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基于状态空间模型的激光再制造熔池温度控制系统

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表面工程与再制造 2024年第2期24卷 50-50页

作者： yang G.-Z. liu T.-m. Song b.-X. jiang X.-y. Wang Z.-S. chen K.-Q. liu W.-j. School of mechanical Engineering Shenyang University of Technology Shenyang China

激光再制造是用于再制造的一项重要技术,在航空航天、冶金、能源等领域应用广泛。然而,形状控制问题一直是制约其规模化和工业化应用的瓶颈。在激光再制造过程中,熔池温度是决定再制造件形状和性能稳定性的关键。基于此,本文提出了一种... 详细信息

激光再制造是用于再制造的一项重要技术,在航空航天、冶金、能源等领域应用广泛。然而,形状控制问题一直是制约其规模化和工业化应用的瓶颈。在激光再制造过程中,熔池温度是决定再制造件形状和性能稳定性的关键。基于此,本文提出了一种基于状态空间模型的激光再制造熔池温度实时在线控制方法,解决了控制机理模型难以建立和多变量约束的问题。

关键词：状态空间模型激光再制造熔池温度航空航天形状控制控制系统变量约束性能稳定性

Verification of Seasonal Prediction by the Upgraded china multi-model Ensemble Prediction System(CmmEv2.0)

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journal of meteorological Research 2024年第05期 880-900页

作者： jie WU Hong-Li REN jianghua WAN jingpeng liu jinqing ZUO Changzheng liu ying liu yu NIE Chongbo ZHAO Li GUO bo LU Lijuan chen Qing bAO jingzhi SU Lin WANG jing-jia LUO Xiaolong jIA Qingchen CHAO CmA Key Laboratory of Climate Prediction Studies National Climate Centre China Meteorological Administration (CMA) Collaborative Innovation Center on Forecast and Evaluation of meteorological Disasters Nanjing University of Information Science & Technology State Key Laboratory of Severe Weather and Institute of Tibetan Plateau meteorology Chinese Academy of Meteorological SciencesChina Meteorological Administration State Key Laboratory of Numerical modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences CmA Earth System modeling and Prediction Centre China Meteorological Administration

based on a combination of six Chinese climate models and three international operational models, the china multimodel ensemble (CmmE) prediction system has been upgraded into its version 2 (CmmEv2.0) at the National Climate Centre (NCC) of the china meteorological Administration (CmA) by including new model members and expanding prediction products. A comprehensive assessment of the performance of the upgraded CmmE during its hindcast (1993–2016) and real-time prediction (2021–present) periods is conducted in this study. The results demonstrate that CmmEv2.0 outperforms all the individual models by capturing more realistic equatorial sea surface temperature (SST) variability. It exhibits better prediction skills for precipitation and 2-m temperature anomalies, and the improvements in prediction skill of CmmEv2.0 are significant over East Asia. The superiority of CmmEv2.0 can be attributed to its better projection of El Ni?o–Southern Oscillation (ENSO; with the temporal correlation coefficient score for Ni?o3.4 index reaching 0.87 at 6-month lead) and ENSO-related teleconnections. As for the real-time prediction in recent three years, CmmEv2.0 has also yielded relatively stable skills; it successfully predicted the primary rainbelt over northern china in summers of 2021–2023 and the warm conditions in winters of 2022/2023. beyond that, ensemble sampling experiments indicate that the CmmEv2.0 skills become saturated after the ensemble model number increased to 5–6, indicating that selection of only an optimal subgroup of ensemble models could benefit the prediction performance, especially over the extratropics, yet the underlying reasons await future investigation.

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microstructural features of Ti-6Al-4V manufactured via high power laser directed energy deposition under low-cycle fatigue

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journal of materials Science & Technology 2021年第24期83卷 18-33页

作者： y.m.Ren X.Lin H.O.yang H.Tan j.chen Z.y.jian j.Q.Li W.D.Huang School of materials and Chemical Engineering Xi’an Technological UniversityXi’an710021China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China

Laser additive manufacturing(LAm)technique has unique advantages in producing geometrically complex metallic ***,the poor low-cycle fatigue property(LCF)of LAm parts restricts its widely ***,the microstructural features of a Ti-6 Al-4 V alloy manufactured via high power laser directed energy deposition subjected to low-cycle fatigue loading were *** fatigue loading,the microstructure of the as-deposited parts was found to exhibit a non-homogeneous distribution of columnar prior-βgrains(200-4000μm)at various scanning velocities(300-1500 mm/min)and relatively coarseα-laths(1.0-4.5μm).Under cyclic loading,fatigue microcracks typically initiated within the alignedαphases in the preferred orientation(45°to the loading direction)at the surface of the fatigue *** Ti-6 Al-4 V exhibited a single straight dislocation character at low strain amplitudes(mplitudes(>1.1%).In addition,dislocation substructure features,such as dislocation walls,stacking faults,and dislocation networks,were also *** findings may provide opportunities to understand the fatigue failure mechanism of additive manufactured titanium parts.

关键词： Laser additive manufacturing Directed energy deposition Titanium alloy Low-cycle fatigue microstructure

Improvement of Weld Quality Using a Weaving beam in Laser Welding

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journal of materials Science & Technology 2004年第5期20卷 633-636页

作者： xudong ZHANG, Wuzhu chen, Gang bAO and Lin ZHAODepartment of mechanical Engineering, tsinghua university, beijing 100084, china Dept. of mech. Eng. Tsinghua Univ. Beijing 100084 China

This paper describes a way to improve the weld quality through suppressing the porosity formation and restraining the growth of columnar grains by using a weaving beam in laser welding. The experimental results show that the N2 porosity of beam-weaving laser welding low carbon steel can be remarkably reduced with increasing weaving frequency, and porosity can be eliminated when the weaving amplitude is only 0.5 mm; and the Ar porosity in the weld metal is decreased with increasing weaving frequency and amplitude when the welding speed is higher than 0.5 m/min. The beam-weaving laser welding of ultra-fine grained steel has been investigated. The experimental results show that beam-weaving laser welding with appropriate amplitude and frequency can partly restrain the growth of the columnar grain and improve the tensile strength of the weld metal.

关键词： Welding beam weaving Porosity Tensile strength

THE FAILURE mECHANISm OF REVERSE SHAPE mEmORyEFFECT IN A Cu-bASE ALLOy

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Acta metallurgica Sinica(English Letters) 1997年第3期10卷 203-205页

作者： C.m Li G.X. Dong S.T- Dai and D. y chen (tsinghua university beijing 100084, china)j yin and D.X. Hu (Shanghai No.5 Steel Works, Shanghai 200940, china) tsinghua Univ Beijing China

The interior structural evolution accompanying reverse shape memory effect (RSmEin a Cu-Zn-Al alloy was studied by means of transmission electron microscopy. It was found that RSmE is closely related to bainitic transformation in this alloy during the isothermal reaction at moderate temperatures. At a given temperature and a certain external constraint stress, the shape memory effect depends mainly on the aging *** the early stage, the shape memory effect enhances with the increase of reactiotn time. Then it will decrease gradually apon further aging. If the alloy is overaged, the stacking faults of bainite will disappear gradually by the motion of partial dislocations through which long range diffusion of solute atoms takes place, giving rise to the deterioration of RSmE. When all the bainite transforms to α phase, RSmE will lose completely.

关键词： reverse shape memory effect Cu-base alloy stacking fault bainite

Grain boundary engineering for enhancing intergranular damage resistance of ferritic/martensitic steel P92

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Nuclear Science and Techniques 2024年第5期35卷 186-199页

作者： Lei Peng Shang-ming chen jing-yi Shi yong-jie Sun yi-Fei liu yin-Zhong Shen Hong-ya He Hui-juan Wang jie Tian State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China School of materials Engineering Shanghai University of Engineering Science333 Long Teng RoadShanghai 201620China Experimental Center of Engineering and material Science University of Science and Technology of ChinaHefei 230026China

Ferritic/martensitic(F/m)steel is widely used as a structural material in thermal and nuclear power ***,it is susceptible to intergranular damage,which is a critical issue,under service *** this study,to improve the resistance to intergranular damage of F/m steel,a thermomechanical process(TmP)was employed to achieve a grain boundary engineering(GbE)microstructure in F/m steel *** TmP,including cold-rolling thickness reduction of 6%,9%,and 12%,followed by austenitization at 1323 K for 40 min and tempering at 1053 K for 45 min,was applied to the as-received(AR)P92 *** prior austenite grain(PAG)size,prior austenite grain boundary character distribution(GbCD),and connectivity of prior austenite grain boundaries(PAGbs)were *** to the AR specimen,the PAG size did not change *** fraction of coincident site lattice boundaries(CSLbs,3≤Σ≤29)and Σ3^(n) boundaries along PAGbs decreased with increasing reduction ratio because the recrystallization fraction increased with increasing reduction *** PAGb connectivity of the 6%deformed specimen slightly deteriorated compared with that of the AR ***,potentiodynamic polarization studies revealed that the intergranular damage resistance of the studied steel could be improved by increasing the fraction of CSLbs along the PAGbs,indicating that the TmP,which involves low deformation,could enhance the intergranular damage resistance.

关键词： Grain boundary engineering Ferritic/martensitic steel Prior austenite grain boundary character distribution Grain boundary connectivity Intergranular damage resistance

Siliceous mesocellular foam supported Cu catalysts for promoting non-thermal plasma activated CO_(2) hydrogenation toward methanol synthesis

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Frontiers of Chemical Science and Engineering 2024年第7期18卷 55-65页

作者： yi chen Shaowei chen yan Shao Cui Quan Ningbo Gao Xiaolei Fan Huanhao chen State Key Laboratory of materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 211816China School of Environmental Science and Engineering Nanjing Tech UniversityNanjing 211816China School of Energy and Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Department of Chemical Engineering School of EngineeringThe University of ManchesterManchester M139PLUK Nottingham Ningbo china beacons of Excellence Research and Innovation Institute University of Nottingham Ningbo ChinaNingbo 315048China Institute of Wenzhou Zhejiang UniversityWenzhou 325006China

Electrified non-thermal plasma (NTP) catalytic hydrogenation is the promising alternative to the thermal counterparts, being able to be operated under mild conditions and compatible with green electricity/hydrogen. Rational design of the catalysts for such NTP-catalytic systems is one of the keys to improve the process efficiency. Here, we present the development of siliceous mesocellular foam (mCF) supported Cu catalysts for NTP-catalytic CO_(2) hydrogenation to methanol. The findings show that the pristine mCF support with high specific surface area and large mesopore of 784 m2·g−1 and ~8.5 nm could promote the plasma discharging and the diffusion of species through its framework, outperforming other control porous materials (viz., silicalite-1, SiO_(2), and SbA-15). Compared to the NTP system employing the bare mCF, the inclusion of Cu and Zn in mCF (i.e., Cu1Zn1/mCF) promoted the methanol formation of the NTP-catalytic system with a higher space-time yield of methanol at ~275 μmol·g_(cat)^(−1)·h^(−1) and a lower energy consumption of 26.4 kj^(−1)·mmol_(CH_(3)OH)^(-1) (conversely, ~225 μmol·g_(cat)^(−1)·h^(−1) and ~71 kj^(−1)·mmol_(CH_(3)OH)^(-1), respectively, for the bare mCF system at 10.1 kV). The findings suggest that inclusion of active metal sites (especially Zn species) could stabilize the CO_(2)/CO-related intermediates to facilitate the surface reaction toward methanol formation.

关键词： non-thermal plasma(NTP)catalysis Cu catalyst CO_(2)hydrogenation methanol siliceous mesocellular foam(mCF)

Seasonal compensation implied no weakening of the land carbon sink in the Northern Hemisphere under the 2015/2016 El Niño

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Science china Earth Sciences 2024年第1期67卷 281-294页

作者： Fangzhong SHI Xiuchen WU Xiaoyan LI Philippe CIAIS Hongyan liu Chao yuE yuting yANG Shulei ZHANG Shushi PENG yi yIN benjamin POULTER Deliang chen State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal UniversityBeijing 100875China Faculty of Geographical Science Beijing Normal UniversityBeijing 100875China Key Laboratory of Tibetan Plateau Land Surface Processes and Ecological Conservation Qinghai Normal UniversityXining 810016China Research and Development Center for Watershed Environmental Eco-Engineering Beijing Normal University(Zhuhai)Zhuhai 519085China Laboratoire des Sciences du Climat et de l’Environnement(LSCE) CEA-CNRS-UVSQUMR821291191Gif-sur-YvetteFrance College of Urban and Environmental Science MOE Laboratory for Earth Surface ProcessesPeking UniversityBeijing 100871China State Key Laboratory of Hydroscience and Engineering Department of Hydraulic EngineeringTsinghua UniversityBeijing 100084China Southern marine Science and Engineering Guangdong Laboratory(Zhuhai) School of Atmospheric SciencesSun Yat-sen UniversityGuangzhou 510275China California Institute of Technology PasadenaCA 91125USA biospheric Sciences Laboratory NASA Goddard Space Flight CenterGreenbeltMaryland 20771USA Regional Climate Group Department of Earth SciencesUniversity of GothenburgGothenburg SE-40530Sweden

The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)*** discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to march of the current year)had a positive *** seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation *** legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six *** findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.

关键词： El Niño Seasonal compensation effect Vegetation greening Land carbon sink Net ecosystem exchange Legacy effect

Improved mechanical properties of SiC fiber reinforced silica-based ceramic cores fabricated by stereolithography

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journal of materials Science & Technology 2022年第21期116卷 161-168页

作者： W.Zheng j.m.Wu S.chen K.b.yu j.Zhang y.S.Shi State Key Laboratory of materials Processing and Die&mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Engineering Research Center of Ceramic materials for Additive manufacturing Ministry of EducationWuhan 430074China

Silica-based ceramic cores have been widely used to fabricate aero-engine hollow blades due to their moderate high temperature mechanical properties and excellent *** this study,silica-based ceramics with SiC fiber addition were prepared via stereolithography,and the influence of SiC fiber content on mechanical properties of the obtained silica-based ceramics was *** the increase of SiC fiber content,linear shrinkage gradually decreased,while room temperature flexural strength and high temperature flexural strength first increased and then *** SiC fiber content increased to 4.0 wt%,linear shrinkage was reduced to 0.62%resulting from the oxidation of ***,room temperature flexural strength was improved from 11.79 mPa to 23.83 mPa and high temperature flexural strength was enhanced from 15.64 mPa to 34.62 mPa with 4.0 wt%SiC fiber addition due to the reinforcement of fibers and the enhancedβ-cristobalite content,which meets the need of ceramic ***,it demonstrates the capability of fabricating high-performance and high-precision silica-based ceramic cores reinforced by SiC fibers via stereolithography for rapid manufacturing of hollow blades.

关键词： Silica-based ceramic cores Stereolithography SiC fiber mechanical properties Hollow blades