磨削表面损伤对RBSiC弯曲强度的影响

借助X射线衍射方法测量了反应烧结碳化硅(RBSiC)材料的磨削表面的残余应力状态,并根据断裂力学评价了磨削引入的裂纹尺寸,分析了RBSiC的弯曲强度受磨削引入裂纹和残余应力的影响.研究表明,由于磨削过程中与磨削方向有关的机械载荷占主导作用,使磨削后的表面残余应力具有方向依赖性.砂轮轴向进给从0.90μm/s增加到1.35μm/s,磨削表面的残余压应力数值降低,计算得到的磨削引入的裂纹尺寸增大,导致强度下降.     

On the Surface Integrity of Precision-Ground Steel Cylindrical Parts

The effects of traditional corundum and boron-nitride (CBN) wheels on the surface integrity of internally and externally ground steel parts has been investigated in respect to microhardness, residual stresses, and change of texture. The microhardness and residual stress components of the surface layer of HSS tools ground with CBN wheels have been measured and texture has been also investigated. Case-hardened steels have been ground with mainly traditional wheels. The change of microhardness, residual stresses, and texture depends to a large extend not only on grinding parameters but also on the grade of sharpness of the wheel. The difference between grinding with sharp and worn wheels is significant. These facts prove the importance of different continuous wheel dressing processes. The effect of the coolant on the surface quality has also been examined.     

GRINDING OF SILICON AND GLASS USING A NEW DRESSING DEVICE AND AN IMPROVED COOLANT SYSTEM

Ductile mode machining of brittle materials such as ceramics is recognized as an emerging technology with important applications. Ductile machining is possible if the depth of cut is less than the critical depth of cut of the machined material. By using a new device for dressing a resin-bonded diamond wheel and an improved coolant system proposed here, ductile mode grinding of silicon and glass was achieved using an inexpensive, conventional surface-grinding machine. The low-cost dressing device also ensured minimum disruption to the grinding operation and a higher level of safety. A flooding supply of coolant at the grinding zone provided better cooling performance and lubrication. A relationship appeared to exist between the surface finish and the lightness values of ground silicon surfaces.     

超声振动辅助铣磨加工对CFRP切削力和表面质量的影响

为研究超声振动辅助铣磨加工对碳纤维增强树脂基复合材料(CFRP)切削力和表面质量的影响,建立了超声振动辅助铣磨加工的切削力模型,进行了磨粒运动轨迹、刀具锋利化效果及单颗磨粒切厚的理论分析及试验验证。结果表明:超声振动辅助铣磨加工与传统铣磨加工相比切削力更小、加工质量更好。当每齿进给量从4μm/z增加到8μm/z时,超声振动辅助铣磨加工的切削力增加了44.7%,小于传统铣磨加工的84.9%;同样,当切深从200μm增加到400μm时,超声振动辅助铣磨加工的切削力增加了187.8%,小于传统铣磨加工的209%;在相同加工参数下,超声振动辅助铣磨加工的工件表面与传统铣磨加工相比,树脂涂覆、表面凹坑和纤维拔出量明显减少。      

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

工程陶瓷高效平面磨削表面波纹度试验研究

 以氧化铝和氧化锆两种工程陶瓷在高效磨削条件下的磨削振动和表面波纹度为研究对象,概述了磨削表面波纹度的定义和评价方法以及产生波纹度的原因,在超高速平面磨削实验台上进行磨削工艺试验,通过改变砂轮线速度、进给速度和磨削深度,分析了磨削参数对零件表面波纹度的影响。在试验研究的基础上,对磨削表面波纹度的影响因素和机理进行分析和讨论。试验结果表明,在陶瓷材料高效平面磨削中,砂轮线速度和进给速度是影响磨削颤振与表面波纹度的主导因素。在如120 m/s的较高砂轮线速度时,磨削过程振动主要是由强迫振动引起,工件表面质量好于低速情况。在保证较高磨削效率的前提下,陶瓷材料的高效磨削更适合在大切深和小进给速度条件下进行。     

Residual stress and damage effect on integrity of ground silicon nitride

Ceramic workpiece integrity and residual surface stresses generated by single pass diamond grinding were evaluated for three flaring cup wheels and four machine-loop stiffnesses. Stresses in silicon nitride bars ground on one face were characterized by X-ray diffraction, strength by four-point bending, and grinding damage depth by scanning electron microscopy. A custom-built workpiece holder was used to tune the grinding machine-loop stiffness. Electrolytic in-process dressing was applied to one of the wheels to provide stable cutting conditions. The experimental results indicate machine stiffness does not have significant influence on flexural strength, but rather affects the depth of cut. All ground surfaces have some degree of damage and residual stress, and differences are revealed between wheel bonds and grit sizes. The competing phenomena of strength enhancement due to residual stress and strength degradation due to damage are discussed.     

先进陶瓷材料超声振动铣磨加工表面粗糙度仿真及实验(英文)

为了对超声振动铣磨加工先进陶瓷的表面粗糙度进行预测,建立了加工表面形貌的仿真模型.通过实验测得砂轮表面形貌和磨粒突出高度信息,并对这些信息进行Kolmogorov-Smirnov正态验证,发现砂轮表面形貌不服从高斯分布.对非高斯分布的数据进行Johnson变换,建立砂轮形貌的数值模型.结合砂轮表面形貌和磨粒与工件的相对运动分析,提出了一种表面轮廓搜索方法,进而生成了加工表面的三维形貌.最后,在DMG ULTRASONIC 70-5 linear机床上进行切削实验,对仿真结果进行了验证,结果表明仿真与实验结果具有较好的一致性,并对仿真误差产生的原因进行了分析.     

New Vitrified Bond Diamond Grinding Wheel for Grinding the Cylinder of Polycrystalline Diamond Compacts

In this work, a kind of new vitrified bond based on Li2O-Al2O3-SiO2 glass ceramics was used to bond the diamond grains, which is made into grinding wheel and the cylindrical grinding process of polycrystalline diamond compacts （PDCs） by using the new vitrified bond diamond grinding wheel was discussed. Several factors which influence the properties of grinding wheel such as amount of vitrified bond and the kinds and amount of stuff in grinding wheel were also investigated. It was found that the new vitrified bond can firmly combine diamond grains, when there are only diamonds and vitrified bond in the structure of grinding wheel, the longevity of the grinding wheel is about 2.5-3 times as that of resin bond grinding wheel for processing PDCs. The grinding size precision of PDCs can be improved from 4-0.03 mm to 4-0.01 mm because of larger Young＇s modulus of vitrified bond than resin bond. The grinding time of a PDC product can be 1.75-2.0 min from 3.25-3.5 min, so this kind of grinding wheel can save much time for processing PDCs. Also, there is hardly noise when using this new vitrified bond diamond grinding wheel to process PDCs. The amount of vitrified bond in grinding wheel influences the longevity of grinding wheel. When the size of diamond grains is 90-107 μm, the optimal amount of vitrified bond in grinding wheel is 21% （wt pct）. When the amount of vitrified bond exceeds 21%, there are many pores in grinding block, which will decrease the longevity of grinding wheel. The existence of addition stuff such as Al2O3 or SiC can reduce the longevity of grinding wheel.     

精细陶瓷材料的金刚石砂轮磨削性能

本文探讨了精细陶瓷材料的金刚石砂轮磨削性能的共同特点以及不同种类陶瓷和不同磨削方式的影响。研究结果表明：陶瓷材料磨削时，砂轮磨损大，磨削比小，磨削力大、磨削效率低，磨后陶瓷零件使用寿命大大降低；必须根据陶瓷种类的不同选择不同的磨削方式。     

应用于磨床砂轮磨钝及故障检测的神经网络研究

磨床在磨削过程中砂轮会逐渐变钝。当它变钝后,需要进行修快。针对砂轮变钝时间的不定性,利用神经网络进行砂轮监控,以便于充分把握修快时机,达到及时、经济的修快。同时对砂轮意外碰撞、破碎进行监控。     

Study on grinding of pre-sintered zirconia using diamond wheel

Zirconia-based ceramics are the most preferred materials used in implants due to their excellent mechanical properties compared with other alternatives. These materials available in the pre-sintered form are appropriate to grind due to their soft nature. However, it is challenging to achieve a required surface finish in grinding these ceramic materials owing to chipping, which limits its usage in industries. In this work, the pre-sintered yttria stabilized tetragonal zirconia (Y-TZP) component was ground using a resin-bonded diamond-grinding wheel under different cooling environments. The components ground under the minimum quantity lubrication conditions exhibited a reduced grinding force with better surface finish compared to wet (flood coolant) and dry conditions. The resultant specific energy was reduced with the increase in maximum chip thickness for different cooling conditions. The critical depth of cut estimated from the pre-sintered zirconia was witnessed to be higher, which indicated that the initiation of ductile to brittle transition occurred at a deeper depth of cut. The material removal mechanism observed in the pre-sintered zirconia was dominated by brittle fracture. This was evident from the obtained chips and ground surface morphology.     

二维超声振动磨削陶瓷的表面质量试验研究

采用金刚石砂轮对陶瓷材料进行了不同参数下的普通磨削和二维超声振动磨削试验,对获得的不同表面质量特征及不同的加工参数对表面质量的影响进行了分析。实验结果表明,在同样的加工条件下,超声振动磨削表面的沟槽浅而宽,在超声振动下砂轮不易堵塞,利于使用细砂轮磨削,因此超声振动磨削可以提高陶瓷材料的表面质量。     

纳米结构陶瓷涂层的外圆磨削力以及磨削表面精度的实验研究

使用功率计监测磨削加工的能量消耗，探讨了纳米结构陶瓷涂层的外圆磨削过程；对纳米陶瓷涂层和传统陶瓷涂层在磨削力和磨削表面精度方面进行了比较．磨削实验使用了外圆磨床和陶瓷结合剂金刚石砂轮．通过测量主轴功率获得切向磨削力，讨论了加工参数，如切深、进给率以及砂轮粒度对切向磨削力的影响．还对磨削后的涂层表面用粗糙度仪和扫描电镜进行了评估，揭示了表面粗糙度与加工参数的关系．     

Ductile Regime Mirror Finish Grinding of Ceramics with Electrolytic In-process Dressing (ELED) Grinding

Advanced structural ceramics, such as silicon nitride based materials, are of interest owing to their unique physical and mechanical properties. However the cost of grinding these ceramics, which is an integral part of their fabrication, is very high. Moreover, grinding can result in surface and sub-surface damage in the material and these defects can significantly reduce the strength and reliability of the finished components. Grinding damage is sensitive to grinding parameters. Two types of silicon nitride based ceramic materials were ground with Electrolytic In-Process Dressing (ELID) using different grit sized metal bonded diamond grinding wheels. With the application of ELID technology, mirror surface finish was realized with a #4000 mesh size wheel (average grain size = 4μm). Differences in ground surface topography caused by wheel grain size were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM studies reveal that material was predominantly removed in the ductile mode when ELID grinding was performed with a #4000 grit size wheel or finer.     

反应烧结碳化硅的磨削特征

采用金刚石砂轮对(RBSiC)进行磨削, 系统研究了表面形貌、残余应力和弯曲强度等磨削特征. 结果显示, 材料主要以脆性断裂去除, 局部区域为塑性切除. 随着轴向进给增大, 表面粗糙度(R_a)增加, 为降低R_a可进行适当光刀. 随着轴向进给增加, 磨削区的冷却效果被削弱, 使磨削残余压应力值下降. 与0.9 μm/s相比, 用1.35 μm/s磨削后试样的表面损伤程度增加. 工作台转速2.1 r/min、轴向进给0.9 μm/s并光刀1 min是保证高加工效率并获得较好质量表面的最优参数.     

Grinding of Single-Crystal Silicon Using a Microvibration Device

This paper presents experimental results of grinding of single-crystal silicon using a microvibration device and a diamond grindingwheel. Samples were cut from (100) silicon. The grinding direction was parallel to the [110] direction of (100) silicon. These samples were ground under the same grinding conditions but with different vibration directions, frequencies, and/or amplitudes. The surface roughness and the surface texture of all samples were analyzed for comparison. The R_a, R_q, and R_t values and the microphotographs of the ground silicon surfaces showed the dependency of surface finish on the grinding with vibrations. Samples ground with vibrations had better surface finish compared with the silicon surfaces ground without vibrations. Out of the 12 experiments, the best surface finish was achieved when (100) silicon was ground with horizontal vibrations at a 70-Hz frequency and 6-μm amplitude perpendicular to the grinding direction.     

Material removal characteristics of 20CrMnTi steel in single grit cutting

The single grit cutting test was regarded as an important approach for understanding a complex grinding process, and revealed the connection between grinding wheel state, grinding parameters, and the surface integrity of workpieces. To investigate the formation mechanisms and morphology of grinding chips of 20CrMnTi steel, experiments on the high-speed grinding of a single grit on the surface of 20CrMnTi steel were performed by the finite element method. Combining this with the analysis of scratch morphology and the use of the finite element method, the authors showed that the process included sliding friction, ploughing, and produced fragmented, and continuous chips which changed with the cutting depth. Moreover, the distributions of physical quantities including stress, strain, heat, and temperature fields in the three areas subjected to cutting deformation were analyzed in greater detail. Moreover, combined with the deduced theoretical formulae, finite element simulation tests were conducted to analyze the undeformed chip thickness, shear angle, chip shape, strain in the formation process of chips from a single grit grain, and its changes with grinding parameters and the shape of abrasive grains.     

结构陶瓷磨削表面微裂纹的研究

结构陶瓷的磨削表面微裂纹是较常见和较危险的磨削损伤，本文应用压痕断裂力学。磨削表面热应务陶瓷微观结构的有关知识分析了结构陶瓷表面裂纹的形成机理、形状特征及奖表面的延伸，并对几种典型结构民磨削表面层的微观状态进行了大量的ＳＥＭ观察，结果表明：（１）磨削微裂纹与陶瓷的断裂韧性Ｋ１Ｃ和显微硬度Ｈ之比、陶瓷的热特性及磨削工艺参数有关；（２）磨削微裂纹的 压痕效应径向裂纹、热裂纹、（３）细晶陶瓷多为穿晶裂纹     

振动辅助磨削——压电平台的设计与制造

旨在研究振动辅助磨削．首先综述了用于不同条件下的振动辅助磨削以及利用振动辅助抑制砂轮堵塞的现象．还论述了振动辅助磨削的优点，例如降低磨削力和磨削温度，提高磨削效率和工件质量等．为了实现振动辅助磨削，设计和制造了一个由平行四连杆机构和压电驱动元件组成的压电平台，并且使用该压电平台进行了陶瓷材料的振动磨削实验．给出了振动磨削实验的初步结果并对结果进行了讨论．