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Flexural behavior of ECC hollow beams incorporating different synthetic fibers

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Frontiers of Structural and Civil Engineering 2021年第2期15卷 399-411页

作者： Ahmmad A.ABBAS Farid H.ARNA'OT Sallal R.ABID Mustafa OZAKCA Civil Engineering Department Gaziantep UniversityGaziantep72310Turkey Building and Construction Materials Department Southern Technical University-Shatrah Technical InstituteShatrah64007Iraq College of Technical Engineering Islamic University in An NajafNajaf54001Iraq Civil Engineering Department Wasit UniversityKut52001Iraq

Twelve ECC beams with three different fiber types,along with four normal concrete beams,were tested in this study to evaluate the influence of cross-sectional hollowing on their flexural *** fiber types used were nylon monofilament(NM),low-cost untreated polyvinyl alcohol(PVA),and polypropylene(PP).Three different square hole sizes of 60,80,and 100 mm with cross-sectional hollowing ratios of 0.16,0.28,and 0.44,respectively,were adopted for each group of beams in addition to a solid *** beams were tested under four-point loading using a displacement-controlled testing *** test results showed that ECC beams can mostly withstand higher cracking and ultimate loads compared to their corresponding normal concrete *** results also showed that both the ductility and toughness of the ECC beams are higher than those of the normal concrete beams and that the ductility values of the hollow beams with a hole size of 60 mm are higher than those of the corresponding solid ***,hollow ECC beams with hole sizes of 60 and 80 mm exhibited a higher ductility than a solid normal concrete beam.

关键词： hollow beam hollowing ratio ECC flexural strength ductility toughness

Current Progress of Mechanical Properties of Metals with Nano-scale Twins

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Journal of Materials Science & Technology 2008年第4期24卷 473-482页

作者： Lei LU Shenyang National Laboratory for Materials Science （SYNL） Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China

Focus on face-centered cubic （fcc） metals with nano-scale twins lamellar structure, this paper presents a brief overview of the recent progress made in improving mechanical properties, including strength, ductility, work hardening, strain rate sensitivities, and in mechanistically understanding the underling deformation mechanisms. Significant developments have been achieved in nano-twinned fcc metals with a combination of high strength and considerable ductility at the same time, enhanced work hardening ability and enhanced rate sensitivity. The findings elucidate the role of interactions between dislocations and twin boundaries （TBs） and their contribution to the origin of outstanding properties. The computer simulation analysis accounts for high plastic anisotropy and rate sensitivity anisotropy by treating TBs as internal interfaces and allowing special slip geometry arrangements that involve soft and hard modes of deformation. Parallel to the novel mechanical behaviors of the nano-twinned materials, the investigation and developments of nanocrystalline materials are also discussed in this overview for comparing the contribution of grain boundaries/TBs and grain size/twin lamellar spacing to the properties. The recent advances in the experimental and computational studies of plastic deformation of the fcc metals with nano-scale twin lamellar structures provide insights into the possible means of optimizing comprehensive mechanical properties through interfacial engineering.

关键词： Nanostructured metallic materials Twin boundary Strengthening ductility Rate sensitivity Deformation mechanism

Experimental research on the seismic behavior of CSPSWs connected to frame beams

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Earthquake Engineering and Engineering Vibration 2011年第1期10卷 65-73页

作者： Guo Lanhui Ma Xinbo Li Ran Zhang Sumei School of Civil Engineering Harbin Institute of Technology Harbin 150090 China

The seismic performance of composite steel plate shear walls （CSPSWs） that consist of a steel plate shear wall （SPSW） with reinforced concrete （RC） panels attached to one or both sides by means of bolts or connectors is experimentally studied. The shear wall is connected to the frame beams but not to the columns. This arrangement restrains the possible out-of-plane buckling of the thin-walled steel plate, thus significantly increasing the bearing capacity and ductility of the overall wall, and prevents the premature overall or local buckling failure of the frame columns. From a practical viewpoint, these solutions can provide open space in a floor as this type of composite shear walls with a relatively small aspect ratio can be placed parallel along a bay. In this study, four CSPSWs and one SPSW were tested and the results showed that both CSPSWs and SPSW possessed good ductility. For SPSW alone, the buckling appeared and resulted in a decrease of bearing capacity and energy dissipation capacity. In addition, welding stiffeners at corners were shown to be an effective way to increase the energy dissipation capacity of CSPSWs.

关键词： steel plate shear wall (SPSW) composite steel plate shear wall (CSPSW) seismic behavior ductility

Enhanced mechanical performance of grain boundary precipitation-hardened high-entropy alloys via a phase transformation at grain boundaries

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Journal of Materials Science & Technology 2021年第27期86卷 271-284页

作者： Y.L.Qi L.Zhao X.Sun H.X.Zong X.D.Ding F.Jiang H.L.Zhang Y.K.Wu L.He F.Liu S.B.Jin G.Sha J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China Analytical&Testing Center Northwestern Polytechnical UniversityXi’an710072China School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing210094China

Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external ***,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at *** in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs.

关键词： Non-equiatomic Grain-boundary precipitation High-entropy alloys ductility Transformation-induced plasticity

Ab initio study of the electronic structure and elastic properties of Al_5C_3N

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Chinese Physics B 2011年第12期20卷 309-314页

作者：徐学文胡龙宇霄卢遵铭范英李养贤唐成春 School of Materials Science and Engineering Hebei University of Technology

We investigate the electronic structure, chemical bonding and elastic properties of the hexagonal aluminum carbonitride, Al5C3N, by ab initio calculations. Al5C3N is a semiconductor with a narrow indirect gap of 0.81 eV. The valence bands below the Fermi level （EF） originate from the hybridized Al p-C p and A1 p-N p states. The calculated bulk and Young＇s moduli are 201 GPa and 292 GPa, which are slightly lower than those of Ti3SiC2. The values of the bulk-to-shear-modulus and bulk-modulus-to-c44 are 1.73 and 1.97, respectively, which are higher than those of Ti2AlC and Ti2AlN, indicating that Al5C3N is a ductile ceramic.

关键词： electronic structure chemical bonding elastic properties ductility

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 439-448页

作者： Yan Changwang Jia Jinqing School of Mining and Technology Inner Mongolia University of Technology Huhhot 010062 China State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

关键词： cyclical test axial load ratio volumetric stirrup ratio ductility strength degradation stiffness degradation steel reinforced ultra high strength concrete beam-column joint

Performance of a novel bent-up bars system not interacting with concrete

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Frontiers of Structural and Civil Engineering 2019年第6期13卷 1301-1315页

作者： Aydin SHISHEGARAN Mohammad Reza GHASEMI Hesam VARAEE School of Civil Engineering Iran University of Science and TechnologyTehran 13114-16846Iran Structural Engineering Department of Civil EngineeringUniversity of Sistan and BaluchestanZahedan 98167-45845Iran Structural Engineering Ale Taha Institute of Higher EducationTehran 14888-36164Iran

Increasing the bending and shear capacities of reinforced concrete members is an interesting issue in structural *** recent years,many studies have been carried out to improve capacities of reinforced concrete members such as using post and pre-tensioning,Fiber Reinforced Polymer and other *** paper proposes a novel and significant technique to increase the flexural capacity of simply supported reinforced concrete *** proposed method uses a new reinforcement bar system having bent-up bars,covered with rubber *** technique will avoid interaction of bent-up bars with *** are located in the zone where compressive and tensile forces act against one anothe匚The compressive force in the upper point of the bent-up bars is exerted to the end point of these bars located under neutral ***,the tensile stress is decreased in reinforcements located under the neutral *** will cause the Reinforced Concrete(RC)beam to endure extra loading before reaching yield *** factors may well be considered as reasons to increase bending capacity in the new *** laboratory work together with finite element method analysis were carried out in this ***,bending capacity,ductility,strength,and cracking zone were assessed for the new proposed system and compared with the conventional *** the FEM simulation and the experimental test results revealed that the proposed system has significant impact in increasing the load bearing capacity and the stiffness of the RC *** the present study,an equation is formulated to calculate bending capacity of a new reinforcement bar system beam.

关键词： bending capacity rubber tube stress transfer bent-up bars ductility cracking

Grain boundary character and stress corrosion cracking behavior of Co-Cr alloy fabricated by selective laser melting

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Journal of Materials Science & Technology 2021年第34期93卷 244-253页

作者： Xin Dong Ning Li Yanan Zhou Huabei Peng Yuntao Qu Qi Sun Haojiang Shi Rui Li Sheng Xu Jiazhen Yan School of Mechanical Engineering Sichuan UniversityChengdu 610065China Chengdu Keningda Materials Co. ChinaChengdu 610065China College of Stomatology Cuangxi Medical UniversityNanning 532201China

In this work,we used the selective laser melting(SLM)fabricated Co-Cr alloy with prominent residual strain,extremely non-equilibrium microstructures,and low stacking fault energy as a precursor to fabricate materials with the optimal grain boundary character *** grain boundary engineering(GBE)of the Co-Cr alloy was achieved by a simple heat treatment of the SLM-fabricated Co-Cr *** obtained GBE Co-Cr alloy exhibited 81.47%of special grain boundaries(∑3^(n)n=1,2,3),while it substantially disrupted the connectivity of the random high-angle boundaries,successfully reducing the propensity of intergranular *** strain rate tests(SSRTs)showed that the GBE Co-Cr alloy possessed lower stress corrosion cracking(SCC)susceptibility and higher ductility in the corrosive environment(0.9%Na Cl solution)than in the *** high fraction of special boundaries,coupled with the stress-induced martensitic transformation(SIMT)in the GBE Co-Cr alloy yielded these results,which unique and rarely simultaneously satisfied for common structural *** current"SLM induced GBE strategy"offers a novel approach towards customized GBE materials with high SCC resistance and ductility in the corrosive environment,shedding new light on developing high-performance structural materials.

关键词： Grain boundary engineering Selective laser melting Co-Cr alloy Stress corrosion cracking ductility

Formation kinetics of austenite in pearlitic ductile iron

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International Journal of Minerals,Metallurgy and Materials 2012年第6期19卷 506-510页

作者： Payam Abdollahi Alborz Amirsadeghi Shahram Kheirandish Shamsoddin Mirdamadi Department of Materials Science and Engineering Iran University of Science and TechnologyTehran ***Iran

This work evaluated the isothermal transformation of austenite in unalloyed pearlitic ductile iron and drew the isothermal phase diagram of austenitization in the ductile iron, Austenite forms at grain boundaries and then grows up to graphite regions during austenitiza- tion. The formation kinetics of austenite complies with the Avrami equation, in which the parameter （n） ranges from 4.71 to 4.99. The start time and finish time of transformation can be calculated at each temperature using the Avrami equation.

关键词： cast iron ductility pearlite austenitization kinetics isothermal transformations