【作者】 刘勇；

【导师】 孙玉文；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 纯铁材料具有优良的电磁性能,因而被广泛应用于加工电子工业、国防工业以及航天航空工业等领域中的关键零部件。数控车削加工是回转体类纯铁材料构件加工制造的主要方法,然而对于刚性较弱的纯铁材料构件,在数控车削加工过程中往往会因加工参数选取不当而导致颤振现象的发生,颤振现象大大制约了弱刚性纯铁材料构件车削加工过程加工质量和生产效率的提高。因此实现对弱刚性纯铁材料构件车削加工过程中颤振稳定性的准确预报对于实现加工工艺参数优选和生产制造能力提高具有重要的意义。本文针对弱刚性纯铁材料构件车削加工过程,基于再生效应,开展了车削加工颤振稳定性预报等方面的研究,主要的研究工作有:(1)基于金属切削宏观力学,建立了同时考虑车削加工过程中剪切效应和刃口效应的车削力模型,且在建模过程中通过离散处理未变形切屑面积的方法,引入了刀尖圆角半径的影响。针对预报模型中待标定的九个车削力系数,提出了一种基于鲍威尔优化方法的系数标定新方法。此外,还进行了针对纯铁材料构件的系列实际切削实验,验证了车削力模型的准确性。(2)根据实际车削加工过程,建立了综合考虑刀具和工件动力学特性的车削加工动力学模型。同时,基于再生效应构造了该动力学模型的二阶时滞微分方程表示形式,并利用实验模态分析方法辨识了刀具和工件的模态参数。(3)通过变换得到了所建车削加工动力学模型的状态空间表示形式,扩展了最新提出的二阶半离散法,构造了单周期内系统的状态转移矩阵,并基于弗洛凯理论实现了对车削加工过程中颤振稳定性的预报,此外,还运用数值仿真的方法探究了加工工艺系统的模态参数对颤振稳定性的影响规律。(4)根据数值仿真得到的稳定性叶瓣图,开展了不同加工参数下的验证实验。实验表明,稳定性的预报结果与实测结果基本吻合,所提方法能够实现对弱刚性纯铁材料构件车削加工过程中颤振稳定性的准确预报。更多还原

【Abstract】 Pure iron material has excellent performance on electromagnetic,hence it is widely utilized to machine key components in electronic industries,national defense industries,aerospace industries and so on.CNC turning is generally used to machine rotary-type components made of pure iron.However,the chatter tends to happen in CNC turning machining of weak-rigidity components made of pure iron if the unreasonable processing parameters are selected,and the chatter can limit the improvement of machining quality and producing efficiency.Therefore the accurate prediction of chatter stability in CNC turning machining of weak-rigidity components made of pure iron is of great significant to the optimization of processing parameters and the improvement of machining capacity.Aiming at the CNC turning machining of weak-rigidity components made of pure iron,the research on the chatter stability prediction in turning machining based on the regenerative effect is carried out in this paper,and the main research contents are as follows:(1)Basing on the macro-mechanics of metal cutting,a modeling of turning forces,which takes the shearing effect and the rubbing effect into account simultaneously,is proposed in this paper,and the effect of the tool nose radius is considered in modeling by discretizing the uncut chip area.Aiming at nine turning force coefficients in proposed modeling,a novel identification method based on the Powell’s optimization method is presented.In addition,numerous actual turning machining tests are conducted on the components made of pure iron to verify the accuracy of the modeling.(2)According to the actual situation of turning machining,a turning machining dynamic model considering the dynamic characteristics of tool and workpiece is built in this paper.Meanwhile second-order differential equations with delays are constructed based on the regenerative effect to represent proposed dynamic model.Besides,the modal parameters of tool and workpiece are identified through the experimental modal analysis.(3)By means of transformation,the state-space representation of proposed turning machining dynamic model is constructed in this paper.In addition,the latest second-order semi-discretization method is extended,and the transition matrix of system in single period is obtained.The chatter stability in turning machining is predicted according to the Floquet theory.Furthermore,the effects of the modal parameters of processing system on the chatter stability are explored through the numerical simulation.(4)According to the stability lobe diagram obtained by the numerical simulation,the verification tests under different processing parameters are conducted.And overall,the test results indicate that the stabilities predicted by stability lobe diagram agree well with the stabilities of actual turning machining tests,and the methods proposed in this paper can achieve the accurate prediction of chatter stability in CNC turning machining of weak-rigidity components made of pure iron.更多还原