Numerical Modelling of Temperature Distribution and Pressure Drop through the Layered Burden Loading in a Blast Furnace

Kwangheok Yang,Sangmin Choi,Jinkyung Chung 한국연소학회 2009 한국연소학회지 Vol.14 No.4

Analysis of the internal state of the blast furnace is necessary to predict and to control the operating conditions. Especially, it is important to develop models of the blast furnace to predict the cohesive zone because shape of the cohesive zone influences overall operating conditions of blast furnace such as gas flow, chemical reactions and temperature. Because many previous blast furnace models have assumed cohesive zone to be fixed, it was not possible to evaluate the shape change of cohesive zone in relation with operating conditions such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace processes. In this model, cohesive zone is determined by the solid temperature. Finite volume method is employed for numerical simulation. To find location of the cohesive zone, entire calculation procedure is iterated until converged. Through this approach, shape of the cohesive zone, velocity and temperature within the furnace are predicted from the model.

Numerical Modelling of Temperature Distribution and Pressure Drop through the Layered Burden Loading in a Blast Furnace

Yang, Kwang-Heok,Choi, Sang-Min,Chung, Jin-Kyung The Korean Society of Combustion 2009 한국연소학회지 Vol.14 No.4

Analysis of the internal state of the blast furnace is necessary to predict and to control the operating conditions. Especially, it is important to develop models of the blast furnace to predict the cohesive zone because shape of the cohesive zone influences overall operating conditions of blast furnace such as gas flow, chemical reactions and temperature. Because many previous blast furnace models have assumed cohesive zone to be fixed, it was not possible to evaluate the shape change of cohesive zone in relation with operating conditions such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace processes. In this model, cohesive zone is determined by the solid temperature. Finite volume method is employed for numerical simulation. To find location of the cohesive zone, entire calculation procedure is iterated until converged. Through this approach, shape of the cohesive zone, velocity and temperature within the furnace are predicted from the model.

Numerical Modelling of Temperature Distribution and Pressure Drop through the Layered Burden Loading in a Blast Furnace

양광혁,정진경,최상민 한국연소학회 2009 한국연소학회지 Vol.14 No.4

Analysis of the internal state of the blast furnace is necessary to predict and to control the operating conditions. Especially, it is important to develop models of the blast furnace to predict the cohesive zone because shape of the cohesive zone influences overall operating conditions of blast furnace such as gas flow, chemical reactions and temperature. Because many previous blast furnace models have assumed cohesive zone to be fixed, it was not possible to evaluate the shape change of cohesive zone in relation with operating conditions such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace processes. In this model, cohesive zone is determined by the solid temperature. Finite volume method is employed for numerical simulation. To find location of the cohesive zone, entire calculation procedure is iterated until converged. Through this approach, shape of the cohesive zone, velocity and temperature within the furnace are predicted from the model.

융착대 예측을 위한 고로공정 모델링

양광혁(Yang Kwangheok),최상민(Choi Sangmin),정진경(Jung Jinkyung) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences overall operating condition of blast furnace such as gas flow, chemical reactions and temperature. because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process. In this model, cohesive zone is changed by solid temperature range, FVM is used for numerical simulation. To find location of cohesive zone whole calculation procedure is iterated Until cohesive zone is converged. Through this approach, shape of cohesive zone, velocity, composition and temperature within the furnace are predicted by model.

Cohesive Zone Model을 이용한 압입자 형상에 따른 균열특성분석

현홍철(Hong Chul Hyun),이진행(Jin Haeng Lee),이형일(Hyungyil Lee),김대현(Dae Hyun Kim),한준희(Jun Hee Hahn) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.12

본 연구에서는 유한요소해석과 압입시험으로 압입자 형상이 압입균열특성에 미치는 영향을 조사했다. 본 논문에서는 Lee 등(2012)이 제시한 cohesive zone 모델특성 및 균열생성, 진전을 위한 해석 조건에 기초해 다양한 균열해석을 수행했다. 우선, 사각뿔 및 삼각뿔 압입균열 시험과 해석을 비교해 해석 모델의 유효성을 검증했다. 아울러 비대칭 압입자에 의한 압입시, 압입하부에서 비대칭 균열의 발생 여부를 해석적으로 관찰했다. 최종적으로 압입발생 균열수와 균열길이 관계를 조사했다. 균열수와 균열길이 관계 및 동일 압입자형상(압입자 모서리수)에서 압입자각에 따른 균열길이 변화를 이용하면, 특정 압입자 형태의 압입시험에서 얻은 균열길이 만으로 다양한 압입자 형태의 균열길이를 예측할 수 있다. In this study, we investigated the effect of the indenter geometry on the crack characteristics by indentation cracking test and FEA. We conducted various cohesive finite element simulations based on the findings of Lee et al. (2012), who examined the effect of cohesive model parameters on crack size and formulated conditions for crack initiation and propagation. First, we verified the FE model through comparisons with experimental results that were obtained from Berkovich and Vickers indentations. We observed whether nonsymmetrical cracks formed beneath the surface during Berkovich indentation via FEA. Finally, we examined the relation between the crack size and the number of cracks. Based on this relation and the effect of the indenter angle on the crack size, we can predict from the crack size obtained with an indenter of one shape (such as Berkovich or Vickers) the crack size for an indenter of different shape.

Cohesive Zone Modeling of Crack Propagation in FCC Single Crystals via Atomistic Simulations

Gi Hun Lee,Jang Hyun Kim,Hyeon Gyu Beom 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4

This paper presents a cohesive zone model of fracture in Cu and Ni single crystals under tension, based on an atomisticanalysis. The molecular-statics approach based on the conjugate-gradient method was used to investigate the crack-growthbehavior at the atomic level. The fracture toughness was evaluated on the basis of energy considerations, and the cohesivetraction was calculated using the J integral and the atomic-scale separation in the cohesive zone. The cohesive traction andseparation curves obtained using computational data from atomistic simulations were compared with the exponential formof continuum mechanics. The results showed that the exponential form satisfactorily represented the cohesive zone propertiesof Cu. However, the cohesive traction and separation curves for Ni were found to deviate from the exponential form inthe softening stage, owing to small-scale nonlinear features near the cohesive zone.

A cohesive zone model for self-similar fractal crack propagation

Chang Xin,Ren Mingfa,Guo Xu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

Cracks in the nature have been proven to be fractal by many experiments. Despite the fractal fracture mechanics has been developed by many researchers, fractal geometry still has few applications in analysis of engineering structures. One of the reasons is that previous studies are somehow inconvenient when apply, e.g. to the finite element method. This study proposes a Cohesive zone model (CZM) for self-similar fractal crack propagation of material interfaces. The determination of the CZM parameters and the simulation of fractal crack propagation are developed by replace the fractal crack with the equivalent smooth crack. The fractal dimension has effects on both the crack extension resistance and the max traction stress. As shown by the simulation of a DCB specimen, the fractal dimension also affect the ultimate load and the crack propagation process. It is shown that it is possible to predict the propagation of fractal cracks without considering geometric modeling of the crack topology by our cohesive zone model.

접착영역 모델을 사용한 2상 리튬 이온 충전 시 실리콘 음극 전극의 균열진전 해석

김용우,한동석 한국전산구조공학회 2019 한국전산구조공학회논문집 Vol.32 No.5

In this research, crack propagation in a silicon anode during two-phase lithiation was evaluated using a cohesive zone model. The phase transition from crystalline silicon to lithiated silicon causes compressive yielding due to the high volume expansion rate. Li-ion diffuses from the surface of the silicon to its core, and the complex deformation mechanisms during lithiation cause tensile hoop stress along the surface. The Park-Paulino-Roesler (PPR) potential-based cohesive zone model that guarantees consistent energy dissipation in mixed-mode fracture was adopted to simulate edge crack propagation. It was confirmed that the edge crack propagation characteristics during lithiation from the FEM simulation results coincided with the real experimental results. Crack turning observed from real experiments could also be predicted by evaluating the angles of maximum tensile stress directions. 본 논문에서는 접착영역 모델을 이용하여 2상 리튬이온 충전 시 실리콘 음극 전극의 균열진전 해석을 수행하였다. 리튬화 실리콘은 결정질 실리콘에 비해 부피가 약 3배 이상 크므로 리튬이온 충전 시 외각의 리튬화 실리콘에 매우 큰 압축력이 작용하여 압축항복이 발생한다. 리튬이온 충전 시 외각의 리튬화 실리콘은 압축항복 후에 내부의 결정질 실리콘이 리튬화 실리콘으로 상 변이하면서 발생하는 부피 팽창으로 인해 인장력이 작용한다. 이러한 인장력으로 인해 발생하는 균열진전을 접착영역 모델을 이용하여 모사하였다. 사용한 접착영역 모델은 PPR 포텐셜 기반 접착영역 모델로 하나의 포텐셜을 사용하여 복합모드에 대해서도 에너지 소산에 일관성을 지니고 있다. 유한요소 수치해석 모델로 2상 리튬이온 충전 시 모서리 균열진전을 모사한 결과가 실제 실험결과와 일치함을 확인하였고, 균열 팁에서의 최대 인장응력의 각도를 분석하여 실제 실험처럼 균열진전 방향이 회전할 것을 예측할 수 있었다.

Assessment of cohesive traction-separation relationships in ABAQUS: A comparative study

Park, Kyoungsoo,Choi, Habeun,Paulino, Glaucio H. Elsevier 2016 Mechanics research communications Vol.78 No.2

<P><B>Abstract</B></P> <P>The definition of a traction-separation relationship is essential in cohesive zone models because it describes the nonlinear fracture process zone. A few models are investigated in this paper and a comparative study is conducted. Among various traction-separation relationships, the one in Abaqus is assessed by evaluating the cohesive traction and its tangent stiffness according to a given separation path. The results demonstrate that the traction-separation relationship in Abaqus can lead to non-physical responses because of a pathological positive tangent stiffness under softening condition. This is reflected in cohesive tractions that increase and decrease repeatedly while the cohesive separation monotonically increases. Thus, together with supporting information, this paper conveys the message that a traction-separation relationship should be developed and selected with great caution, especially under mixed-mode conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The traction-separation relationship of Abaqus can lead to non-physical responses. </LI> <LI> Negative tangent stiffness within the softening region is not guaranteed in the Abaqus model. </LI> <LI> The consistency of the traction-separation relationships is addressed. </LI> </UL> </P>

LS-DYNA의 복합재파손 모델링 및 응집영역 모델링 방법을 이용한 복합재 적층판의 저속충격 손상거동 예측

배홍수 ( Hongsu Bae ),우경식 ( Kyeongsik Woo ) 충북대학교 건설기술연구소 2019 建設技術論文集 Vol.38 No.1

본 논문에서는 저속 충격에 의하여 탄소-에폭시 복합재 적층판에서 발생하는 파손거동을 연속체 파괴역학 기반의 방법과 응집영역 모델링 방법을 이용하여 예측하였다. 먼저, 직교([0/90]_6s) 적층판과 준대칭([45/0/ -45/90]_3s) 적층판에 대하여 ASTM 규정을 따라 충격실험을 수행하고 이를 복합재 파손 모델과 응집영역 모델링을 이용하여 수치적으로 모사하였다. 해석에서는 면내 파손은 최대 응력기반의 파손기준을 채용한 탄소성 손상 모델을, 그리고 층간분리는 응집요소를 이용한 응집영역 모델링을 사용하여 모델링 하였다. 전산해석을 통하여 예측된 충격하중이력과 손상 형상을 실험의 결과와 비교하였다. 직교적층판과 준대칭 적층판에서 비교적 유사한 결과를 보였으며 이를 통하여 해석 모델의 타당성을 입증하였다. 또한, 다른 해석방법을 통한 결과와 비교를 통하여 기지의 손상 모델이 전체적인 손상에 미치는 영향에 대하여 보였다. In this study, damage behavior of carbon/epoxy laminated composite under low velocity impact was studied using intra and inter lamina damage modeling. First, experiment were performed based on ASTM standard with cross-ply ([0/90]_6s) and quasi-symmetric[45/0/0 -45/90]_3scking sequence. The experiments were simulated using composite damage modeling and cohesive zone modeling. The intra-laminar damage was modeled with elasto-plastic damage modeling adopting the maximum stress based failure model and the inter-laminar damage was considered with cohsive zone modeing using cohesive elements in LS-DYNA. Predicted damage behaviors in terms of impact force history and damage shape were compared with those from experiments and showed very good agreement. Also, by comparing with the predicted result using different analysis approach, the effect of the matrix cracking on the impact damage of laminated composites was exhibited.