亚固结线锯切割实验研究

针对目前游离磨料线锯切割效率低、切缝损失大的缺点,提出了一种亚固结线锯切割的新方法,即在线锯表面增加凹槽,在线锯切割时让磨粒嵌入凹槽实现瞬间固结,从而达到提高效率和减小切缝损失的目的。应用VW-6000/5000动态分析三维显微系统,观测切割区域内磨粒的运动状态,结果表明磨粒可以实现瞬间固结。通过亚固结线锯和游离磨料线锯的切割对比实验,分析了两者在切割效率、切缝宽度和表面粗糙度方面的差距。     

固结磨粒金刚石线锯技术的研究

金刚石线锯是一种对硬脆性材料进行精密、窄缝切割技术。其中,固结磨粒金刚石线锯以其切割速度快、耗材成本低及环保等优点被广泛应用于半导体和太阳能电池硅材料的切割加工中。利用目前国内现有的设备和国际上较好的金刚石线锯丝,从切割工艺参数、失效机理等方面对硅材料的固结磨粒金刚石线锯进行了试验和分析,对提高硅材料切割效率与切割质量有一定的指导意义。     

游离磨料线锯切割机理实验研究

应用VW-6000/5000动态三维显微系统对游离磨料线锯切割过程中磨粒的运动状态进行分析,结果表明磨粒在切割区域存在两种状态:一种为接触状态,另一种为非接触状态。同时应用0.16mm表面涂有树脂的线锯和普通线锯对光学玻璃K9进行切割实验,验证了游离磨料线锯切割去除机理。实验结果显示,普通线锯的切割效率大大高于涂有树脂的线锯的切割效率,切割工件表面均为微细凹坑,没有划痕,而且切割后涂有树脂的线锯表面嵌有许多磨粒,普通线锯表面有许多微细凹坑,均表明游离磨料线锯切割机理主要以"滚压"去除为主。     

固结磨粒线锯的随机力建模与振动分析

固结磨粒线锯是目前切割脆硬材料的主要方法,由于线锯属于柔性刀具,在切割过程中线锯的振动不可避免,其中存在磨粒对线锯的激励以及机床本身传递的振动等。为了研究切割过程中磨粒对线锯振动的影响,本文主要以弦线振动理论为基础,建立了有阻尼轴向匀速运动线锯的振动方程并分析了线锯切割过程中的受力,进而构建了对线锯横向振动产生主要影响的法向随机力模型,分析在小偏移状态下线锯的线性振动情况。基于WXD170往复式金刚石线锯切割机的切割实验,验证了法向随机力模型的有效性,结果表明该随机力模型用于振动模型的仿真可以准确地预测线锯加工过程中的振动情况。     

YAG晶体切割参数对线锯寿命影响的试验研究

YAG(Y3Al5O12)晶体以优异的特性正被广泛使用,选择合适的切割方式来降低其加工成本十分重要。对固结线锯的种类和失效形式进行总结,环形电镀多丝绞合金刚石线锯适合硬脆YAG晶体切割。采用往复线机床和环线机床进行切割试验,发现往复线金刚石线锯机床切割线锯寿命短,切割过程易发生断线,环形线锯切割时无换向可实现高速切割。通过环线机床正交试验发现切割线速度提高线锯寿命显著增加,线锯进给速度增加则寿命先提高后降低,线锯张紧力对线锯寿命没有影响。     

SiC浓度对游离磨料线锯切割性能的影响

目前游离磨料线锯切割技术广泛应用于水晶、硅等脆硬材料的切割。它主要是通过具有一定速度的钢丝线,将浆料中的SiC磨粒带入切割区域,从而实现材料的去除。因此,浆料在游离磨料线锯切割中起着至关重要的作用。文中通过切割实验研究了浆料中SiC浓度对切割性能的影响,结果表明,切割效率和切缝宽度随着浆料中SiC浓度的增加而增加,而表面粗糙度Ra则随着浆料中SiC浓度的增加而减少。     

磁感应游离磨粒线锯吸附机理及切割性能分析

传统游离磨粒线锯切割过程中,磨粒难以进入到切割区域,这使得切割区域工况变差,线锯切割效率降低,切缝损失增大。提出了一种磁感应游离磨粒线锯切割的新方法,通过磁场力的作用将磁性磨粒吸附于锯丝表面顺磁区,使更多磁性磨粒进入切割区域,从而提高线锯切割性能。通过分析锯丝在不同磁场强度下的吸附磁性磨粒情况,验证了磁感应游离磨粒吸附机理的正确性。最后,进行磁感应游离磨粒线锯切割实验。结果表明,磁场强度的变化对游离磨粒线锯的切割效率、表面粗糙度和切缝宽度都会产生显著的影响。     

游离磨料线锯切割机改造与试验

游离磨料多线锯切割技术广泛应用于硅碇、水晶等材料的切片加工。为了方便研究游离磨料线锯的切割机理、切片工艺等,对电火花线切割设备进行改造,使其满足游离磨料线锯切割的要求。并采用准0.14 mm的钢丝线,对水晶材料（K9）进行切割实验,结果表明改造的切割设备满足切割实验需求,为后续的实验提供了基础保障。     

游离磨料线锯切片流体动压效应的数值分析

游离磨料线锯切割技术是目前单晶硅切片的主要加工方法。建立了游离磨料线锯切片过程中流体动压效应的数学模型,并采用有限差分法进行了数值分析,得到了游离磨料线锯切片的流体动压力分布和膜厚。结果表明,当磨粒尺寸较小时,锯丝与晶体间的膜厚大于磨粒尺寸,磨粒悬浮在研磨液中,因此研磨液中磨粒与晶体的碰撞将是材料去除的主要因素。     

金刚石线锯的焊接性能及参数优化

与传统往复式运动线锯相比,环形金刚石线锯为单向运动,无换向时的机械惯性作用,可实现高速锯切。研究采用电容储能焊焊接固结金刚石磨粒的线锯丝,分析了焊接过程中影响焊点的物理机械性能的工艺参数,采用中心组合设计实验,考察焊接电容、焊接电压和热处理温度三因素对环形金刚石线锯丝焊接性能的影响,建立了环形金刚石线锯焊接断裂拉力的响应曲面模型,方差分析和满意度函数(DFM)确定了最大断裂拉力值对应的最佳焊接工艺参数,验证试验表明该模型能实现相应的断裂拉力值的预测。     

Effects of grit size on abrasion with coated abrasives

This paper is concerned with identifying the causes of grit size effects in the initial performance of fresh coated abrasives and the deterioration of coated abrasive performance with continued use. Abrasion tests were performed on an instrumented pin-on-cylinder apparatus which had removable segments for observing the coated abrasive surface in the scanning electron microscope (SEM). This allowed for a direct correlation between measurements of coated abrasive performance and SEM observations of coated abrasive morphology. With coated abrasives containing finer grit sizes, numerous adhesive wear particles were found on the coated abrasive surface; this supports the theory that the smaller initial abrasion rate with finer grits is due to abrasive grains making “elastic” contact with the metal specimen at loads insufficient for cutting. With continued use, the rapid deterioration in performance with finer grits was accompanied by a buildup of metal caused by capping of the abrasive grain tips with metal chips and by clogging due to metal chips and adhesive wear particles becoming stuck between the grains. With coarser grits, which were found to experience extensive grain fracture followed by some grain capping and flattening but virtually no clogging, the deterioration in coated abrasive performance was very much less.     

Effects of magnetic field distributions on wire sawing performance

To transport more abrasive grains into the cutting zone, the method of magnetic-induction free-abrasive wire sawing is proposed. A uniform magnetic field is used to magnetize a steel wire and forms a high gradient magnetic field around the wire. The magnetic abrasive grains are adsorbed on the magnetized wire and are transported into the cutting zone, which improves the wire sawing performance. The adsorption of the magnetic abrasive grains is observed using an experimental setup along the wire cross-sectional direction. The results suggest that magnetic abrasive grains are increasingly adsorbed in the paramagnetic region of the wire with increasing magnetic field intensity. Single-wire sawing experiments are conducted on a WXD170 reciprocating wire sawing machine at variable magnetic field intensity and distribution. The results suggest that the change in magnetic field intensity strongly affects the cutting efficiency, kerf loss, and surface roughness. The performance of the magnetic-induction free-abrasive wire sawing under different magnetic field intensities and distributions are compared. The wire sawing performance improves when the uniform magnetic field is evenly distributed in the cutting zone and at the top of cutting zone.     

环形电镀金刚石线锯锯切工艺参数的正交试验研究

这里对环形电镀金刚石线锯锯切工艺参数进行了正交试验研究。分析了金刚石粒度、进给压力和锯丝速度对锯切过程的影响。获得了基于提高锯切效率和锯丝寿命,降低锯切力的最佳锯切工艺参数。锯切花岗岩时,要保证较高的锯切效率和锯切比,在本试验范围内,最佳工艺参数为:采用金刚石粒度为200～230#的锯丝,进给压力为9N,锯丝速度为20m/s。     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

陶瓷CBN砂轮地貌建模与磨削仿真

针对砂轮表面上磨粒形状的不规则性、尺寸的不确定性以及分布的随机性特点,采用随机空间平面切分实体的方法生成了具有实际磨粒几何特征的不规则多面体磨粒;提出了虚拟格子法,实现了磨粒空间位置的随机分布,构建了陶瓷CBN砂轮地貌仿真模型;采用有限元法和光滑粒子流体动力学法的耦合方法进行了砂轮地貌模型磨削仿真,通过切削层SPH粒子的运动情况,分析了磨粒的切削机理及工件表面的创成机理。     

Topography and microstructure of the cutting surface machined with abrasive waterjet

Abrasive waterjet (AWJ) technology has been widely used for cutting materials in precision machining. The present paper reports the surface topography and microstructure of the cutting surfaces machined by AWJ. Four different kinds of ductile metallic materials were used for preparation of specimens. With the AWJ processing technique, smooth surfaces were easily obtained with a lower surface roughness about 2 to 3 μm. By comparing the microhardness of the specimens with the control surface sample obtained by wire electrodischarge machining, it is found that there is no heat-affected zone on the cutting surfaces machined by AWJ. By observing the surface morphology and microstructure, the features of friction and wear marks are revealed. The results show that a smooth cutting surface is more easily obtained on hard materials, while erosions on soft material surfaces are more serious. All scratches have a clear consistent direction, under the action of mechanical abrasive wear.     

Experimental investigation on cutting mechanisms in fixed diamond wire sawing of bone

Bone sawing has been widely used in performing bone surgery. However, thermal necrosis, loss of cutting precision and surface damage may occur in cutting process. The primary objective of this research is to improve cutting performance of bone by advantages of diamond wire sawing. Mechanism of material removal, cutting force, temperature and surface quality are analyzed based on experimental results. It is indicated that wire sawing provides small depth of cut, which is effective to obtain ductile material removal mode. Due to small material removal rate per abrasive, thermal energy is low and most of the heat can be taken away by the cyclic wire and bone chips. Consequently, cutting force and temperature in cutting zone are lower than that of traditional sawing. Due to the high efficiency of chip ejection, burrs and fracture are reduced and a significant improvement in surface quality is achieved. Based on cutting experiments with various values of cutting parameters, it is observed that better performance is achievable at higher wire speeds. These results provide a valuable basis for application of wire sawing and understanding of bone cutting mechanisms.     

Effects of process parameters on surface roughness in abrasive waterjet cutting of aluminium

Abrasive waterjet cutting is a novel machining process capable of processing wide range of hard-to-cut materials. Surface roughness of machined parts is one of the major machining characteristics that play an important role in determining the quality of engineering components. This paper shows the influence of process parameters on surface roughness (R_a) which is an important cutting performance measure in abrasive waterjet cutting of aluminium. Taguchi’s design of experiments was carried out in order to collect surface roughness values. Experiments were conducted in varying water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting aluminium using abrasive waterjet cutting process. The effects of these parameters on surface roughness have been studied based on the experimental results.