피로 수명 예측)

  • Kim, Wan-Soo;Kim, Wan-Doo;Hong, Sung-In
    • Elastomers and Composites
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    • v.42 no.4
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    • pp.209-216
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    • 2007
  • Fatigue life prediction methodology of the rubber component made of vulcanized natural rubber under variable amplitude loadings was studied. The displacement-controlled fatigue tests were conducted at different levels and the maximum Green-Lagrange strain was selected as damage parameters. A fatigue life curve of the rubber represented by the maximum Green-Lagrange strain was determined from the nonlinear finite element analysis. The transmission load history of SAE as variable amplitude loading was used to perform the fatigue life prediction. And then a signal processing of variable loading by racetrack and simplified rainflow cycle counting methods were performed. The modified miner's rule as cumulative damage summation was used. Finally, when the gate value is 30%, the predicted fatigue life of the rubber component agreed well with the experimental fatigue lives with a factor of two.

Analysis of Compressive Deformation Behaviors of Aluminum Alloy Using a Split Hopkinson Pressure Bar Test with an Acoustic Emission Technique (SHPB 시험과 음향방출법을 이용한 알루미늄 합금의 압축 변형거동 분석)

  • Kim, Jong-Tak;Woo, Sung-Choong;Sakong, Jae;Kim, Jin-Young;Kim, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.7
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    • pp.891-897
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    • 2013
  • In this study, the compressive deformation behaviors of aluminum alloy under high strain rates were investigated by means of a SHPB test. An acoustic emission (AE) technique was also employed to monitor the signals detected from the deformation during the entire impact by using an AE sensor connected to the specimen with a waveguide in real time. AE signals were analyzed in terms of AE amplitude, AE energy and peak frequency. The impacted specimen surface and side area were observed after the test to identify the particular features in the AE signal corresponding to the specific types of damage mechanisms. As the strain increased, the AE amplitude and AE energy increased whereas the AE peak frequency decreased. It was elucidated that each AE signal was closely associated with the specific damage mechanism in the material.

An Experimental Study on the Dynamic Characteristics of Rubber Isolator (실험에 의한 방진고무의 동특성에 관한 연구)

  • Kim, W.D.;Kim, K.S.;Kwon, J.D.;Woo, C.S.
    • Elastomers and Composites
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    • v.37 no.3
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    • pp.183-191
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    • 2002
  • Rubber materials with excellent damping property are widely applied for vibration isolators. The dynamic characteristics of the rubber materials for vibration isolators were investigated. Dynamic tests for rubber materials with five different hardness were performed. In dynamic tests for test specimen, non-resonance method was used to obtain the dynamic storage modulus and loss factor. Moreover, the effect of dynamic vibration frequency, strain amplitude and temperature were investigated. As results, the storage modulus and loss factor generally increase when the hardness and frequency increase, and the glass transition temperature is $-50^{\circ}C$ by a large change in modulus and loss factor.

A Study on the Cyclic Hardening Property and the Low Cycle Fatigue Behavior of Marine Materials (박용재료(舶用材料)의 반복경화(反復硬化) 및 저(低)싸이클 피로특성(疲勞特性)에 관한 연구)

  • S.M. Cho;K. Horikawa
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.1
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    • pp.108-116
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    • 1991
  • In the non-linear behavior of many materials, there is difference between the monotonic behavior by static load and the cyclic behavior by cyclic load. In particular, the short fatigue cracks to propagate in elasto-plastic stress concentrations(notches), are governed significantly by the cyclic behavior of materials. Accordingly, it is needed to investigate and compare the monotonic and cyclic behavior of materials. In the pressent study, the stress-strain relations of materials by monotonic and cyclic load tests were examined for 2 kinds of steels(SS41, HT80) and 5 kinds of Al-alloys(A5083-O, A6N01-T5, A7N01-T4, A7016-T6, A7178-T6). And the constants for mechanical properties of the materials were determined by experimental results, Moreover, when a notch was subjected to cyclic load, the effect of cyclic hardening property of materials on the variation of stress-strain amplitude in the notch tip was discussed by the application of Neuber's rule and experiments for a center notched plate.

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Low cycle fatigue behaviour of TMCP steel in as-received and welded states (TMCP 고장력강재와 그 용접부의 저사이클피로특성에 관한 연구)

  • 김영식;한명수
    • Journal of Welding and Joining
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    • v.8 no.4
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    • pp.46-57
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    • 1990
  • TMCP steel manufactured by controlled rolling followed by accelerated cooling process is known to have extra-ordinary mechanical properties such as tensile strength and toughness. However, there is much uncertainty about the fatigue fracture characteristics, especially, in the welded state of this steel. In case of this steel, the softening zone by welding is generated in heat affected zone in contrast with the case of conventional normalized high strength steel. This softening zone is considered to play significant roles in low cycle fatigue fracture of the welded part of this steel. In this paper, the low cycle fatigue behaviors of TMCP steel were inspected in as-received and welded state using the smooth specimen. The fatigue life-time was seperately investigated on the basis of failure of the specimen and crack initiation which is detected by differential strain method. Moreover, the low cycle fatigue characteristics of TMCP steel were quantitatively compared with those of the conventional normalized steel of same strength level.

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Prediction of Thermal Fatigue Life of Engine Exhaust Manifold under Thermo-mechanical Cyclic Loading (열적-기계적 반복하중을 받고 있는 엔진 배기매니폴드의 열피로 수명예측)

  • Choi, Bok-Lok;Chang, Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.7
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    • pp.911-917
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    • 2010
  • In this study, we performed structural and fatigue analyses of the engine exhaust manifold that was subjected to thermo-mechanical cyclic loading. The methodologies used in this study are based on an approach in which the techniques for modeling the exhaust system, the temperature-dependent properties of the material, and thermal cyclic loading are taken into consideration and a reliable strategy is adopted for failure prediction. An application example shows that at an elevated temperature, considerable compressive plastic deformation is observed and that at a low temperature, tensile stresses remain in those parts of the test exhaust manifold where failure is observed. In order to predict fatigue life, mechanical damage is determined on the basis of the stress.strain hysteresis loops by using the classical Coffin.Manson equation and by adopting a method in which the dissipated plastic energy is taken into consideration.