Development and Prospectives of Ultra-High-Speed Grinding Technology

Ultra-high-speed grinding(UHSG)is a significant and powerful machining method in view of the enhanced productivity and precision demands.Previous researches regarding formation mechanisms and crucial technologies are comprehensively and thoroughly summarized to highlight state-of-art technology of UHSG.On the basis of the interdependence between process and machine innovations,theoretically,grinding mechanisms in strain hardening,strain rate strengthening,thermal softening,size effect and process characteristics need more in-depth studies to clarify the dominance of UHSG.Technically,CFRP wheel integrating with the brazed bonding has a prominent advantage in bonding strength and grit′s configuration over vitrified bonding,which would be superior in UHSG.Furthermore,external high pressure cooling combining with inner jet cooling methods,accompanied by scraper plates to alleviate the effect of air boundary,are crucial and practical measures for realizing effective cooling in UHSG.Grinding processes,especially those being related to grinding parameters and precise in-process measuring approaches,are also prerequisite for fitting and investigation of UHSG.

An Overview of High-efficiency Synchronous Reluctance Machines

In recent years the synchronous reluctance machines(SynRMs)have received much attention.They have some good features such as high torque density,high reliability and low cost.This paper aims to give an overview of SynRMs with particular emphasis on the history,research status and industrial application.Besides,concept and basic operating principles of such machines are also described.Moreover,some hot spots of the research on the SynRMs are introduced.Several methods to improve the average torque and reduce torque ripple of the SynRMs in the past literatures are presented including topology design and control strategies.An overview of the methods from different aspects to realize high efficiency for the SynRMs is given which contain rotor optimization,winding configuration,material improvement,control schemes and so on.Some approaches suitable for high speed application are also introduced.It can be seen that the SynRMs have broad development prospects and great potential in industrial application.

Air flow patterns and noise analysis inside high speed angular contact ball bearings

The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.

MECHANICAL-ELECTRIC COUPLING DYNAMICAL CHARACTERISTICS OF AN ULTRA-HIGH SPEED GRINDING MOTORIZED SPINDLE SYSTEM

On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply, taking high-frequency converting current of inverter power switches into further consideration, a modified mechanical-electric coupling model is created. The created model consists of an inverter, a motorized spindle, a grinding wheel and grinding loads. Some typical non-stationary processes of the grinding system with two different supplies, including the starting, the speed rising and the break in grinding loads, are compared by making use of the created model. One supply is an ideal sinusoidal voltage source, the other is an inverter. The theoretical analysis of the high-order harmonic is also compared with the experimental result. The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.

INVESTIGATION OF SURFACE TEMPERATURE IN HIGH-EFFICIENCY DEEP GRINDING

A new thermal model with triangular heat flux distribution is given in high-efficiency deep grinding. The mathematical expressions are driven to calculate the surface temperature. The transient behavior of the maximum temperature on contact area is investigated in different grinding conditions with a J-type thermocouple. The maximum contact temperatures measured in different conditions are found to be between 1 000 ℃ and 1 500 ℃ in burn-out conditions. The experiment results show good agreement with the new thermal model.

Optimization Design of the Grinding Wheel Topography for High Efficiency Grinding

On the basis of the measurement of grains distribution on the grinding wheel surface, many experiential models of the grinding wheel topography were set up. But it is pity that few of them yield practical and valuable achievement as yet. The essential reason is that the common foundation of all these models was based on the actual measurement of specific wheel topography. So it didn’t have universal applicability. Considering that the absolute irregular distribution of grains is not the requirement of the grinding process, contrarily it will bring much negative influence to grinding process. By conversely reasoning, a new conception on the relatively regular and reasonable distribution of grains on the wheel surface in accordance with different machining demands is put forward in this paper, and furthermore a creative idea of optimization design of grinding wheel topography in accordance with machining demands and grinding parameters as well as the optimization of grinding parameters in accordance with machining demands and grinding wheel topography is proposed. In the light of this idea, not only the modeling and simulation of grinding process can be really carried out, but also the optimization of grinding process and the estimation of grinding results can be realized straightway. In conclusion, a superabrasive slotted grinding wheel is designed as a practical application of the optimization model and a creep feed deep grinding experiment is carried out to verify the optimization results.

Applications of High-Efficiency Abrasive Process with CBN Grinding Wheel

High-efficiency abrasive process with CBN grinding wheel is one of the important techniques of advanced manufacture. Combined with raw and finishing machining, it can attain high material removal rate like turning, milling and planning. The difficult-to-grinding materials can also be ground by means of this method with high performance. In the present paper, development status and latest progresses on high-efficiency abrasive machining technologies with CBN grinding wheel relate to high speed and super-high speed grinding, quick point-grinding, high efficiency deep-cut grinding, creep feed deep grinding, heavy-duty snagging and abrasive belt grinding were summarized. The efficiency and parameters range of these abrasive machining processes were compared. The key technologies of high efficiency abrasive machining, including grinding wheel, spindle and bearing, grinder, coolant supplying, installation and orientation of wheel and workpiece and safety defended, as well as intelligent monitor and NC grinding were investigated. It is concluded that high efficiency abrasive machining is a promising technology in the future.

Theoretical Study on Non-transmission High Efficient Parallel Camber Grinding Machine

Be directed against the development trend of modern CNC grinding machine towards high precision and high efficiency, some general weaknesses of existing camber grinding machine are analyzed in detail. In order to develop new type CNC camber grinding machine that can grind complex die, and genuinely achieved accurate feed and high efficient grinding, a new type camber grinding machine is put forward, called non-transmission virtual-shaft CNC camber grinding machine. Its feed system is a parallel mechanism that is directly driven by linear step motor. Therefore, traditional transmission types, such as the ball lead-screw mechanisms, the gears, the hydraulic transmission system, etc. are cancelled, and the feed system of new type CNC camber grinding machine can truly possess non-creep, good accuracy retentiveness a wide range of feed-speed change, high kinematical accuracy and positioning precision, etc. In order to realize that the cutting motion is provided with high grinding speed, step-less speed variation, high rotational accuracy, good dynamic performance, and non-transmission, the driving technology of hollow rotor motor is applied to drive the spindle of new type grinding machine,thus leading to the elimination of the transmission parts of cutting motion. The principle structure model of new type camber grinding machine is advanced. The selection, control gist and driving circuit line of the linear step motor are expounded. The main technology characteristics and application advantages of non-transmission virtual-shaft CNC camber grinding machine are introduced.

Research on Experimental and Application for the High Efficient Enrichment of the Low-grade Precious Metal Materials

On the basis of reviewing the progress in the high efficient enrichment from secondary resources of low grade precious metals at home and abroad, a process route of the high efficient enrichment precious metals from secondary resources of low-grade metals by adding iron oxide as the trapping agent, reducing agent, additive, mixing uniformly and grinding, pelletizing, reduction, grinding and separation, and selectively acid leaching iron has been put forward in this paper. The experiments of reduction, grinding and separation, and selectively acid leaching iron were carried out mainly. Under the decided experiment parameters and conditions, iron generated during the reduction can trap precious metals during reduction, high active alloy powders were obtained from the reduced products by grinding and separation, the concentration of precious metals was obtained by acid leaching high active alloy powders. The better enrichment effect was obtained by adopting the technical route of processing. Other low grade noble metal materials and enrichment ratio of precious metals from the materials to acid products was high through acid leaching. This process has the advantages of simple process, environmental-friendly, strong adaptability of raw materials, high concentration ratio, which was regarded as a kind of the general efficient enrichment technology of low grade precious metal materials.

基于Dinkelbach-Quadratic算法的高速铁路通信能效优化功率分配研究

为了提高高速铁路通信能量效率,提出一种基于Dinkelbach-Quadratic变换的迭代算法来解决高速铁路通信下行链路的功率分配问题。通过在小区内部署远程天线单元构建高速铁路通信分布式天线系统模型,基于完美信道状态信息(CSI)和列车内接入点反馈的最小速率要求建立能效优化模型;基于所建立的非凸优化模型,采用Dinkelbach变换将分数形式的非线性规划问题转换为求差形式;利用Quadratic变换特性对目标函数进一步展开;采用交替迭代的方法完成能效最优的功率分配。仿真结果表明:所提算法在满足最小传输速率和最大发射功率的同时,可以兼顾系统能量效率和频谱效率;随着发射天线数量和接收中继数量的增加,系统性能也有明显提升,相比传统算法系统的能效和频谱效率至少提升5%。

400 km/h高铁隧道出入口缓解微气压波综合效果分析

为准确预测高速铁路隧道出口微气压波幅值,以三维、非定常、可压缩流动理论为基础,利用Fluent软件模拟时速400 km的列车驶入100 m2端墙式双线隧道时,分析列车在不同入口侧部开口缓冲结构、出口侧部开口缓冲结构及出口仰坡斜率下对出口微气压波的影响效应,并结合出入口缓冲结构综合分析微气压波联合缓解效果。结果表明:1)对出口微气压波峰值、出口缓冲结构、仰坡斜率进行相关性分析,结合辐射立体角公式线性拟合立体角变化趋势,得出立体角随缓冲结构开口率、洞门仰坡斜率的增大均呈现由急到缓的2段式上升曲线;2)数值分析得到在不同入口缓冲结构开口率下初始压缩波压力梯度变化规律和出口微气压波缓解效率规律,再结合隧道出口缓冲结构、仰坡斜率提出微气压波联合缓解效率预测公式,预测分析微气压波联合缓解效果在不同影响因素下的变化趋势;3)针对预测结果结合数值模拟验证工况进行误差分析,表明可以将出口立体角分析结果与入口缓冲结构缓解规律相结合。

高铁开通对城市能源利用效率的影响机制及空间溢出效应研究

将高铁开通视为一项准自然实验,基于2006—2019年城市面板数据,运用多期双重差分法实证检验高铁开通对城市能源利用效率的影响,并进一步分析其影响机制及空间溢出效应。研究发现:(1)高铁开通对城市的能源利用效率具有显著的提升作用。(2)高铁开通通过提高铁路货运效率、替代公路客运、优化产业结构及促进技术创新,提升了城市的能源利用效率。(3)高铁开通对邻近城市的能源利用效率存在正向空间溢出效应,并存在800公里的空间距离衰减边界。(4)高铁开通对城市能源利用效率的提升作用在不同区域、等级、规模、资源禀赋的城市存在显著的异质性,其中对中西部城市、小城市、普通城市、资源型城市的能源利用效率提升作用更为显著;此外,高铁开通对衰退型的资源型城市能源利用效率的促进效果最大,对成熟型的资源型城市的影响次之,但对成长型和可再生型的资源型城市不存在显著性影响。研究结论为理解高铁在能源利用效率方面的作用提供了新视角和新证据,也为实现“节能减排”和“交通强国”提供了政策启示。

Spatial relationship of high-speed transportation construction and land-use efficiency and its mechanism:Case study of Shandong Peninsula urban agglomeration

Land-use efficiency is low for the urban agglomeration of China. High-speed transportation construction has been an important factor driving land use change. It is critically important to explore the spatial relationship between the high-speed transportation superiority degree and land-use efficiency. We built a model to evaluate the benefits of convenient high-speed transportation using the relative density of highways and the distance from high-speed rail stations and airports as a metric. We used 42 counties of the Shandong Peninsula urban agglomeration as an example. Land-use efficiency was calculated by a DEA model with capital, labor, economic benefits and environmental benefits as input and output factors. We examined the spatial relationships between high-speed transport superiority degree and land-use efficiency and obtained the following results. First, there are significant spatial differences in the relationships between the high-speed transportation superiority degree and land-use efficiency. Taking the two major cities of Jinan and Qingdao as the hubs, the core surrounding counties show significant spatial relationship between land-use efficiency and the high-speed transportation superiority degree. Spatial correlation declines as the distance from the hubs increases. Land-use efficiency is less than high-speed transportation convenience in areas along the transportation trunks that are distant from the hub cities. Correlation is low in areas that are away from both hub cities and transportation trunk routes. Second, high-speed transportation has a positive relationship with land-use efficiency due to the mechanism of element agglomeration exogenous growth. Third, high-speed transportation facilitates the flow of goods, services and technologies between core cities and peripheral cities as space spillover(the hub effect). This alters the spatial pattern of regional land-use efficiency. Finally, the short-board effect caused by decreased high-speed transport construction can be balanced by highway construction and the proper node layouts of high-speed rail stations and airports, resulting in a well-balanced spatial pattern of land-use efficiency.

红层地区高铁路堑基底上拱等级预测研究

轨面平顺性是高速铁路安全运行的重要保证。近年来,四川红层部分高速铁路(客运专线)出现路基上拱病害,致使轨面不平顺并影响高铁正常运营。对于高速铁路无砟轨道线路,基底上拱整治十分困难,如能在铺轨前进行上拱预测,就可采取相应措施以减缓路基上拱,因此高铁路基上拱预测研究势在必行。以成渝客运专线为研究对象,在综合分析路基上拱主要影响因素的基础上,选取路基中心开挖深度、岩层倾角、砂泥岩互层关系、泥岩饱和单轴抗压强度、泥岩膨胀性5个评价指标,采用熵权法确定各指标权重,运用功效系数法建立高铁红层路基上拱等级预测模型。将该模型应用于成渝客专和沪渝蓉高铁建设前期主要上拱段及上拱等级预测,验证了该模型的可行性与实用性。

轴承内圆轴向超声高速磨削理论建模与试验研究

目的以GCr15材料的6309型轴承内圆为研究对象,探究高转速超声磨削过程中超声辅助振动对磨粒运动轨迹、磨削后表面粗糙度、圆度以及微观形貌的影响规律。方法基于超声内圆磨削磨粒切削轨迹及超声振幅与砂轮转速对轨迹影响的理论仿真,构建磨削去除量与磨削表面粗糙度的理论模型,通过对轴承内圆进行超声磨削试验,研究高转速(16000~22000 r/min)下各工艺参数对内圆表面质量的影响并验证理论粗糙度评价模型。结果超声振幅的增大使磨粒与内圆接触轨迹变长,但随砂轮转速的提高,磨粒切削轨迹的密集程度也有所下降。振幅和砂轮转速的增大可使切削去除量增大、粗糙度降低,铬刚玉粒度100#陶瓷结合剂砂轮磨削GCr15轴承内圆后,其表面质量更有优势,单因素下表面质量变化趋势与理论分析结果相一致。结论在相同磨削参数下,1.5μm振幅超声磨削可使内圆圆度降至0.92μm,粗糙度降至130.5 nm,与传统磨削相比,粗糙度最高减小了41.5%,圆度最高减小了52.6%。在高转速下,各因素按砂轮对磨削后表面质量的影响由大到小的顺序依次为砂轮转速、超声振幅、进给速度,当磨粒线速度超过41.8 m/s、进给速度超过600 mm/min、振幅超过1.5μm时,表面质量呈下降趋势。

站城融合理念下高铁站点换乘导视系统优化设计研究

目的本文以重庆建设国际性综合交通枢纽城市为研究背景,满足各类人群高铁出行的适宜性与多样性需求,升级城市形象展示窗口。深入剖析高铁站点导视系统在换乘枢纽中的实际应用情况,紧密关注城市智慧交通导视系统的发展趋势与最新动态,致力于解决用户在换乘过程中可能遇到的视觉困扰和引导不足等核心问题,并在此基础上提出具有针对性的优化设计方案。方法对城市高铁站轨道换乘导视系统的设计要点和布设方法进行举证研究,重点就城市智慧出行、数字导视系统进行分析,结合对乘客空间寻路、安全感、舒适感等心理需求的调研,总结轨道交通换乘站点导视系统的设计思路。综合考虑色彩及应用、字号及对比度、字体及视觉度、布设逻辑与信息分级,把控导视系统的视觉度、布设尺度、色彩材质、技术工艺。结合我国高铁站轨道换乘导视系统的发展现状,提出重庆西站换乘导视系统的优化设计策略。结论在尊重空间动向、用户体验、视觉流程的基础上,以智慧交通导视系统为研究对象,充分探寻高铁站点轨道换乘导视系统的高效性、便捷性,旨在提升枢纽的建设水平、运行效率,以及人民群众的出行体验。

ELID高效磨削机理仿真研究

为了揭示ELID高效磨削的机理,首先,基于单颗磨粒与工件接触模型,借助有限元方法研究了氧化膜厚度y、磨粒突出高度h、下压位移z对单颗磨粒压入深度m的影响。通过回归分析,获取了单颗磨粒压入深度m的预测模型。然后,根据砂轮表面磨粒突出高度概率分布函数,建立了不同突出高度磨粒与工件的接触条件。通过对磨粒有效突出高度的离散化处理,提出了磨粒不同突出高度的离散区间的概率计算模型,最后运用概率统计学的方法得到了材料去除率模型。结果表明:ELID磨削砂轮表面生成的适当厚度的氧化膜会使得单颗磨粒压入深度m增大,尤其是突出高度较小的磨粒。氧化膜的弹性变形大,使得更多的磨粒参与工作,材料去除率理论上最大可增加48%。

600 Gbit/s速率传输系统的实验研究

【目的】由于数据中心网络的高速发展,对高速率、大容量数据中心光传输系统的性能研究也极为迫切,单载波400或600 Gbit/s传输将逐渐成为下一代通信网络主流的传输速率,当前人们对400 Gbit/s传输系统在数据中心网络中应用的研究较为广泛,而对600 Gbit/s传输系统的详细研究较少。【方法】为了满足数据中心通信容量日益增长的需求,文章基于单载波600 Gbit/s速率下一代数据中心弹性光网络(EON)传输系统,对影响传输系统的传输距离和频谱利用效率问题进行了详细的理论分析和实验研究。【结果】分析表明,单载波最大入纤光功率决定传输系统的最大传输距离,而传输系统的频谱利用效率与传输通道带宽有关,同时对单载波600 Gbit/s EON传输系统进行实验研究,实验通过对比不同入纤光功率与系统Q因子和纠前误码率的关系,以及不同通道数3 dB通道滤波带宽与系统Q因子的关系,证实系统传输距离和频谱利用效率分别与最佳入纤光功率和滤波带宽有关,并且实验表明,600 Gbit/s传输系统最佳单波入纤光功率和最佳滤波带宽分别为+4 dBm和77 GHz,此时系统传输距离最远,频谱利用效率最高。并且在此实验数据下实现了600 Gbit/s传输系统48 h无误码长期稳定运行,这说明该入纤光功率和带宽可有效延长和提高600 Gbit/s通信系统的传输距离和频谱利用率。【结论】对于600 Gbit/s速率EON传输系统存在一个最佳入纤功率和滤波带宽,使得系统在不引起明显光纤非线性代价和通道串扰情况下传输距离最远,带宽利用率最大,文章提出的600 Gbit/s传输系统最佳入纤光功率和滤波带宽对600 Gbit/s传输系统的工程建设具有非常有意义的参考作用。

高含气井低速叶轮动态气液分离设备参数优化

针对目前高含气井电潜螺杆泵举升效率低的问题,提出一种低速叶轮动态气液分离方法。综合高气油比、低转速、低液量等因素的影响,建立低速叶轮气液分离场气泡运移数学模型和动态气液分离RNG k-ε模型,依据SIMPLE压力-速度耦合算法求解结果,揭示叶片数目、叶片螺距和叶片长度等参数对动态气液分离效率的影响规律,并依据叶轮结构优化正交试验结果,探究转速和含气量等操作参数的敏感性及其对分离效率的影响。研究结果表明:增加叶片数目、叶片螺距和叶片长度时,低速叶轮动态分离效率先增大后减小;叶片数目为15片,叶片螺距为250 mm,叶片长度为420 mm时,分离效率达到最大值81%;增大转速可有效提升低速叶轮动态分离效率,转速由150 r/min提至300 r/min,分离效率由38%显著升至81%;同时低速叶轮动态分离效率随含气量的增加而不断减小,入口含气量由35%增至50%,分离效率则由87%降至63%。所得结论可为适用于电潜螺杆泵的低速叶轮动态气液分离设备的参数优化提供指导。