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A NEURAL NETWORK FOR WELD PENETRATION CONTROL IN GAS TUNGSTEN ARC WELDING

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Acta Metallurgica Sinica(English Letters) 2006年第1期19卷 27-33页

作者： C.S. Wu J. Q. Gao y.h. Zhao Institute of Materials Joining Shandong University Jinan 250061 China

Realizing of weld penetration control in gas tungsten arc welding requires establishment of a model describing the relationship between the front-side geometrical parameters of weld pool and the back-side weld width with sufficient accuracy. A neural network model is developed to attain this aim. Welding experiments are conducted to obtain the training data set （including 973 groups of geometrical parameters of the weld pool and back-side weld width） and the verifying data set （108 groups）. Two data sets are used for training and verifying the neural network, respectively. The testing results show that the model has sufficient accuracy and can meet the requirements of weld penetration control.

关键词： neural network weld penetration control back-side weld width,gas tungsten arc welding

ATOMIZATION CAUSED By BOTTOM FLOW ENERGy DISSIPATION

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Journal of hydrodynamics 2001年第1期13卷 23-27页

作者： hu, M.L. Liang, Z.C. Zeng, y.h. Wuhan Univ. of hydraulic and Electr. Wuhan 430072 China

Bottom flow energy dissipation is one of the common energy dissipation methods for flood-releasing structures with high water head. Measures of this energy dissipation depend mainly on the turbulent action of hydraulic jump. In this paper, the physical process and the calculating methods of the atomization caused by bottom flow energy dissipation were studied, the computation models of atomization quantity for the self-aerated flow in overflow and hydraulic jump regions are presented, and the main results are of theoretical and practical significance for the hydraulic and electric engineering.

关键词： Energy dissipation hydraulic jump hydrodynamics

TENSILE PROPERTIES AND CREEP RESISTANCE OF AZ91 ALLOy CONTAINING ANTIMONy

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Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 867-871页

作者： yuan, G.y. Sun, y.S. Zhang, W.M. Bao, y.h. Southeastern Univ Nanjing China

Small amount of antimony addition to the Mg-9Al-0.8Zn-0.2Mn(AZ91) alloy results in the obvious increase of tensile strength at both ambient and elevated temperatures. The creep resistance at the temperatures up to 200°C is also improved significantly by antimony addition. Microstructural observations revealed that the addition of antimony modifies morphology of the β(Mg17Al12) phase and causes the formation of some rod-shaped precipitates Mg3Sb2 at grain boundaries. These precipitates have high thermal stability and play an important role for strengthening grain boundaries at elevated temperatures.

关键词： Aluminum alloys Antimony Automobile materials Creep testing Grain boundaries Microstructure Tensile stress Tensile testing Zinc alloys

LOW CyCLE FATIGUE AND CREEP-FATIGUE BEhAVIOR OF A hIGh TEMPERATURE ALLOy ON SMOOTh AND NOTChED SPECIMENS

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Acta Metallurgica Sinica(English Letters) 1999年第1期12卷 40-45页

作者： Shi, h.J. Liu, S.L. he, y.h. duan, Z.X. Tsinghua Univ Beijing China

A series of low cycle fatigue and creepfatigue tests on smooth specimens and notched specimens were performed with a high temperature alloy used in the manufacture of aeroengine turbine discs. The cyclic stressstrain behavior and fracture characteristics of the notched specimens were emphatically investigated. A comparison of fatigue behavior between smooth and notched specimens was done and lifetime of notched specimens was evaluated. At the same temperature, the fatiguecreep lives of the smooth specimens are far greater than that of the notched specimens.

关键词： low cycle fatigue creepfatigue stress concentration notch effect

Template-free Fabrication and Luminescent Characterization of highly Uniform and Monodisperse y_2O_2S:Sm^(3+) hollow Submicrospheres

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Journal of Materials Science & Technology 2012年第7期28卷 666-672页

作者： S.Q. Deng Z.P. Xue y.h. yang Q. yang y.L. Liu Department of Chemistry Jinan University Guangzhou 510632 China

Well dispersed and homogeneous y2O2S：Sm3＋ hollow submicrospheres were successfully achieved by a template- free solvothermal method combining with a postcalcining process. The crystalstructure and particle morphology were investigated by the X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectra, scanning and transmission electron microscopy （SEM and TEM）, respectively. A possible growth mechanism was proposed to reveal the formation process. Luminescence properties of the y202S：Sm3＋ long-lasting phosphor were an- alyzed by measuring the excitation spectra, emission spectra, afterglow decay curve and thermoluminescence curve. The excitation spectra indicated that the phosphor could be excited effectively by the ultraviolet-light emitting diode （UV-LED） or blue LED, and the emission spectra showed that the phosphor could emit red light from 600 to 650 nm.

关键词： yttrium oxysulfide hollow submicrosphere Luminescence Long-lasting phosphor

CONSTITUTIVE RELATIONShIP OF IN718 ALLOy FOR ThERMOVISCOPLASTIC AND MICROSTRUCTURE EVOLUTION COUPLED ANALySIS

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Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 373-379页

作者： D. Liu y.h. yang J. Geng Z.J. Luo School of Materials Science Northwestern Polytechnical University Xi＇an 710072 China

The interaction between thermomechanical parameters and microstructure evolution is so intense that it must be considered during the finite element method （FEM） simulation of the hot plastic working process, for materials that are difficult to deform. Taking the microstructure evolution into account, a novel type of constitutive relationship has been put forward for the IN718 alloy. The microstructure evolution model was first established for the dominant microstructure evolution processes. Then the microstructure evolution models and the method to determine the local flow stress of the corresponding microstructure for current thermomechanical parameters and deformation history were presented. Once the local flow stresses of different structures and their volume contributions were defined, the apparent flow stress of the material could be determined as the weighted sum of the local flow stresses and volume contributions. To validate the proposed method, a thermoviscoplastics and microstructure evolution coupled analysis for a forging process of a critical IN718 disk forging was performed. The predicting results were in close agreement with the experimental data.

关键词： constitutive relationship microstructure evolution numerical simulation IN718 alloy

Main α relaxation and slow β relaxation processes in a La30Ce30Al15Co25 metallic glass

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Journal of Materials Science & Technology 2019年第6期35卷 982-986页

作者： J.C. Qiao y.h. Chen R. Casalini J.M. Pelletier y. yao School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi'an 710072 China Chemistry Division Naval Research Laboratory Code 6120 Washington DC 20375-5342 United States Universite de Lyon MATEIS UMR CNRS5510 Bat. B. Pascal INSA-Lyon F-69621 Villeurbanne cedex France

Dynamic relaxation processes are fundamental to understand the mechanical and physical properties of metallic glasses. In the current work, mechanical relaxations in a La30Ce30Al15Co25 bulk metallic glass were probed by dynamic mechanical analysis. In contrast to many metallic glasses, La30Ce30Al15Co25 metallic glass shows a pronounced slow β relaxation peak. Physical aging below the glass transition temperature Tgleads to an increase of the apparent activation energy and a decrease of the slow β relaxation magnitude. The correlation between the slow β relaxation and the main α relaxation is discussed.

关键词： Mechanical relaxation Dynamic mechanical relaxation α Relaxation β relaxation Physical aging

MICROSTRUCTURAL EVOLUTION OF hIGhLy UNDERCOOLED EUTECTIC Ni78.6 Si21.4 ALLOy

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Acta Metallurgica Sinica(English Letters) 2006年第1期19卷 43-50页

作者： y.P. Lu G. C. yang C.L. yang h.P. Wang y.h. Zhou State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi＇an 710072 China Department of Applied Physics Northwestern Polytechnical University Xi＇an 710072China

A large undercooling level up to 550K （0.386Te） was achieved in eutectic Ni78.6Si21.4melt by the combination of molten-glass and cyclic superheating. A microcrystaUine structure is obtained at large undercooling. Surprisingly, the morphology of ct（Ni） phase transits from the non-faceted phaseto faceted phase at large undercooling of 390K. Based on the classical nucleation theory and transient nucleation theory, the process of microstructure evolution and competitive nucleation was analyzed, and the refinement of crystal structure is determined by the high nucleation rate under large undercooling.

关键词： high undercooling molten-glass eutectic rapid solidification

INFLUENCE OF FIBER COATING ON TENSILE BEhAVIOR OF UNIDIRECTIONAL C/Mg COMPOSITES

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 398-402页

作者： Zhang, K. Wang, y.Q. Zhou, B.L. Zhou, y.h. Li, h.L. Inst of Metal Research Chinese Acad of Sciences Shenyang China

The mechanical properties and deformation mechanisms of unidirectional carbon fiber reinforced magnesium composites under tensile loading are studied. Two different materials are used as fiber coatings: a single silica and a gradient C/SiC/SiO[sb 2]. The results show that, under the same preparation conditions, composite with the former coating is broken in a non-cumulative mode and its failure stress is rather low. Conversely, the latter coating demonstrates much better efficiency and the corresponding composite is broken in a cumulative mode.

关键词： Metallic matrix composites Carbon fibers Tensile strength Elastic moduli Coatings Silica Deformation Crack propagation Crack initiation Fracture Stresses Strain