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Damage-constitutive model for seawater coral concrete using different stirrup confinements subjected to axial loading

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Frontiers of Structural and Civil Engineering 2023年第3期17卷 429-447页

作者： Jiasheng JIANG Haifeng YANG Zhiheng DENG Yu ZHANG Guangxi Key Laboratory of Disaster Prevention and Structural Safety College of Civil Engineering and ArchitectureGuangxi UniversityNanning 530004China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education Guangxi UniversityNanning 530004China

Recently,the application of detrital coral as an alternative to natural aggregates in marine structures has attracted increased attention.In this study,research on the compressive performance of coral aggregate concrete(CAC)confined using steel stirrups with anti-rust treatment was experimentally conducted.A total of 45 specimens were cast,including 9 specimens without stirrups and under different strength grades(C20,C30,and C40)and 36 specimens under different strength grades(C20,C30,and C40).Moreover,three stirrup levels(rectangular,diamond-shaped compound,and spiral stirrups)and different stirrup spacings(40,50,60,and 70 mm)were used.Subsequently,the stress−strain curves of specimens subjected to axial loading were measured.The effects of the stirrup spacing and stirrup configurations on the stress and strain were investigated,respectively,and the lateral effective stress of the different stirrups was calculated based on the cohesive-elastic ring model and modified elastic beam theory.Moreover,a damageconstitutive model of CAC considering the lateral stress was set up based on damage mechanics theory.The results indicated an increase in the stress and strain with a decrease in the stirrup spacing,and the adopted stirrup ratio had a better strengthening effect than the different concrete grades,and the variation in the deformation was restricted by the performance of coral coarse aggregate(CA).However,an increment in the lateral strain was observed with an increase in the axial strain.The lateral stress model showed a good agreement with the experimental data,and the proposed damageconstitutive model had a good correlation with the measured stress−strain curves.

关键词： coral aggregate concrete stress−strain curves lateral effective stress peak stress axial−lateral curves damage-constitutive model

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Hot Deformation Behavior of ATI 718Plus Alloy with Different Microstructures

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1383-1396页

作者： Chang Liu Jianbo Zhang Yikai Yang Xingchuan Xia Tian He Jian Ding Ying Tang Zan Zhang Xueguang Chen Yongchang Liu School of Material Science and Engineering Hebei University of TechnologyTianjin 300130China College of Physics and Electronic Engineering Xingtai UniversityXingtai 054001China School of Science Hebei University of TechnologyTianjin 300130.China School of Material Science and Engineering Tianjin UniversityTianjin 300130China

In this work, the eff ect of microstructure on hot deformation behavior of ATI 718Plus(hereinafter refers to 718Plus) alloy was studied by isothermal compression test. The results showed that when the strain rate was 0.01–0.1s^(-1) with deformation temperature of 980 and 1030℃, hot deformation behavior was mainly aff ected by dislocation density. Dislocation density of the air-cooling alloy was larger than that of the furnace-cooling alloy, which makes its critical strain smaller and peak stress higher than that of the furnace-cooling alloy. When the strain rate was 1 s^(-1), hot deformation behavior of the alloy was mainly aff ected by twins and γ ′ phase, and high-density deformation twins in air-cooling alloys resulted in higher critical strain. γ ′ phase exists in furnace-cooling alloy, which makes its peak stress higher than that of air-cooling alloy. 718Plus alloy is sensitive to cooling rate;dislocation and γ ′ phase have obvious eff ects on its hot deformation behavior.

关键词： 718Plus alloy Hot deformation peak stress Dynamic recrystallization Critical strain

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Hot deformation behavior and microstructure evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment

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Rare Metals 2013年第4期32卷 338-346页

作者： Yan Xu Lian-Xi Hu Yu Sun School of Materials Science and Engineering Harbin Institute of Technology School of Mechanical Engineering Beihua University

The deformation behavior and the microstruc-ture evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment were systematically inves-tigated. The flow stress behavior was studied by com-pression tests in strain rate range of 0.001-1.000 s^-1 and deformation temperature range of 220-380 ℃ with a maximum deformation strain of 60 %. The dependence of flow stress on deformation temperature and strain rate was described by hyperbolic sine constitutive equation. Through regression analysis, the average apparent activa- tion energy and coefficient of strain rate sensitivity were estimated to be 181.98 kJ.mol^-1 and 0.14, respectively. The results also reveal that the variation of peak stress depends on strain rate and deformation temperature. Microstructure observation shows that, at temperatures higher than 300 ℃ and strain rates lower than 0.01 s^-1, DRX developed extensively at the grain boundaries and in the core of coarse grains, resulting in a more homogeneous microstructure. Furthermore, the effects of strain, defor-mation temperature, strain rate, and eutectic β phase on the microstructure evolution of as-cast AZ91D magnesium alloy were discussed.

关键词： AZ91D magnesium alloy Isothermalcompression Constitutive equation peak stress Microstructure evolution

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DYNAMIC MECHANICAL BEHAVIOURS OF HIGH Mo AUSTENITIC STAINLESS STEEL DURING HOT DEFORMATION

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Acta Metallurgica Sinica(English Letters) 1992年第7期5卷 60-64页

作者： XU Yourong GU Qing WANG Deying, Shanghai University of Science and Technology, Shanghai, ChinaGU Jufang Q U Tiancai, Shanghai Iron and Steel Research Institute, Shanghai, China XU Yourong, Professor, Department of Materials Science, Shanghai University of Science and Technology, Shanghai 201800, China

The dynamic mechanical behaviours of super low carbon high Mo austenitic stainless steel (00Cr20Nil8Mo6CuN)during hot deformation have been studied by using Formaster-Press hot working simulator. The hot deformation equation, as well as the relationship between peak strain, peak stress and Zener-Hollman parameter, together with the deformation activation energy have been resulted through the experiments.

关键词： hot deformation austenitic stainless steel peak strain peak stress dynamic behaviour

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Deformation behavior of Fe-Mn-C TWIP steel within the temperature range of hot rolling

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Baosteel Technical Research 2008年第4期2卷 8-11页

作者： Ma Fengcang Feng Weijun Wang Li Zhang Di Auto Steel Division Baosteel Research Institute Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China State Key Laboratory of Metal Matrix Composites Shanghai Jiaotong University Shanghai 200030 China

The hot-deformation behavior of Fe-Mn-C twinning induced plasticity （TWIP） steel was investigated by conducting hot compression tests within a recommended hot rolling temperature range at various strain rates. Flow resistance curves during hot-deformation were obtained, and strain rate sensitivities and activation energies for plastic deformation were calculated using the power law. It is found that the addition of Al and Si clearly increases the peak stresses for the present alloys, especially at 950℃. But Mn has a minor effect on the stress-strain curves and activation energy when its content varies from 15 mass% to 22 mass% for the present alloys.

关键词： TWIP steel hot deformation behavior peak stress activation energy for plastic deformation

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COMPLETE stress- STRAIN BEHAVIOR FOR SHEAR FAILURE OF ROCKS

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岩石力学与工程学报 2001年第1期20卷 137-137页

作者： Zhou Guolin (Depantmentof Civil Engineering,The University of Hong Kong, Hong Kong, China) 香港大学香港

The investigation of complete stress- strain behavior and compressive failure behavior of some Hong Kong rocks are carried out.A large number of tests have been conducted to study the deformation and failure features of rocks.Some interesting test results have been obtained.These results show that localized deformation and failure strongly affect the deformation and failure process of the specimens just prior to the peak stress and in the post- peak stage. The two types of failure modes,namely exfoliation and shear failure have been investigated in detail. For the exfoliation failure mode,an experimentmethod has been proposed to observe the exfoliating process. A proposed model has been used to explain the influence of exfoliation on the gross stress- strain curve.It is found that the exfoliation during loading may be one of the reasons that a granite specimen exhibits Class behavior.The influences of machine stiffness control modes,end constraints,loading rate and confining pressure on the test results have been discussed and investigated.A new classification method of rock failure has been proposed. Special attention has been devoted to the investigation of the localized deformation and failure process of intact rock in the shear failure mode.A test method is proposed to detect the process.It is found that the deformation of rock material may be divided into three stages:namely uniform stage,pre- peak bifurcation stage and post- peak bifurcation stage.This phenomenon has been explained by a proposed qualitative analysis. It is further found thatthis localized process will significantly influence the shape of stress- strain curves, that is,the localized deformation is one of reasons that rock displays the effect of length to diameter ratio.A constitutive model is proposed to simulate the localized deformation and failure process.It can simulate the strain softening,strain localization,effect of length todiameter( L / D) ratio,unloading- reloading respons, and elastic modulus degradation,etc.Based on the model,a

关键词： rock test shear failure localized deformation peak stress gross stress- strain curve strength criterion

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