【作者】 林海龙；

【导师】 王庆明；

【作者基本信息】 华东理工大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 金属切削加工是机械制造业的主导加工方法,其机理分析成果对各种生产线和各类零部件的加工具有重大的指导意义。金属切削过程是一个复杂的非线性动力学变形过程,传统的研究方法都对切削过程进行了大量的简化,使得研究结果不能很好地完全反映实际的切削过程。因此,为了提高切削结果预测的准确度,仍需要对切削加工基础机理做进一步的研究。剪切角是切削加工中一个重要的物理量,几乎各种计算都与剪切角有关。本文对切削能量平衡方程V·F=WS+Wf进行变换,提出一种新的关于直角切削的剪切角预报模型。与以往剪切角的预报模型相比,由于在加工过程中对模型中的重要参数主切削力F进行了测量,该模型能够考虑到实际的复杂切削状况对剪切角的影响,减少了以往单纯的理论推导对剪切角预报精度带来的影响,具有较理想的预报精度。作为一种普遍存在的切削方式,三维切削具有刀具主副刃同时参与切削的特点。本文首次研究了刀具参与切削的主副刃长之比对切削力的影响,分析了各向切削力随参与切削的主副刃长比的变化特点。分析结果与通过切削力经验公式得到的定性理论分析结果一致。针对三维切削中的Usui双刃切削模型和V型槽切削模型,本文分别提出了两种流屑角预测模型,Usui双刃切削模型条件下的流屑角预测模型从总剪切面积最小的角度阐述了切屑流出机理；V型槽切削条件下的流屑角预测模型则由切削能量平衡方程推导得到。这两种预测模型的预测结果与实验测量值都具有较好的一致性。本文首次研究了Usui双刃切削模型和V型槽切削条件下的流屑角与参与切削的刀具主副刃长比之间的关系：在等效切削面积一定的前提下,流屑角随着切削刃长比RATIO的增加而减小,切削刃长比RATIO等于4为转折点,在此之前和之后流屑角变化曲线的下降趋势相异。刀具的磨损状况对零件的加工质量、机床的寿命以及操作者的安全具有重要的影响。本文采用图像处理技术,通过对内窥镜数字摄像系统获取的反映刀具磨损情况的图形进行处理,从而实现刀具状态的直接监测；通过力传感器采集切削过程中的切削力信号,借助小波变换对其进行了多分辨率分析。利用小波变换模的极大值和信号奇异点的关系,分析了用Lip指数来描述的切削力信号局部奇异性,通过观察奇异点的位置等信息得到切削刀具的磨损情况,从而实现了对刀具状态的间接监测。实验表明,通过对切削力信号进行小波分析来实现刀具磨损的监测具有较好的可靠性。本文对剪切角以及三维切削过程中流屑角、切削力等若干方面进行了研究,并通过有限元软件仿真以及实验进行验证,同时还对刀具磨损监测方法进行了研究。本文的研究结果将为切削加工理论与应用的进一步发展提供有益的借鉴。更多还原

【Abstract】 Metal cutting is a leading machining method in manufacturing industry, and its mechanism research has great directive significance to all kinds of production lines and machining of parts. Metal cutting is a complicated nonlinear deformation process which has been simplified in previous researches. However, the simplified models in previous researches didn’t have good performances to reflect actual cutting process. Further studies of cutting mechanism are still needed to improve prediction results of metal cutting.Shear angle is an important parameter in metal cutting and is almost used in all kinds of cutting calculation. Using the cutting power equilibrium equation V-F=Ws+Wf, a new shear angle prediction model for orthogonal cutting was proposed in the study. The principal cutting force F which can reflect the complicated cutting situation was experimentally measured in the study. By substituting into the cutting power equilibrium equation with the measured value of the principal cutting force F, the prediction model has more accurate prediction than just theoretical derivation without experimental data.Three-dimensional (3D) cutting is a common cutting situation with the main and the minor cutting edge in engagement with workpiece. In this study, RATIO is defined as the ratio of the main to the minor cutting edge length engaged in cutting, and the effect of RATIO on cutting force was first proposed. The research results are in good accordance with qualitative analysis results derived from empirical formula of cutting force. Two prediction models of chip flow angle were proposed for Usui cutting model and helical V grooves turning:the minimum value of the total shear area produced by the two cutting edges was calculated to determine the chip flow direction for Usui cutting model; chip flow angle prediction model was expressed as the transformed cutting power equilibrium equation for V grooves turning. The relation between chip flow angle and the value of RATIO was first studied for the two cutting situations:chip flow angle decreases with the increase of RATIO at the constant equivalent cutting area; RATIO equal to 4 is the turning point before and after which the drop trend of the chip flow angle is different comparatively.Tool wear greatly affects quality of workpiece, machine life and safety of machine operators. In this study, image processing technology was applied to direct monitoring of tool condition by processing tool wear image obtained via endoscopy digital photographic system. Multi-resolution analysis was applied to the analysis of cutting force signals acquired by a turning dynamometer. Using the relationship between wavelet transform modulus maxima and singular point, the signal point location can be analyzed, and the local singularity was described by Lipschitz index. The wearing condition of cutting tool can be acquired by location of singular point and its other information to realize indirect tool condition monitoring. The feasibility of cutting tool wearing detection by wavelet transformation was validated by experiments.Shear angle, cutting force and chip flow angle in 3D cutting were analyzed in this study, and the research results were validated by FEM software and experimental measurement. In addition, tool wear monitoring was investigated in this study. The research conclusions obtained in this dissertation will be very helpful for the further application and studies of metal cutting.更多还原