Grinding process monitoring is key to assessing the intelligence of grinding processing and ensuring manufacturing quality of the intended product. The grinding force in the grinding process is an important characteristic, and the grinding force signal has a close relationship with the degree of wheel wear, grinding heat, grinding wheel and workpiece contact state, and other entities. Therefore, the analysis of the grinding force signal using the time domain and frequency domain analysis methods can effectively reveal the grinding characteristics and wheel wear evolution mechanism in the gear grinding process. In this study, the microcrystalline corundum grinding wheel was used to conduct the profile grinding test on 20CrMnTi steel gears installed in vertical machining centers. A high-performance general-purpose dynamometer was used to collect the discrete time series data of the grinding force in real time; a confocal laser microscope and scanning electron microscope were used to observe the wear characteristics of the microcrystalline wheel surface; finally, a micrometer was used to measure the thickness of the wheel’s end-top surface to assess the degree of wheel wear in a quick and simple way. To improve the precision, automation, and intelligence level of the gear grinding process considering the microcrystalline corundum grinding wheel, online monitoring of the grinding process and wear mechanism of the grinding wheel was performed. The intrinsic correlation between the time-frequency domain signals of the grinding force, the contact status of the grinding wheel and workpiece, and the wear degree of the grinding wheel was established. Thus, in this study, a new online monitoring method for monitoring the grinding process of the grinding wheel was proposed based on real-time force signals. Meanwhile, the wear mechanism underlying the morphology of microcrystalline corundum grinding wheels was characterized and analyzed using laser confocal microscopy and scanning electron microscopy. The results showed that the distribution pattern of waveform characteristic indicators such as kurtosis, waveform index, peak index, and pulse index in the time domain spectrum of the grinding force showed a distinct trend of varying cutting depth grinding state ≥ steady-state grinding state of a significantly worn grinding wheel ≥ steady-state grinding state of a lightly worn grinding wheel > noncontact state. However, the variation of the two waveform characteristic values of the grinding force, amplitude spectrum and pulse indicator under different grinding states is completely opposite to that of the time domain signals. After assessing the three-dimensional roughness of the working surface of the grinding wheel, it is observed that there is a slight decrease and a subsequent rapid increase in the roughness of the working surface of the wheel with the evolution of wheel wear. The polycrystalline structure of the microcrystalline corundum abrasive particles gives them the ability to update and sharpen along the microcrystalline interface, showing layer-by-layer cleavage peeling.

为了探究成形法磨削齿轮的磨削温度生成机制与变化规律,构建了单位接触宽度齿面磨削力与成形法磨齿温度的理论模型,揭示了它们与砂轮特性、齿轮规格、磨削用量与材料特性的内在关系.成形磨齿温度随着砂轮磨刃密度、磨削速度、径向进给量的增大而增大,却随着砂轮直径、齿轮压力角增大而减小.齿轮的模数对齿廓磨削温度的影响较弱,而齿数对齿顶与齿根两处磨削温度的影响态势却截然相反.成形法磨削齿轮的砂轮特性系数τ越大,则磨削性能越差,并在一定程度上决定了轴向进给速度对磨削温度的影响规律.此外,通过正交试验回归模型分析法证实了成形法磨齿温度理论模型具有较好的实际适用性,且微晶刚玉砂轮的磨削性能优于白刚玉砂轮.

碳化硅陶瓷在磨削加工中极易产生崩碎损伤,在碳化硅陶瓷磨削层实时涂覆增韧剂是降低崩碎损伤的新方法.以E51双酚A型环氧树脂、无水乙醇、651型低相对分子质量聚酰胺树脂和1,8-二氮杂二环十一碳-7-烯(DBU)为主要成分制备了一种增韧剂,通过测量增韧剂在碳化硅陶瓷表层的接触角、浸润深度与固化时间,探究了增韧剂各组分的添加量与碳化硅陶瓷表面粗糙度对增韧剂润湿性能与固化速率的影响规律,优化出一种润湿性能好、固化速率快的增韧剂.结果表明:增韧剂的最佳质量配比为m(E51双酚A型环氧树脂):m(无水乙醇):m(651型低相对分子质量聚酰胺树脂):m(DBU)=1:0.9:0.5:0.02,该增韧剂在碳化硅陶瓷表层的浸润时间约为160 s,浸润深度约为40μm,可使碳化硅陶瓷的表层硬度降低约25％;增韧剂的润湿性能随着溶剂的增加或碳化硅表面粗糙度的增大而提高,促进剂添加量的改变对增韧剂的润湿性能几乎无影响;增韧剂的固化速率随溶剂的增加而降低,随促进剂的增加而提高,但当促进剂达到饱和时,固化速率不再提高.

金刚石砂轮磨削加工仍然是最有应用前景的硬脆材料高效加工途径,而弄清磨削加工机理对实现硬脆材料元器件的高效超精密加工具有重要意义.介绍硬脆材料微纳切削的静态压痕断裂力学模型与动态切削加工近似模型这两种经典模型,诠释了塑脆转变机制.深入分类探讨了硬脆材料的脆性去除、塑性域去除与粉末化去除这3项加工机理,材料去除是裂纹演化、挤压微破碎、相变与位错等因素导致而成.塑性域加工是改善硬脆材料加工损伤的重要措施,而力热耦合作用场、材料晶面晶向等因素都是影响塑性域去除机制的关键.

为了探究硅片器件精密磨削加工的切削特征与机理,运用三棱锥形状的金刚石磨粒以不同加载压力划刻单晶硅材料表面模拟磨削加工过程,分析了划痕形貌特征、切削力与切削深度的演变规律,阐释了单晶硅的微米级切削加工机理.单晶硅微破碎去除发生的临界条件为法向切削力80 mN,临界切削深度2.03μm;剥落去除发生的临界条件为法向切削力800 mN,切削深度5.65μm.切削深度、切削力比在不同切削机理条件下具备可区分的差异化特征.平均切削深度随加载压力的变化规律呈现出鲜明的自相似性特征.此外,还分别构建了塑性去除、微破碎去除、剥落去除三个阶段的切削力方程,更准确地描述了切削力与切削深度的密切关系.

为了研究蜗杆砂轮展成法磨削齿轮的加工系统中不同因素对齿轮精度的影响规律,采用空间坐标系转换法构建了蜗杆砂轮磨削齿轮系统的运动学模型,并模拟分析了砂轮磨粒磨削齿面的运动空间轨迹.研究表明,砂轮廓形径向误差对齿轮精度影响较小.齿廓偏差与螺旋线偏差主要受砂轮廓形切向误差、安装夹角误差与机床传动比误差的影响,而齿距偏差主要受安装夹角误差、机床传动比误差的影响.此外,齿轮精度随工装误差、砂轮廓形误差、机床传动精度等影响因素误差值的增大而变差.

工程陶瓷等硬脆材料在切削加工过程中极易发生裂纹、破碎和剥落等碎裂损伤现象,从而影响元器件的使用性能与寿命.碎裂损伤已成为制约硬脆材料切削加工领域的一项难题,促生了延性域加工、热软化辅助加工、增韧抑制辅助加工等低损伤先进加工技术.本文从硬脆材料的碎裂损伤及其控制技术角度介绍了硬脆材料加工领域的重要研究进展与亟待解决问题,为开发新型高效精密加工与质量可控技术提供新思路.

微纳切削加工是硬脆材料最高效的精密/超精密加工方法,而模拟简化试验与计算机模拟能为错综复杂的切削加工过程提供重要研究手段,便于从宏微观跨尺度层面阐释硬脆材料切削加工机理.有限元、离散元与分子动力学等计算机模拟手段能可视化虚拟实际切削加工难以展示的应力应变、裂纹演化、材料去除等动态过程.微纳切削加工模拟研究证实了硬脆材料在特定临界条件下发生脆塑转变效应,为纳米尺度的塑性域超精密加工技术提供重要依据.然而,微纳切削模拟研究方法因受限于理想化模型与时空尺度差异等因素,还存在一些亟待优化解决的复杂难题.

为了探究硅片器件精密磨削加工破碎的损伤规律与演变机制,开展了单颗金刚石磨粒切削单晶硅片的微米划痕实验,分析了硅片边缘有无胶粘包裹作用两种条件下的划痕入口、内部与出口三个区段的破碎损伤形貌特征,并建立了声发射强度、磨削力、切削深度、摩擦系数与破碎损伤之间的内在密切关联。单晶硅破碎损伤随着加载压力或切入深度的增大而越加严重,伴随释放的声发射信号强度增大。单晶硅内部破碎发生的临界阈值条件:载荷约80 mN,切入深度约2μm,声发射强度约8%。胶粘包裹对单晶硅片边缘的增韧效果显著,边缘崩碎发生临界阈值条件为:载荷约800 mN,切入深度约6μm,声发射强度约55%。

为了研究不同粗糙度表面、载荷与摩擦频率对20CrMnTi钢齿轮磨削表面的摩擦磨损性能影响规律和机理,分别在干接触状态与润滑接触状态下开展了往复滑动摩擦磨损试验.研究结果表明:摩擦系数随着接触表面粗糙度和载荷的增大而增大,但随着摩擦频率的增大而减小;磨损深度随着表面粗糙度、载荷和摩擦频率的增大而增大.因此,在干接触与润滑接触两种状态下,不同粗糙度表面、载荷与摩擦频率对摩擦学特性的影响机制均存在显著的差异.

为了探究安装角度误差、中心距误差、砂轮廓形误差等因素对齿轮精度的影响规律,构建了成型砂轮磨削齿轮系统的运动学模型o研究表明,齿向偏差、齿廓偏差、单个齿距偏差主要由工装安装角度误差与砂轮廓形切向误差的影响较大,中心距误差与砂轮廓形径向误差的影响微弱o工装误差与砂轮廓形误差越大,导致齿轮精度越差.此外,通过调节安装角度误差能较好实现齿廓修形与齿向螺旋角修形.

针对C/SiC复合材料传统机械加工效率低、成本高的缺点,采用切槽-推磨复合式加工对平板C/SiC复合材料进行了实验研究,通过正交实验分析了不同因素对块占比和推磨力的影响规律,采用扫描电子显微镜对加工表面进行显微观测,分析了材料损伤形式.结果表明,C/SiC复合材料可采用切槽-推磨复合式加工方法,块占比可达到30％以上,具有较好的推磨加工效果.材料损伤形式主要为碳化硅基体微裂纹、碳纤维分层、断裂和界面层脱粘.