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Mechanical properties and microstructure of multilayer graphene oxide cement mortar

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 1058-1070 doi: 10.1007/s11709-021-0747-3

摘要： This study reports on the effects of multilayer graphene oxide (MGO) on compressive strength, flexural strength, and microstructure of cement mortar. The cement mortar was prepared with type P. II. 52.5 Portland cement, standard sand, and MGO. Four mixes were prepared with inclusion of MGO (0%, 0.02%, 0.04%, and 0.06% by weight of cement). The testing result shows that the compressive of GO-cement mortar increased by 4.84%–13.42%, and the flexural strength increased by 4.37%–8.28% at 3 d. GO-cement mortar’s compressive strength and flexural strength at 7 d increased by 3.84%–12.08% and 2.54%–13.43%, respectively. MGO made little contribution to the increases of compressive strength and flexural strength of cement mortar at 28 d. The results of X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen (N2) adsorption/desorption tests show that the types of hydration products and crystal grain size did not change after adding MGO. Still, it can help to improve the microstructure of the cement mortar via regulating hydration products and can provide more condensed cores to accelerate hydration. Furthermore, the regulating action of MGO for the microstructure of cement mortar at an early age was better than that at 28 d.

关键词： graphene oxide     cement     mortar     mechanical properties     microstructure    

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Facile synthesis of polyaniline nanorods to simultaneously enhance the mechanical properties and wear

《化学科学与工程前沿（英文）》 2023年 第17卷 第9期   页码 1254-1266 doi: 10.1007/s11705-023-2297-3

摘要： To enhance the mechanical properties and wear resistance of epoxy resin, polyaniline nanorods were first synthesized using a facile route, and then introduced into the epoxy matrix to yield composites via solution mixing. Several measurements were conducted to investigate the phase structures and compositions of polyaniline nanorods, and their positive influences on the mechanical and tribological properties of epoxy resin were also characterized. The results confirmed that the as-synthesized polyaniline exhibited representative rod-like morphologies and dispersed well in the epoxy matrix, leading to significant enhancements in the tensile strength and elastic modulus of epoxy composites. The highest values of 110.33 MPa and 2.04 GPa were obtained by adding 5%–7% polyaniline nanorods, which were 43% and 62% higher than the pure sample, respectively. The wear rate was increased first and then decreased along with polyaniline nanorods, presenting the lowest value of 2.12 × 10−5 mm3·Nm–1 by adding 5% filler, which was markedly reduced by ca. 70% compared to the control sample. Finally, the possible wear mechanism was proposed and discussed in detail. This study tried to broaden the applications of polyaniline nanorods in the field of tribology.

关键词： epoxy resin     polyaniline nanorods     mechanical property     tribological performance     wear mechanism    

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Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 495-503 doi: 10.1007/s11709-018-0492-4

摘要： Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the influence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

关键词： phaqraphene     mechanical properties     crack propaqation     molecular dynamics     thermal effects    

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Assessment and prediction of the mechanical properties of ternary geopolymer concrete

Jinliang LIU; Wei ZHAO; Xincheng SU; Xuefeng XIE

《结构与土木工程前沿（英文）》 2022年 第16卷 第11期   页码 1436-1452 doi: 10.1007/s11709-022-0889-y

摘要： This paper utilized granulated blast furnace slag (GBFS), fly ash (FA), and zeolite powder (ZP) as the binders of ternary geopolymer concrete (TGC) activated with sodium silicate solution. The effects of alkali content (AC) and alkaline activator modulus (AAM) on the compressive strength, flexural tensile strength and elastic modulus of TGC were tested and the SEM micrographs were investigated. The experimental results were then compared with the predictions based on models of mechanical properties, and the amended models of TGC were proposed taking account of the effects of AC and AAM. The results indicated that increasing AC and reducing AAM which were in the specific ranges (5% to 7% and 1.1 to 1.5, respectively) had positive effects on the mechanical properties of TGC. In addition, the flexural tensile strength of TGC was 27.7% higher than that of OPC at the same compressive strength, while the elastic modulus of TGC was 25.8% lower than that of OPC. Appropriate prediction models with the R2 of 0.945 and 0.987 for predicting flexural tensile strength and elastic modulus using compressive strength, respectively, were proposed. Fitting models, considering the effects of AC and AAM, were also proposed to predict the mechanical properties of TGC.

关键词： Ternary Geopolymer Concrete (TGC)     alkaline activator modulus     alkali content     mechanical properties     assessment    

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Influence of recycled polyethylene terephthalate fibres on plastic shrinkage and mechanical properties

Necat ÖZAŞIK; Özgür EREN

《结构与土木工程前沿（英文）》 2022年 第16卷 第6期   页码 792-802 doi: 10.1007/s11709-022-0849-6

摘要： Polyethylene terephthalate bottles production has drastically increased year after year due to high versatility of polyethylene terephthalate plastics and considerable consumption of beverages. In tandem with that increase, the major concern of society has been the improper disposal of this non-biodegradable material to the environment. To deal with this concern, recycled polyethylene terephthalate bottles were incorporated in concrete as fibre reinforcements in this study. The objective of this research is to evaluate the mechanical properties of recycled polyethylene terephthalate fibre reinforced concrete (RPFRC) in comparison with control concrete without fibres. polyethylene terephthalate fibres with three different diameters (0.45, 0.65, and 1.0 mm) and two lengths (20 and 30 mm) were added at various proportions (0.5%, 1.0%, 1.5% and 2.0%) by volume of concrete in order to determine the effect of fibres initially on compressive, flexural and splitting tensile strengths of concrete. The results revealed that none of the fibres have detrimental effects up to 1% volume fraction, however further addition caused slight reductions on mechanical properties in some conditions. Plastic shrinkage resistance and impact resistance tests were also performed according to related standards. Polyethylene terephthalate fibres were observed to have marked improvements on those properties. Such a good performance could be attributed primarily to the bridging effect of fibres.

关键词： recycled PET     fibre-reinforced concrete     mechanical properties     plastic shrinkage     impact energy    

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A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 36-45 doi: 10.1007/s11709-014-0243-0

摘要： This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete (SCC) mix with that of a corresponding conventional concrete (CC) mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials ( / ) ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

关键词： admixture     conventional concrete (CC)     creep     fracture mechanic     mechanical Properties     self-consolidating concrete (SCC)     shrinkage    

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Unified calculation method and its application in determining the uniaxial mechanical properties of concrete

Faxing DING, Xiaoyong YING, Linchao ZHOU, Zhiwu YU

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 381-393 doi: 10.1007/s11709-011-0118-6

摘要： This paper presents a unified calculation method and its application in determining the uniaxial mechanical properties of concrete with concrete strengths ranging from 10 to 140 MPa. By analyzing a large collection of test results of the uniaxial mechanical properties of normal-strength, high-strength and super high-strength concrete in China and performing a regression analysis, unified calculation formulas for the mechanical indexes of concrete are proposed that can be applied to various grades of concrete for determining the size coefficient, uniaxial compressive strength, uniaxial tensile strength, elastic modulus, and strain at peak uniaxial compression and tension. Optimized mathematical equations for the nonlinear stress-strain relationship of concrete, including the ascending and descending branches under uniaxial stress, are also established. The elastic modulus is almost constant throughout the elastic stage for the ascending branches of the stress-strain relationship for concrete. The proposed stress-strain relationship of concrete was applied to the nonlinear finite element analysis of both a steel-concrete composite beam and a concrete-filled steel tubular stub column. The analytical results are in good agreement with the experiment results, indicating that the proposed stress-strain relationship of concrete is applicable. The achievements presented in this paper can be used as references for the design and nonlinear finite element analysis of concrete structures.

关键词： concrete     mechanical properties     stress-strain relationship     uniaxial stress     application    

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Mechanical properties of vanadium-alloyed austempered ductile iron for crankshaft applications

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0746-2

摘要： This study focused on the development of austempered ductile iron (ADI) with desirable combination of mechanical properties for crankshaft applications by the combined effect of vanadium (V) alloying and an optimized heat treatment process. The produced unalloyed GGG60, 0.15% V-alloyed GGG60 (V-15), and 0.30% V-alloyed GGG60 samples were subjected to austenitizing at 900 °C for 1 h and subsequent austempering processes at 250, 300, and 350 °C for 15, 30, 60, 90, and 180 min. As a result of these austempering processes, different bainitic structures were obtained, which led to the formation of diverse combinations of mechanical properties. The mechanical properties of the austempered samples were tested comprehensively, and the results were correlated with their microstructures and the stability of the retained austenite phases. From the microstructural observations, the V-alloyed samples exhibited a finer microstructure and a more acicular ferrite phase than unalloyed samples. The V addition delayed the coarsening of the acicular ferrite structures and considerably contributed to the improvement of the mechanical properties of GGG60. Moreover, the X-ray diffraction results revealed that the retained austenite volume and the carbon enrichment of austenite phases in ADI samples were remarkably affected by the addition of vanadium. The increase in volume fraction of retained austenite and its carbon content provided favorable ductility and toughness to V-15, as confirmed by the elongation and impact test results. Consequently, the dual-phase ausferrite microstructure of V-15 that was austempered at 300 °C for 60 min exhibited high strength with substantial ductility and toughness for crankshaft applications.

关键词： austempered ductile iron (ADI)     vanadium alloying     mechanical properties     crankshafts     retained austenite    

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Combination form analysis and experimental study of mechanical properties on steel sheet glass fiber

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 834-850 doi: 10.1007/s11709-021-0743-7

摘要： The concept of steel sheet glass fiber reinforced polymer (GFRP) composite bar (SSGCB) was put forward. An optimization plan was proposed in the combined form of SSGCB. The composite principle, material selection, and SSGCB preparation technology have been described in detail. Three-dimensional finite element analysis was adopted to perform the combination form optimization of different steel core structures and different steel core contents based on the mechanical properties. Mechanical tests such as uniaxial tensile, shear, and compressive tests were carried out on SSGCB. Parametric analysis was conducted to investigate the influence of steel content on the mechanical properties of SSGCB. The results revealed that the elastic modulus of SSGCB had improvements and increased with the rise of steel content. Shear strength was also increased with the addition of steel content. Furthermore, the yield state of SSGCB was similar to the steel bar, both of which indicated a multi-stage yield phenomenon. The compressive strength of SSGCB was lower than that of GFRP bars and increased with the increase of the steel core content. Stress-strain curves of SSGCB demonstrated that the nonlinear-stage characteristics of SSGCB-8 were much more obvious than other bars.

关键词： steel sheet GFRP composite bar     combination form     numerical modeling     mechanical properties test     strength    

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Effects of coarse and fine aggregates on long-term mechanical properties of sea sand recycled aggregate

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 754-772 doi: 10.1007/s11709-021-0711-2

摘要： Typical effects of coarse and fine aggregates on the long-term properties of sea sand recycled aggregate concrete (SSRAC) are analyzed by a series of axial compression tests. Two different types of fine (coarse) aggregates are considered: sea sand and river sand (natural and recycled coarse aggregates). Variations in SSRAC properties at different ages are investigated. A novel test system is developed via axial compression experiments and the digital image correlation method to obtain the deformation field and crack development of concrete. Supportive results show that the compressive strength of SSRAC increase with decreasing recycled coarse aggregate replacement percentage and increasing sea sand chloride ion content. The elastic modulus of SSRAC increases with age. However, the Poisson’s ratio reduces after 2 years. Typical axial stress–strain curves of SSRAC vary with age. Generally, the effect of coarse aggregates on the axial deformation of SSRAC is clear; however, the deformation differences between coarse aggregate and cement mortar reduce by adopting sea sand. The aggregate type changes the crack characteristics and propagation of SSRAC. Finally, an analytical expression is suggested to construct the long-term stress–strain curve of SSRAC.

关键词： sea sand recycled aggregate concrete     recycled coarse aggregate replacement percentage     sea sand chloride ion content     long-term mechanical properties     stress–strain curve    

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Dual cross-linked MXene/cellulose nanofiber/nickel alginate film with improved mechanical properties

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1460-1469 doi: 10.1007/s11705-023-2335-7

摘要： Electromagnetic interference pollution has raised urgent demand for the development of electromagnetic interference shielding materials. Transition metal carbides (MXenes) with excellent conductivity have shown great potential in electromagnetic interference (EMI) shielding materials, while the poor mechanical strength, flexibility, and structural stability greatly limit their further applications. Here, cellulose nanofibers and sodium alginate are incorporated with MXene nanosheets as flexible matrices to construct strong and flexible mussel-like layered MXene/Cellulose nanofiber/Sodium Alginate composite films, and nickel ions are further introduced to induce metal coordination crosslinking of alginate units. Benefited from the dual-crosslinked network structure of hydrogen bonding and metal coordination, the tensile strength, Young’s modulus, and toughness of the MXene/cellulose nanofiber/nickel alginate composite film are significantly increased. After subsequent reduction by ascorbic acid, excess nickel ions are reduced to nickel nanoparticles and uniformly dispersed within the highly conductive composite film, which further improved its hysteresis loss effect toward the incident electromagnetic waves. Consequently, the MXene/cellulose nanofiber/nickel alginate-Ni composite film presents a considerably enhanced electromagnetic interference shielding effectiveness (47.17 dB) at a very low thickness of 29 μm. This study proposes a feasible dual-crosslinking and subsequent reduction strategy to synergistically enhance the mechanical properties and electromagnetic interference shielding performance of MXene-based composite materials.

关键词： Ti3C2Tx MXene     double crosslinking     mechanical properties     EMI shielding performance    

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Influence of surface modified mixed metal oxide nanoparticles on the electrochemical and mechanical properties

《化学科学与工程前沿（英文）》 2023年 第17卷 第1期   页码 1-14 doi: 10.1007/s11705-022-2176-9

摘要： Newly synthesized functional nanoparticles, 3-amino-1,2,4-triazole (ATA)/SiO2–TiO2 were introduced to the polyurethane (PU) matrix. Electrochemical techniques were used to investigate the barrier properties of the synthesized PU–ATA/SiO2–TiO2 nanocomposite coated steel specimen. In natural seawater, electrochemical impedance spectroscopy experiments indicated outstanding protective behaviour for the PU–ATA/SiO2–TiO2 coated steel. The coating resistance (Rcoat) of PU–ATA/SiO2–TiO2 was determined to be 2956.90 kΩ·cm–2. The Rcoat of the PU–ATA/SiO2–TiO2 nanocomposite coating was found to be over 50% higher than the PU coating. The current measured along the scratched surface of the PU–ATA/SiO2–TiO2 coating was found to be very low (1.65 nA). The enhanced ATA/SiO2–TiO2 nanoparticles inhibited the entry of electrolytes into the coating interface, as revealed by scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray diffraction analysis of the degradation products. Water contact angle testing validated the hydrophobic nature of the PU–ATA/SiO2–TiO2 coating (θ = 115.4°). When the concentration of ATA/SiO2−TiO2 nanoparticles was 2 wt %, dynamic mechanical analysis revealed better mechanical properties. Therefore, the newly synthesised PU–ATA/SiO2–TiO2 nanocomposite provided excellent barrier and mechanical properties due to the addition of ATA/SiO2–TiO2 nanoparticles to the polyurethane, which inhibited material degradation and aided in the prolongation of the coated steel’s life.

关键词： SiO2/TiO2 nanoparticle     nanocomposite coatings     dynamic mechanical analysis     electrochemical techniques     corrosion     colloids and interfaces    

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Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要： One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词： plastic concrete     sulfate resistance     natural zeolite     triaxial compression test     SEM     permeability    

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Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Chao CHEN, Huiyang ZHANG, Shengdun ZHAO, Xiaoqiang REN

《机械工程前沿（英文）》 2021年 第16卷 第2期   页码 410-419 doi: 10.1007/s11465-020-0618-y

摘要： The flat clinching process is attracting a growing attention in the joining field of lightweight materials because it avoids the geometric protrusion that appears in the conventional clinching process. In this paper, the effects of sheet thickness and material on the mechanical properties of the clinched joint were studied. Al1060 and Al2024 sheets with 2 mm thickness were employed to develop the clinched joint by using different material configurations, and Al1060 sheets with 2.5- and 1.5-mm thicknesses were used to produce the clinched joint by using different thickness configurations. The clinched joints using various sheet configurations were sectioned, and dimensional analysis was conducted. Cross-tensile and shearing tests were carried out to analyze the mechanical properties of the clinched joint, including tensile strength, shearing strength, and absorbed energy. In addition, the failure modes of the clinched joints were discussed. Results indicated that the clinched joint with a stiff top sheet had increased static strength regardless of the test type. The clinched joint with a thick top sheet demonstrated lower static strength than the joint with a thick bottom sheet in the cross-tensile test. However, this result was reversed in the shearing tests. The flat clinching process has a great potential in joining dissimilar and various thickness materials.

关键词： clinched joint     flat clinching process     thickness configuration     material configuration     mechanical property    

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Correction to: Effect of wood dust type on mechanical properties, wear behavior, biodegradability, and

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 1071-1071 doi: 10.1007/s11709-021-0736-6

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标题 作者 时间 类型 操作

Mechanical properties and microstructure of multilayer graphene oxide cement mortar

期刊论文

Facile synthesis of polyaniline nanorods to simultaneously enhance the mechanical properties and wear

期刊论文

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

期刊论文

Assessment and prediction of the mechanical properties of ternary geopolymer concrete

Jinliang LIU; Wei ZHAO; Xincheng SU; Xuefeng XIE

期刊论文

Influence of recycled polyethylene terephthalate fibres on plastic shrinkage and mechanical properties

Necat ÖZAŞIK; Özgür EREN

期刊论文

A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

期刊论文

Unified calculation method and its application in determining the uniaxial mechanical properties of concrete

Faxing DING, Xiaoyong YING, Linchao ZHOU, Zhiwu YU

期刊论文

Mechanical properties of vanadium-alloyed austempered ductile iron for crankshaft applications

期刊论文

Combination form analysis and experimental study of mechanical properties on steel sheet glass fiber

期刊论文

Effects of coarse and fine aggregates on long-term mechanical properties of sea sand recycled aggregate

期刊论文

Dual cross-linked MXene/cellulose nanofiber/nickel alginate film with improved mechanical properties

期刊论文

Influence of surface modified mixed metal oxide nanoparticles on the electrochemical and mechanical properties

期刊论文

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

期刊论文

Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Chao CHEN, Huiyang ZHANG, Shengdun ZHAO, Xiaoqiang REN

期刊论文

Correction to: Effect of wood dust type on mechanical properties, wear behavior, biodegradability, and

期刊论文