冷锯机锯片的瞬态动力学分析

针对φ1800mm冷锯机锯片在锯切H型钢过程中出现剧烈横向振动、锯缝变宽、产生过多材料损耗等问题,利用ANSYS软件对普通锯片和侧隙锯片进行瞬态动力学分析,研究锯片在受到轴向冲击时,锯片不同位置的振动衰减情况和锯片厚度、夹径比、侧隙对锯片横向振动的影响。对锯片进行锤击试验,研究锯片在锤击后的振动衰减情况。仿真与试验研究表明,增加锯片厚度和夹径比能有效减小锯片在受冲击后的最大振幅并缩减振动的衰减时间,侧隙锯片较普通锯片能减小片体的整体刚度,但影响较小。     

电镀金刚石线锯的制造工艺与使用性能分析

分析了金刚石线锯的电镀工艺过程;研究了金刚石线锯使用时的失效原理及两种失效形式（宏观失效与微观失效）,认为宏观失效以线锯疲劳断裂为主,微观失效则包括金刚石颗粒的磨损脱落和锯丝镀层的磨损。     

高速锯切用超薄金刚石圆锯片的优化设计

为了降低加工成本、提高石材利用率,在结构静力分析、模态分析和屈曲分析的基础上,采用有限元分析软件ANSYS优化设计出一种适用于高速锯切的超薄金刚石圆锯片结构：锯片厚度为2．4mm,锯齿结块数为60,锯齿长度为18mm,U型水槽与竖直方向夹角为0°、U型水槽深度为7．8mm,径向槽数目为3,径向槽与水平方向夹角为0°,径向槽长度为60mm,径向槽宽度为26．7mm。     

大型圆环类工件高效锯切系统设计及负载研究

针对传统金属带锯床锯切大型圆环类工件存在的锯切效率低、精度差和能耗高的问题,研究设计了一种新型高效锯切系统。不同于传统锯架进给锯切方式,所设计的大型圆环类工件的锯切系统采用工件进给锯切方式。分析了该锯切系统的主要组成以及工作原理,特别对工件旋转装置进行了详细设计;基于西门子300系列PLC,设计了该锯床的电气控制系统;此外,基于经典锯切负载模型,通过对锯切过程中参与锯切齿数的分段计算,建立了该系统的锯切负载数学建模,并进行了Matlab仿真研究。研究结果表明:切削进给方式改变后,所设计的锯切系统不仅锯架体积较小,而且锯切效率、精度、能耗以及带锯条使用寿命等指标较传统带锯床都有大幅度提升。     

Advanced lumber manufacturing model for increasing yield in sawmills using GPR-based defect detection system

This paper proposes an advanced lumber manufacturing model for real-time process control in saw mills in order to increase the yield of high value defect-free lumber. Detecting subsurface defects by scanning canted logs and generating a process plan to cut the logs can increase the yield of high-grade lumber in a saw mill industry. The defect detection process is performed using the ground-penetrating radar (GPR) system. More recently, a defect detection algorithm was developed to process GPR scanned data using the MATLAB? software. This research uses the distance and depth coordinates generated by the defect detection algorithm to develop the process plan that generates a cutting sequence for the resaw machine. The process plan is in the form of an algorithm written in MATLAB? with a simple user interface. The generated cutting sequence was validated by comparing to the conventional sawing sequence, where the operator of the resaw machine randomly performs the cutting of boards. An increase in the yield (in terms of dollar value) of about 27% was noticed using the GPR-based detection system which can map interior defects prior to sawing the log and enable an optimal sawing pattern.     

Parametric studies on the CO2 laser cutting of Kevlar-49 composite

In the present study, the cutting performance of a CO₂ laser on Kevlar-49 composite materials has been studied. The Taguchi technique is employed to identify the effect of laser control parameters, i.e., laser power, cutting speed, material thickness, assistance gas pressure, and laser mode, on the quality of cut parameters, namely, kerf width, dross height, and slope of the cut. From the analysis of variance (ANOVA) and signal-to-noise (S/N) ratio response tables, the significant parameters and the optimal combination levels of cutting parameters are determined. The obtained results are interpreted and modeled to closely understand the behavior and quality of CO₂ laser cutting. Kevlar-49 composites are found to be cut satisfactorily by the CO₂ laser at the optimum process parameter ranges. The results showed that laser power is the most significant parameter affecting the quality of cut parameters. The optimal combination of cutting parameters minimized the kerf width, dross height, and slope of cut to 0.103 mm, 0.101 mm, and 2.06°, respectively. The error between experimental results with optimum settings and the predicted values for the kerf width, dross height, and slope of cut lie within 2.9%, 7.92%, and 6.3%, respectively.     

车轮残余应力测试方法研究

采用仿真分析的方法研究了火车轮径向锯切过程中锯缝宽度的变化以及锯缝附近踏面上应力/应变的变化规律。分析表明,当锯切深度达到轮辋与辐板连接处时,锯缝附近残余应力的释放已经十分充分,可根据残余应力的释放情况计算踏面上残余应力的大小。按照径向锯切方法,在锯缝附近粘贴应变片,径向锯切到轮辋与辐板连接圆弧处时停止锯切,依据应变片记录的应变值可计算踏面上的残余应力。     

High-performance circular sawing of AISI 1045 steel with cermet and tungsten carbide inserts

This work investigated the influence of cutting speed and feed rate on cutting forces, surface roughness, and slot width circular sawing of AISI 1045 steel. The effects of tool material (cermet and tungsten carbide) and geometry (chip breaker flute and pre-cutting/post-cutting teeth) were also investigated. Thrust and radial forces generally tended to decrease as the cutting speed increased and tended to increase with the feed rate. The lowest values of thrust and radial forces were obtained using a tungsten carbide saw ground with precutting and post-cutting teeth. With regard to the quality of the machined wall, the lowest surface roughness was obtained by applying the highest cutting speed and lowest feed rate and employing a cermet brazed saw. Under this condition, roughness values comparable to face turning and parting off operations were obtained. The cermet brazed saw was responsible for producing the narrowest slot widths.     

Free abrasive wire saw machining of ceramics

Currently, many kinds of ceramics are used in advanced industrial fields due to their superior mechanical properties, such as thermal, wear, corrosion resistance, and lightweight features. Wire saw machining ceramic (Al₂O₃) was investigated by ultrasonic vibration in this study. Taguchi approach is a powerful design tool for high-quality systems. Material removal rate, wafer surface roughness, steel wire wear, kerf width, and flatness during machining ceramic were selected as quality character factors to optimize the machining parameters (swinging angle, concentration, mixed grain and direction of ultrasonic vibration) to get the larger-the-better (material removal rate) and the smaller-the-better (wafer surface roughness, steel wire wear, kerf width and flatness) machining characteristics by Taguchi method. The results indicated that wire swinging produces a higher material removal rate and good wafer surface roughness. Ultrasonic vibration improved material removal rate, without affecting the flatness under different machining conditions. Experimental results show that the optimal wire saw machining parameters based on grey relational analysis can be determined effectively and material removal rate increases from 2.972 to 3.324 mm²/min, wafer surface roughness decreases from 0.37 to 0.34 μm, steel wire wear decreases from 0.78 to 0.77 μm, kerf width decreases from 0.352 to 0.350 mm, and flatness decreases from 7.51 to 7.22 μm are observed.     

不锈钢板的CO2激光切割工艺研究

实验用CO2激光切割厚0.8mm的1Cr18Ni9Ti不锈钢板。研究了激光功率、辅助气体类型及压力、切割速度对切割质量的影响。实验显示提高切割速度能降低切缝宽度和切口横截面的表面粗糙度;而提高激光功率和氧气压力,切缝宽度也会随之提高,切口横截面更粗糙。功率650~700W、氧气压力0.3~0.5MPa、切割速度3.5~4.5m/min时切割质量最好。另外发现功率在780~1450W,氮气压力低于0.8MPa不能得到良好的切割质量。     

FUZZY EXPERT SYSTEM FOR PREDICTION OF KERF QUALITIES IN PULSED LASER CUTTING OF TITANIUM ALLOY SHEET

Laser cutting is an advanced thermal cutting process of complex nature. It's process behavior drastically changes with slight variation in processing conditions. The prediction of process performance becomes more difficult if cutting materials have non-favorable optical and thermal properties. Titanium (Ti) alloys are characterized by their low thermal conductivity and high chemical reactivity at elevated temperature and hence difficult to cut by laser. It has been found that complex and nonlinear behavior of manufacturing process can better be dealt with the application of artificial intelligence (AI) tools. The aim of present research is to develop a fuzzy expert system for prediction of the laser cutting process behavior of Ti alloy (Ti-6Al-4 V) sheet. A hybrid approach of neural network and fuzzy logic theory has been applied to develop the fuzzy expert system to predict the kerf widths and kerf deviation. The predicted results have been compared with the experimental data and found appropriate. The effects of significant process parameters on the different quality characteristics such as kerf widths and kerf deviation have been discussed.     

基于气熔比的氧化锆陶瓷薄板激光切割质量研究

采用一种基于气熔比控制的激光精密切割方法,研究了气熔比和板厚对激光切割氧化锆陶瓷板质量的影响,即气熔比对切缝质量、切面条纹形貌及粗糙度的影响。对气熔比分别为0.099、0.160、0.184和0.202的4组试件进行观测,发现提高气熔比可明显改善切缝质量,增大切面条纹光滑区长度和条纹波长,切面粗糙度由6.969μm降低到2.482μm。同时对板厚分别为0.8mm、1.0mm、1.5mm、3.0mm的4组试件进行观测,随着板厚的增加,气熔比减小,切缝质量降低,切面粗糙度由5.946μm降低到2.287μm。板厚为0.8mm、1.0mm时,切面为较光滑的周期性条纹;板厚为1.5mm时,切面呈现两个区域,即光滑区和粗糙区;当板厚增加到3.0mm时,切面呈现三个区域,即光滑区、粗糙区和鳞状层叠区。综合研究气熔比和板厚可以加深对激光切割机理的认识,为提高氧化锆陶瓷板的激光切割质量提供理论与实验依据。     

表面冶金高速钢机用锯条的研制

采用低碳合金钢作为基材 ,在锯条齿部渗入合金元素W Mo Cr V形成表面高合金层 ,经渗碳、高温淬火和回火处理后 ,研制出一种齿部具有高速钢锯切性能、背部具有高强韧性、成本低廉的表面冶金高速钢机用锯条。     

Approaches for improvement of EDM cutting performance of SiC with foil electrode

Electrical discharge machining by foil electrode serves as an alternative method for SiC slicing. This technology uses a highly tensioned thin foil as the tool electrode. The main advantages over wire EDM are that the foil thickness can be made smaller than the wire diameter, vibrations can be avoided by applying high tension, and higher current can be supplied since there is less risk of tool breakage. However, due to the large side surface area of the foil electrode, there is a high occurrence probability of side surface discharges and high concentration of debris, which affects kerf width accuracy and machining stability. In the aim to overcome both problems, this study proposes two foil electrode designs: a foil electrode in which holes are machined and the insulation of the side surface areas by a resin coating layer of 5 μm thickness. The influences of both foil electrodes were tested with three different slicing strategies: no strategy, applying jump motion of the tool electrode, and applying reciprocating motion. From machining experiments and comparative studies of the discharge delay time, it was found that with both foil tools, the occurrence probability of side surface discharges can be reduced. In addition, the chip pocketing effect of the holes enhance the flushing conditions, resulting in a higher cutting speed.     

基于轮廓法的金刚石线锯整周三维表面形貌测量和评价

针对毫米级尺度线径和微米级尺度磨粒的金刚石线锯整周三维表面形貌测量难以实现与定量评价问题,提出一种基于轮廓法的圆周扫描表面磨粒形貌测量与分析方法。通过显微测量系统沿周向扫描采集金刚石线锯对应的边缘轮廓图像序列,经图像处理后获得金刚石线锯整个圆周表面形貌的坐标点云,采用三次样条插值法对数据进行平滑处理,经圆柱坐标变换处理,可重构金刚石线锯三维表面形貌。在金刚石线锯常用评价参数基础上,提出基于扫描过程二维投影轮廓和三维重构形貌的综合评价参数。采用自行研制的测量系统,对两个规格的线锯（线径外径分别为0.250 mm、0.320 mm;磨粒粒径范围30~40 μm）进行测量和评价。试验结果表明：该方法无需多次拼接,就可完成金刚石线锯整周三维微观形貌测量,并能实现对线锯特征参数的全面评价,可为线锯本身制造及使用过程中的工艺优化提供更加客观的基础数据。     

水轮机主轴磁流体密封间隙流场关键参数研究

水轮机主轴磁流体密封装置间隙流场因工况和物理场的复杂性一直是磁流体密封研究难点。为研究水轮机主轴磁流体密封装置间隙内磁流体流动特性,建立主轴密封间隙流场数值模型并通过试验进行了验证;通过数值计算研究密封间隙、极齿宽度、极齿高度和极齿槽宽度对磁流体流动的影响。结果表明：极齿附近磁流体不受结构参数影响,基本保持不动;当密封间隙小于0.6 mm时,间隙内磁流体基本不发生流动,当密封间隙超过该值后,极齿槽和永磁体附近磁流体随间隙增加流动加剧,速度线性递增;极齿槽和永磁体附近磁流体随极齿宽度递增流动减弱,速度先线性递减,在3.0~3.5 mm极齿宽度时急剧减小,最后趋于稳定;随着极齿高度和极齿槽宽度逐渐增加,极齿槽和永磁体附近磁流体流动会减弱,极齿槽附近磁流体速度在极齿高度为1.0~3.5 mm和极齿槽宽为3.0~12 mm速度急剧减小,最后趋于稳定,而永磁体附近磁流体速度一直呈线性递减。     

Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

An Experimental Analysis and Optimisation of the CO2 Laser Cutting Process for Metallic Coated Sheet Steels

An experimental investigation is presented which analyses the CO2 laser cutting process for difficult-to-cut metallic coated sheet steels, which are called GALVABOND. It shows that by proper control of the cutting parameters, good quality cuts are possible at high cutting rates. Plausible trends of the energy efficiency (percentage of energy used in cutting) with respect to the various process parameters are analysed. Visual examination indicates that when increasing the cutting rate to up to 5000 mm min⁻¹ , kerfs of better quality than those produced using the parameters suggested in an early study can be achieved. Some kerf characteristics such as the width, heat affected zone and dross, in terms of the process parameters are also discussed. A statistical analysis has arrived at the relationships between the cutting speed, laser power and workpiece thickness, from which a recommendation is made for the selection of optimum cutting parameters for processing GALVABOND material.     

Multiple quality optimization in laser cutting of difficult-to-laser-cut material using grey–fuzzy methodology

This paper investigates the laser cutting performance of 1 mm Duralumin sheet with the aim to improve quality of cut by simultaneously optimising multiple performances such as cut edge surface roughness, kerf taper and kerf width. The experimental data obtained by Taguchi methodology-based L₂₇ orthogonal array experimentation have been used in the hybrid approach optimization of grey relational analysis and fuzzy logic theory. The predicted optimum results have been verified by conducting confirmation experiments. The verification results show an overall improvement of 19 % in multiple quality characteristics. The effects of significant factors on quality characteristics have also been discussed.     

多试件垫片加速寿命试验装置试验垫片预紧应力误差分析

垫片是螺栓法兰连接系统的核心部件,对垫片寿命进行预测可提高连接系统的可靠性,而减小垫片寿命评价装置试验误差则可提高垫片寿命预测的准确性。以柔性石墨缠绕垫为例,研究多试件垫片加速寿命试验装置的法兰和垫片厚度偏差、加载的同轴度偏差和垫片安装偏差对垫片上应力分布的影响,得到在不同温度和预紧应力下的载荷比,确定试验装置所允许的最大偏差;揭示温度和预紧应力大小对试验垫片预紧应力误差的影响,提出控制预紧应力误差的方法。结果表明：预紧应力误差都随着温度的升高而减小;法兰和垫片厚度偏差引起的预紧应力误差随着预紧应力增大而减小;试验装置加载的同轴度偏差和垫片安装偏差引起的试验垫片的预紧应力误差随着预紧应力增大而增大。以试验垫片预紧应力误差1%为指标,得到法兰和垫片之间的厚度偏差应控制在-0.02～0.005 mm之间,试验装置加载的同轴度偏差应不大于0.33 mm,试验垫片的安装偏差应不大于1.24 mm。对于其他种类垫片,也可以通过提出的方法确定法兰和垫片之间的厚度偏差、试验装置加载的同轴度偏差、试验垫片的安装偏差的范围。