面向工程陶瓷的单颗金刚石磨粒划擦磨损规律

为了研究工程陶瓷平面磨削中金刚石砂轮的磨粒磨损规律,制备圆锥形单颗粒金刚石磨具模拟实际磨粒切削刃。以金刚石磨粒的尖端圆弧半径表征磨粒切削刃锋利程度与磨削能力,并用圆弧半径的磨损规律等效描述切削刃磨损特性。采用基于扫描电镜与数据拟合的技术测量单颗磨粒金刚石尖端圆弧半径。运用单因素试验及正交试验分析了金刚石颗粒尖端形状、材料种类与加工参数对磨粒磨损规律的影响。实验结果表明,当顶锥角2θ为120°、磨削深度ap0.01 mm时,金刚石磨粒具有较高划擦寿命。各因素的影响主次顺序为:顶锥角>磨削深度>工作台速度。本研究为金刚石砂轮磨粒规格和磨削用量的选取提供了重要参考。     

单颗粒金刚石平面划擦大理石的实验研究

本文采用单颗粒金刚石沿不同的切削路径（不同间距切痕或重叠切痕）与不同切削深度的组合形式进行了平面划擦广西白大理石的试验。分析了两种切削路径下各加工参数对切削力FZ的影响,结果表明：当切削深度小于10μm时,两种切削路径对各道切痕的切削力FZ无明显影响;当切削深度大于30μm时,切削路径对切削力FZ影响增大,且在相等切削深度的条件下,切痕重叠时的加工性能比不同切痕间距时的加工性能差;在不同间距切痕条件下,小间距大切削深度（L〈200μm,ap〉70μm）或大间距小切削深度（L〉600μm,ap〈10μm）的组合形式的加工性能较好。     

单颗金刚石磨粒磨削SiC的磨削力实验研究

选取两种不同锥度角的金刚石磨粒,分别用其对SiC陶瓷和单晶SiC进行了单颗磨粒磨削实验,检测了磨削过程中的磨削力大小,分析了磨削参数对磨削力的影响。实验结果表明:磨削力随着切削深度的增大而增大,随磨削速度的减小而增大;随着磨粒顶锥角的增大,磨削力明显增大;磨削单晶SiC(6H)的磨削力大于磨削SiC陶瓷的磨削力。     

单颗磨粒磨削玻璃的声发射实验研究

采用单颗金刚石压头作为磨粒对玻璃进行磨削实验,采集了磨削过程中的声发射信号,分析了磨削参数变化对声发射信号参数特征值的影响。结果表明:磨削过程中产生的声发射信号特征参量值振铃计数值、信号均方根值RMS随着磨削深度和磨削速度的增大而增大;随着工作台移动速度的增大而减小。在本实验条件下得到的声发射信号频率峰值主要在15.53 kHz以及18.65 kHz两个部分,且实验时主要研究玻璃材料脆性方式去除过程,说明了玻璃脆性断裂时产生的声发射信号频率峰值集中在15.53kHz和18.65 kHz。     

评价金刚石绳锯性能的单颗串珠试验

本介绍的是不同操作参数对金刚石绳锯性能影响的研究试验结果。在试验过程中,绳锯的线速度,绳子的张紧力和冷却水流量都保持恒定,主要变量是锯切率,进给速度,金刚石型号和试验块的长度。本的作是P.W.ButlerSmith,J.Grgzagoridis和P.R.Davis.     

单颗磨粒划擦SiCf/SiC陶瓷基复合材料的试验研究

为研究SiC纤维(SiC_f)增强SiC陶瓷基复合材料(SiC_f/SiC)的磨削损伤机理,搭建试验平台开展单颗磨粒划擦试验,测量划擦力并观察其表面损伤形式,研究磨粒形状、划痕深度和SiC_f取向对复合材料磨削机理的影响。试验结果表明:SiC_f/SiC陶瓷基复合材料的划擦损伤形式主要有基体崩碎、纤维裂纹、断裂和拔出等。在SiC_f/SiC陶瓷基复合材料划擦过程中,尖锐状磨粒的划擦力更小,且整条划痕的表面损伤范围较扁平状磨粒的小。用扁平状磨粒划擦但纤维取向γ= 0°时,划痕形貌中纤维断裂、纤维拔出等损伤形式出现较少。      

单颗CBN磨粒高速磨削过程的仿真研究

为研究单颗CBN磨粒高速/超高速磨削的微观机理,以随机形状CBN磨粒为模型,采用Lagrange/Euler流固耦合方法,仿真分析不同工艺参数下的CBN磨粒磨削SHK-9高速钢的过程。结果表明:CBN磨粒（124~150μm）在切削深度a_p 20 μm、30 μm,切削速度120m/s时,切向磨削力达到最大,但在a_p 40 μm切削深度下反而最小。随着CBN磨料粒度尺寸变小,磨削力下降明显,磨粒可以在工件表面形成更为窄密的耕犁沟痕,配合适当的磨削深度有助于提高表面磨削质量。      

基于DEFORM的单颗磨粒对零件表面冲击仿真与实验

磨削加工过程中,工件表面材料的去除是磨粒冲击、切削、划擦等综合作用的结果。为了研究磨削过程中的冲击现象,针对45~#钢工件,运用DEFORM-3D软件对单颗磨粒对工件表面的冲击强化过程进行有限元仿真,获得了工件内部应力场的分布情况,对磨削过程中工件表面等效应力与应变率进行了分析,得到了磨削参数对磨削过程的影响规律。对等效应力的分析表明:磨削过程中,工件受力是由很多脉冲力合成的。对应变率的分析表明:磨粒对工件表面的冲击强化效应显著。实验研究结果验证了理论与仿真分析结果的正确性,采用的仿真方法可有效分析与预测工件表面强化层指标。     

钨合金超声辅助划擦试验及仿真研究

目的 揭示钨合金在超声辅助磨削加工下的材料去除行为。方法 通过超声辅助划擦试验与有限元仿真相结合的方式,分析超声振动作用对材料表面形貌、截面轮廓、划擦力、温度、塑性应变及应变率的影响,探究超声振动作用下的材料去除和表面创成机理。结果 钨合金在划擦过程中发生严重的塑性变形,在划痕两侧出现由耕犁作用而形成的隆起现象。超声辅助划擦形成的划痕表面鳞刺更少且未出现犁沟现象,且划痕深度相较于普通划擦增大14.1%,划痕宽度增大39%。随着划擦深度的增加,试验划擦力与仿真划擦力均线性增大,且仿真值与试验值误差为18.1%,验证了有限元仿真模型的有效性。超声振动作用下的划擦力呈周期性变化特征,使平均划擦力降低了43.2%。此外,仿真结果表明,超声辅助划擦相较于普通划擦,温度最高降低50%,表面塑性应变最高降低20%,超声冲击过程中材料的塑性应变率相较于普通划擦提高1个数量级,分离过程中塑性应变率最大降低2个数量级。结论 超声振动作用可以有效降低划擦过程中的划擦力和划擦区域温度,增大冲击过程中材料的瞬时应变率,改善压头的切屑黏附现象,从而抑制划擦表面鳞刺的生成和犁沟的形成,改善表面质量。此外,超声振动作...     

SPH and FE coupled 3D simulation of monocrystal SiC scratching by single diamond grit

An investigation was carried out to study the material removal modes in single diamond grinding of monocrystal SiC. In order to reveal the influences of diamond shapes on the removal regions of SiC, six diamonds of different shapes were used for scratching. Three shapes - cube, rectangular pyramid, and cubic octahedral were chosen to simulate ideal diamond shapes, whereas cone, ball, and triangular pyramid were used to express wear diamond shapes. Through combining two different simulation methods - FEM and SPH, the material removal process was simulated respectively for the grinding of SiC with single diamond grit of different shapes. A grinding test was also carried out for the diamond of cone shape in order to check the validity of simulation. It was shown that the simulation results agree basically well with the corresponding experimental results. Therefore, the influences of the different diamond shapes on the removal modes of SiC were analyzed and discussed mainly based on the simulation. The scratching length and the ratio of width to depth of the groove generated in scratching were used as the parameters to discuss the influence of diamond shapes. The forces in grinding with different diamond grits were also analyzed.     

Material removal behavior in ultrasonic-assisted scratching of SiC ceramics with a single diamond tool

Ultrasonic-assisted grinding (UAG) has been extensively employed in manufacturing industries for processing hard and brittle materials. However, its potential has not been sufficiently developed because the material removal mechanism in UAG has not been elucidated. This paper focuses on the material removal mechanism in the UAG of silicon carbide (SiC) ceramics by investigating the material removal behaviors in ultrasonic-assisted scratching (UAS) of SiC ceramics. The UAS test was conducted on an NC (Numerical Control) surface grinder connected to a self-designed ultrasonic unit; a single diamond tool was fixed onto the end-face of the ultrasonic unit to achieve an ultrasonic vibration (UV). Conventional scratching (CS) test was also carried out on the same experimental rig but without UV for comparison. During testing, the material deformation/fracture behavior and the scratching forces were investigated. The experimental results show that (1) there are two scratching modes in the UAS process depending on actual depth of cut: an intermittent mode and a continuous mode; (2) the mean groove depth in UAS is much bigger than that in CS, indicating that the cutting ability of the tool was significantly improved by the assistance of the UV; (3) the critical depth of cut is increased by 56.25% once UV is applied; the stiffness of the experiment setup is improved in the UAS compared to CS; the UV in y-direction strongly contributes to the material removal, whereas the UV in z-direction only results in variation of the cutting trace and hardly contributes to the material removal in the UAS process; (4) in UAS, the scratching forces sinusoidally fluctuate with the same period as that of the UV of the tool when the material removal is in ductile mode, when the material removal is in brittle mode, the forces heavily vary but the period is different from that of the UV of the tool; (5) the cutting efficiency of the tool is improved by the assistance of the UV. The impact and cutting action at the tool tip on the machining surface are the main factors contributing to the material removal. The observed features were rationalized by analyzing kinematic characteristics of the tool and material removal mechanism in UAS. This study confirms that UAG is a highly effective processing method for machining hard and brittle materials.     

单颗粒金刚石划擦脆硬材料的表面形貌影响因素研究

本文通过以材料、进给速度及切深为因素的正交实验研究加工工艺对磨削力的影响,了解其对表面形貌影响的显著性,并通过单颗磨粒在已有轨迹表面上以一定的间距重复划擦来了解复杂轨迹对表面形貌及切削力的影响。结果表明各个加工参数影响因素的主次排序为:材料切深进给速度,且重复轨迹划擦时表面形貌的变化与一次划擦不同,轨迹之间相互影响,在前一道大裂纹及破碎的影响下下一道轨迹的切削力急剧减小。     

钎焊金刚石铣磨刀具磨粒粒度尺寸与排布间距对CFRP磨削质量的影响

碳纤维增强复合材料（carbon fiber reinforced plastics,CFRP）由于其低层间结合力和各向异性导致其加工过程中易出现分层、毛刺、撕裂等加工缺陷和刀具耐用度低等问题。采用有序排布钎焊金刚石磨削刀具及"以磨代切"加工工艺能够有效减轻分层缺陷。为制备出适合CFRP磨边加工的钎焊金刚石刀具,本试验制备了不同磨粒排布间距与不同磨粒粒度尺寸的5种刀具,对比分析了刀具结构变化对CFRP磨边加工磨削力与加工表面质量的影响。试验结果表明:在一定范围内,在相同磨粒排布间距和加工参数下,随着磨粒粒度尺寸变大,磨削力变化很小,加工表面质量变差;在相同磨粒粒度尺寸与加工参数下,随着磨粒排布间距减小,磨削力先增大后减小,加工表面质量变好。      

Marble cutting with single point cutting tool and diamond segments

An investigation has been undertaken into the frame sawing with diamond blades. The kinematic behaviour of the frame sawing process is discussed. Under different cutting conditions, cutting and indenting-cutting tests are carried out by single point cutting tools and single diamond segments. The results indicate that the depth of cut per diamond grit increases as the blades move forward. Only a few grits per segment can remove the material in the cutting process. When the direction of the stroke changes, the cutting forces do not decrease to zero because of the residual plastic deformation beneath the diamond grits. The plastic deformation and fracture chipping of material are the dominant removal processes, which can be explained by the fracture theory of brittle material indentation.