基于微晶刚玉磨粒切削的20CrMnTi齿轮钢磨削机理研究

为了研究微晶刚玉砂轮对20CrMnTi低碳合金钢的磨削机制与磨削力规律,采用单颗微晶刚玉磨粒划擦实验模拟20CrMnTi钢的磨削加工过程,进而推导出了单颗磨粒划擦的磨削力数学模型公式。研究表明:20CrMnTi钢划痕呈现显著的塑性去除形式,且划擦过程伴随着显著的力值特征。法向力与切向力均随着划擦深度、进给速度的增大而增大,划擦深度对磨削力的作用更明显。单颗磨粒的磨削力源于切屑变形和摩擦,切屑变形引起的法向力和切向力之比为0.75,磨粒顶部与材料的摩擦系数为0.46。     

单颗磨粒超声辅助磨削SiC陶瓷材料去除机理

为研究不同磨削速度下超声振动作用对SiC陶瓷磨削过程中材料去除机理的影响,采用钎焊单颗金刚石磨粒工具,基于连续变磨削深度试验方法,在SiC陶瓷抛光表面开展了超声辅助磨削与普通磨削对比试验。结果表明,随着单颗磨粒磨削深度的逐渐增大,SiC陶瓷超声辅助磨削与普通磨削时的材料去除机理均经历了“塑性去除→脆-塑转变→大尺寸脆性断裂”的变化;在磨削速度为1 m/s时,相比于普通磨削,单颗磨粒超声辅助磨削可显著增大SiC陶瓷的脆-塑转变临界切厚及相应的磨削划痕横截面积,并减小切向磨削力与磨削比能;而随着磨削速度的增大,超声辅助磨削与普通磨削在单颗磨粒磨削划痕尺寸、磨削力之间的差异逐渐减弱。     

钛合金Ti6Al4V高速磨削试验研究

为实现难加工材料钛合金的高效磨削,进一步发挥高速磨削的潜力,开展了钛合金Ti6Al4V高速磨削工艺试验研究,对磨削过程的磨削力、磨削比能以及磨削温度随单颗磨粒最大切屑厚度agmax的变化特征进行了分析。研究结果表明：不同砂轮线速度vs条件下,磨削力、磨削比能及磨削温度三者随单颗磨粒最大切屑厚度agmax变化的特征曲线略有不同,具体表现为,单颗磨粒最大切屑厚度agmax一定条件下,磨削力及磨削比能随着磨削速度的提高呈减小趋势,磨削温度则呈上升趋势,同时钎焊CBN砂轮的磨削力、磨削比能低于陶瓷结合剂及电镀CBN砂轮的磨削力、磨削比能,因此,利用钎焊CBN砂轮磨料有序排布的优势,选择合理的单颗磨粒最大切屑厚度,可在提高砂轮线速度的同时提高进给速度,从而提高磨削效率,实现钛合金的高速高效磨削。     

单颗磨粒超声ELID复合磨削试验研究

基于超声ELID复合磨削的运动特性建立简单的超声ELID复合磨削模型,并对砂轮表面的磨粒在内圆磨削过程中的运动特性进行了系统分析。根据磨粒的运动特点建立了单颗磨粒运动轨迹的数学表达式,并应用MATLAB软件建立了单颗磨粒运动轨迹模型,重点分析了单颗磨粒运动轨迹在内圆磨削过程中对工件材料去除率及工件表面质量的影响。采用对比试验加以分析,对Zr O2陶瓷分别进行了超声ELID复合磨削和普通ELID磨削,试验结果表明超声ELID复合磨削较普通ELID磨削具有更高的加工效率和良好的表面质量。     

基于ABAQUS的单颗磨粒磨削GH4169高温合金有限元分析

通过建立单颗磨粒磨削模型,采用ABAQUS软件对GH4169高温合金的磨削过程进行有限元仿真,探究单颗磨粒在不同参数下对GH4169高温合金工件磨削过程的影响。研究表明：磨粒从切入工件后到切出工件前,磨削力稳定波动,且与磨粒前角和磨削深度显著相关,切向磨削力随着磨粒前角增大而显著减小,随着磨削深度的增大而显著增大;最高磨削温度出现在磨粒切入工件的时刻,且与磨粒前角、磨削深度和磨削速度相关;磨粒前角对磨屑的形状影响显著,磨粒前角越大,磨屑越难排出,磨削速度对磨屑的形状影响较小,磨削深度影响磨屑的厚度和长度。     

微晶刚玉磨料磨削性能研究

选用超强度钢作为磨削对象,采用单颗磨粒磨削划痕实验法对微晶刚玉磨料与白刚玉磨料(WA)进行了对比磨削实验,给出了实验设备,采用单颗磨粒磨削划痕实验法进行了实验,得出了表征磨粒磨损特性的t-n曲线,并对实验结果进行了分析,最后得出结论当初始划痕磨削深度a_g=0.008mm,磨削速度v_g=20m/s时,微晶刚玉磨料的破碎率及磨损速率均较低,与普通白刚玉磨料相比微晶刚玉磨料更适用于磨削诸如超高强度钢这类难磨材料,并且微晶刚玉磨削超高强度钢时,在磨粒顶部磨损平面上不存在粘附物,未出现粘附磨损。     

基于单颗磨粒磨削的超声振动参数与磨削参数匹配性研究

超声辅助磨削是一种适于加工陶瓷等硬脆材料的先进复合加工技术。超声辅助磨削过程中,超声振动参数与磨削用量的匹配性决定了超声振动作用对磨削过程的影响程度,目前尚缺乏深入的研究。针对这一问题,采用单颗磨粒工具对SiC陶瓷工件抛光表面进行超声辅助磨削及普通磨削试验,通过单颗磨粒磨削力、力比、磨削划痕形貌的对比,分析超声振动作用对磨削过程的影响随磨削用量变化的规律。结果表明,相同条件下单颗磨粒超声辅助磨削的磨削力与力比均小于普通磨削时;磨削用量较小时,单颗磨粒超声辅助磨削划痕形貌呈明显的锤击作用及断续磨削特征。随磨削用量的增大,超声辅助磨削过程中的锤击作用显著弱化,断续磨削特征趋于消失,两种方法之间的磨削力差异减小,即超声振动参数与磨削用量的匹配性变差。     

21NiCrMo5H齿轮钢超声磨削力建模研究

磨削力的建模研究是认识超声磨削机理的重要基础。在超声磨削单颗磨粒运动特性分析基础上,基于工件上被切削掉的磨屑体积应等于砂轮磨削去除的体积的原则,推导出超声磨削平均未变形磨屑厚度公式,得到切屑变形力模型;考虑超声振动对摩擦因数的影响,建立磨粒与工件摩擦力模型。综合切屑变形力模型、摩擦力模型,推导出超声辅助磨削下的磨削力模型,进行21NiCrMo5H齿轮钢材料渗碳淬火后超声磨削试验研究,确定磨削力模型中相关材料系数,得到超声磨削力模型。与现有文献的计算模型相比较,给出的超声磨削力模型与磨削试验测量结果具有更好的一致性,并对超声磨削机理提出了新的认识,为后续研究提供更多的参考与基础。     

单颗粒磨削合金钢20CrMo磨削力仿真

根据单颗CBN磨粒的实际几何特征和磨削特点,CBN磨粒被简化成切头方锥形,分别建立了单颗CBN磨粒微切削合金钢20CrMo的力学模型和相应的有限元仿真模型,从微观角度分析了单颗CBN磨粒的切削成屑机理和磨削力。研究结果表明:磨粒的推挤使工件材料发生塑性变形,沿磨粒的前方及两侧隆起,并最终于磨粒的前方流出而形成磨屑,但是当磨粒前角比较小时很难形成连续的磨屑;研究了磨粒速度、切削深度及前角变化对法向及切向磨削力的影响规律。     

钎焊金刚石砂轮高速磨削氧化铝的磨削比能研究

采用自制的钎焊金刚石砂轮对氧化铝陶瓷进行高速磨削试验研究,重点探讨不同磨削参数对磨削比能的影响。结果表明:磨削比能随砂轮线速度的增大而增大,而随磨削深度、工件速度和材料去除率的增大而减小;磨削比能与单颗磨粒最大切削厚度有直接的关系;在磨削过程中,大部分磨削能量消耗于金刚石磨粒对陶瓷工件的滑擦与塑性耕犁。     

基于单颗磨粒玻璃磨削机理的仿真研究

从仿真角度研究了单颗金刚石磨粒的磨削机理;建立了单颗磨粒磨削玻璃等脆性材料的仿真模型,在此基础上,通过有限元软件对不同磨削条件下的单颗金刚石磨粒的磨削过程进行了仿真。最后从最大拉应力、磨削力两个方面对仿真结果进行了分析,研究了砂轮线速度、磨削深度对最大拉应力和磨削力的影响。     

Precision grinding of binderless ultrafine tungsten carbide (WC) microstructured surfaces

The primary objective of this study was to produce binderless ultrafine tungsten carbide (WC) microstructured surfaces in the ductile grinding regime and to optimize machining parameters to generate microstructural features and sharp edges without chipping. The micro-deformation, fracture properties, and grinding mechanisms were characterized using micro/nano-indentation and single-grit grinding experiments. The effects of grinding conditions (such as grinding mode, feed rate, and spindle speed) on ground surface quality and the radius and chipping of edges were investigated using microstructural grinding experiments. It was found that in nano-indentation, the binderless WC indentation was accommodated by plastic deformation. An average critical depth of cut of 146 nm could be achieved on single-grit scratching tests using atomic force microscopic procedures. In grinding of microstructured surfaces, the surface roughness of side surfaces was always smaller than that of the bottom surface of the machined feature. The better surface quality and sharper edges were obtained by using the upcut grinding mode. Reducing the tool feed rate did necessarily help to improve the surface roughness and edges of structures. The best ground surface could be obtained at the grinding speed of 2,500 rpm. According to the grinding experimental results, an echelle grating was manufactured using the optimized parameters. The average surface roughness SRa of the bottom surface was 78 nm and that of the side surface was 60 nm. The radius of the edge was less than 1 μm, and the radius of corner was about 3 μm. No visible evidence of grinding-induced cracks and chipping on the ground surfaces was found.     

Tribological characteristics in high-speed grinding of alumina with brazed diamond wheels

In this work, two brazed diamond wheels fabricated by brazing in vacuum were used to grind alumina at different grinding speeds. During the process, the horizontal and vertical grinding forces were measured by a force measurement device. The grinding forces, specific grinding energy, and friction in grinding of alumina at low and at high speeds were investigated. The results show that the friction coefficient decreases with the increase of the grinding speed and also relates to the grinding mode. A nearly proportional relationship between grinding power per unit width (P _m ) and the rate of plowed surface area generated per unit time per unit width (S _w ) reveals the effects of friction in grinding and most of the grinding energy is expended by friction. The surface energy per unit area generated by plowing friction (J _s ) for high-speed grinding is found to be lower than for low-speed grinding.     

磨削加工中的尺寸效应机理研究

从比切削能和比摩擦能的大小变化与磨削参数的关系出发,研究了磨削加工中的尺寸效应问题,结果认为：比切削能的尺寸效应是金属剪切流动应力的尺寸效应和磨粒顶端钝圆影响的综合作用结果;当磨削深度或工件进给速度减小时,平均未变形切屑厚度减小,金属材料的剪应变效应和剪应变率效应增强,而热软化效应减弱,从而金属材料的剪切流动应力增大;当未变形切屑厚度减小时,磨粒顶端钝圆的影响增大;比摩擦能的尺寸效应是由于工件和砂轮的实际接触面积与磨削深度之间存在非线性关系及工件和砂轮间的摩擦因数的速度效应造成的;当工件进给速度减小时,工件与砂轮磨损平面间的摩擦因数增大。     

Face Grinding Surface Quality of High Volume Fraction SiCp/Al Composite Materials

The existing research on SiCp/Al composite machining mainly focuses on the machining parameters or surface morphology.However,the surface quality of SiCp/Al composites with a high volume fraction has not been extensively studied.In this study,32 SiCp/Al specimens with a high volume fraction were prepared and their machining parame-ters measured.The surface quality of the specimens was then tested and the effect of the grinding parameters on the surface quality was analyzed.The grinding quality of the composite specimens was comprehensively analyzed taking the grinding force,friction coefficient,and roughness parameters as the evaluation standards.The best grinding parameters were obtained by analyzing the surface morphology.The results show that,a higher spindle speed should be chosen to obtain a better surface quality.The final surface quality is related to the friction coefficient,surface roughness,and fragmentation degree as well as the quantity and distribution of the defects.Lower feeding amount,lower grinding depth and appropriately higher spindle speed should be chosen to obtain better surface quality.Lower feeding amount,higher grinding depth and spindle speed should be chosen to balance grind efficiently and surface quality.This study proposes a systematic evaluation method,which can be used to guide the machining of SiCp/Al composites with a high volume fraction.     

浸渍石墨/38CrMoAlA (喷涂)配对密封摩擦副的干摩擦性能

针对干摩擦机械密封在高速运转工况下密封端面的摩擦磨损而导致密封失效问题,通过试验分析几种典型摩擦副材料组对在干摩擦下的摩擦磨损性能。选择浸锑石墨M106D和浸树脂石墨M106K分别与38CrMoAlA以及喷涂Cr2O3、Al2O3的38CrMoAlA硬环组对,采用Plint摩擦磨损试验机,监测摩擦副在高速干摩擦条件下的摩擦因数,分析轴向载荷及线速度对摩擦因数的影响,通过白光干涉仪观测试验前后端面形貌。结果表明：干摩擦下,喷涂的硬环表面石墨转移附着较少,其更耐磨、磨损程度小,浸锑石墨较浸树脂石墨磨损少;6组配对试验主要磨损形式为磨粒磨损,其中浸锑石墨/喷涂Al2O3的38CrMoAlA摩擦副摩擦因数最小;由于石墨的自润滑性,适当增加转速和轴向载荷均有利于降低端面摩擦因数。     

Coefficient of friction under flat profile creep-feed grinding

The process of flat creep-feed grinding of a wheel by the periphery of a wheel is studied. A method of determining the coefficient of friction for creep-feed grinding procedures is developed. The coefficient of friction is experimentally found depending on the grade and temperature of the blank and the grade of the cutting lubricant, as well as the granularity, hardness, and number of the structure of the grinding wheel. The statistical processing of the experimental data has yielded econometric models for calculating the coefficient of friction. The values of the coefficient of friction are used in the mathematical modeling of cutting forces under creep-feed grinding.     

Machinability of ultrasonic vibration-assisted micro-grinding in biological bone using nanolubricant

Bone grinding is an essential and vital procedure in most surgical operations. Currently, the insufficient cooling capacity of dry grinding, poor visibility of drip irrigation surgery area, and large grinding force leading to high grinding temperature are the technical bottlenecks of micro-grinding. A new micro-grinding process called ultrasonic vibration-assisted nanoparticle jet mist cooling (U-NJMC) is innovatively proposed to solve the technical problem. It combines the advantages of ultrasonic vibration (UV) and nanoparticle jet mist cooling (NJMC). Notwithstanding, the combined effect of multi parameter collaborative of U-NJMC on cooling has not been investigated. The grinding force, friction coefficient, specific grinding energy, and grinding temperature under dry, drip irrigation, UV, minimum quantity lubrication (MQL), NJMC, and U-NJMC micro-grinding were compared and analyzed. Results showed that the minimum normal grinding force and tangential grinding force of U-NJMC micro-grinding were 1.39 and 0.32 N, which were 75.1% and 82.9% less than those in dry grinding, respectively. The minimum friction coefficient and specific grinding energy were achieved using U-NJMC. Compared with dry, drip, UV, MQL, and NJMC grinding, the friction coefficient of U-NJMC was decreased by 31.3%, 17.0%, 19.0%, 9.8%, and 12.5%, respectively, and the specific grinding energy was decreased by 83.0%, 72.7%, 77.8%, 52.3%, and 64.7%, respectively. Compared with UV or NJMC alone, the grinding temperature of U-NJMC was decreased by 33.5% and 10.0%, respectively. These results showed that U-NJMC provides a novel approach for clinical surgical micro-grinding of biological bone.     

光学玻璃磨削机理的仿真研究

采用有限元仿真分析方法,利用有限元增量理论建立了玻璃材料的弹塑性本构关系,对单颗金刚石磨粒的磨削过程进行了仿真,最后从最大拉应力、磨削力、磨削力比3个方面对仿真结果进行了分析研究,为玻璃磨削加工的工艺参数优化和工艺规划奠定了基础。     

磨削力的数学模型的研究

磨削力由切屑变形力和摩擦力构成。在这种认识的基础上,我们建立了新的磨削力的数学模型。它由两项构成,分别相应于切屑变形力和摩擦力。试验测定了磨削不同工件材料时磨削用量与磨削力之间的关系,试验结果与建立的磨削力模型相符合。从切屑变形力与摩擦力两方面分析了切向磨削力与法向磨削力的比值,大体上应在0.2～0.59范围。磨削不同工件材料时,切向磨削力与法向磨削力的比值的实测值在这个范围内,根据建立的磨削力模型,讨论了当量切削厚度的意义、高速磨削的效果等问题。