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Indirect Measurement of Material Thermal and Mechanical Properties during Welding

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Journal of Materials Science & Technology 2003年第Z1期19卷 173-175页

作者： dongqing li Jun TAO Qingguo Meng Hongyuan FANG State Key Laboratory of Welding Harbin Institute of Technology 150001 Chins State Key Laboratory of Welding Harbin Institute of Technology 150001 Chins State Key Laboratory of Welding Harbin Institute of Technology 150001 Chins State Key Laboratory of Welding Harbin Institute of Technology 150001 Chins

By means of a newly developed non-contact detecting method, electronic speckle pattern interferometry (ESPI), a method of determining material property data during welding is studied. A TIG fixed-point welding process is modeled in which some achievements of simulation, such as the effect of welding pool on temperature field and nonlinear relation between convection coefficient and temperature, are all considered. In addition, by taking into account effect of heating rate, the workpiece is divided into near-weld zone and far-weld zone, which will be treated with different property values. When the displacement field computed with original property data is compared and matched with the experimental displacement field, which is measured by ESPI, these original data are adjusted properly. A group of raw properties are obtained and are corrected by statistical regression before they enter the simulation process *** such a loop of "simulation-comparison-modification", a set of property data that best satisfy the real condition are achieved finally. In such a way, a new method for measuring material properties during welding is found.

关键词： Material properties, Welding displacement field, Numerical simulation, ESPI

Local Buckling-Induced Forming Method to Produce Metal Bellows

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Chinese Journal of Mechanical Engineering 2023年第1期36卷 104-114页

作者： Tianyin Zhang dongqing li Tianjiao Xu Yongfeng Sui Xianhong Han Institute of Forming Technology&Equipment School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200030China Hangzhou Steam Turbine&Power Group Co. LtdHangzhou310100China National Engineering Research Center of Die and Mold CAD Shanghai Jiao Tong UniversityShanghai200030China

A novel buckling-induced forming method is proposed to produce metal *** tube billet is firstly treated by local heating and cooling,and the axial loading is applied on both ends of the tube,then the buckling occurs at the designated position and forms a *** this paper,a forming apparatus is designed and developed to produce both discontinuous and continuous bellows of 304 stainless steel,and their characteristics are discussed ***,the influences of process parameters and geometric parameters on the final convolution profile are deeply studied based on FEM *** results suggest that the steel bellows fabricated by the presented buckling-induced forming method have a uniform shape and no obvious reduction of wall ***,the forming force required in the process is quite small.

关键词： Buckling-induced forming Dieless No wall-thinning Stainless-steel bellows

Isothermal Oxidation Behavior of Dysprosium/S-Doped β-NiAl Alloys at 1200°C

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Journal of Materials Science & Technology 2014年第3期30卷 229-233页

作者： Lu Wang dongqing li Jian Chang Hongbo Guo Shengkai Gong Huibin Xu School of Materials Science and Engineering Beihang University AVIC Shenyang liming Aero-engine Group Corporation Ltd.

A β--NiAI alloy with normal purity, a S-doped and a Dy and S co-doped （Y-NiAI alloys were prepared by arc-melting and their corresponding S contents were less than 20 ×10-6, 33 ×10-6 and 22 × 10-6, respectively. The isothermal oxidation behavior of the alloys at 1200 ℃ was investigated and the extent of S segregation at the scale-alloy interface was determined by scanning Auger microscopy. S-doping had no significant effect on the phase transformation rate from e- to β-Al2O3, while the addition of Dy retarded this process. For the S- doped alloy, scale rumpling occurred only after 2 h thermal exposure and numerous large voids were observed at the scale-alloy interface where S segregated. In contrast to this, the oxide scale formed on the Dy and S co-doped alloy still remained flat even after 50 h isothermal oxidation and only small voids existed at the interface where S segregation was not detected.

关键词： NiAl Dy S Isothermal oxidation Phase transformation Segregation

Aerobic Oxidation of 2,3,6-Trimethylphenol with Reusable Homogenized Copper Catalysts

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Chemical Research in Chinese Universities 2021年第3期37卷 751-756页

作者： li Meng WU Mingwei PAN Biwei XU Dandan LVSONG Zhuopu li dongqing ZHANG Fangrong HUANG Jun State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing211816P.R.China

The oxidation of 2,3,6-trimethylphenol(TMP)can produce both 2,3,5-trimethyl-1,4-benzoquinone(TMQ)and 2,3,5-trimethyl-1,4-hydroquinone(TMHQ)as important intermediates of vitamin *** a soluble and porous polymer of intrinsic microporosity(PIM-1),we developed a highly active and reusable CuO@PIM-1 catalyst for the aerobic oxidation of TMP to TMQ and *** CuO@PIM-1 catalyst is high active and selective for the aerobic oxidation of TMP,and TMQ and TMHQ can be obtained in yields of 81%and 19%,*** CuO@PIM-1 catalyst has both advantages of homogeneous and heterogeneous and the CuO@PIM-1 catalyst showed a higher activity than homogeneous(CuCl_(2))and heterogeneous(supported CuO)***,CuO@PIM-1 catalyst can be recovered easily and reused at least 5 times without deactivation.

关键词： Aerobic oxidation Trimethylphenol Trimethylbenzoquinone Copper PIM-1 CuO@PIM-1

Cyclic oxidation behavior of β-NiAlDy alloys containing varying aluminum content at 1200℃

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Progress in Natural Science:Materials International 2012年第4期22卷 311-317页

作者： dongqing li Lu Wang Hui Peng Xiaoyu Zhao Hongbo Guo Shengkai Gong School of Materials Science and Engineering Beihang University Shenyang liming Aero-engine Group Corporation Ltd. AVICShenyang 110043China

β-NiAlDy cast alloys containing varying aluminum content were prepared by arc-melting. The microstructures and cyclic oxidation behavior of the alloys at 1200 ℃ were investigated. Grain refinement was achieved by increasing aluminum content in the alloy, which is beneficial to selective oxidation. The Ni-55Al-0.1Dy alloy showed excellent cyclic oxidation resistance due to the formation of a continuous, dense and slow-growing oxide scale. In contrast to this, severe internal oxidation as well as large void formation at the scale/alloy interface occurred in the Ni-45Al-0.1Dy alloy. The aluminum content dependence of the reactive element effects in β-NiAlDy was established that Dy doping strengthened the scale/alloy interface by pegging mechanism in high-aluminum alloys but accelerated internal oxidation in low-aluminum alloys during high-temperature exposure.

关键词： β-NiAl Reactive elements Dysprosium Aluminum content High-temperature oxidation

Experimental study on moisture migration of remodeled clay under different overburden pressure and temperature gradients

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Research in Cold and Arid Regions 2013年第5期5卷 562-571页

作者： Feng Ming dongqing li Xing Huang JianHong Fang State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences Qinghai Research Institute of Transportation

Unidirectional freezing experiments under overburden pressure were carried out, in order to study the driving force of mois- ture migration of remodeled clay during freezing, through improving the indoor moisture migration test device. Overburden pressure and cooling temperature with the same circumstance were changed to determine the influence on water migration of a single factor. Results show that water content increases above the location of the final ice lenses and decreases below the loca- tion. When the overburden pressure increases, water intake gradually decreases and the time starting to absorb water is delayed. The location of the final ice lens is not sensitive to overburden pressure but influenced by the temperature boundary. The im- pact of overburden pressure and maximum temperature is not obvious. Freezing rate is not sensitive to overburden pressure but influenced by temperature, and it increases when the cold temperature decreases. Frost heave and water intake flow in- creases with increasing time and rises up to a peak value, and then decreases. During the freezing process, water intake flow increases when freezing rate decreases. Water intake flow decreases when the overburden pressure increases when the cold temperature decreases. Finally, we expanded the segregation theory, and proposed a model to describe the relationship between water intake flow and freezing rate.

关键词： frost heave moisture migration overburden pressure temperature gradient open system indoor experiments

An experimental study on the relationship between acoustic parameters and mechanical properties of frozen silty clay

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Research in Cold and Arid Regions 2013年第5期5卷 596-602页

作者： Xing Huang dongqing li Feng Ming JianHong Fang State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences Qinghai Research Institute of Transportation

To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.

关键词： artificially frozen soil frozen soil strength ultrasonic wave velocity critical water content dynamic elastic mechanical parameters

Concrete durability under different circumstances based on multi-factor effects

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Research in Cold and Arid Regions 2017年第4期9卷 384-391页

作者： Feng Ming ChengCheng Du YuHang liu XiangYang Shi dongqing li State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Lanzhou Gansu 730000 China

Concrete durability has become a hot research field in civil engineering. Concrete structures suffer salt-erosion damage to different degrees in the semi-arid region of North China. The environmental condition is one of the important factors affecting the durability of concrete constructions. To realize fully the interaction between various environmental factors, this paper researched concrete durability in the salt environment under combined actions(immersing, freeze–thaw cycles, and wet–dry cycles). According to the laboratory test data, the concrete-durability degradation law under coupling-effect factors was investigated. The results show that concrete's compressive strength decreases with the increase of salt concentration and immersion time. No matter what the environmental conditions were, the compressive strength-loss ratio increased with the test time. The compressive strength-test results indicate that sodium sulfate has the strongest corrosive effect on concrete durability, followed by calcium chloride, with sodium chloride having the weakest corrosion. Compared with the other two environmental factors, the wet–dry cycle is the key factor affecting concrete durability. Therefore, in engineering practice, the influence of environment conditions on the strength and durability of concrete should be taken into full consideration, especially in the wet–dry environment with salt conditions.

关键词： concrete durability compressive strength salt solution wet–dry cycles freeze–thaw cycles

Wave propagation characteristics in frozen saturated soil

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Research in Cold and Arid Regions 2018年第2期10卷 95-103页

作者： ChengCheng Du dongqing li Feng Ming YuHang liu XiangYang Shi State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China University of Chinese Academy of Sciences Beijing 100049China

Ultrasonic detection technology is of great significance in the detection and evaluation of physical and mechanical properties of frozen soil, but wave propagation characteristics in frozen soil are unclear. Based on the three-phase composition of frozen saturated soil and the mixture theory, considering Bishop's effective stress formula, the wave propagation equations are establish for frozen saturated soil. In wave propagation, an entropy inequality was introduced to describe the coupling of different phases. The analytic expressions of propagation velocity and attenuation law of waves in frozen soil are obtained, and wave propagation characteristics in frozen saturated soil are discussed. Results show that four types of waves(i.e., P1, P2, P3 and S) are found in frozen saturated soil and all four wave types are dissipative waves, in which the attenuation of P3 is the maximum. The velocity of four waves increases sharply at the excitation frequency range of 10~3–10~9 Hz,but the wave velocity at high-frequency and low-frequency is almost constant. When volume ice content increases, the wave propagation velocity of P1 and S decreases dramatically, and the velocity of P2 increases gradually, but P3 velocity increases first and then decreases to zero with increasing saturation. The attenuation coefficients of P1 and S waves begins to increase gradually when the volume ice content is about 0.4, P2 increases first and then decreases with an increase of volume ice content and P3 increases with the volume ice content and decreases rapidly from extreme to zero.

关键词： frozen saturated soils excitation frequency saturation wave equations propagation characteristics