铝复合材料超精密加工表面微观分析

用聚晶金刚石PCD刀具对SiC晶须增强铝复合材料SiCw／2024进行了精密超精密切削试验，并用原子力显微镜和电子探针扫描显微镜进行了检测分析，结果证明，SiCw／2024铝复合材料加工表面粗糙度值达到超精密级的最大障碍在于SiC晶须拔出或压入型的破坏方式，而直接剪断的破坏方式则几乎无影响；SiCw／2024超精密加工表面会产生很薄的加工变质层。     

SiC_W/A1复合材料的铣削加工

作者根据SiC/LD2零件的实际铣别加工情况及SiCW／6061材料切削试验资料，绘出了K类硬质合金锐刀是加工SiC晶须增强铝合金复合材料较合适的刀具，并给出了纤维体积含有率yi，切削速度v。，每齿进给量fz，切削路程I。对刀具后刀面磨损值yB及表面粗糙度值Rz的影响规律。供同行借鉴和参考。SIC晶须增强铝合金复合材料（记为SiCW／6061），具有很高的比强度和比刚度（比强度与钛合金TC4相近，比刚度比TC4高出50％左右），耐磨．导热性好，具有热膨胀系数小等特点，故在航天、航空、汽车工业领域有着广阔的应用前景。5iCW／A1复合材料…     

碳化硅增强颗粒含量和尺寸对铝基复合材料超精密车削表面的影响

用聚晶金刚石刀具(PCD)研究了增强颗粒的含量、尺寸等对SiC颗粒增强铝基复合材料超精密车削表面的影响.结果表明:SiC增强颗粒的去除方式主要有拔出、破碎和切断等,SiC颗粒的含量和平均尺寸越大,其拔出和破碎现象就越多,复合材料获得的加工表面粗糙度值也越大;当SiC颗粒主要以切断方式被去除时,可望获得含有较少坑洞和裂纹等加工缺陷的超精密切削表面.     

铝基复合材料专用ELID磨削液的开发

铝基复合材料加工过程中铝基体易软化涂抹产生积屑瘤,存在砂轮严重堵塞、刀具磨损严重、加工表面质量低和加工精度低等加工难题。在研发的已有塑性材料和硬脆材料ELID磨削液基础上,根据铝基复合材料的机械加工性能,开发适合铝基复合材料磨削特点的专用ELID磨削液,既能使金属结合结砂轮中的金属和粘附在砂轮表面的铝基磨屑电解去除达到修锐砂轮的作用,又能在被加工铝基材料表面上形成一层抗腐蚀氧化膜减少划伤,减小其残余加工应力,提高其加工质量和加工精度,实现铝基复合材料的精密磨削加工。实验结果证明:采用该磨削液磨削体积分数60%的铝基碳化硅复合材料,表面粗糙度Ra可达0.098μm,比采用普通磨削液的粗糙度减小了0.016μm。     

SiCp/Al复合材料旋转超声辅助磨削的试验研究

铝基碳化硅颗粒增强复合材料(SiCp/Al)有许多优异的特性,但其加工非常困难,限制了该种材料在工程中的应用。旋转超声辅助磨削加工非常适合中、高体分SiCp/Al复合材料的加工。针对增强体体积分数45%、增强颗粒尺寸3μm、基体材料A12的SiCp/Al复合材料进行了实验研究,分析了加工表面形貌、表面粗糙度和切削力随切削参数的变化规律。实验结果表明,工件加工表面质量较高,表面粗糙度Ra值在0.131~0.340μm之间;切削过程平稳,轴向切削力Fz值在23.33~51.31N。     

SiC颗粒增强铝基复合材料高速铣削实验研究

对SiC颗粒增强铝基复合材料的高速切削加工性能进行了试验分析，研究了铣削速度对铣削力、切削温度、加工表面粗糙度、表面形貌和刀具磨损的影响，从而获得了能够保证对其进行高效率、高精度加工的合理工艺参数。     

模具钢高速切削表面粗糙度的试验研究

用硬质合金刀具对NAK80模具钢进行了高速精密切削试验,研究了切削条件、切削用量对加工表面粗糙度的影响。切削试验结果表明:提高切削速度与减小进给量有利于改善模具钢工件的加工表面质量;当切削速度超过某一范围后,随着切削速度的进一步提高,加工表面粗糙度的降低并不明显。     

超精密车削时切屑形成及表面微观形貌形成机理的研究

在亚微米级CNC超精密车床上进行了单晶金刚石刀具切削试验 ,根据试验结果分析了切屑形成机理和最小切削厚度与表面粗糙度之间的关系 ,建立了加工表面微观形貌的几何模型。研究结果表明 :通过计算最小切削厚度值可预测金刚石车削加工可获得的表面粗糙度值。     

铝合金高速切削表面粗糙度的实验研究

使用硬质合金刀具对LY12高强度铝合金进行了高速精密切削试验。研究了切削条件、切削用量对加工表面粗糙度的影响。高速切削试验表明:提高切削速度与减小进给量有利于改善铝合金工件的加工表面质量;当切削速度超过某一范围后,随着切削速度的进一步提高,加工表面粗糙度的降低并不明显。     

碳化硅及其颗粒增强铝基复合材料超精密加工研究进展

针对碳化硅及其颗粒增强铝基复合材料超精密加工的研究状况,重点关注了碳化硅超精密切削过程中的脆塑性转变以及铝基碳化硅的加工表面形成机理,对其加工过程中切削力、表面形成、刀具磨损、切屑形成等超精密加工过程中的机理以及各自超精密加工过程中的特点及各种其他影响因素进行了分析和总结,以期全面了解碳化硅及其颗粒增强铝基复合材料超精密加工的研究进展。     

金刚石刀具高速精密切削加工的研究

采用聚晶金刚石刀具和天然金刚石刀具对LY12高强度铝合金进行了高速精密切削试验 ,系统研究了切削条件、切削用量对加工表面粗糙度的影响规律。结果表明 ,在比常用切削速度高 8倍的高速切削速度范围内(v=80 0～ 12 0 0m/min) ,采用圆弧刃天然金刚石刀具可获得Ra0 0 4～ 0 0 6 μm的高光洁加工表面 ;采用直线刃聚晶金刚石刀具可获得Ra0 0 7～ 0 1μm的光洁加工表面。切削速度对加工表面粗糙度的影响主要受到机床动态特性的制约 ;进给量的选择范围较大 ;背吃刀量对加工表面质量影响极大 ,为获得较小表面粗糙度必须合理选用背吃刀量     

FUZZY CLUSTERING MODELLING FOR SURFACE FINISH PREDICTION IN FINE TURNING PROCESS

ABSTRACT

In this paper, fuzzy subtractive clustering based system identification and Sugeno type fuzzy inference system are used to model the surface finish of the machined surfaces in fine turning process to develop a better understanding of the effect of process parameters on surface quality. Such an understanding can provide insight into the problems of controlling the quality of the machined surface when the process parameters are adjusted to obtain certain characteristics. Surface finish data were generated for aluminum alloy 390 (73 BHN), ductile cast iron (186 BHN), and inconel 718 (BHN 335) for a wide range of machining conditions defined by cutting speed, cutting feed rate and cutting tool nose radius. These data were used to develop a surface finish prediction fuzzy clustering model as a function of hardness of the machined material, cutting speed, cutting feed rate, and cutting tool nose radius. Surface finish of the machined part is the output of the process. The model building process is carried out by using fuzzy subtracting clustering based system identification in both input and output space. Minimum error is obtained through numerous searches of clustering parameters. The fuzzy logic model is capable of predicting the surface finish for a given set of inputs (workpiece hardness, cutting speed, cutting feed rate and nose radius of the cutting tool). As such, the machinist may predict the quality of the surface for a given set of working parameters and may also set the process parameters to achieve a certain surface finish. The model is verified experimentally by further experimentation using different sets of inputs. This study deals with the experimental results obtained during fine turning operation. The findings indicate that while the effects of cutting feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved for aluminum alloy and ductile cast iron but it deteriorated with speed for inconel.     

FUZZY CLUSTERING MODELLING FOR SURFACE FINISH PREDICTION IN FINE TURNING PROCESS

In this paper, fuzzy subtractive clustering based system identification and Sugeno type fuzzy inference system are used to model the surface finish of the machined surfaces in fine turning process to develop a better understanding of the effect of process parameters on surface quality. Such an understanding can provide insight into the problems of controlling the quality of the machined surface when the process parameters are adjusted to obtain certain characteristics. Surface finish data were generated for aluminum alloy 390 (73 BHN), ductile cast iron (186 BHN), and inconel 718 (BHN 335) for a wide range of machining conditions defined by cutting speed, cutting feed rate and cutting tool nose radius. These data were used to develop a surface finish prediction fuzzy clustering model as a function of hardness of the machined material, cutting speed, cutting feed rate, and cutting tool nose radius. Surface finish of the machined part is the output of the process. The model building process is carried out by using fuzzy subtracting clustering based system identification in both input and output space. Minimum error is obtained through numerous searches of clustering parameters. The fuzzy logic model is capable of predicting the surface finish for a given set of inputs (workpiece hardness, cutting speed, cutting feed rate and nose radius of the cutting tool). As such, the machinist may predict the quality of the surface for a given set of working parameters and may also set the process parameters to achieve a certain surface finish. The model is verified experimentally by further experimentation using different sets of inputs. This study deals with the experimental results obtained during fine turning operation. The findings indicate that while the effects of cutting feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved for aluminum alloy and ductile cast iron but it deteriorated with speed for inconel.     

Multiple-response optimisation of electrochemical grinding characteristics through response surface methodology

This paper comprehensively evaluates the influence of voltage and cutting speed on electrochemical grinding of composite carbide inserts. A complete 4² factorial experiment was planned and carried out where each treatment combination has been replicated twice to achieve an acceptable degree of precision. Mathematical models have been developed for the major performance indices like current density, material removal rate (MRR) and surface finish of the job by multiple linear regression analysis. Then multiple-response optimisation has been carried out to find the optimum parameter settings to get a desired yield both by desirability functions as well as by contour overlapping method. It has been found that passivation occurs increasingly at higher voltages and it is removed almost instantaneously at higher speed leading to higher current density and MRR. The surface finish is not very much dependent on grinding speed. The optimum surface finish is obtainable at 12 to 13 V (app.) in electrochemical grinding of composite carbides.     

Influence of cutting fluids on surface finish of holes drilled into aluminium 390

The primary objective of this research was to compare the surface finish resulting when using a semi-synthetic cutting fluid to that of a premium soluble oil. The secondary objective was to determine the effects of drill diameter, cutting speed, and fluid concentration on surface finish. The surface measurements were made on the walls of 6.350 and 9.525 mm lind holes drilled 25.4 mm into aluminium 390. Each cutting fluid was introduced using a flood application. Additional factors in the experimental design for each cutting fluid included two levels of cutting speed and two levels of fluid concentration. Variations in drill diameter, cutting speed, and the interaction between these factors were significant with respect to surface finish for both the semi-synthetic fluid and the soluble oil. Fluid concentration for the semi-synthetic fluid also had a significant effect on the surface finish. The surface finish produced while using the semi-synthetic fluid was approximately the same as that with the soluble oil.     

再生颤振的稳定性模型研究

在刀具和工件之间产生的自激颤振不仅影响工件的表面粗糙度和加工精度,而且对刀具寿命有不利影响,甚至无法进行切削加工,这就直接影响生产效率的提高。本文对切削颤振的稳定性模型进行了研究,推导出了稳定切削极限条件下,主轴转速和轴向切深的关系表达式,并用Matlab进行了仿真计算。     

MACHINABILITY STUDY OF CARBON/PEEK COMPOSITES

Composites are generally fabricated to near nett-shape, however, there is often a need to conduct some additional machining operations such as trimming of the edges. High tool wear and the need for good surface finish are some of the major concerns in machining. This study deals with the machining of Carbon/PEEK, a high performance thermoplastic matrix composite, which is being used extensively in aerospace industries because it is light and posses high specific properties compared to conventional metallic materials. The technique of the full factorial design of experiment is used to investigate the relative effects of the various machining parameters on the amount of tool wear and the surface quality of the workpiece.

Experimental results show that the cutting speed, depth of cut and feed-rate are the main factors that contribute to tool wear of the inserts. The surface finish is found to be independent of the machining parameters and much better than those obtained in the conventional machining of metals provided a critical cutting speed is exceeded. This critical cutting speed is found to be in the range of 70m/min to 75m/min. The cutting point temperature at this speed is found to have exceeded the glass transition temperature of the material, indicating that cutting is done in the rubbery regime. This leads us to conclude that the smooth surface finish of the workpiece is caused by some form of polymer softening action rather than determined by the tool geometry of the cutter.     

Optimization of wire electrical discharge machining (WEDM) process parameters using Taguchi method

Wire electrical discharge machining (WEDM) is extensively used in machining of conductive materials when precision is of prime importance. Rough cutting operation in WEDM is treated as a challenging one because improvement of more than one machining performance measures viz. metal removal rate (MRR), surface finish (SF) and cutting width (kerf) are sought to obtain a precision work. Using Taguchi’s parameter design, significant machining parameters affecting the performance measures are identified as discharge current, pulse duration, pulse frequency, wire speed, wire tension, and dielectric flow. It has been observed that a combination of factors for optimization of each performance measure is different. In this study, the relationship between control factors and responses like MRR, SF and kerf are established by means of nonlinear regression analysis, resulting in a valid mathematical model. Finally, genetic algorithm, a popular evolutionary approach, is employed to optimize the wire electrical discharge machining process with multiple objectives. The study demonstrates that the WEDM process parameters can be adjusted to achieve better metal removal rate, surface finish and cutting width simultaneously.     

Ball burnishing of tool steel

In place of the traditional methods of finishing a surface, the ball-burnishing process was investigated. Experimental work was conducted on a vertical machining center to establish the effects of various burnishing parameters on the surface finish of ASSAB XW-5 steel (high-carbon, high-chrome steel), including burnishing speed, ball material, lubricant, burnishing forces (depth of penetration), and feed. Within the parameter space explored, it was found that the burnishing speed affects the surface finish, with a burnishing speed of 1,200 mm/min giving the worst surface finish. WC (Tungsten carbide) ball gave the best and most consistent surface finish. Grease was a better lubricant than cutting oil. By varying the burnishing speed, the burnishing forces varied also, and these forces showed no obvious relationship to the surface finish of the burnished workpiece.     

Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites

Non-traditional process like wire electro-discharge machining is found to show a promise for machining metal matrix composites. However, the machining information for the difficult-to-machine particle-reinforced material is inadequate. This paper is focused on experimental investigation to examine the effect of electrical as well as non-electrical machining parameters on performance in wire electro-discharge machining of metal matrix composites (Al/Al₂O₃p). Taguchi orthogonal array was used to study the effect of combination of reinforcement, current, pulse on-time, off-time, servo reference voltage, maximum feed speed, wire speed, flushing pressure and wire tension on cutting speed, surface finish, and kerf width. Reinforcement percentage, current, and on-time was found to have significant effect on cutting rate, surface finish, and kerf width. The optimum machining parameter combinations were obtained for surface finish, cutting speed, and kerf width separately. Wire breakages were found to pose limitations on the cutting speed in machining of these materials. Wire shifting was found to deteriorate the machined surfaces.