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Motion Planning for Industrial Robots Based on Task Process Decomposition

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Chinese Journal of Mechanical Engineering 2010年第2期23卷 135-141页

作者： BU Wanghui liu Zhenyu TAN jianrong State Key Laboratory of CAD ＆ CG Zhejiang University Hangzhou 310027 China

The existing research of the industrial robotic motion planning mainly focuses on the trajectory planning and the path planning, which aim at obtaining a minimum-time trajectory and finding an obstacle-free path respectively. In the trajectory planning, the jerks of robotic joints are usually not considered, so the smoothness of the robotic motion cannot be ensured. In the path planning, the complex spatial curves generally cannot be tracked easily, and it needs the fussy teach-and-playback operation. In this paper, based on the different constraint characteristic of the variable motion phases in the practical robotic task, the complicated task is decomposed into two kinds of sub processes, which are the free motion process and the constrained motion process. In the free motion process, the kinematic models of quasi trapezoidal waveform and quasi triangular waveform are proposed with the dynamic limits of maximum velocities, accelerations and jerks of robotic joints, so the minimum-time trajectory can be obtained with the motion smoothness. In the constrained motion process, the mathematical presentation of the task paths is extracted from the CAD models of the workpieces, so the complex spatial curves can be tracked autonomously without much teaching operation. In addition to the theoretical research, a robotic virtual prototyping system is also developed for the industrial arc welding production. The proposed research ensures the robotic motion smoothness, enhances the ability for tracking the complex spatial curves, and improves the quality and efficiency of the robotic motion planning.

关键词： robotic manipulator trajectory planning path planning virtual prototyping

Investigation of beta fleck formation in Ti-17 alloy by directional solidification method

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Journal of Materials Science & Technology 2020年第13期47卷 36-43页

作者： Xuchen Yin jianrong liu Qingjiang Wang Lei Wang School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China Institute of Metal Research Chinese Academy of SciencesShenyang110016China

Beta flecks are one of the most common defects occur in someα+βandβtitanium *** this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification *** were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/*** find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat *** of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/*** critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification *** and light contrast areas in macrostructure are directly related to elemental *** contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast *** conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification *** on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.

关键词： Titanium Alloy Beta flecks Directional solidification Elemental segregation Microstructure heterogeneity

Utility and Weight of Factors of Bus Transit's Service Quality Analysis in Nanjing

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Journal of Harbin Institute of Technology(New Series) 2015年第3期22卷 115-122页

作者： jianrong liu Tangyi Guo School of Civil Engineering and Transportation South China University of Technology School of Automation Nanjing University of Science and Technology

Service quality is a major factor that affects how public transport users evaluate bus service. In order to evaluate how bus users make trade-offs across travel cost,time,reliability,etc.,and to investigate the extent to which the components of service quality vary according to relevant trip characteristics,this paper analyzes service quality of bus transit with the conjoint analysis. Through data analysis,the levels 'utility values of reliability,waiting time,walking time,etc.,on the commuter trip and the non-commuter trip are gotten,so it is the utility function of the transit system. Then the factors' weights are obtained through the utility values. The results show that on the commuter trip,passengers value reliability the most,which is followed by waiting time and walking time,while in-bus environment,price and station environment's weights are small. While on the non-commuter trip,the weights in a higher order to lower order are the first for reliability,the second for in-bus environment,the third for walking time,the fourth for station environment and the last for ticket price.

关键词： service quality bus transit utility score weight

ADAPTIVE LAYERED CARTESIAN CUT CELL METHOD FOR THE UNSTRUCTURED HEXAHEDRAL GRIDS GENERATION

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Chinese Journal of Mechanical Engineering 2007年第2期20卷 6-12页

作者： WU Peining TAN jianrong liu Zhenyu State Key Laboratory of CAD＆CG Zhejiang University Hangzhou 310027 China

Adaptive layered Cartesian cut cell method is presented to solve the difficulty of the tmstructured hexahedral anisotropic Cartesian grids generation from the complex CAD model. ＂Vertex merging algorithm based on relaxed AVL tree is investigated to construct topological structure for stereo lithography （STL） files, and a topology-based self-adaptive layered slicing algorithm with special features control strategy is brought forward. With the help of convex hull, a new points-in-polygon method is employed to improve the Cartesian cut cell method. By integrating the self-adaptive layered slicing algorithm and the improved Cartesian cut cell method, the adaptive layered Cartesian cut cell method gains the volume data of the complex CAD model in STL file and generates the unstructured hexahedral anisotropic Cartesian grids.

关键词： Cut cell Unstructured Cartesian grids Adaptive slicing STL file Anisotropic

How do Users Evaluate Service Quality of the Dockless Bicycle Sharing System?

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Journal of Harbin Institute of Technology(New Series) 2020年第1期27卷 19-35页

作者： jianrong liu School of Civil Engineering and Transportation South China University of Technology

In order to improve the public transit’s accessibility and promote service quality of the public transit,it is necessary to alleviate the“last⁃mile”*** combination of the public transit and bicycle⁃sharing system is competitive compared with the private *** 2016,the dockless bicycle⁃sharing system has been undergoing tremendous *** the dockless bicycle⁃sharing system is different from previous bicycle⁃sharing systems,components of service quality of the dockless bicycle⁃sharing system ***,there are few articles about the service quality of the dockless bicycle⁃sharing *** paper examined the evaluation of service quality of the dockless bicycle⁃sharing system along with a measurement of users’satisfaction.A questionnaire about service quality was designed,which includes 15 *** the analysis of travelers’evaluation of factors of the dockless bicycle⁃sharing system with Rasch Model,these original ordinal data(Likert data)was transformed to the interval data:the person parameter(ability)and the item parameter(difficulty).Through the analysis of interviewees’abilities,it was found that only education and monthly consumption have significant influence on interviewees’evaluation of service quality of the dockless bicycle⁃sharing system,while there is no significant influence of gender,weekly use of dockless shared⁃bicycle,private car ownership,or monthly income on the ***,it was found that users were dissatisfied with cycling under the adverse weather,disturbance from pedestrians and cars,continuity of the bicycle lane,complaint channel,and staff service the most.

关键词： dockless bicycle sharing system service quality Rasch Model demographic characteristic evaluation of travelers

Effect of Crowding in Metro Carriages on Travelers’ Disutility: An Evidence from Guangzhou Metro

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Journal of Harbin Institute of Technology(New Series) 2020年第2期27卷 36-45页

作者： jianrong liu School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 510641China

Overcrowding has become a non negligible issue for metros in *** paper analyzes the impact of crowding in metro carriages on people’s travel behaviors based on the stated preference survey data from college students and full time workers in *** data were analyzed by using the constant value per trip model and the travel time multiplier model with the multinomial logit modeling *** show that there is a significant impact of crowding in metro carriages on passengers’*** relationship between the disutility of crowding and the standee density is not *** do not care much about crowding in the metro,whereas non commuters and college students pay special attention to crowding in metro carriages,especially when the carriage is *** paper presents new findings of the impact of demographic characteristics on the evaluation of crowding in metro carriages in developing countries.

关键词： crowding standee density stated preference disutility metro

Creep Behavior of Fusion Zone and Base Metal of the Electron Beam Weldments of a Near-alpha Titanium Alloy

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Journal of Materials Science & Technology 2010年第6期26卷 564-571页

作者： Zhiyong Chen Jinwei Li Jie liu Qingjiang Wang jianrong liu Rui Fang Division of Titanium alloys Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Research Department of High Energy Density Beam Processing Technology Beijing Aeronautical Manufacturing Technology Research Institute Beijing 100024 China AVIC Shenyang Liming Aero-engine (Group) Corporation LTD Shenyang 110043 China

The high temperature creep behavior of fusion zone （FZ） and of a near-alpha titanium alloy Ti-60 has been investigated. base metal （BM） of the electron beam weldments While the BM shows a fully transformed, coarse primary β grains with large colonies consisting of aligned α lamellar, the FZ exhibits thin martensitic α′ platelets in the columnar β grains. The creep results show that the steady state creep rates of FZ follow the power-law creep, with the stress exponents obtained in the range from 5.6 （550℃） to 5.9 （600℃）, and corrected activation energies of 309-352 kJ/mol; the stress exponents of BM exhibit different values when the creep testing stress and temperature alternate. The values of 2.4-3.2 are obtained when the stresses are under 220 MPa or the temperature is 550℃, also an exponent of 6.6 is achieved at stresses above 220 MPa at 600℃. The corrected activation energies of BM corresponding to the stress exponents are 123-161 kJ/mol （n=2.4-3.2） and 344 kJ/mol （n=6.6）. The creep mechanisms of FZ and BM have been discussed in light of the creep microstructures, activation energies and the stress exponents. The creep mechanisms of FZ is the diffusion controlled dislocation climb, the creep of BM is controlled by ＇solute drag＇ creep and dislocation climb when the stress and temperature are different. Transmission electron microscopy （TEM） observations of the dislocation structures of crept specimens are presented to give some supports for the creep behavior of FZ and BM. In addition to the creep mechanism of dislocation movement, the interface sliding has been found to play an important role during creep of FZ.

关键词： Steady state creep Stress exponent Activation energy Electron beam welding Near-alpha titanium alloy

Mechanical properties of electron beam welded dissimilar joints of TC17 and Ti60 alloys

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Journal of Materials Science & Technology 2018年第10期34卷 1859-1866页

作者： Chao Cheng Bingbing Yu Zhiyong Chen jianrong liu Qingjiang Wang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China

Microstructure, hardness, tensile and high cycle fatigue （HCF） properties of the welded dissimilar joints of Ti60 and TC17 titanium alloys had been investigated in this study. A significant microstructural change was observed to occur after welding, with rod-like α and β phases in the fusion zone （FZ）, equiaxed et phases, fine α laths and β phases in the heat-affected zone （HAZ） of TCl7 side and acicular martensite α＇ phases＋＂ghost＂ α phases in the HAZ of Ti60 side, The microhardness across the joints exhibited an inhomogeneous distribution with the highest hardness of ~404 HV in FZ and the lowest hardness of ~304 HV in base material （BM） of Ti60. All the joints tested in tension fractured at BM of Ti60 side. Fatigue limits of the joints at 107 cycles were 425 MPa at room temperature and 380 MPa at 400 ℃, respectively. Welding micropores were found to be the main source of fatigue crack initiation.

关键词： Titanium alloy Electron beam welding Dissimilar joints Mechanical properties

Evaluation of Oxidation of Ti-Al and Ti-Al-Cr Coatings Arc-ion Plated on Ti-60 High-temperature Titanium Alloy

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Journal of Materials Science & Technology 2009年第5期25卷 637-644页

作者： Wei Yan Qingjiang Wang jianrong liu Shaoqiang Li Fengjiu Sun College of Sciences Northeastern University Shenyang 110004 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016

High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al （at. pct） and Ti-48Al-12Cr （at. pct） protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating （ALP） method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray analysis （EDX）. The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.

关键词： Oxidation Ti-48Al coating Ti-48Al-12Cr coating High temperature titanium alloy