A Study on a Wire Tension Adaptive Control System of a Multi-wire Saw in Computer Simulation

Based on the analysis of the mechanism of wire tension control by using torque motors in the multi-wire saw machining process, some mathematical models of a tension control system are studied, and an adaptive algo- rithm is designed for controlling the wire tension. In this algorithm of tension control, the rotation speeds and waving angle of motors are measured and fed back to the controller, and the NLMS（ normalized least mean squares） algorithm is used to calculate the adaptive correction value and control the wire tension accurately. The computer simulation results in Matlab software validate the high accuracy for controlling the system of the wire tension with the NLMS algorithm in the multi-wire saw machining process.

Sawing Performance Comparison of Brazed and Sintered Diamond Wires

Great attention has been paid on fabricating diamond wire by using the brazing diamond because of its strong chemical bonding strength and controllability of grits distribution. Although several serving performances of brazed diamond wire have been reported, seldom do these studies refer to its process characteristics. Sawing performances of a brazed diamond wire are investigated and compared with those of a sintered diamond wire on a wire saw machine. The surface topographies of beads selected from the two wires are micro observed before sawing. The sawing tests are carried out in constant feed rate feeding（CFF） and constant normal force feeding（CNFF）. In CFF test, sawing force, power, and the cut depths of positions on contact curve are measured. Then, coupled with the observations of beads topographies, sawing force and its ratio, relations of power against material removal rate, and contact curve linearity are compared and discussed. In CNFF test, the sawing rates of the two wires are investigated. The results indicate that the brazed wire performs with lower sawing force（less 16% of tangential force and 28% of normal force）, more energy efficiency（nearly one-fifth of sawing power is saved）, at a higher sawing rate （the rate is doubled） and with better contact curve linearity as compared with the sintered wire. This proposed research experimentally evaluates the sawing performances of brazed diamond wire from the aspect of process parameters, which can provide a basis for popularizing the brazed diamond wire.

Quantitative Analysis of the Loads Acting on the Abrasive Grits in the Diamond Sawing of Granites

An experimental study was carried out to quantitati ve ly evaluate the loads acting on the diamond grits during circular sawing of two kinds of typical granite with diamond segmented saw blade. Measurements were mad e of the horizontal and vertical force components and the consumed power in order to obtain the tangential and the normal force components. The temperatures at the diamond-granite contact zone were measured using a foil thermocouple. T he measurement, together with the net sawing power, was subsequently used to est imate the energy partition to the granite by a temperature matching technique. B ased on the energy partition values, the temperatures at individual cutting poin ts were estimated using an analytical model. SEM was used to follow the topograp hies of worn diamond segments. The average force acting on each diamond grit was found to be only 4% of the diamond compressive strength measured by a static me thod. The strength disparity of diamond grits and the random protrusion of grits beyond bond matrix should be significant factors in accounting for the wear of diamond grits. The wear of diamond grits was also found to be closely related to the high temperatures generated at individual cutting points and the pop-outs of diamonds from the bond matrix might be mainly attributed to the heat conducte d to the segments.

Simulation and prototype testing of multi-wire drift chamber arrays for the CEE

The building of a large-scale external-target experiment, abbreviated as CEE, in the cooling storage ring at the Heavy Ion Research Facility in Lanzhou has been planned. The CEE is a multi-purpose spectrometer that will be used for various studies on heavy-ion collisions. A multi-wire drift chamber(MWDC) array is the forward tracking detector of the CEE. In this work, GEANT4 simulations were performed for the MWDC forward tracking array with a focus on the track reconstruction algorithm. Combined with the time of flight information,particle identification is achieved. The residue is about 30 μm, while the tracking efficiency is higher than 90%with the current redundancy. In addition, a prototype of the forward tracking system using three MWDCs was assembled and tested using a high-energy proton beam. The firing efficiency of the detector and the reconstruction accuracy of the prototype were derived. The track residue for the protons at about 400 MeV/c is better than 300 μm, meeting the requirements of the CEE. Suggestions for improving the performance of the forward tracking system are given.

Polycrystalline diamond mini-cubes for sawing applications

Diamond grits are indispensable for sawing granite or concrete.Each year about 1 000 tons of diamond grits are consumed for such purposes.In all cases,mono crystalline diamond is used.However, polycrystalline grits(polygrits) are generally better performed than mono grits as abrasives.For example,poly grits of cubic boron nitride(e.g.Borazon(?) CBN-550 of Diamond Innovations) can cut faster and they last longer than mono grits(e.g.Borazon(?) CBN-500). Polygrits of alumina(e.g.Cubitron(?) of 3M) also out perform by far glassy grits(e.g.white alumina).For diamond superabrasives,micron polygrits formed by shock waves may polish as fast as mono grits of the same size,but without causing as much scratches due to the presence of smaller sintered grains.The improved performance of poly grits is attributed to their ability to micro chipping that renews the sharp cutting corners from time to time.By contrast,mono grits tend to round off at low cutting force or macro fracture at high cutting force,so they may lose the cutting ability rapidly. For sawing granite with mesh sizes 40/50 or coarser,poly grits of diamond have not been available until recently.In this research,we have made polygrits in mini cube with sizes of 18/20,20/25,and 30/40.Turbo grinders and wire saws were made by brazing both mono grits and polygrits on steel substrates.Cutting performance on granite demonstrated that grinding speed was faster with turbo grinder,and the surface finish was smoother with wire saw for poly grits than mono ones. Polygrits and mono grits of diamond were mixed for comparison(upper left).Polygrits of mini cubes were brazed on the pearl of a wire saw(upper right).Mono diamond grits were brazed on a turbo grinder(bottom diagrams ).

Key Technologies and Development Trends in Advanced Intelligent Sawing Equipments

As a starting point in equipment manufacturing,sawing plays an important role in industrial production.Intelligent manufacturing equipment is an important carrier of intelligent manufacturing technologies.Due to the backwardness of intelligent technology,the comprehensive performance of sawing equipments in China is obviously different from that in foreign countries.State of the art of advanced sawing equipments is investigated along with the technical bottleneck of sawing machine tool manufacturing,and a new industrial scheme of replacing turning-milling by sawing is described.The key technologies of processing-measuring integrated control,multi-body dynamic optimization,the collaborative sawing network framework,the distributed cloud sawing platform,and the self-adapting service method are analyzed;with consideration of the problems of poor processing control stableness,low single machine intelligence level,no on-line processing data service and active flutter suppression of sawing with wide-width and heavy-load working conditions.Suggested directions for further research,industry implementation,and industry-research collaboration are provided.

Study on swarf when sawing granite with diamond wire

The diamond wire-sawing process was developed to cut granite in both quarries and block processing plants.In this paper,swarf was collected from different areas along the sawing arc when sawing three granites.The particle size distribution and the morphology of the swarf were investigated systematically,along with the swarf formation mechanism in sawing.Granite swarf formation was dominated by transgranular fractures based on the morphology of sawn granite chips and the analysis of sawn chip size.A long cutting arc increased the movement among the swarf,tool,and workpiece,thereby inducing a secondary fracture in the sawn chip.

Characterization of Band Sawing Dusts Generated in Cutting of Multi-crystalline Silicon Ingots

Physical-chemical characteristics of the band sawing dusts regarding to recovery of pure silicon from them were investigated.The experimental results show 50vol%-60vol% amorphous phases exist in the dusts,which is mostly amorphous silica.The as-received saw dusts are found to form hard agglomerates of larger than 50 microns in diameter.The iron-based inclusions collected by magnets are found to match well with the band saw material in XRD patterns.Weight loss in heating was observed by thermal gravity tests,up to 900 ℃,presumably due to reaction of the amorphous silica with carbon contaminant in the dusts.The saw dusts were variously treated to examine their physical-chemical responses,and the results were also presented.

THE WEAR MODES AND MECHANISMS OFDIAMONDS IN SAWING HARD STONE

Four wear modes and four wear mechanisms of diamonds in sawblades are identified in a study of varied segments damaged in field operation of sawing hard stone. The four wear mechanisms are impactshearing, fatiguing, pullingout and thermal effects. Surface erosion is the result of thermal effects, while impactshearing and fatiguing lead to macro and microfracture, and pullingout results in wholesale dislodgement of diamonds provided the inequality Fn>M/(μλδ) is satisfied.

基于SAW滤波器的电磁寄生提取

针对封装管壳和版图电磁寄生参数导致射频声表面波(SAW)滤波器通带变窄及驻波增大等问题,提出一种能快速提取封装管壳和版图中电磁寄生效应的方法,精准模拟了封装和版图对滤波器性能的影响。首先利用有限元法(FEM)电磁仿真软件提取封装管壳的电磁寄生参数,再使用电路仿真软件将所设计出的滤波器结合所提取的封装寄生参数和滤波器版图直接进行联合仿真,此方法不需将版图在FEM软件中再次进行电磁仿真,可提高时间利用率。此方法在中心频率为1 268 MHz、通带插入损耗小于1 dB、带内驻波小于1.6、带内波动为0.5 dB、带宽为24 MHz(相对带宽为1.8%)的SAW滤波器上进行了验证,结果表明仿真结果与实测值吻合度较高。该设计中所用的SAW谐振器均经过去嵌操作,能更精准地模拟实测滤波器的结果。

SAW滤波器功率容量研究

为了提高声表面波(SAW)滤波器的使用寿命和设计效率,有必要研究谐振单元对滤波器功率耐受力的影响。首先通过FEM有限元软件搭建由Al电极、42°Y-X LiTaO_(3)压电材料薄膜和SiO_(2)/Poly-Si/Si衬底构成的谐振器模型,并分析IDT、声孔径、半周期对其阻抗的影响。同时,提出了一种谐振器功率测试方法,该方法可以计算出谐振器的各个频点下加载功率随输入功率的变化。为了验证功率测试方法的可靠性,对采用3030C封装的B41(2515~2675 MHz)滤波器进行功率测试,结果显示在输入功率为23 dBm时,滤波器被烧毁,与仿真数据一致。最后结合电容公式和仿真数据证实了谐振器的面积变化会改变滤波器的电容比,进而影响滤波器的散热,因此可以通过改变SAW滤波器各支路串并联结构以及各谐振器叉指对数、孔径、半周期,来提高滤波器功率耐受性。

Preparation and Optimization of High-Purity Silicon Carbide Magnetic Abrasives for the Magnetic Induction-Wire Sawing Process

In this study,magnetic abrasives were obtained by crushing and sieving sintered iron-silicon carbide(Fe-SiC)composites.Fe and SiC powders with different mesh numbers were pre-compacted using different pressures and then sintered at various temperatures and with different holding times.The dispersion uniformity of the SiC powder was improved through surface modification using polyethylene glycol(PEG)300.The resulting magnetic abrasives were characterized in terms of phase composition,density,relative permeability,and microstructure;this was followed by a comprehensive analysis to reveal the optimal processing parameters.The ideal combination of process parameters for preparing SiC magnetic-abrasive grains for the magnetic induction-wire sawing process was obtained,which are preparation load of 60 kN,a SiC mesh number of 1,500,a sintering temperature of 1100℃,and a holding time of 4 h.

陶瓷封装SAW滤波器除金工艺研究

针对陶瓷封装声表面波(SAW)滤波器焊盘除金问题,提出了载板搪锡工艺的解决方案。通过制作外扩焊盘的搪锡载板进行滤波器批量贴装,在加热台上进行回流以溶解焊盘镀金层,取下上锡器件后用真空吸锡枪吸去焊盘表面焊锡,即可达到除金目的。详细介绍了搪锡载板的焊盘设计,利用红外测温仪对操作过程进行监控,对除金后的器件进行焊盘表面、焊点界面分析以及环境试验验证。试验表明,焊盘表面镀金层被完全去除,除金后的器件具有较高的可靠性。

压电复合薄膜的SAW器件杂波抑制及仿真方法

针对任意复杂膜系结构压电复合薄膜声表面波(SAW)器件横向杂波抑制及精确快速仿真方法,从数学上严格分析推导了有限长结构分层级联理论和色散2D-COM模型,可精确快速地计算压电复合薄膜SAW器件传播方向及孔径方向结构对杂波模式的影响,并通过色散2D-COM模型对SAW器件杂波抑制进行综合分析。通过对41°Y-X LiNbO_(3)/SiO_(2)/Si_poly/Si(111)复合衬底SAW谐振器的优化设计与研制,结果表明,设计优化结果与实验结果吻合较好,验证了该方法的有效性和可行性。

电磁寄生参数对SAW滤波器性能的影响

设计了B41频段的声表面波(SAW)滤波器,利用三维电磁场仿真工具HFSS建立表面贴装器件(SMD)封装和芯片级(CSP)封装模型,对比两种封装的声-电磁联合仿真结果得出,在滤波器电路拓扑结构中,当2条不同并联支路连接在一起时,由于SMD封装键合引线的电磁寄生参数影响,滤波器在高频处的带外抑制会出现“上翘”。建立不同键合线数量、直径及长度的SMD封装模型,并仿真计算S参数。对比仿真结果可知,随着键合线直径的增大和长度的减小,其等效电感逐渐变小,即键合线的电磁寄生参数逐渐减小,对SAW滤波器性能的影响逐渐减弱,高频处的带外抑制性能得到优化。结果表明,CSP封装植球倒扣的电磁寄生参数更小,声-电磁联合仿真的结果更优,与实测结果吻合较好。

基于软件无线电方案无线无源SAW温度阅读器设计

目前谐振型声表面波(SAW)阅读器射频电路大多采取分立器件设计,针对系统整体工作频段受限,硬件设计繁琐的问题,该文提出了一种软件无线电方案。软件无线电系统主体由ZYNQ和AD9361组成,射频收发端口添加LNA、PA进行信号功率放大,使用射频开关隔离收发。通过发射步进频率5 kHz、带宽1 MHz扫频信号,并对回波进行频谱分析求取最大值,最终得到谐振频率。针对SAW传感器回波持续时间较短而导致FFT计算分辨率的不足,使用重复采集增加数据长度,将阅读器的分辨率提高到468.75 Hz。实验结果表明,该阅读器能够正确探测传感器温度变化。

面内传播方向对SAW滤波器性能的影响研究

为了满足窄带声表面波滤波器对品质因数Q值和带外抑制日益增长的需求,提出了一种窄带滤波器设计方法。在基于新型POI结构谐振器的基础上,通过旋转谐振器达到改变波传播角度的目的,并利用二维全模型得到准确的实验数据,与原结构谐振器分别代入滤波器设计中进行比较。实验结果表明,该方法在一定程度上能够有效地增加带外抑制,对过渡带抑制能力有2~4 dB的提升,且具有设计简便,占用空间小等优点。

NUMERICAL SIMULATION OF HOT SAWING PROCESS

The present paper gives a numerical simulation of hot sawing process by using elastic- plastic finite element method. The simulation is carried out for the moment from the beginning of deformation to the local yield in work piece. In order to treat the work hardening on deformation resistance, a correction of stress based on deformation rate is taken into consideration. The calculation results shows, there are two stress peaks both on the lower and upper sides ahead of the tooth tip during the elastic press stage, in which the displacement of tooth is below 0.735*10-6 cm. Following the push of saw tooth and rise of saw load, metal at the corner of filing reaches the yield point and a local plastic area appears,where metal shapes new filing part towards the free surface under the extrusion forces. Meanwhile the stress peaks ahead of tooth tip initial also yield regions. The displacement of saw tooth is between 0.735*10-6cm and 1.274*10-6cm in this stage. With the further push of the saw tooth, metal bounded to tooth tip is torn under the combination of tensile and sheer stress. The slide of metal and its local plastic flow form the extension of filing. Then the saw load rises no longer and static sawing procedure continues.

Effect of Cutting Speed on Surface Quality by Bandsawing

The surface profile behavior of workpieces sawn has been investigated. Six species were sawn under the condi-tion of four different kinds of cutting speed by the band saw. The real surface profile of a sawn workpiecc is composed of twosections, which arc the additivity of the waviness of filtered wave and roughness curve. The roughness of center line avernge aswell as amplitude decrease with the increasing of cutting speed for different kinds of species used in the experiment.

Utilization of Basalt Saw Mud as a Spherical Porous Functional Aggregate for the Preparation of Ordinary Structure Concrete

To promote the production and application of artificial aggregates,save natural sand resources and protect the ecological environment,we evaluated the feasibility of using spherical porous functional aggregates(SPFAs) formed by basalt saw mud under autoclave curing in ordinary structural concrete.In our work,two types of prewetted functional aggregates were taken as replacements for natural aggregates with different volume substitution rates(0%,5%,10%,15%,20%,25%,and 30%) in the preparation of ordinary structural concrete with water-to-binder ratios(W/B) of 0.48 and 0.33.The effects of the functional aggregate properties and content,W/B,and curing age on the fluidity,density,mechanical properties and autogenous shrinkage of ordinary concrete were analyzed.The experimental results showed that the density of concrete declined at a rate of not more than 5%,and the 28 d compressive strength could reach 31.0-68.2 MPa.Low W/B,long curing age and high-quality functional aggregates were conducive to enhancing the mechanical properties of SPFAs concrete.Through the rolling effects,SPFAs can optimize the particle gradation of aggregate systems and improve the fluidity of concrete,and the water stored inside SPFAs provides an internal curing effect,which prolongs the cement hydration process and considerably reduces the autogenous shrinkage of concrete.SPFAs exhibits high strength and high density,as well as being more cost-effective and ecological,and is expected to be widely employed in ordinary structural concrete.