检索结果-南通市图书馆

Experimental study on behavior of mortar-aggregate interface after elevated temperatures

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2017年第2期11卷 158-168页

作者： Wan WANG Jianzhuang XIAO Shiying XU Chunhui WANG Department of Structural Engineering Tongji University Shanghai 200092 China

A push-out test program was designed and conducted to study the meso-scale behavior of mortaraggregate interface for concrete after elevated temperatures ranging from 20℃ to 600℃ with the concept of modeled concrete （MC） and modeled recycled aggregate concrete （MRAC）. The MCs and MRACs were designed with different strength grade of mortar and were exposed to different elevated temperatures. Following that the specimens were cooled to room temperature and push-out tests were conducted. Failure process and mechanical behaviors were analyzed based on failure modes, residual load-displacement curves, residual peak loads and peak displacements. It is found that failure modes significantly depended on specimen type, the elevated temperature and the strength grade of mortar. For MC, major cracks started to propagate along the initial cracks caused by elevated temperatures at about 80% of residual peak load. For MRAC, the cracks appeared at a lower level of load with the increasing elevated temperatures. The cracks connected with each other, formed a failure face and the specimens were split into several parts suddenly when reaching the residual peak load. Residual load-displacement curves of different specimens had similarities in shape. Besides, effect of temperatures and strength grade of mortar on residual peak load and peak displacement were analyzed. For MC and MRAC with higher strength of new hardened mortar, the residual peak load kept constant when the temperature is lower than 400℃ and dropped by 43.5% on average at 600℃. For MRAC with lower strength of new hardened mortar, the residual peak load began to reduce when the temperatures exceeded 200℃ and reduced by 27.4% and 60.8% respectively at 400℃ and 600℃. The properties of recycled aggregate concrete （RAC） may be more sensitive to elevated temperatures than those of natural aggregate concrete （NAC） due to the fact that the interracial properties of RAC are lower than those of NAC, and are deteriorated at lower

关键词： mortar-aggregate interface push-out test elevated temperatures modeled concrete (MC) modeled recycled aggregate concrete (MRAC)

A new die-cast magnesium alloy for applications at higher elevated temperatures of 200-300℃

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2021年第1期9卷 90-101页

作者： Xixi Dong Lingyun Feng Shihao Wang Eric A.Nyberg Shouxun Ji Brunel Centre for Advanced Solidification Technology(BCAST) Brunel University LondonUxbridge UB83PHUnited Kingdom Tungsten Parts Wyoming LaramieWY 82072USA

The development of lightweight magnesium(Mg)alloys capable of operating at elevated temperatures of 200-300℃and the ability of using high pressure die casting for high-volume manufacturing are the most advanced developments in manufacturing critical parts for internal combustion engines used in power *** we report the microstructure and mechanical properties of a newly developed die-cast Mg-RE(La,Ce,Nd,Gd)-Al alloy capable of working at higher elevated temperatures of 200-300℃.The new alloy delivers the yield strength of 94 MPa at 300℃,which demonstrates a 42%increase over the benchmark AE44 high temperature die-cast Mg *** new alloy also has good stiffness at elevated temperatures with its modulus only decreasing linearly by 13%from room temperature up to 300℃.Thermal analysis shows a minor peak at 364.7℃in the specific heat curve of the new alloy,indicating a good phase stability of the alloy up to 300℃.Nd and Gd have more affinity to Al for the formation of the minority of divorced Al-RE(Nd,Gd)based compounds,and the stable Al-poor Mg_(12)RE(La_(0.22)Ce_(0.13)Nd_(0.31)Gd_(0.31))Zn_(0.39)Al_(0.13)compound acts as the continuous inter-dendritic network,which contribute to the high mechanical performance and stability of the new die-cast Mg alloy at 200-300℃.

关键词： Magnesium alloys High pressure die casting elevated temperatures Microstructure Mechanical properties

A new approach on necking constitutive relationships of ductile materials at elevated temperatures

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2016年第6期29卷 1626-1634页

作者： Yao Di Cai Lixun Bao Chen School of Mechanics and Engineering Southwest Jiaotong University

A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element analysis(FEA). An iteration method using FEA APDL(ANSYS parametric design language) programming has been developed to approach the necking constitutive relationship of materials. Test results from SAE 304 stainless steel at room temperature show that simulated load vs displacement curve,diameter at funnel root vs displacement curve, and funnel deformation contours are close to modeled results. Due to this new method, full-range constitutive relationships and true stress and effective true strain at failure are found for 316 L stainless steel, TA17 titanium alloy and A508-III stainless steel at room temperature, and 316 L stainless steel at various elevated temperatures.

关键词： Ductile material elevated temperatures Finite element aided testing(FAT) method Fracture stress-strain True stress-strain

Mechanism of aluminum corrosion in LiFSI-based electrolyte at elevated temperatures

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2021年第5期31卷 1439-1451页

作者： Chun-lei LI Shuang-wei ZENG Peng WANG Zhao-juan LI Li YANG Dong-ni ZHAO Jie WANG Hai-ning LIU Shi-you LI College of Petrochemical Technology Lanzhou University of TechnologyLanzhou 730050China CAS Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources Qinghai Institute of Salt LakeChinese Academy of SciencesXining 810008China

Lithium bis(fluorosulfonyl)imide(LiFSI) is a promising replacement for lithium hexafluorosphate due to its excellent properties. A solution to the corrosion of aluminum(Al) current collectors by LiFSI at elevated temperatures is essential. The mechanisms of Al corrosion in LiFSI-based electrolyte at 45 ℃ were studied with density functional theory calculations and spectroscopic investigations. It is found that the irregular, loose and unprotected AlF3 materials caused by the dissolution of co-generated Al(FSI)3 can exacerbate Al corrosion with the increase of temperature. Lithium bis(oxalate)borate(LiBOB) can effectively inhibit the Al corrosion with a robust and protective interphase;this can be attributed to the interfacial interactions between the Al foil and electrolyte. Boron-containing compounds promote the change from AlF3 to LiF, which further reinforces interfacial stability. This work allows the design of an interface to Al foil using LiFSI salt in lithium-ion batteries.

关键词： lithium-ion batteries LiFSI-based electrolyte lithium bis(oxalate)borate(LiBOB) corrosion inhibition elevated temperatures interfacial film

Behaviour of cold-formed stainless steel beams at elevated temperatures

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1507-1513页

作者： Ju CHEN Wei-liang JIN Department of Civil Engineering Zhejiang University Hangzhou 310058 China

A study of the behaviour of constructional cold-formed stainless steel beams at elevated temperatures was conducted in this paper. An accurate finite element model (FEM) for stainless steel beams was developed using the finite element program ABAQUS. Stainless steel beams having different cross-sections were simulated in this study. The nonlinear FEM was verified against the experimental results. Generally, the developed FEM could accurately simulate the stainless steel beams. Based on the high temperature stainless steel material test results, a parametric study was carried out on stainless steel beams at elevated tem- peratures using the verified FEM. Both high strength stainless steel EN 1.4462 and normal strength stainless steel EN 1.4301 were considered. A total of 42 stainless steel beams were simulated in the parametric study. The effect of temperatures on the behaviour of stainless steel beams was investigated. In addition, a limiting temperature for stainless steel beams was also proposed.

关键词： elevated temperatures Finite element model (FEM) Fire Stainless steel beams

Investigation of the friction coefficient evolution and lubricant breakdown behaviour of AA7075 aluminium alloy forming processes at elevated temperatures

在线全文

学校读者我要写书评

暂无评论

International Journal of Extreme Manufacturing 2021年第2期3卷 99-105页

作者： Xiao Yang Qunli Zhang Yang Zheng Xiaochuan Liu Denis Politis Omer El Fakir Liliang Wang Department of Mechanical Engineering Imperial College LondonSW72AZ LondonUnited Kingdom Department of Mechanical and Manufacturing Engineering University of Cyprus1678 NicosiaCyprus School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China

The lubricant behaviour at elevated temperatures was investigated by conducting pin-on-disc tests between P20 tool steel and AA7075 aluminium alloy. The effects of temperature, initial lubricant volume, contact pressure and sliding speed on the lubricant behaviour(i.e. evolutions of the coefficient of friction(COF) and the breakdown phenomenon) were experimentally studied. The evolutions of COF at elevated temperatures consisted of three distinct stages with different friction mechanisms. The first stage(stage Ⅰ) occurred with low friction when the boundary lubrication was present. The second stage(stage Ⅱ) was the transition process in which the COF rapidly increased as the lubricant film thickness decreased to a critical value. In the final plateau stage(stage Ⅲ), lubricant breakdown occurred and intimate contact at the interface led to high friction values. At the low friction stage(stage Ⅰ), the value of COF increased with increasing temperature. The increase in temperature, contact pressure and sliding speed as well as the decrease in initial lubricant volume accelerated the lubricant breakdown.

关键词： elevated temperatures friction evolution lubricant breakdown behaviour pin-on-disc test

Static behavior of offshore two-planar tubular KT-joints under axial loading at fire-induced elevated temperatures

在线全文

学校读者我要写书评

暂无评论

Journal of Ocean Engineering and Science 2019年第4期4卷 352-372页

作者： Neda Azari-Dodaran Hamid Ahmadi Faculty of Civil Engineering University of TabrizTabriz ***Iran

A total of 540 nonlinear steady-state finite element analyses were performed to study the influence of temperature and dimensionless geometrical parameters(β,γ,θ,andτ)on the ultimate strength,failure modes,and initial stiffness of two-planar tubular *** joints were analyzed under two types of axial loading and five different temperatures(20℃,200℃,400℃,550℃,and 700℃).So far,there has not been any equation available for calculating the ultimate strength of two-planar tubular KT-joints at elevated ***,after parametric study,a set of design formulas were developed through nonlinear regression analyses,to calculate the ultimate strength of two-planar tubular KT-joints subjected to axial loading at elevated temperatures.

关键词： Ultimate strength Two-planar tubular KT-joint Axial loading elevated temperatures Parametric equation

Perspectives on plant virus diseases in a climate change scenario of elevated temperatures

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Stress Biology 2022年第1期2卷 223-248页

作者： Wei‑An Tsai Christopher A.Brosnan Neena Mitter Ralf G.Dietzgen Centre for Horticultural Science Queensland Alliance for Agriculture and Food InnovationThe University of QueenslandSt.LuciaQLD 4072Australia

Global food production is at risk from many abiotic and biotic stresses and can be affected by multiple stresses *** diseases damage cultivated plants and decrease the marketable quality of ***,the progression of virus diseases is strongly affected by changing climate *** climate-changing vari-ables,temperature increase is viewed as an important factor that affects virus epidemics,which may in turn require more efficient disease *** this review,we discuss the effect of elevated temperature on virus epidem-ics at both macro-and micro-climatic *** includes the temperature effects on virus spread both within and between host ***,we focus on the involvement of molecular mechanisms associated with tempera-ture effects on plant defence to viruses in both susceptible and resistant *** various mechanisms proposed in different pathosystems,we also offer a view of the possible opportunities provided by RNA-based technologies for virus control at elevated ***,the potential of these technologies for topical field applications has been strengthened through a combination of genetically modified(GM)-free delivery *** approach represents a promising and important climate-resilient substitute to conventional strategies for managing plant virus diseases under global warming *** this context,we discuss the knowledge gaps in the research of temperature effects on plant-virus interactions and limitations of RNA-based emerging technologies,which should be addressed in future studies.

关键词： elevated temperatures Virus epidemics Plant virus control RNA-based approaches Nanoparticles

Correlation between test temperature, applied load and wear transition of Mg97Zn1Y2 alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2021年第2期9卷 592-603页

作者： J.An Y.X.Tian C.Q.Feng Key Laboratory of Automobile Materials Ministry of EducationDepartment of Materials Science and EngineeringJilin UniversityChangchun 130025PR China

Dry sliding wear tests were performed on Mg97 Zn1 Y2 alloy at various temperatures of 20,50,100,150 and 200°C using a pin-on-disc wear testing machine in order to reveal mild-severe(M-S)wear transition mechanism during elevated-temperature wear *** was shown that at each test temperature,the wear rate increased with increasing load,and all wear rate-load curves demonstrated two distinct stages *** and severe wear *** predominant wear mechanisms operating in mild and severe wear stages were analyzed,and they were indicated in the mild and severe wear regimes of a wear mechanism transition map,respectively.M-S wear transition mechanism was analyzed by comparison of microstructure transformation and hardness change in subsurfaces of samples tested in mild and severe wear stages,from which M-S wear transition mechanism was confirmed as softening of surface material arising from dynamic recrystallization(DRX)microstructure *** M-S wear transition load was found to have a linear relationship with test temperature,and decreased with rising test temperature.M-S wear transition obeyed a critical surface DRX temperature(SDT)criterion under given conditions,and the transition loads were estimated at various test temperatures by using the criterion.

关键词： Mg-alloys elevated temperatures Wear rate Wear mechanism Wear transition