电铸制备SiC颗粒增强镍基复合材料的工艺与性能

采用电铸技术(氨基磺酸镍电铸液)成功制备了SiC颗粒增强镍基复合材料;用Leica Qwin图形分析软件和显微硬度计分析了电铸工艺参数对SiC颗粒增强镍基复合材料中SiC颗粒含量以及SiC含量对该复合材料显微硬度的影响;用场发射扫描电镜分析了复合材料的截面形貌和SiC分布.结果表明:在SiC加入量50 g·L-1、电流密度3 A·dm-2和磁力搅拌强度1.5次/min条件下,复合材料中SiC颗粒体积分数达到最高值27%,其显微硬度值也最高,为710 HV.     

硬脆颗粒增强铝基复合材料的已切削加工表面形貌及影响因素

为深入了解铝基复合材料的已加工表面形貌进行了切削实验研究。实验表明,因硬脆的增强颗粒阻碍基体塑性变形,铝基复合材料的已加工表面形成过程有许多特点,已加工表面中包含各种加工缺陷。经检测分析可知,增强颗粒的体积分数和颗粒大小是决定复合材料已加工表面形貌的主要因素,刀具材料、结构和切削参数也对此有重要影响。     

SiC颗粒增强铝基复合材料高速铣削工艺研究

从颗粒增强金属基复合材料的应用和切削加工现状出发 ,针对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。通过铣削试验 ,研究了铣削速度对铣削力、加工表面粗糙度、表面形貌以及刀具磨损的影响 ,分析了该材料的高速切削机理 ,并获得了能够保证对其进行高效高精度加工的合理工艺参数。     

等温变形参数对15％SiC颗粒增强铝基复合材料组织性能的影响

研究了15％SiC铝基复合材料等温变形后的显微组织和室温拉伸性能的变化,得出结论为在经过等温变形后晶粒有一定的变化,但程度较小,变形速度加快时SiC颗粒的分布出现局部的聚集现象;而拉伸性能随总变形量的增大而提高,变形温度升高和变形速度加快时拉伸性能降低,而变形火次的影响很小。     

颗粒增强铝基复合材料铣削加工实验研究

使用K10硬质合金铣刀,在不使用冷却液的条件下,对A12024/SiCp复合材料进行铣削加工实验,研究切削参数和颗粒尺寸对表面质量、切削力、刀具磨损的影响.研究表明,随着增强颗粒尺寸的增大,表面变粗糙、切削力增大和刀具磨损加重;在不同的切削条件下,法向力均大于切向力.随着切削用量的增大,铣削力呈增大趋势,其中,吃刀量对铣削力的影响最大,切削速度的影响最小;加工表面上存在凹坑、颗粒突起和基体材料涂敷等缺陷,表面粗糙度随着颗粒尺寸增大而增大,随着切削速度的提高而减小.     

双向载荷对SiC颗粒增强铝基复合材料变形行为的影响

利用有限元方法研究了单轴和双轴拉伸条件下,SiC颗粒增强铝基复合材料的变形行为,分析了SiC颗粒体积百分比和双向载荷比,对复合材料宏观力学性质的影响.结果表明,对同一颗粒体积比而言,复合材料的宏观等效应力应变曲线随三轴应力约束的增加而降低;与单轴加载不同,在双轴加载条件下,即使SiC颗粒的体积比很小,其增强效果也很明显.     

铺粉工艺对SiC 颗粒增强铝基表面复合材料性能的影响*

搅拌法制备SiC颗粒增强铝基复合材料时铺粉工艺对材料性能影响很大,影响SiC颗粒能否均匀地嵌入基体中。研究黏接剂、SiC颗粒粒径、颗粒铺粉厚度等对搅拌摩擦制备SiC颗粒增强铝基复合材料的影响。以焊缝宏观质量、SiC颗粒体积分数与硬度、基体组织及颗粒、复合材料不同深度维氏硬度、复合区面积(宏观)为表征参量对制备的复合材料进行表征,并得出最佳的铺粉工艺。结果表明:相比于α-氰基丙烯酸乙酯,聚乙烯醇作为黏接剂时,复合材料中SiC颗粒的分布更加均匀;嵌入基体的SiC颗粒体积分数随着SiC粉末粒径的增加而增加,而基体中SiC颗粒体积分数相同情况下,SiC颗粒的粒径越小对基体材料硬度的提高越明显;复合材料中SiC颗粒增强区面积会随着铺粉厚度的增加而增加,但增加铺粉厚度会使得SiC颗粒增强区硬度、体积分数的变化梯度增加。     

碳纤维增强树脂基复合材料加工表面粗糙度对疲劳性能的影响

采用磨削和铣削(顺铣、逆铣)加工工艺获得不同表面粗糙度Sa的碳纤维增强树脂基(CFRP)复合材料试样并进行拉-拉疲劳试验,基于刚度退化模型分析了加工表面粗糙度对疲劳性能的影响.结果表明:磨削、顺铣和逆铣试样的Sa分别为1.2,3.2,5.9μm;磨削试样0°纤维铺层表面纤维缺失,存在空隙,铣削试样在45°纤维铺层表面存...     

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.     

Simulation of the burnishing process on real surface structures

Burnishing is a finishing manufacturing process that provides the required surface integrity of metal parts. Precise process simulation enables optimization to guarantee the quality of the product. A literature review showed that most researches in this field have used an idealized smooth surface for simulations and have not considered the influence of surface roughness on the simulation results. However, for burnishing processes, the initial roughness has a measurable effect on the simulation quality. Hence, an innovative approach for the preparation of the FEM process model was developed. The approach based on reverse engineering. Using 3D scanning, models of the workpiece and the tool were created and imported in the process model. The developed approach was validated through a case study. The results of the simulation with surface roughness demonstrate a better compatibility to the real process than the results of the same simulation on the idealized surface. Hence, using this approach, it is possible to create a precise model of the process and achieve more qualitative result of the burnishing simulations.     

Investigation of the burnishing process with PCD tool on non-ferrous metals

It is well known that the no-chip machining process, burnishing, can easily improve surface roughness, waviness and hardness. To get the practical useful parameters, the effects of various burnishing parameters (spindle speed, depth, feed, burnishing radius and lathe) on surface roughness and waviness of the non-ferrous components were studied experimentally with a theoretical analysis. The experiments were conducted with a simply designed cylindrical surfaced polycrystalline diamond tool developed by us. It was found that smaller parameters do not mean lower surface roughness or waviness and different optimum burnishing parameters can be got under different burnishing conditions.     

颗粒增强金属基复合材料的制备进展

介绍颗粒增强金属基复合材料的常用制备工艺,分析各种制备方法的优缺点;论述对颗粒增强金属基复合材料制备技术研究的难点,并展望金属基复合材料的发展。     

Precision surface finish of the mold steel PDS5 using an innovative ball burnishing tool embedded with a load cell

A load-cell-embedded burnishing tool has been newly developed and integrated with a machining center, to improve the surface roughness of the PDS5 plastic injection mold steel. Either the rolling-contact type or the sliding-contact type was possible for the developed ball burnishing tool. The characteristic curves of burnishing force vs. surface roughness for the PDS5 plastic injection mold steel using the developed burnishing tool for both the rolling-contact type and the sliding-contact type, have been investigated and constructed, based on the test results. The optimal plane surface burnishing force for the PDS5 plastic injection mold steel was about 420 N for the rolling-contact type and about 470 N for the sliding-contact type, based on the results of experiments. A force compensation strategy that results in the constant optimal normal force for burnishing an inclined surface or a curved surface, has also been proposed to improve the surface roughness of the test objects in this study. The surface roughness of a fine milled inclined surface of 60 degrees can be improved from R_a 3.0 μm on average to R_a 0.08 μm (R_max 0.79 μm) on average using force compensation, whereas the surface roughness was R_a 0.35 μm (R_max 4.56 μm) on average with no force compensation.     

Wear behavior of SiC particulate reinforced aluminum composites sliding against steel balls under dry and lubricated conditions

Wear behavior of Al–Si alloys reinforced with SiC particulate has been investigated under dry and lubricated reciprocating sliding conditions using a ball-on-block wear test method. It was shown that in the dry sliding wear of the composite/steel ball system, the wear mechanism of the composite was predominantly adhesive. With further sliding motion, delamination and abrasive wear occurred as a result of fracture and debonding of the SiC particles. Under lubricated conditions, the wear rate of the composite was drastically reduced due to the presence of the lubricant, and a boundary lubrication condition existed and dominated the normal wear process. The debonding of the SiC particles from the matrix of the composite was a predominant factor in determining the wear loss of the composite in the boundary lubrication sliding process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of working parameters on surface finish in ball-burnishing of hardened steels

Burnishing is a chipless finishing method, which employs a rolling tool, pressed against the workpiece, in order to achieve plastic deformation of the surface layer. Recent developments made possible burnishing of heat-treated steel components up to 65 HRC. Features of burnishing include a good roughness (comparable to grinding), as well as improvement of mechanical characteristics of the surface (fatigue strength, corrosion resistance, and bearing ratio), due to implementation of compressive stresses into the surface layer. This paper will present influences of certain burnishing parameters upon roughness, for a hardened steel component (64 HRC).     

Unique regenerative chatter in wiper-turning operation with burnishing process Part 2: Experimental verification of predicted generation mechanism,critical stability,and characteristics

In this paper, the predicted generation mechanism, chatter stability, and characteristics of the unique regenerative chatter with the burnishing process in wiper-turning operations are verified experimentally. It was found in the first part of the paper that the vibration regenerates in the burnishing process by the wiper part of the insert causing a novel type of chatter. In this second part, this chatter phenomenon is investigated in an experimental manner to verify its mechanism. The specific burnishing force, which is a gain factor characterizing the burnishing process, is determined by the Hertzian contact law. In addition, the specific cutting force is measured by a cutting test, the compliance of the flexible structure is measured by a hammering test, and the residual compliance is measured by a static indentation test. Then, experiments are conducted where the tilt angle and the feed rate are varied to find the critical stability. The conducted chatter experiments prove that the predicted generation mechanism, critical stability, and characteristics are true.     

Unique regenerative chatter in wiper-turning operation with burnishing process Part 1: Prediction and analytical investigation of generation mechanism,critical stability,and characteristics

The purpose of this paper is to understand the generation mechanism and to propose an analytical model of a unique regenerative chatter with the burnishing process in wiper-turning operations. The authors have found a unique chatter when using wiper inserts, which cannot be explained by the existing chatter theory found in the literature. The authors believe that this occurs because of the burnishing process of the wiper insert, which is the only difference from ordinary turning. At first, the burnishing process, which accompanies wiper inserts, is explained, and the turning operation with this process and the well-known regenerative effect in the cutting process is discussed. Then, the stability of the turning process with the regenerative effects in the cutting and burnishing processes are investigated, and an analytical model is proposed to evaluate the critical stability. Finally, the stability analysis of this unique chatter is conducted, and its generation mechanism and characteristics are examined clearly.     

Influence of ball burnishing on surface quality and tribological characteristics of polymers under dry sliding conditions

In this paper, the application of ball burnishing as a new surface treatment process for polymers is investigated. The polymers used were polyoxymethylene (POM) and polyurethane (PUR). The lowest surface roughness value achieved for POM was 0.44 μm (45% decrease) and for PUR was 0.46 μm (42% decrease). The lowest coefficient of friction value achieved was 0.22 (32.9% decrease) for POM and 0.24 (28.8% decrease) for PUR. The lowest specific wear rate value achieved was 0.31×10⁻⁶ mm³/N m (38.6% decrease) for POM and 0.41×10⁻⁶ mm³/N m (37.9% decrease) for PUR.     

高性能铁基预混合粉的温压工艺性能研究

简要介绍温压工艺,着重从工艺稳定性、生坯密度、生坯强度以及拉伸强度等方面研究自制高性能铁基预混合粉的温压工艺性能。研究结果表明,自制高强度铁基粉末具有良好的温压工艺性能。