【作者】 陈勇；

【导师】 刘雄伟；

【作者基本信息】 华侨大学 ， 机械制造及其自动化， 2004， 博士

【摘要】 铣削加工作为机械制造中一种常用的切削加工工艺,被广泛应用于汽车、航空及模具制造业中机械零件的粗、精加工。由于铣削加工过程中的多刃断续切削、半封闭加工以及切削厚度随时间改变等特性,使得铣削加工机理较为复杂,加工过程容易出现颤振现象。颤振是影响零件加工质量和限制铣削加工效率的主要因素,还会降低刀具的使用寿命,损害机床的安全性。 由于缺乏较为合理和实用的虚拟仿真系统对铣削加工过程动态特性的预测和振动预报,目前大多数企业在常规铣削加工(包括使用计算机数控加工系统)中,往往采用经验数据或是参考切削用量手册来选择铣削加工参数。为避免加工过程中颤振的出现及其不良影响,加工中常被迫强制改变切削加工参数,如降低切削深度或进给速度,但这却妨碍充分利用机床额定功率,导致加工工时,也即加工成本上升。在寻找解决该问题的办法中,提出一个对动态铣削加工过程进行深入、系统的理论和实验研究,开发一套实用的铣削加工过程虚拟仿真系统应是较为有效的方法。这样,在实际铣削加工之前,能够根据加工条件的变化准确地反映出铣削加工参数和刀具几何参数与铣削加工动态特性的关系,并在工艺设计阶段尽量优化加工条件,包括选择合理的刀具几何参数以及主轴转速、切削深度、切削宽度、进给量等参数。 本文正是基于上述思想,并借助于Matlab/Simulink环境,建立和研制了平面铣削加工过程虚拟仿真系统(VSS),采用离线振动控制策略对建立虚拟仿真系统各个模块的关键技术进行了深入研究。研究内容与主要成果为: (1)以平面铣削加工动力学为研究对象,考虑铣削加工过程的再生振动效应,分析了瞬态切削厚度、刀具有效前角以及刀具偏心模型对动态切削力的影响,对传统的铣削加工动力学解析模型提出改进算法,建立实用有效的铣削加工动力学数学模型和物理模型。 (2)在改进的铣削加工动力学数学模型和物理模型的基础上,综合分析和研究仿真建模过程中的常见算法精度及其效率,确定采用变步长数值积分算法(四阶Runge—Kutta算法)和递推算法建立动态铣更多还原

【Abstract】 Peripheral milling is broadly used for the manufacture of profiled components in aerospace, automotive and mould/die industries. The mechanism of milling process is very complex due to occurrence of the periodical and intermittent cutting process, semi-closed-form machining and chip thickness variation. The periodical cutting force excites vibration between the cutter and workpiece. Under certain conditions, the vibration with significant amplitude, or the so-called self-excited chatter, occurs due to the interaction between the cutter and workpiece. Unless avoided, machining with the presence of chatter leads to poor surface finish, low productivity, excessive tool wear even breakage or damage of machine.Cutting parameters in peripheral milling are determined usually based on either experience or reference handbooks rather than a mature virtual simulation system of milling process. As a result, sometimes it leads to low metal removal rate, low productivity and even high cost for the avoidance of chatter and its influence. To solve the problem, it is recommendable to develop an effective and practical virtual simulation system for peripheral milling on the basis of a systemic investigation on the machining dynamics. The system should be capable to demonstrate the machining dynamics of the milling process and predict the vibration between the cutter and workpiece under different cutting parameters and cutter dimensions, and to be used for optimization of the above parameters, such as spindle speed, radial and axial depth of cut, feedrate and cutter dimensions etc.Based on machining dynamics analysis, a virtual simulation system for peripheral milling(VSSPM) is hereby designed and developed using Matlab/Simulink. The main contents and conclusions of this thesis include:1. An improved practical mathematical machining dynamics model is developed with consideration of regenerative chatter theory. In particular, the size effect of uncut chip thickness, the influence of the effective rake angle and cutter runout that are usually missed in most existing models of the same sort, are included in the proposed model.2. Based on the proposed machining dynamics model, a computer simulation model for peripheral milling in time domain using Matlab/Simulink is developed byapplying variable-step numerical integral algorithm (fourth-order Runge-Kutta formula) and recurrence algorithm.3. Integrating experimental modal analysis and ARMAX model, research on system identification and modal analysis theory are conducted on establishment of transfer function models of the relevant milling vibration systems. The transfer function models of the milling vibration systems are presented consequently based on ARMAX identification model. Verified by many milling dynamics experiments and modal analysis tests, accuracy on predicting the vibration of VSSPM based on ARMAX identification model that reflects the dynamic characters of milling process is far better than that of the model based on traditional modal analysis tests.4. A series of computer simulation on the dynamics of milling process, including the dynamic forces and the vibration between the cutter and workpiece are conducted. The visual simulation results that exhibit the same trends as those obtained in actual machining, including dynamic cutting force and vibratory displacement between the cutter and workpiece and their power spectral density, demonstrate the accurate estimating capability of the proposed VSSPM and can be further used to analyze characters of milling process in time and frequency domain.5. Dynamics and phase characters of milling process are discussed on the basis of the analysis of the proposed VSSPM and energy consumed during milling. The optimal process parameters of milling and cutter geometric parameters are designed according to the minimum of amplitude of relative vibratory displacement in cutter-workpiece system.6. An optimal artificial neural networks (ANN) model with lower prediction errors and better performance function is proposed by adopting cu更多还原