• Title/Summary/Keyword: 반복변형

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Influence of mean strain on the behavior of early stage stress amplitude in low cycle fatigue of quenched and tempered SM45C steel (퀜칭-템퍼링한 SM45C강의 저주기 피로에 있어서 초기단계 응력진폭 거동에 미치는 평균변형의 영향)

  • Choe, Jae-Yeong;Lee, Nae-Seong;Kim, Chang-Ju;Kim, Gyeong-Hyeon
    • 한국기계연구소 소보
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    • s.18
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    • pp.169-175
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    • 1988
  • The influence of mean strain on the behavior of early stage stress amplitude was investigated quantitatively in low cycle fatigue. It was obtained that the exponent of cyclic strain(n') and the coefficient of cyclic strain(C') decreased with increasing cycle numbers in compressive mean strain level. But it was the opposite in 0% mean strain and tensile mean strain level. And the cyclic yield strength ($\delta_(yc)$) was constant irrespective of mean strain or cyclic strain

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A Modified Parallel Iwan Model for Cyclic Hardening Behavior of Sand(I) : Model Development (수정 IWAN 모델을 이용한 사질토의 반복경화거동에 대한 연구(I): 모델 개발)

  • 이진선;김동수
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.5
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    • pp.47-56
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    • 2003
  • In this paper, the cyclic soil behavior model. which can accommodate the cyclic hardening, was developed by modifying the original parallel IWAN model. In order to consider the irrecoverable plastic strain of soil. the cyclic threshold strain, above which the backbone curve deviates from the original curve, was defined and the accumulated strain was determined by summation of the strains above the cyclic threshold in the stress-strain curve with applying Masing rule on unloading and reloading curves. The isotropic hardening elements are attached to the original parallel IWAN model and the slip stresses in the isotropic hardening elements are shown to increase according to the hardening functions. The hardening functions have a single parameter to account for the cyclic hardening and are defined by the symmetric limit cyclic loading test in forms of accumulated shear strain. The model development procedures are included in this paper and the verifications of developed model are discussed in the companion paper.

Repeated Load Triaxial Tests on Unbound Geomaterials in Pavement Foundations (반복재하시험에 의한 도로기초의 변형특성 평가)

  • Park, Seong-Wan;Hwang, Kyu-Young
    • International Journal of Highway Engineering
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    • v.10 no.1
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    • pp.49-62
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    • 2008
  • This paper presents the results of a study that was performed to evaluate the characteristics of deformation under repeated loadings in unbound geomaterials of pavements. Two important parameters, resilient and permanent deformation were estimated using the repeated load triaxial test. In addition, the effects of different stress state and environmental conditions with various materials were evaluated. Due to the locking mechanism and resiliency of unbound geomaterials, a consistent increase in permanent deformation on unbound geomaterials was observed and the asymptotic condition is slightly reached. In conclusion, the results show that selected models and parameters are satisfactory to predict permanent deformations after a certain number of loadings.

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Deformation Characteristics of Clayey Soil Subject to Repeated Compressive Loading (반복재하(反復載荷)에 의한 점성토(粘性土)의 변형특성(變形特性))

  • Chun, Byung Sik;Park, Heung Gyu
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.9 no.1
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    • pp.89-95
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    • 1989
  • In this study, it is attempted to examine (1) the residual deformation and elastic deformation induced from the repeated loads (up to the maximum of 100,000 times) on fully compacted soil specimen, the relation between stress and strain by performing the unconfined compressive test, after repeated loads and (2) the effect of water content, dry density, number of cycle, repeated loads, etc. on the effect of the stress-strain relation. The rate of deformation caused by repeated loads greatly depends on to the condition whether the water content is above or below the plastic limit. It is possible to estimate the initial tangent modulus of soil by means of modulus of elastic deformation obtained by putting repeated loads on the clay soil.

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Observation of Dislocation Structures in IN 617 During Cyclic and Stress Reduced Deformation at 1073K (1073K에서 IN 617의 반복주기변형과 회복변형에 따른 전위구조의 관찰)

  • An, Seong-Uk
    • Korean Journal of Materials Research
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    • v.5 no.3
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    • pp.261-267
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    • 1995
  • IN 617의 시편으로 1073K의 온도와 107과 180 MPA의 응력에서 $\varepsilon$=0.18까지 정압크\ulcorner을 한 직후 107 MPa로 응력을 낮추고 (응력강하시험), 또 다른 시편에는 180 ↔ 0.2 MPa의 응력으로 각각 17초씩 반복주기변형을 수행하여 정압크\ulcorner 변형시의 크\ulcorner곡선과 비교를 하엿다. 그 결과 IN 617 의 반복주기변형에서는 변형속도둔화(CCD)가 발생함을 알 수 있었고, 응력강하와 반복변형시험은 모두 거의 같은 모양의 회복 크\ulcorner곡선을 나타내었다. 이러한 회복 크\ulcorner은 아결정립크기와 자유전위밀도로서 그 회복기구를 설명할수 있었다.

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A Study of Low Cycle Fatigue Properties in CR60,SM50Q Steel and the Weldments (CR60강, SM58Q강과 그 용접부의 저사이클 피로특성)

  • 김창주;염태동;유인석;위창욱
    • Journal of Welding and Joining
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    • v.12 no.1
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    • pp.73-79
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    • 1994
  • Low cycle fatigue test was performed by companion specimens method to compare the properties of cyclic strain for the weldments of controlled rolling steel CR60 and welding structural steel SM58Q. And the result does not showed any difference of low cycle fatigue life between weldments. Especially, the values of coefficient of cyclic plastic strain $C_{p}$ and exponent of cyclic plastic strain $K_{p}$ of heat affected zones of CR60 steel and SM58Q steel were same. And $C_{p}$ and $K_{p}$ of CR60 steel were equal to the values of weld it means a good combination between the base metal, the heat affected zone and the weld of CR60 steel.eel.eel.

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Cyclic Strength and Deformation Characteristics of Marine Cohesive Soil (해성 점성토의 동적 강도 및 변형 특성)

  • Kim, Yong-Seong;Seo, Min-Woo;Oh, Sang-Eun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.3
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    • pp.159-168
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    • 2012
  • 본 연구에서는 해성 점성토에 대하여 반복 삼축시험을 실시하고 응력-변형률 관계 및 유효응력경로 특성 분석을 통해 동적 변형 및 강도 특성을 조사하였다. 시험에 사용된 시료는 일본 도쿠시마현의 코마츠시마 항 인근에서 채취된 점성토이며, 반복 삼축시험으로 동적 비배수 삼축시험, 동적 비배수 삼축시험 후 동적 삼축변형시험, 다단계 동적 비배수 삼축시험, 동적 삼축 변형시험 등 4종류의 시험을 수행하고, 시험 주파수로서 0.1 및 0.01 Hz을 적용하였다. 본 연구 결과 0.01 Hz로 수행된 동적 삼축시험 결과는 0.1 Hz로 수행된 삼축시험 결과보다 평균유효응력의 감소량이 크며, 반복 하중은 해성 점성토의 구조적 약화를 초래하고 초기 거동시 발생하는 간극수압과 밀접하게 관련이 있는 것으로 나타났다. 또한 미소변형률 영역에서 등가 탄성계수는 시험 횟수가 증가함에 따라 점차 감소하며, 감쇠비는 점차 증가하는 것으로 보아 변형계수는 반복 하중으로 인한 전단변형률의 축척에 따른 변형률 의존 거동에 관련하는 것으로 판단된다.

Predicting Long-Term Deformation of Road Foundations under Repeated Traffic Loadings (반복 교통하중에 의한 도로지반의 장기변형 예측)

  • Park, Seong-Wan;An, Dong Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.5D
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    • pp.505-512
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    • 2010
  • Generally, the repeated traffic loading condition should be considered to predict the long-term deformation on road foundations or foundation systems. However, it is not easy to estimate long-term deformation on multi-layered system like roads and railways. For more quantitative analysis, mechanistic-empirical approach requires proper analytical tool, material's model, and material properties of foundation geomaterials under both traffic and environmental loadings. In this study, therefore, laboratory data from the long-term repeated load triaxial tests were used to predict accumulated deformation on pavement foundations and the results were analyzed based on the nonlinear models and stress state considered. All these results are presented and verified on laboratory based scale using the finite element analysis with the deformation characteristics of foundation geomaterials at various stress states.

Prediction of Plastic Settlement of Roadbed Materials through Cyclic Loading Test (반복하중에 따른 철도 노반재료의 소성침하예측)

  • Choi, Chan-Yong;Shin, Eun-Chul;Kang, Hyoun-Hoi
    • Journal of the Korean Geosynthetics Society
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    • v.11 no.3
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    • pp.1-9
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    • 2012
  • If the railways consisting of soil subgrade is applied to repetitive loading, elastic deformation and plastic deformation will occur at the same time. So the repeat traffic loading condition should be considered to predict the long-term deformation on railway roadbed. In this study, laboratory data from the repeated load triaxial tests and cylinder model test were used to predict accumulated settlement on railway foundation and results were analyed based on the nonliear models and stress state considered. It has proposed predict model using power function model on plastic settlement of roadbed materials.

Stall Prediction of Wing Using the Nonplanar Lifting Surface Theory and an Iterative Decambering Approach (비평면 양력면 이론과 반복적 캠버변형 기법을 이용한 날개의 실속 특성 예측)

  • 조정현;조진수;조연우
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.10
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    • pp.1-6
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    • 2006
  • This paper predicts the stall characteristics of three-dimensional wings. An iterative decambering approach is introduced into the nonplanar lifting surface method to take into consideration the stall characteristics of wings. An iterative decambering approach uses known airfoil lift curve and moment curve to predict the stall characteristics of wings. The multi-dimensional Newton iteration is used to take into consideration the coupling between the different sections of wings. Present results are compared with experiments and other numerical results. Computed results are in good agreement with other data. This scheme can be used for any wing with the twist or control surface and for wing-wing configurations such as wing-tail configuration or canard-wing configuration.