高速铣削过程中薄壁壳类零件非线性振动研究

Thin-walled workpieces with complex shapes are well demanded in Aerospace and Automative industry. These workpieces are usually manufactured through high-speed milling. However, because of the low stiffness, thin-walled workpieces are prone to complex vibrations, which may cause low accuracy and surface finishing quality. This project aims to investigate nonlinear vibrations of thin-walled shell-shaped workpieces during high-speed milling and to theoretically analyze the impact of cutting parameters and time-delay effect on nonlinear vibrations of the tool-workpiece coupled system. The thin-walled shell-shaped workpiece is modeled as a cylindrical shell, and the cutting force of a spiral milling tool is chosen as the external excitation. Considering regenerative chatter, dry friction and time-delay effect, the equations of motion of the thin-walled shell-shaped workpiece during high-speed milling are derived by using the Hamilton’s principle based on the classical shell theory and von Karman strain-displacement relation. Two different boundary conditions are studied by two clamping methods of thin-walled shell-shaped workpieces. Numerical simulations are used to investigate the impact of cutting speed, cutting depth and time-delay effect on nonlinear vibrations of the thin-walled shell-shaped workpieces, respectively. Stability lobes are also provided based on different cutting parameters and time-delay parameters. This research will help determine the dynamic stability of the tool-workpiece system, and provide theoretical guidance to optimize the cutting parameters.

具有复杂构型的薄壁类零件在航空航天产业和汽车工业中有着大量的需求，该类零件通常通过铣削加工而成，但是，由于其自身刚度较低，在切削过程中易产生振动，从而降低切削精度和零件表面光洁度。本项目针对一类薄壁壳零件在高速铣削过程中出现的振动问题，研究铣削参数和时滞对加工系统动态稳定区域的影响。主要包括：考虑再生颤振、干摩擦和时滞效应，以螺旋形导屑槽铣刀铣削力为激励源，建立高速铣削过程中一类薄壁壳零件在两种不同夹持边界条件下的非线性动力学方程；利用非线性动力学理论分析系统在不同内共振情况下的分叉、混沌等动力学特性；研究切削速度、切削深度和时滞参数对系统振动响应的影响，给出该类薄壁壳零件的铣削动态稳定区域。

高速铣削过程中开口薄壁壳类零件的非线性振动问题日益突出，逐渐成为了限制高速铣削加工生产技术水平和生产效率的主要问题。对高速铣削过程中薄壁壳类零件非线性问题的研究有着重要的理论意义和工程实际价值。本课题主要采用理论研究和数值分析相结合的方法对于切削力作用下的高速铣削中薄壳零件的非线性振动、分叉和混沌动力学特性进行研究。考虑铣削系统的再生颤振、干摩擦和时滞效应，建立了两种不同夹持边界条件薄壁壳零件在高速铣削过程中的非线性动力学方程。研究刀具-薄壁壳零件系统在铣削力作用下的非线性动力学响应，具体完成的研究内容包括以下几个方面。.1.高速铣削过程中薄壁壳的非线性动力学建模.考虑干摩擦和时滞效应，建立高速铣削中薄壁壳零件的非线性动力学模型。螺旋形导屑槽铣刀铣削力产生激励作用，考虑两种不同的夹持类型，即一边固定三边自由和两边固定两边自由的夹持方式，确定薄壁壳零件在高速铣削加工中边界条件，建立刀具-薄壁壳零件系统的非线性动力学方程。.2.刀具-薄壁壳零件系统非线性振动特性分析.研究一边固定三边自由边界条件下和两边固定两边自由边界条件下，刀具-薄壁壳零件系统1:1和1:2内共振情况下的周期、分叉和混沌等非线性振动的响应特征。并且通过外激励参数的改变，获得全局分叉图，研究系统在一定参数条件下保持稳定区域的外激励改变区域。.3.薄壁壳零件高速铣削动态稳定性分析.利用理论分析和数值模拟相结合的方法研究了刀具-薄壁壳零件系统在切削速度、切削深度和时滞参数三个特征指标变化时的系统非线性响应特征，以及铣削参数空间的分叉特性，给出在时滞参数变化时系统的动态稳定区域的变化。.4.时滞参数的改变对两种夹持条件下薄壁壳类零件非线性振动的影响.通过数值模拟研究时滞参数对非线性振动特性的影响，研究高阶模态的响应与低阶模态的能量转化的关系。通过数值分析，研究系统产生跳跃的条件，在保证加工精度，避免高额损失，为实际加工提供理论依据。