• Structural Engineering and Mechanics
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• 제83권3호
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• pp.377-386
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• 2022

This paper considers dynamic impedance functions and presents a detailed analysis of the soil plasticity influence on the pile-group foundation dynamic response. A three-dimensional finite element model is proposed, and a calculation method considering the time domain is detailed for the nonlinear dynamic impedance functions. The soil mass is modeled as continuum elastoplastic solid using the Mohr-Coulomb shear failure criterion. The piles are modeled as continuum solids and the slab as a structural plate-type element. Quiet boundaries are implemented to avoid wave reflection on the boundaries. The model and method of analysis are validated by comparison with those published on literature. Numerical results are presented in terms of horizontal and vertical nonlinear dynamic impedances as a function of the shear soil parameters (cohesion and internal friction angle), pile spacing ratio and frequencies of the dynamic signal.

• Earthquakes and Structures
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• 제26권2호
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• pp.97-115
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• 2024

In this paper, a database consisting of the dynamic shear modulus ratio and damping ratio test data of clay obtained from 406 groups of triaxial tests is constructed with the starting area of Xiong'an New Area as the research background. The aim is to study the nonlinear dynamic properties of clay in this area under cyclic loading. The study found that the effective confining pressure and plasticity index have certain influences on the dynamic shear modulus ratio and damping ratio of clay in this area. Through data analysis, it was found that there was a certain correlation between effective confining pressure and plasticity index and dynamic shear modulus ratio and damping ratio, with fitting degree values greater than 0.1263 for both. However, other physical indices such as the void ratio, natural density, water content and specific gravity have only a small effect on the dynamic shear modulus ratio and the damping ratio, with fitting degree values of less than 0.1 for all of them. This indicates that it is important to consider the influence of effective confining pressure and plasticity index when studying the nonlinear dynamic properties of clays in this area. Based on the above, prediction models for the dynamic shear modulus ratio and damping ratio in this area were constructed separately. The results showed that the model that considered the combined effect of effective confining pressure and plasticity index performed best. The predicted dynamic shear modulus ratio and damping ratio closely matched the actual curves, with approximately 88% of the data falling within ±1.3 times the measured dynamic shear modulus ratio and approximately 85.1% of the data falling within ±1.3 times the measured damping ratio. In contrast, the prediction models that considered only a single influence deviated from the actual values, particularly the model that considered only the plasticity index, which predicted the dynamic shear modulus ratio and the damping ratio within a small distribution range close to the average of the test values. When compared with existing prediction models, it was found that the predicted dynamic shear modulus ratio in this paper was slightly higher, which was due to the overall hardness of the clay in this area, leading to a slightly higher determination of the dynamic shear modulus ratio by the prediction model. Finally, for the dynamic shear modulus ratio and damping ratio of the engineering site in the starting area of Xiong'an New Area, we confirm that the prediction formulas established in this paper have high reliability and provide the applicable range of the prediction model.

• 대한토목학회논문집
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• 제26권3A호
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• pp.465-471
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• 2006

지진과 같은 동적 반복하중을 받는 강구조물의 이력거동을 구현하기 위해서는 사용된 강재의 정 동적 상태에서의 응력-변형률 관계 및 특성을 고려한 동적반복소성모델이 필요하다. 본 연구에서는 SM490강재의 정 동적 단조 및 반복하중 실험을 수행하여 역학적 특성 및 응력-변형률 관계를 명확히 하였다. 그리고 실험결과에 기초하여 SM490강재의 동적반복소성모델을 제안하였으며 이를 유한변위이론에 기초한 3차원 탄소성 유한요소해석에 적용하였다. 실험시편을 모델링하여 정 동적 단조, 반복 및 변형률속도변화에 따른 3차원 탄소성 유한요소해석을 수행하였으며 이를 실험결과와 비교하였다. 비교를 통하여 본 연구에서 개발한 해석기법이 강부재의 정 동적 변형상태를 정도있게 예측할 수 있음을 검증하였다.

• 소성∙가공
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• 제7권2호
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• pp.107-113
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• 1998

The high temperature mechanical behaviour of duplex stainless steels was examined. The relation-ship between the dynamic recrystallization substructures and the flow behaviour was analyzed in detail, and the flow behaviour was analyzed in detail, and the mechanisms of dynamic recrystallization were also discussed. The formation of disloca-tion cells and subgrain structures is of great significance to the understanding of high temperature deformation.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.131.1-134
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• 1999

The effect of dynamic recrystallization during hot forming process was implemented to a commercial FEM code by conditioned remeshing and remapping of sate variables. A datum strain for stress compensation was determined as a strain for maximum softening rate and was able to be formulated as a function of critical strain f($\varepsilon$). The validity of remapping criterion was examined by a series of mechanical tests and microstructural observation. The application of suggested datum resulted in better estimation of load-stroke during forging processes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.203-206
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• 1999

The shift of flow behavior due to dynamic recrystallization during hot forming process is investigated, A series of load relaxation and compression tests has been conducted at various temperatures Constitutive relations and recrystallization behaviors were formulated from the mechanical test results, The consideration of dynamic recrystallization during a specific forming process was implemented to commercial FEM package by conditioned remeshing and remapping of state variables. Improvement of Load-Stroke prediction was validated by comparison with experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.173-176
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• 2002

Viscoplastic deformation and sheet forming behavior of multicomponent Zr-based bulk metallic glass alloy has been investigated. From a series of mechanical test results, basic processing maps based on Dynamic Materials Model have been constructed to establish feasible forming conditions. Stamping in laboratory scale was then performed at the various stroke speeds and temperatures using a hydraulic press. Failure in macroscopic level was examined to check the validity of constructed processing maps.

• 지질공학
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• 제9권2호
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• pp.135-145
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• 1999

동적 하중을 받는 지반반응 평가시 필요한 가장 중요한 변수 중에 하나가 지반의 전단탄성계수(G)이다. 지반의 동특성은 시간에 따라 변화하게 되는데, 이 점은 흔히 간과되어져 왔다. 이번 연구를 통하여 일정구속압에서 시간에 따라 변하는 토질 최대전단탄성계수($G_{max}$) 및 그 영향요소에 관해 고찰해보고 몇몇 경험식을 제안하고자 한다. 경험식 작성을 위해 고려된 요소는 선행응력과 선행변형율, 입자크기와 지속응력, 소성지수 등이고, 실제로 가장 큰 영향을 미치는 평균입자직경과 소성지수를 이용한 두개의 경험식을 작성하였다. 끝으로 $G_{max}$의 일시적 변화와 그 원인, 그리고 시간에 따라 증가하는 G가 시사하는 점에 대해 서술한다

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.126-131
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• 1999

In order to reduce the length of off-gauge at FGC(Flying gauge change) point, We adopted dynamic set up in No. 4 cold rolling mill. The conventional set-up of FGC(Flying gauge change) was calculated on the basis of preset values in the process control computer, so the difference between actual strip thickness and preset thickness cause long off-gauge. The dynamic SET-UP control was calculated on the basis of actual strip thickness of FGC(Flying gauge change) point from X-ray gauge of mill entry and No.i stand. We applied dynamic SET-UP control in September last year. Compare to the previous result, the length of off-gauge is reduced by about 36%.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.21-22
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• 2008