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Chatter stability prediction in four-axis milling of aero-engine casings with bull-nose end mill

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Chinese Journal of Aeronautics 2015年第6期28卷 1766-1773页

作者： Zhou Xu Zhang dinghua Luo Ming Wu Baohai Key Laboratory of Contemporary Design and Integrated Manufacturing Technology Ministry of EducationNorthwestern Polytechnical University

An analytical model for chatter aero-engine casings is presented in this paper stability prediction in bull-nose end milling of And the mechanics and dynamics variations due to the complex cutter and workpiece geometry are considered by analyzing the effects of the lead angle on the milling process. Firstly, the tool-workpiece engagement region is obtained by using a previously developed method and divided into several disk elements along the tool-axis direction. Secondly, a 3D dynamic model for stability limit calculation is developed and simplified into a 1D model in normal direction considering only the dominant mode of the workpiece. Then the cutting force coefficients, the start and exit angles corresponding to each disk element are determined. And the total stability lobe diagram is calculated using an iterative algorithm. Finally, several experimental tests are carried out to validate the feasibility and effectiveness of the proposed ~rediction approach.

关键词： Aero-engine casings Bull-nose end mill Chatter Four-axis milling Stability lobe diagram

Effects of Cutting Parameters on Tool Insert Wear in End Milling of Titanium Alloy Ti6A14V

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Chinese Journal of Mechanical Engineering 2017年第1期30卷 53-59页

作者： LUO Ming WANG Jing WU Baohai ZHANG dinghua Key Laboratory of Contemporary Design and Integrated Manufacturing Technology of Ministry of Education Northwestern Polytechnieal UniversityXi'an 710072China

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6A14V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6A14V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as： feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6A14V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.

关键词： tool wear Ti6A14V cutting parameter hard-to-cut material

三联预康复护理在骨科大手术患者中的应用实践

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卫生职业教育 2024年第15期42卷 154-157页

作者：黄如飞李凤梁丁华广东省吴川市人民医院广东吴川524500

目的探讨将三联预康复护理模式应用于骨科大手术患者术前干预中,以改善患者的心理状态、应对能力和营养状况,加快术后康复。方法选择2022年1月1日至2023年10月30日期间拟接受骨科大手术治疗的100例患者,采用随机数字表法分为观察组和... 详细信息

目的探讨将三联预康复护理模式应用于骨科大手术患者术前干预中,以改善患者的心理状态、应对能力和营养状况,加快术后康复。方法选择2022年1月1日至2023年10月30日期间拟接受骨科大手术治疗的100例患者,采用随机数字表法分为观察组和对照组,各50例。对照组采用传统护理模式,观察组在对照组基础上增加三联预康复护理。干预前后采用焦虑自评量表(SAS)、抑郁自评量表(SDS)、压力应对能力量表(MSI)对两组进行焦虑与抑郁程度、压力应对能力测评,并比较营养状况。结果干预前两组SAS、SDS、MSI得分比较差异无统计学意义(P>0.05),干预后观察组SAS、SDS得分均低于对照组,而MSI得分高于对照组,营养状况亦优于对照组,差异有统计学意义(P<0.05)。结论三联预康复护理模式应用于骨科大手术患者术前干预中,可稳定患者的情绪,提高压力应对能力,改善营养状况,减少并发症的发生,促进患者顺利康复。

关键词：康复护理骨科大手术患者

高水平综合大学参与中小学教师培养的挑战与方略

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教师教育学报 2024年第2期11卷 22-28页

作者：吴瑞瑞王定华北京外国语大学国际教育学院北京100089

高水平综合大学参与教师培养是建设教育强国的必然要求。面向新时代新要求,如何平衡教师教育中的“师范性”与“专业性”,弥补教师培养中理想与现实的落差,“国优计划”为高水平综合大学切实参与中小学教师培养指明了方向。高水平综合... 详细信息

高水平综合大学参与教师培养是建设教育强国的必然要求。面向新时代新要求,如何平衡教师教育中的“师范性”与“专业性”,弥补教师培养中理想与现实的落差,“国优计划”为高水平综合大学切实参与中小学教师培养指明了方向。高水平综合大学可以加强与师范院校的合作,为乐教适教的非教育类学生提供系统的教师教育课程。依托覆盖面广的专业设置以及素质较高的生源基础,结合能够调动丰富社会资源的能力与平台,以及进一步优化提升的研究生层次人才选拔机制,高水平综合大学参与教师教育可以有效提升有从教意愿的非师范生的知识能力水平和教育教学素养,丰富我国中小学教师队伍人才储备,进一步营造尊师重教的良好社会风气。

关键词： “国优计划” 高水平高校教师培养中小学教师科学教育

Machining Error Control by Integrating Multivariate Statistical Process Control and Stream of Variations Methodology

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Chinese Journal of Aeronautics 2012年第6期25卷 937-947页

作者： WANG Pei ZHANG dinghua LI Shan CHEN Bing Key Laboratory of Contemporary Design and Integrated Manufacturing Technology Ministry of Education Northwestern Polyteehnical University Xi'an 710072 China

For aircraft manufacturing industries, the analyses and prediction of part machining error during machining process are very important to control and improve part machining quality. In order to effectively control machining error, the method of integrating multivariate statistical process control （MSPC） and stream of variations （SoV） is proposed. Firstly, machining error is modeled by multi-operation approaches for part machining process. SoV is adopted to establish the mathematic model of the relationship between the error of upstream operations and the error of downstream operations. Here error sources not only include the influence of upstream operations but also include many of other error sources. The standard model and the predicted model about SoV are built respectively by whether the operation is done or not to satisfy different requests during part machining process. Secondly, the method of one-step ahead forecast error （OSFE） is used to eliminate autocorrelativity of the sample data from the SoV model, and the T2 control chart in MSPC is built to realize machining error detection according to the data characteristics of the above error model, which can judge whether the operation is out of control or not. If it is, then feedback is sent to the operations. The error model is modified by adjusting the operation out of control, and continually it is used to monitor operations. Finally, a machining instance containing two operations demonstrates the effectiveness of the machining error control method presented in this paper.

关键词： machining error multivariate statistical process control stream of variations error modeling one-step ahead forecast error error detection

High-efficiency magnetophoretic separation based on synergy of magnetic force field and flow field in microchannels

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Science China(Technological Sciences) 2011年第12期54卷 3311-3319页

作者： WU XinYu WU HuiYing HU dinghua School of Mechanical and Power Engineering Shanghai Jiao Tong University Shanghai 200240 China

Magnetophoresis is one of the most important separation methods in biological and chemical engineering. In this paper,a novel impact parameter on separation efficiency,i.e.,the angle between the vectors of magnetic force and fluid velocity,was derived from the basic equation describing the motion of magnetic beads in microchannels. It is proposed that one of the most important approaches for separation efficiency enhancement is to improve the coordination of magnetic force field and fluid flow field. A T-shaped microchannel magnetophoretic separator was designed based on the angle. And then a two-dimensional dynamic model of magnetic beads moving in microchannels was established to study the separation efficiency of T-shaped microseparator by combined use of finite element method and Runge-Kutta method. The results show that the capture effi-ciency of T-shaped microseparator is much higher than that of the straight microseparator at the same conditions. For small magnetic beads at high fluid velocities,the designed T-shaped microseparator could still keep high separation efficiency whereas the conventional straight microseparator fails to separate the magnetic beads. Further analysis shows that the mechanism of separation efficiency enhancement lies in the synergy of magnetic force field and flow field,which directly leads to large deflected velocity of the magnetic beads from the main stream,and thus increasing the separation efficiency. It is anticipated that the results in this paper are theoretically helpful for the optimum design of highly efficient magnetophoretic separators.

关键词： magnetophoretic separation T-shaped microchannel field synergy separation efficiency

A new production technique for wear resistant ring-hammers

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China Foundry 2011年第4期8卷 407-412页

作者： Li Shifeng Zhang dinghua Bu Kun College of Mechanical and Electrical Engineering Northwestern Polytechnical University Xi ＇an 710072 China

Based on a great number of laboratory experiments, a new technique has been developed for producing wear resistant ring-hammers. In this technology, lost foam casting with iron sand was combined to make mold; a special alloy was used to inoculate the molten steel, and proper heat treatment was used to further improve mechanical properties of wear resistant ring-hammers. The influence of this new production technology on the microstructure and mechanical properties of wear resistant ring-hammers was studied. Results show that iron sand molding, having the inherent characteristic of sand molding, changes the type of metallic compounds, refines crystal grains and increases the fineness of microstructure. Practical experience verified that the properties of the ring-hammers produced with this new technique are as follows: tensile strength (Rm) 720 MPa, impact toughness (ak) > 210 J·cm-2 and hardness > 200 HB. After water quenching from 1,080℃ (holding for 4 h) and tempering at 320℃ for 3 h, the best wear resistance is obtained, and the wear resistance is 1.6 times higher than that of common high manganese ring-hammers.

关键词： new production technology wear resistant ring-hammer compound modification lost foam casting with iron sand molding

An improved analytical model of cutting temperature in orthogonal cutting of Ti6Al4V

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Chinese Journal of Aeronautics 2019年第3期32卷 759-769页

作者： Chenwei SHAN Xu ZHANG Bin SHEN dinghua ZHANG Key Laboratory of Modern Design and Integrated Manufacturing Technology of Ministry of Education Northwestern Polytechnical University 206 Institution North Electronics Research Institute Co. Ltd

Cutting heat has significant effects on the machined surface integrity of titanium alloys in the aerospace field. Many unwanted problems such as surface burning, work hardening, and tool wear can be induced by high cutting temperatures. Therefore, it is necessary to accurately predict the cutting temperature of titanium alloys. In this paper, an improved analytical model of the cutting temperature in orthogonal cutting of titanium alloys is proposed based on the Komanduri-Hou model and the Huang-Liang model. The temperatures at points in a cutting tool, chip, and workpiece are calculated by using the moving heat source method. The tool relief angle is introduced into the proposed model, and imaginary mirrored heat sources of the shear plane heat source and the frictional heat source are applied to calculate the temperature rise in a semi-infinite medium. The heat partition ratio along the tool-chip interface is determined by the discretization method. For validation purpose, orthogonal cutting of titanium alloy Ti6Al4V is performed on a lathe by using a sharp tool. Experimental results show to be consistent well with those of the proposed model,yielding a relative difference of predicted temperature from 0.49% to 9.00%. The model demonstrates its ability of predicting cutting temperature in orthogonal cutting of Ti6Al4V.

关键词： Cutting temperature Moving heat source method Orthogonal cutting Relief angle Titanium alloy

Tectonic Constraints on the Transformation of Paleozoic Framework of Uplift and Depression in the Ordos Area

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Acta Geologica Sinica(English Edition) 2006年第6期80卷 944-953页

作者： WANG Qingfei DENG Jun HUANG dinghua yang Liqiang GAO Bangfei XU Hao JIANG Shaoqing State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of the Ministry of Education China University of Geosciences Beijing 100083 Faculty of Earth Sciences China University of Geosciences Wuhan Hubei 430074

During the Paleozoic, the Ordos area in the western North China Plate was located at the intersecting position of microplates and controlled by their interaction. The structural framework in the Ordos area, which underwent transformations in the Ordovician, the Carboniferous and the Permian respectively, was dominated by the alternation of uplift and depression. The transformations of structural framework are utilized as the clues to investigate the microplates＇ interacting type and its response in the Ordos area. According to the regional structural evolution, the Ordos area is simplified into an isopachous, isotropic and elastic shell model, and under proposed various boundary conditions, three series of numerical simulations corresponding to the three structural transformations are carried out to determine the detailed tectonic constraints. Numerical simulations reveal that the structure of the uplift and depression, which is similar to the actual pattern, develops only under one special boundary condition in each of the three series, indicating that the structural framework responds to the unique tectonic background. The simulation results show that in the Early Paleozoic, the L-shaped paleouplift formed nearby the southwestern corner of the Ordos area because the intensity of the compressions in the southern and western boundaries resulting from the ocean-continent collisions was similar. In the Late Paleozoic, it evolved into continent-continent （or arc-continent） interaction in the southern and northern boundaries; in the preliminary stage of the interaction, since the interface between the North China Plate and the plates on the south and north was narrow, the relative acting force was little and the regional western boundary immobile, and the structural framework in the basin was characterized by the N-S trending slender-waist-shaped uplift; as the interface between the plates expanded gradually, the extrusive force in the southern and northern boundaries o

关键词： Ordos Basin Paleozoic microplate strain numerical simulation