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In-situ X-ray computed tomography tensile tests and analysis of damage mechanism and mechanical properties in laser powder b e d fused Invar 36 alloy

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Journal of Materials Science & Technology 2024年第8期175卷 29-46页

作者： Qidong yang Shuo yang Shiyu Ma Junhan Zhou Ye Zhou Rongzheng Huang kai wei Zhaoliang Qu Xujing yang Key Laboratory of Advanced Design and Simulation Techniques for Special Equipment Ministry of EducationHunan UniversityChangsha 410082China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of Precision Manufacturing for Extreme Service Performance Central South UniversityChangsha 410083China

Laser powder bed fusion(LPBF)is a potential additive manufacturing process to manufacture Invar 36 alloy components with complicated *** it inevitably introduces specific microstructures and pore defects,which will further influence the mechanical ***,aiming at exploring the LPBF process-related microstructures and pore defects,and especially their influences on the damage mechanism and mechanical properties,Invar 36 alloy was manufactured by LPBF under designed different laser scanning *** microstructure observations reveal that higher scanning speeds lead to equiaxed and short columnar grains with higher dislocation density,while lower scanning speeds result in elongated columnar grains with lower dislocation *** pore defects analyzed by X-ray computed tomography(XCT)suggest that the high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion(LOF)pores,and the excessively low laser scanning speed produces relatively small keyhole pores with high ***,the insitu XCT tensile tests were originally performed to evaluate the damage evolution and failure ***,high laser scanning speed causes brittle fracture due to the rapid growth and coalescence of initial lamellar LOF pores along the scan-ning *** laser scanning speed induces ductile fracture originating from unstable depressions in the surfaces,while metallurgical and keyhole pores have little impact on damage ***,the process-structure-property correlation is *** presence of high volume fraction of lamel-lar LOF pores,resulting from high scanning speed,leads to inferior yield strength and ***,specimens without LOF pores exhibit larger grain sizes and lower dislocation density at decreased scanning speeds,slightly reducing yield strength while slightly enhancing *** understanding lays the foundation for widespread applications of LPBF-processed Invar 36 alloy

关键词： Invar 36 alloy Laser powder bed fusion Microstructure Pore defects Mechanical property X-ray tomography in-situ tensile test

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Adaptive learning-based optimal tracking control system design and analysis of a disturbed nonlinear hypersonic vehicle model

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Science China(Technological Sciences) 2024年第6期67卷 1893-1906页

作者： AN kai WANG ZhenGuo HUANG wei Hypersonic Technology Laboratory National University of Defense TechnologyChangsha410073China

We propose an adaptive learning-based optimal control scheme for height-velocity control models considering model uncertainties and external disturbances of hypersonic winged-cone *** longitudinal nonlinear model is first established and transformed into the control-oriented error equations,and the control scheme is organized by a steady-compensation *** overcome and eliminate the impact of model uncertainties and external disturbances,an adaptive radial basis function neural network(RBFNN)is designed by a q-gradient *** the height-velocity error system with estimated uncertainties into account,the adaptive learning-based optimal tracking control(ALOTC)scheme is proposed by combining the critic-only adaptive dynamic programming(ADP)framework and parameter optimization of system settling ***,a novel weight update law is proposed to satisfy the online iteration requirements,and the algorithm convergence and closedloop stability are discussed by the Lyapunov ***,four simulation cases are provided to prove the effectiveness,accuracy,and robustness of the proposed scheme for the hypersonic longitudinal control system.

关键词： optimal tracking control adaptive dynamic programming RBFNN hypersonic vehicle

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Modeling on impact zone volume generated by coherent supersonic jet and conventional supersonic jet

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Journal of Iron and Steel Research International 2018年第7期25卷 681-691页

作者： Guang-sheng wei Rong Zhu Ling-zhi yang kai Dong Run-zao Liu School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Beijing Key Laboratory of Research Center of Special Melting and Preparation of High-end Metal Materials University of Science and Technology Beijing Beijing 100083 China School of Minerals Processing and Bioengineering Central South University Changsha 410083 Hunan China

The supersonic oxygen supply technology, including the coherent supersonic jet and the conventional supersonic jet, is now widely adopted in electric arc furnace steelmaking process to increase the bath stirring, reaction rates and energy efficiency. However, there has been limited study on the impact characteristics of the coherent supersonic jet and the conventional supersonic jet. Thus, integrating theoretical models and numerical simulations, an optimized theoretical model was developed to calculate the volume of the impact zone generated by coherent and conventional supersonic jets. The optimized theoretical model was validated by water model experiments. The results show that the jet impact zone volume with coherent supersonic jet is much larger than that with conventional supersonic jet at the same lance height. The kd value, a newly defined variable that is the product of the dimensionless quantity of velocity and free distance, reflects the velocity attenuation and the potential core length of the main supersonic jet, which is a key parameter of the optimized theoretical model. The optimized theoretical model can well predict the jet impact zone volumes of coherent and conventional supersonic jets with the error no more than 3.62 and 9.37%, respectively.

关键词： Coherent supersonic jet Conventional supersonic jet Impact zone volume Numerical simulation Optimized theoretical model

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Leaching improvement of ceramic cores for hollow turbine blades based on additive manufacturing

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Advances in Manufacturing 2019年第4期7卷 353-363页

作者： wei-Jun Zhu Guo-Qiang Tian yang Lu kai Miao Di-Chen Li School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191People's Republic of China State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong UniversityXi'an 710049People's Republic of China School of Aeronautical Engineering Zhengzhou University of AeronauticsZhengzhou 450046People's Republic of China

The precision casting method based on aluminabased ceramic cores is one of the main techniques used to manufacture hollow turbine *** manufacturing(AM)technology provides an alternate solution to fabricating ceramic cores quickly and *** the complexity of the structure increases and the strength of the material improves,the leaching process of the cores becomes more *** study proposes a compound pore-forming method to increase the porosity of ceramic cores by adding a preformed-pore agent and materials that convert to easy-to-corrode *** preformed-pore agents(e.g.,carbon fibers)can be burned off during sintering to form pores before the leaching,and the easy-to-corrode phases(e.g.,CaCO3,SiO2,^-A12O3)can be leached firstly to form pores during the leaching *** pores formed in the aforementioned two stages increase the contact area of the cores and leaching solution,thus improving the leaching *** the current study,the additive amount of the preformed-pore agent was optimized,and the effect of the easy-to-corrode phases on the comprehensive properties of the cores was then *** on this,the corresponding model was established.

关键词： Alumina-based ceramic core Leaching Alkali solution Additive manufacturing(AM) Stereolithography

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Spheroidizing Behavior and Spheroidizing Kinetics of W-phase During Solid-Solution Treatment in Mg–Zn–Y–Mn–(B)Alloys

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Acta Metallurgica Sinica(English Letters) 2017年第5期30卷 464-469页

作者： kai yang Jin-Shan Zhang Xi-Mei Zong wei Liu Chun-Xiang Xu College of Materials Science and Engineering TaiyuanUniversity of Technology Taiyuan 030024 China Shanxi Key Laboratory of Advanced Magnesium-based Materials Taiyuan 030024China

The spheroidizing mechanism of W-phase in the Mg–Zn–Y–Mn–（B） alloys during solid-solution treatment was investigated by using kinetic methodologies. The microstructure and mechanical properties of heat-treated Mg_（94）Zn_（2.5）-Y_（2.5）Mn_1 alloy containing 0.003 wt% B were compared with heat-treated Mg_（94）Zn_（2.5）-Y_（2.5）Mn_1 alloy. The heat-treated Mg_（94）Zn_（2.5）-Y_（2.5）Mn_1 alloy with 0.003 wt% B contained fine and uniform W-phase particles, which exhibited optimal mechanical performance. The ultimate tensile strength, yield strength and elongation were 287.7, 125.5 MPa and 21.1%,respectively.

关键词： Magnesium alloys W-phase Spheroidizing Kinetics Microstructure Mechanical properties

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Photocatalytic activity of ferric oxide/titanium dioxide nanocomposite films on stainless steel fabricated by anodization and ion implantation

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International Journal of Minerals,Metallurgy and Materials 2013年第8期20卷 725-732页

作者： wei-ting Zhan Hong-wei Ni Rong-sheng Chen Gao Yue Jun-kai Tai Zi-yang Wang Key Laboratory for Ferrous Metallurgy and Resources Utilization of the Ministry of Education Wuhan University of Science and Technology

A simple surface treatment was used to develop photocatalytic activity for stainless steel. AISI 304 stainless steel specimens after anodization were implanted by Ti ions at an extracting voltage of 50 kV with an implantation dose of 3 × 10^15 ***-2 and then annealed in air at 450℃ for 2 h. The morphology was observed by scanning electron microscopy. The microstructure was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The photocatalytic degradation of methylene blue solution was carried out under ultraviolet light. The corrosion resistance of the stainless steel was evaluated in NaCl solution （3.5 wt%） by electrochemical polarization curves. It is found that the Ti ions depth profile resembles a Gaussian distribution in the implanted layer. The nanostructured Fe203/TiO2 composite film exhibits a remarkable enhancement in photocatalytic activity referenced to the mechanically polished specimen and anodized specimen. Meanwhile, the annealed Ti-implanted specimen remains good corrosion resistance.

关键词： surface treatment stainless steel nanocomposite films photocatalysis ion implantation electrochemicalanodization

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A DISSIPATION-PRESERVING INTEGRATOR FOR DAMPED OSCILLATORY HAMILTONIAN SYSTEMS

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Journal of Computational Mathematics 2022年第4期40卷 570-588页

作者： wei Shi kai Liu College of Mathematical Sciences Nanjing Tech UniversityNanjing 211816China School of Statistics and Data Science Nanjing Audit UniversityNanjing 210023China

In this paper,based on discrete gradient,a dissipation-preserving integrator for weakly dissipative perturbations of oscillatory Hamiltonian system is *** solution of this system is a damped nonlinear ***,lots of nonlinear oscillatory mechanical systems including frictional forces lend themselves to this *** new integrator gives a discrete analogue of the dissipation property of the original ***,since the integrator is based on the variation-of-constants formula for oscillatory systems,it preserves the oscillatory structure of the *** properties of the new integrator are *** convergence is analyzed for the implicit iterations based on the discrete gradient integrator,and it turns out that the convergence of the implicit iterations based on the new integrator is independent of k Mk,where M governs the main oscillation of the system and usually k Mk≫*** significant property shows that a larger stepsize can be chosen for the new schemes than that for the traditional discrete gradient integrators when applied to the oscillatory Hamiltonian *** experiments are carried out to show the effectiveness and efficiency of the new integrator in comparison with the traditional discrete gradient methods in the scientific literature。

关键词： Weakly dissipative systems Oscillatory systems Structure-preserving algorithm Discrete gradient integrator Sine-Gordon equation Continuousα-Fermi-Pasta-Ulam system

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Effect of Ni interlayer on microstructures and mechanical properties of 2205 duplex stainless steel joint by laser oscillating welding

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Journal of Iron and Steel Research International 2024年第10期31卷 2463-2474页

作者： Jing-wei yang Xu-yang Liu Tao Li Lai-cai Chen kai yang Zong-ye Ding Jie Zhang Jian Qiao School of Mechatronic Engineering and Automation Foshan UniversityFoshan528000GuangdongChina Key Laboratory of Advanced Manufacturing Technology of the Ministry of Education Guizhou UniversityGuiyang550025GuizhouChina State Key Laboratory of Advanced Brazing Filler Metals&Technology Zhengzhou Research Institute of Mechanical Engineering Co.Ltd.Zhengzhou450001HenanChina China National United Engineering Laboratory for Advanced Bearing Tribology Henan University of Science and TechnologyLuoyang471023HenanChina School of Mechanical Engineering University of Science and Technology BeijingBeijing100083China

Laser oscillating welding of 2205 duplex stainless steel was performed using Ni interlayer as filler *** influence of stirring effect caused by laser oscillating and Ni addition in the behavior of molten pool and the microstructure evolution was *** results shows that Ni addition decreased the ratio of chromium equivalent and nickel equivalent in the molten pool and accelerated the austenitic *** austenite/ferrite ratio was regulated,and the precipitation of nitrides was suppressed in the weld *** stirring effect caused by the oscillating beam facilitated the uniform distribution of Ni elements within the molten pool,promoting the formation of the homogeneous microstructures in the weld *** increasing the thickness of Ni interlayer,both the dimension and the peak temperature of molten pool decrease,further increasing the cooling rate and refining the grain *** the thickness of Ni interlayer was 50μm,the austenite/ferrite ratio in the weld seam was close to 1:1,and the grain size reached the minimum *** tensile strength and ductility of the welded joint using Ni interlayer with thickness were 774 MPa and 25%,respectively,significantly improving the mechanical properties of 2205 duplex stainless steel joint welded without Ni addition.

关键词： 2205 duplex stainless steel Ni interlayer Laser welding Microstructure Mechanical property

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Field observation of debris-flow activities in the initiation area of the Jiangjia Gully, Yunnan Province, China

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Journal of Mountain Science 2022年第6期19卷 1602-1617页

作者： yang Hong-juan ZHANG Shao-jie HU kai-heng wei Fang-qiang WANG kai LIU Shuang Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China

The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has mainly been studied by experiments in this watershed. To further reveal debris-flow formation mechanism in the Jiangjia Gully, debris-flow activities in the initiation zone were observed with hand-held video cameras in the summer of 2016 and 2017. In these two years, six debris-flow events were triggered in Menqian Gully, a major tributary of the Jiangjia Gully, while debrisflow activities in some sub-watersheds of Menqian Gully were recorded with video cameras in four events. The video recording shows that landslides constituted an important source for sediment supply in debris flow. Some landslides directly evolved into debris flows, while the others released sediment into rills and channels, where debris flows were generated for sediment entrainment by water flow. Therefore, debris-flow occurrence in the Jiangjia Gully is influenced both by infiltration-dominated processes and by runoff-dominated processes. In addition, rainfall data from four gauges installed in Menqian Gully were analyzed using mean intensity(I), duration(D), peak 10-minute rainfall(R10min) and antecedent rainfall(AR) up to 15 days prior to peak 10-minute rainfall. It reveals that debris-flow triggering events can be discriminated from nontriggering events either by an I-D threshold or by an R10min-AR threshold. However, false alarms can be greatly reduced if these two kinds of thresholds are used together. Moreover, behaviors including intermittency of debris flow, variance in moisture content and volume among surges, and coalescence of multiple surges by temporary damming were observed, indicating the complexity of debris-flow initiation processes. These findings are expected to enhance our knowledge on debris-flow formation mechanism in regions with similar environmental settin

关键词： Debris flow Field observation Initiation mechanism Rainfall threshold Jiangjia gully

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Hierarchical porous NiO as a noble-metal-free cocatalyst for enhanced photocatalytic H_(2) production of nitrogen-deficient g-C_(3)N_(4)

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Rare Metals 2022年第2期41卷 396-405页

作者： Yu-wei Liao Jing yang Guo-Hong Wang Juan Wang kai Wang Su-Ding Yan College of Chemistry and Chemical Engineering Hubei Normal UniversityHuangshi 435002China Hubei Key Laboratory of Pollutant Analysis and Reuse Technology Hubei Normal UniversityHuangshi 435002China

Graphitic carbon nitride with nitrogen vacancies(NV-g-C_(3)N_(4))as a photocatalyst has been studied in solardriven energy ***,expensive and rare noble metal co-catalysts such as Pt or Pd are required in the photocatalytic H_(2)***,the exploration of low-cost and high-performance co-catalysts to replace expensive and rare noble metals has received more and more ***,a novel hierarchical porous NiO anchored on NV-g-C_(3)N_(4)is successfully *** NV-g-C_(3)N_(4)/NiO photocatalysts exhibited outstanding H_(2)evolution rate under visible light irradiation in absence of noble metal *** optimized NV-g-C_(3)N_(4)/NiO(the mass ratio of NiO is*1.7%)achieved a maximum H2 evolution rate of 170.60 lmol·g^(-1)·h^(-1),exhibiting*8.3-fold enhancement as compared to that of *** as co-catalyst provided more active sites for photocatalytic H2 ***,on the interface of NV-g-C_(3)N_(4)/NiO,an interface electric field is formed between NiO and host nitrogen-vacated g-C3N4,facilitating the transfer of the photogenerated electrons from NV-g-C_(3)N_(4)to NiO co-catalyst,resulting in significantly promoted migration and separation efficiency of the photogenerated charge carriers.

关键词： Graphitic carbon nitride Hierarchical porous NiO Photocatalysis H_(2)evolution

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