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Experimental Study on Surface Integrity of Ti-6Al-4V in High Speed Side Milling

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Transactions of Tianjin University 2012年第3期18卷 206-212页

作者：杨晓勇任成祖王焱陈光 School of mechanical engineering Tianjin University Beijing Aeronautical manufacturing technology Institute

Aiming at the surface integrity of titanium alloy Ti-6Al-4V in high speed side milling, a series of side mill- ing tests were carried out with uncoated carbide milling cutter at various milling speeds. Surface roughness, residual stress, subsurface microstructure and microhardness variations were investigated. The surface roughness measurement results present that the milling speed from 80 to 120 m/min fails to produce better and more stable roughness values compared with the result obtained from 320 to 380 m/min. The residual stresses in the feed direction and axial depth of cut direction are in similar trends for the two milling speed levels mentioned above. Moreover, the residual stress pro- duced at 320 to 380 m/min is lower and more stable than that at 80 to 120 m/min. The microstructure analysis shows that the volume of β phase in the near surface becomes smaller and the deformation of β phase in the near surface be- comes obvious with the increase of the milling speed. Subsurface microhardness variation was observed down to 200 μm below the machined surface at 80 to 120 m/min and down to 160 μm at 320 to 380 m/min. It is concluded that better surface integrity and higher material removal rate can be obtained at 320 to 380 m/min than at 80 to 120 m/min.

关键词： surface roughness residual stress microhardness microstructure

Design of a Two-Step Calibration Method of Kinematic Parameters for Serial Robots

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Chinese Journal of mechanical engineering 2017年第2期30卷 438-448页

作者： Wei WANG Lei WANG Chao YUN School of mechanical engineering and Automation Beihang University State Key Lab of Digital manufacturing Equipment and technology Huazhong University of Science and Technology

Serial robots are used to handle workpieces with large dimensions, and calibrating kinematic parameters is one of the most efficient ways to upgrade their accuracy. Many models are set up to investigate how many kinematic parameters can be identified to meet the minimal principle, but the base frame and the kinematic parameter are indistinctly calibrated in a one-step way. A two-step method of calibrating kinematic parameters is proposed to improve the accuracy of the robot＇s base frame and kinematic parameters. The forward kinematics described with respect to the measuring coordinate frame are established based on the product- of-exponential （POE） formula. In the first step the robot＇s base coordinate frame is calibrated by the unit quaternion form. The errors of both the robot＇s reference configuration and the base coordinate frame＇s pose are equivalently transformed to the zero-position errors of the robot＇s joints. The simplified model of the robot＇s positioning error is established in second-power explicit expressions. Then the identification model is finished by the least square method, requiring measuring position coordinates only. The complete subtasks of calibrating the robot＇ s 39 kinematic parameters are finished in the second step. It＇s proved by a group of calibration experiments that by the proposed two-step calibration method the average absolute accuracy of industrial robots is updated to 0.23 mm. This paper presents that the robot＇s base frame should be calibrated before its kinematic parameters in order to upgrade its absolute positioning accuracy.

关键词： Kinematic parameter Calibration Error model Product of exponential Industrial robot

Thermal and tilt effects on bearing characteristics of hydrostatic oil pad in rotary table

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Journal of Hydrodynamics 2016年第4期28卷 585-595页

作者：刘志峰湛承鹏程强赵永胜李小燕王义达 College of mechanical engineering and Applied Electronics technology Beijing University of Technology State Key Laboratory of Digital manufacturing Equipment and technology Huazhong University of Science and Technology

Hydrostatic pads are key components of a constant flow compensation hydrostatic rotary table. The tilt and thermal effects due to the partial load, the manufacturing errors and the friction must be considered. However, designers are more likely inclined to ignore these effects. In this work, the coupled characteristics of the tilt and thermal effects are studied. A coupled mathematical model to calculate the bearing properties of the pads is built. This model takes into consideration of tilt and thermal effects and is used to solve the flow problem by the finite difference method. The characteristics of the oil pad, including, the recess pressures, the load carrying capacity and the damping coefficients, are obtained and the tilt and thermal effects are analyzed. It is observed that the tilt has a tremendous impact on the bearing characteristics of the hydrostatic pad. The recess pressure, the load carrying capacity and the stiffness are reduced by 50% and the pressure distribution and the temperature distribution of the oil film also change significantly. When the pads work under a tilt operation, a larger land width is better for its bearing properties. It is also observed that the thermal effect is significant and cannot be ignored.

关键词： thermo-hydrodynamic lubricant tilting Reynolds equations constant flow compensation

Polybenzimidazolium-reinforced polyimide separators to inhibit dendrites for high-security lithium-ion batteries

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Science China Chemistry 2025年

作者： Guohua Sun Jiaqi Cui Qingsong Zhang Yisong Zhou Xinluo Li Yingying Zhang Zhanao Zhang Xin Zhang Jiantao Fan Pengpeng Li Lianlong Hou Nanjun Chen Hebei Key Laboratory of Flexible Functional Materials School of Materials Science and Engineering Hebei University of Science and Technology State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Academy for Advanced Interdisciplinary Studies Southern University of Science and Technology State Key Laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical Engineering Xiamen University

Lithium dendrite formation poses a significant safety hazard in lithium-ion batteries（LIBs）, severely impeding their widespread adoption and further technological advancements. Here, we present a novel quaternized polybenzimidazolium（q-PBI） to armor polyimide（PI） nanofiber separator（q-PBI@PI）, in which the q-PBI containing lithiophilicity and anionphilicity sites serves as the multifunctional nano-layers to suppress the Li dendrite and reinforce the mechanical properties of PI nanofiber ***, the q-PBI@PI separator displays an unprecedented mechanical strength of 82.8 MPa, significantly outperforming previously reported PI nanofiber membranes（typically below 50.0 MPa）. Besides, we demonstrate that the q-PBI@PI separator simultaneously possesses low nucleation overpotential（59 mV） and exceptional average coulombic efficiency due to the suppression of Li dendrite. Importantly, q-PBI@PI-based Li||Li battery enables a stable Li plating-stripping at 1.0 m A cm-2for600 h. Attributing to these exceptional merits, the armored PI separator-based LIBs display remarkable specific capability and capacity retention. The density function theory calculations reveal that q-PBI is conducive to the desolvation of Li+and can immobilize Li+and PF6-ions near affinity sites of PI nanofibers for inhibiting the formation of Li dendrites. Our work paves a new avenue for the design of next-generation high-performing separators in LIBs.

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Flow regimes of the immiscible liquids within a rectangular microchannel

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Acta Mechanica Sinica 2021年第10期37卷 1544-1556,I0003页

作者： Xiang Wang Yan Pang Yilin Ma Yanlin Ren Zhaomiao Liu College of mechanical engineering and Applied Electronics technology Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China Beijing Key Laboratory of Advanced manufacturing technology Beijing University of TechnologyBeijing100124China

Flow regimes of two immiscible liquids at the cross junction within a rectangular microchannel are experimentally *** of the flow regimes including critical conditions and interfacial deformations are *** is found that the occurrence of the tubing regime is favored by increased viscosity of the dispersed phase or reduced cross-sectional aspect ratio,leading to the shrinkage of the flow rate range that could produce *** order to reveal the physical mechanism,the force analysis is carried out based on the tunnel structure formed between the interface and channel side walls within the rectangular *** reshaping stage and pinch-off stage are mainly driven by the interfacial tension,leading to far larger neck thinning rate compared to the superficial velocity of either *** filling stage and squeezing stage are dominated by the pressure drop across the dispersed tip while the role of the shear force becomes more important with increasing tunnel *** filling period is estimated as t2≈kHwn02/Qd with k=1.34 and the squeezing period is expressed as t3/Tc=0.3Cac−*** to the force analysis,the critical tip velocity under dripping scales with three key parameters,which can be expressed as(utip/U)*~QcLtip/wtunnel3.

关键词： Cross junction Flow regime Liquid interface Force analysis Rectangular microchannel

Flexible Job Shop Composite Dispatching Rule Mining Approach Based on an Improved Genetic programming Algorithm

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Tsinghua Science and technology 2024年第5期29卷 1390-1408页

作者： Xixing Li Qingqing Zhao Hongtao Tang Xing Guo Mengzhen Zhuang Yibing Li Xi Vincent Wang Hubei Key Laboratory of Modern manufacturing and Quality engineering School of Mechanical EngineeringHubei University of TechnologyWuhan 430068China Hubei Digital manufacturing Key Laboratory School of Mechanical and Electronic EngineeringWuhan University of TechnologyWuhan 430070China Department of Production engineering KTH Royal Institute of Technology Stockholm SE-10044Sweden

To obtain a suitable scheduling scheme in an effective time range,the minimum completion time is taken as the objective of Flexible Job Shop scheduling Problems(FJSP)with different scales,and Composite Dispatching Rules(CDRs)are applied to generate feasible ***,the binary tree coding method is adopted,and the constructed function set is ***,a CDR mining approach based on an Improved Genetic programming Algorithm(IGPA)is *** population initialization methods are introduced to enrich the initial population,and a superior and inferior population separation strategy is designed to improve the global search ability of the *** the same time,two individual mutation methods are introduced to improve the algorithm’s local search ability,to achieve the balance between global search and local *** addition,the effectiveness of the IGPA and the superiority of CDRs are verified through comparative ***,Deep Reinforcement Learning(DRL)is employed to solve the FJSP by incorporating the CDRs as the action set,the selection times are counted to further verify the superiority of CDRs.

关键词： flexible job shop scheduling composite dispatching rule improved genetic programming algorithm deep reinforcement learning

Additive manufacturing of high-strength Inconel 718 alloy through the addition of Ti_(2) AlC MAX particles

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Journal of Materials Science & technology 2023年第27期158卷 180-193页

作者： Yu Kong Kaiyuan Peng Haihong Huang School of mechanical engineering Hefei University of TechnologyHefei 230009China Key Laboratory of Green Design and manufacturing of mechanical Industry Hefei University of TechnologyHefei 230009China

Decreasing the content of detrimental Laves phase in additively manufactured Inconel 718 alloy is highly *** the present study,we introduce a novel approach to effectively suppress the precipitation of Laves *** ex-situ incorporation of Ti_(2) AlC MAX particles,Ti_(2) AlC/Inconel 718 composites with Ti_(2) AlC volume fractions of 5%and 10%are successfully fabricated using the directed energy deposition(DED)*** comparison to the Inconel 718 alloy,the 10 vol.%Ti_(2) AlC/Inconel 718 composite exhibits 70.9%higher yield strength,39.1%higher ultimate tensile strength,and 61.4%higher hardness.A detailed microstructure examination confirms that the detrimental Laves phase,which is abundantly present in the inter-dendritic region,is replaced by in-situ formed(Nb,Ti)(C,N)andγ’particles with average diam-eters of 1.12μm and 10 nm,*** non-equilibrium solidification process simulation,the suppression of Laves phase,in-situ formation of multi-scale precipitates,and the microstructural evolu-tion due to Ti_(2) AlC addition are illustrated at the mechanistic ***,a theoretical model of Ti_(2) AlC/Inconel 718 composite is developed to reveal its underlying strengthening *** is indi-cated that Ti_(2) AlC/Inconel 718 composites possess the capability to be a next-generation high-end nickel-based alloy.

关键词： Additive manufacturing Inconel 718 Max phase Microstructure mechanical properties

Kinetostatic Modeling and Analysis of an Exechon Parallel Kinematic Machine(PKM) Module

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Chinese Journal of mechanical engineering 2016年第1期29卷 33-44页

作者： ZHAO Yanqin JIN Yan ZHANG Jun School of mechanical engineering Anhui University of Technology School of mechanical and Aerospace engineering Queen's UniversityBelfastUK State Key Laboratory for manufacturing Systems engineering Xi'an Jiaotong University

As a newly invented parallel kinematic machine（PKM）, Exechon has found its potential application in machining and assembling industries due to high rigidity and high dynamics. To guarantee the overall performance, the loading conditions and deflections of the key components must be revealed to provide basic mechanic data for component design. For this purpose, a kinetostatic model is proposed with substructure synthesis technique. The Exechon is divided into a platform subsystem, a fixed base subsystem and three limb subsystems according to its structure. By modeling the limb assemblage as a spatial beam constrained by two sets of lumped virtual springs representing the compliances of revolute joint, universal joint and spherical joint, the equilibrium equations of limb subsystems are derived with finite element method（FEM）. The equilibrium equations of the platform are derived with Newton＇s 2nd law. By introducing deformation compatibility conditions between the platform and limb, the governing equilibrium equations of the system are derived to formulate an analytical expression for system＇s deflections. The platform＇s elastic displacements and joint reactions caused by the gravity are investigated to show a strong position-dependency and axis-symmetry due to its kinematic and structure features. The proposed kinetostatic model is a trade-off between the accuracy of FEM and concision of analytical method, thus can predict the kinetostatics throughout the workspace in a quick and succinct manner. The proposed modeling methodology and kinetostatic analysis can be further expanded to other PKMs with necessary modifications, providing useful information for kinematic calibration as well as component strength calculations.

关键词： parallel kinematic machine substructure synthesis kinetostatic stiffness Exechon

3D Progressive Damage Based Macro-mechanical FE Simulation of Machining Unidirectional FRP Composite

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Chinese Journal of mechanical engineering 2018年第3期31卷 128-143页

作者： Yan-Li He Joao-Paulo Davim Hong-Qian Xue Key Laboratory of Contemporary Design and Integrated manufacturing technology of Ministry of Education School of Mechanical EngineeringNorthwestern Polytechnical University Department of mechanical engineering University of AveiroCampus Santiago

Finite element(FE) simulation is a powerful tool for investigating the mechanism of machining fiber?reinforced polymer composite(FRP). However in existing FE machining simulation works,the two?dimensional(2 D) progressive damage models only describe material behavior in plane stress,while the three?dimensional(3 D) damage models always assume an instantaneous sti ness reduction pattern. So the chip formation mechanism of FRP under machin?ing is not fully analyzed in general stress state. A 3 D macro?mechanical based FE simulation model was developed for the machining of unidirectional glass fiber reinforced plastic. An energy based 3 D progressive damage model was proposed for damage evolution and continuous sti ness degradation. The damage model was implemented for the Hashin?type criterion and Maximum stress criterion. The influences of the failure criterion and fracture energy dissipa?tion on the simulation results were studied. The simulated chip shapes,cutting forces and sub?surface damages were verified by those obtained in the reference experiment. The simulation results also show consistency with previous 2 D FE models in the reference. The proposed research provides a model for simulating FRP material behavior and the machining process in 3 D stress state.

关键词： FRP Macro mechanical Machining Finite element Progressive damage