基于时域仿真法的断续铣削颤振预测

颤振是影响铣削加工表面质量和限制切削效率的重要原因,准确获取稳定性叶瓣图是避免颤振的有效途径.精加工铣削常使用小径向切深/刀具直径比,产生过小的实时切削厚度,刀具容易脱离工件,造成显著非线性因素;过小的径向切深/刀具直径比也导致铣削加工高度断续.因此,常用的圆弧切削厚度已不能近似实际切削厚度,进而影响断续铣削加工颤振预测.采用考虑实际切削厚度的时域仿真法预测断续铣削加工颤振稳定性.该方法使用刀具实际运动轨迹计算切削厚度,并综合考虑了铣削过程中刀具和工件的动力学特性对切削厚度的影响.提出基于相关系数的无量纲颤振判定准则,并用于铣削仿真结果加工状态的判定.通过钛合金Ti6Al4V铣削验证试验结果,所提出的时域仿真法能准确预测小径向切深/刀具直径比所致的断续铣削加工稳定性叶瓣图,为高断续铣削加工无颤振加工参数选择提供了一种有效方法.     

碳纤维薄壁圆筒车削加工工艺研究

对碳纤维复合材料薄壁圆筒车削加工工艺进行分析研究,主要从工件的加工特性、切削颤振对工件加工精度的影响进行分析,研制专用定位夹紧装置,进行切削刀具几何参数研究试验与确定,采用正交实验方法进行切削试验,确定最优切削参数组合,通过实验验证该加工工艺的可行性。解决了薄壁碳纤维圆筒加工中出现拉丝起毛、装夹变形和加工变形的关键技术难点,确定的加工工艺方法应用于生产实践中,取得了显著效果。     

切削颤振模型及机理研究

提出了同时考虑工件系统和刀具系统对切削颤振影响的２自由度切削系统模型,用此模型解释了双频颤振和单频颤振产生的机理,提出了产生的条件,并进行了试验验证。     

切削颤振机理及控制

切削颤振是加工过程中刀具和工件之间产生的强烈自激机械振动,如果不加以控制,将会导致工件加工表面粗糙,刀具寿命降低并产生噪声,限制了生产率的提高,严重时使加工过程无法进行。     

刀具颤振与动力减振浅析

1引言 颤振是金属切削加工中最常见的失效方式之一。颤振发生时，在刀具的切削刃和工件之间，除了正常的切削运动以外，还会叠加一个周期性的相对运动。     

大型蜗杆铣削颤振稳定性研究

颤振通常会降低产品质量和生产效率,缩短机床和刀具的使用寿命。针对工业现场某大型蜗杆工件铣削加工中出现的颤振问题,建立其铣削颤振数学模型,采取对时滞项进行离散化的方法,利用Floquet理论进行判稳。在不同切削加工参数下试验对比稳定与失稳状态时刀具的振动信号特征,验证稳定性理论分析的正确性,避免了铣削过程颤振的发生。     

基于动态切削过程仿真的外圆车削稳定性判定

建立考虑工件轴向和径向两个方向刀具刃倾角和模态方向的车削颤振模型。利用试验得到的切削力系数和模态参数,获得给定机床、刀具和工件组合下的颤振稳定域曲线。建立外圆车削轴类零件的动力学模型,主要包括刀具相对工件的动态切削力和动态位移模型。提出一种借助动态切削力和刀具动态位移时域仿真,以及相邻两转的切削力和位移动态成分映射截面来综合判断切削过程稳定性的方法。通过切削试验验证颤振稳定域判据和动态切削过程判据的准确性。利用该方法了解稳定切削和颤振切削的信号特点和分布规律。对比颤振稳定域和动态切削仿真两种稳定性判据的有效性、优缺点和适用场合,尤其通过典型零件的切削过程仿真说明动态切削仿真方法的优点。此外,还通过对动态切削过程的变模态参数仿真,分析模态参数对切削过程稳定性的影响。     

基于数值模型的数控加工中切削力与稳定域仿真

针对数控铣削加工工艺参数选择存在的问题,以球头铣刀高速铣削过程为研究对象,建立了考虑机床-刀具-工件系统振动的非线性动力学模型,分析了铣削力中的动态分量对切削颤振的影响,在考虑再生颤振的基础上建立非线性动力学模型.基于动态铣削力建模和颤振稳定域分析计算,提出了机床切削系统稳定性极限预测方法,并对其进行仿真分析,为铣削加...     

基于颤振预报和预测的稳定性控制理论及方法研究

针对由颤振预测控制策略指导的稳定切削控制方法实时动态调整能力差的缺点,综合颤振预报、预测理论,进行了稳定性在线寻优控制理论及方法的研究。基于刀具—工件系统铣削再生颤振动力学模型,研究了考虑系统结构参数(刀具、工件装夹刚度)和加工参数(切削加工参数优化选择)的切削稳定性评价方法,提出了以扩大稳定性区域和稳定最大材料切除率为控制目标的机床稳定性控制方法。形成了以"预报—控制—效果评估—再控制"为步骤的在线监测、智能诊断和实时控制的集成一体化策略。设计并实施了稳定性控制理论验证实验,获得了与理论分析一致的结论。     

电流变液双电极复合结构在车削颤振控制中的应用

应用电流变液复合结构的特殊性能，研究开发了一种双电极智能颤振抑制结构，用于机床车削过程颤振的控制。实验结果证明，利用电流变智能颤振抑制结构对机床车削振动可以进行有效的控制，从而提高工件表面的加工质量，改善刀具切削加工性能。     

Stability analysis of turning process with tailstock-supported workpiece

This paper proposes an analytical scheme for stability analysis in turning process by considering the motion of tailstock-supported workpiece using a compliance model of tool and work. A dynamic cutting force model based on relative motion between the cutting tool and workpiece is developed to study the chatter stability. Linear stability analysis is carried out in the frequency domain and the stability charts are obtained with and without considering workpiece flexibility. Variations of stability limits with workpiece dimensions and cutter position as well as the effects of cutting tool dynamics are studied and wherever possible results are compared with existing models. Experimental analysis is conducted on tailstock-supported workpiece to examine the correctness of the proposed stability model.     

基于SVR-GA算法的广义加工空间机床切削稳定性预测与优化研究

针对机床零件加工位置和进给方向不确定造成刀尖频响函数变化,导致切削稳定性叶瓣图与无颤振工艺参数预测具有不确定性问题,提出一种耦合支持向量回归机(SVR)与遗传算法(GA)的切削稳定性预测与优化方法。该方法采用锤击法模态实验和空间坐标变换,获取样本空间不同加工位置与进给方向的刀尖频响函数;进而结合传统切削稳定性预测方法构建以各向运动部件位移、进给角度、主轴转速、切削宽度、每齿进给量为输入的极限切削深度SVR预测模型;采用该SVR模型作为切削稳定性约束建立材料切除率优化模型,通过遗传算法求解各运动轴位移、进给角度与切削参数的最优配置。以某型加工中心展开实例研究,实验结果表明获取的优化配置能实现稳定切削,验证了该方法的有效性。     

Structural–energetic approach to the wear and diagnostics of hard-alloy tools

By multifractal parameterization of the contact surfaces of the tool and the supporting surface of the chip in the cutting process, the relation of the fractal dimensionality with the tool’s wear rate and the informational entropy is established. In addition, the nonlinear dependence of the tool life on the cutting speed is found. A diagnostic system for monitoring the dynamic stability of the cutting system and the tool wear is proposed.     

基于动力学不确定性的重型切削工艺参数优化

针对数控重型切削加工过程的切削稳定性具有不确定性的特点,提出了在切削稳定性和机床工作能力的约束下,获得最大材料去除率的工艺参数优化方法。根据重型切削加工的工艺特点建立三维动力学模型,以机床的固有频率、阻尼比、刚度和切削力系数作为不确定因素,结合排零定理和边理论对其进行不确定性分析,获得稳健的切削稳定性叶瓣图,结合切削深度、刀具直径和刀具齿数的关系,为加工过程选择能获得最大切削深度的刀具。在此基础上,建立工艺参数优化模型,选择最佳的轴向切削深度、径向切削深度和主轴转速的组合,最后以一台加工中心上某型号发动机缸体表面的粗加工过程为例进行了验证。     

Analysis and Design of a Haptic Control System: Virtual Reality Approach

In this paper, the analysis and design of telerobotics based on the haptic virtual reality (VR) approach for simulating the clay cutting system is proposed. The main components of the approach include a user interface, networking, simulation, and a robot control scheme. The telerobotics for the clay cutting system and the environment is simulated by a haptic virtual system that enables operators to feel the actual force feedback from the virtual environment just as they would from the real environment. The haptic virtual system integrates the dynamics of the cutting tool and the virtual environment whereas the handle actuator consists of the dynamics of the handle and the operator on the physical side. The control scheme employs a dynamical controller which is designed considering both the force and position that the operator imposes on the handle and feedforward to the cutting tool, and the environmental force imposed on the cutting tool and the feedback to the handle. The stability robustness of the closed-loop system is analysed based on the Nyquist stability criterion. It is shown that the proposed control scheme guarantees global stability of the system, with the output of the cutting tool approaching that of the handle when the ratios of the position and the force are selected correctly. Experiments in the virtual environment on cutting a virtual clay system are used to validate the theoretical developments.     

一种新的切削刚度系数识别方法

在研究机床切削系统稳定性极限预测的过程中，切削刚度系数ke的准确识别是其中最为关键的一项工作。文中在对刀架施加振动激励，变稳态切削为动态切削的基础上．以动态切削力为研究对象，推导切削刚度系数ke的数学模型，并在切削试验中通过对动态切削力信号及其与振动位移信号相位差的测量，准确有效地识别切削刚度系数ke。试验结果表明，文中的切削刚度的识别方法可以为机床切削系统稳定性预测理论分析和试验研究提供更为准确的动力学参数。     

高速主轴系统切削稳定性预测及影响因素分析

高速主轴系统切削稳定性直接影响产品的表面加工精度和切削系统的使用寿命,是评价高速主轴系统性能优劣的重要因素,而研究影响切削稳定性的因素并制定提高稳定性的合理途径同样也受到关注。提出从稳定性评价准则及系统频响函数的不同求解方法入手,分析无条件稳定区和有条件稳定区的影响因素,总结出系统所受激励、主轴转速及系统结构是影响切削稳定性的重要因素。以德国GMN高速主轴系统为例,在采用5自由度轴承受力与变形关系模型模拟角接触球轴承和分布式弹簧模型模拟主轴-刀柄-刀具结合部的基础上,建立完整高速主轴系统通用有限元模型;利用三维稳定性叶瓣图、极限切削深度和叶瓣交点随参数的变化曲线表征切削力幅值、转速及阻尼比等参数对切削稳定性的影响规律,为优化加工工艺、提高系统切削稳定性提供理论依据。     

Improving machinability of Inconel 718 with a new hybrid machining technique

In this paper, by joining three non-traditional machining methods — plasma-enhanced machining, cryogenic machining, and ultrasonic vibration assisted machining — a new hybrid machining technique for machining of Inconel 718 is presented. Cryogenic machining reduces the temperature in the cutting zone, and therefore decrease tool wear and increases tool life, while plasma-enhanced machining helps to increase the temperature in the workpiece to make it softer. Also, applying ultrasonic vibrations to the tool helps to improve cutting quality and to prolong tool life by lowering, mainly, the cutting force and improving the dynamic cutting stability. This study experimentally investigates the effect of cutting parameters on cutting performance in the machining of Inconel 718 and compares the results of hybrid machining and conventional machining (CM). It is found that the hybrid method results in better surface finish and improves tool life in hard cutting at low cutting speeds as compared to the CM method.     

Parametric self-excitation of a dynamic end-milling machine

The parametric self-excitation of a dynamic end-milling machine is considered. Parametric selfexcitation, accompanied by stability loss, significantly impairs the properties of the system. The factors affecting parametric self-excitation include the cutting conditions—in particular, the tool speed—and the tool geometry, which determines the orientation of the cutting forces. Some regions of stability during parameter variation are noted.     

FUZZY STABILITY ANALYSIS OF MODE COUPLING CHATTER ON CUTTING PROCESS

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