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金属振动切削过程的数值模拟及理论分析
英文题名Simulation and theoretical analysis of metal cutting process under tool vibration
孙宗涛
导师马维
2018-05-18
学位授予单位中国科学院大学
学位授予地点北京
学位类别硕士
学位专业固体力学
关键词高速切削 材料失稳 振动切削 数值模拟
摘要

制造业是国民经济的支柱产业,金属切削作为一种常见的材料加工工艺,在制造业中有着广泛的应用。然而在实际切削过程中不可避免的存在振动现象,成为影响加工质量的重要因素之一。因此深入认识和了解振动切削过程和相关机理是十分必要的。

金属切削过程中刀具的振动分为强迫振动和自激振动。强迫振动切削过程中刀具的振动由人为附加条件引起,在合适的频率范围,刀具振动可以改善加工质量。切削过程中刀具的自激振动指刀具-工件系统本身经物理自反馈现象引起的振动。粗糙的加工表面、多重剪切带失稳以及刀具与切屑的摩擦等均可以激发系统的振动。自激振动对加工质量,特别是对刀具的寿命产生不利的影响。

本文应用数值模拟试验和理论分析的方法,研究了切刀强迫振动和自激振动切削过程。基于耦合的欧拉拉格朗日有限元方法,采用单刀模型和双刀模型分别对强迫振动和自激振动切削过程进行了模拟。在理论分析中,应用线性摄动方法研究了强迫振动切削中切屑的形成机理,同时对刀具自激振动的稳定性进行了分析。主要包括以下几个方面的内容:

1、基于CEL有限元模型,进行刀具强迫振动切削过程的数值模拟研究。着重探究了刀具振动频率对切屑形貌的影响,以及不同切削条件下,切削力的变化和材料的塑性失稳行为;

2、通过摄动分析方法,对切削过程中材料绝热剪切带的失稳行为进行了理论分析,考虑了刀具强迫振动对剪切带失稳的影响。分析得到的剪切带失稳准则,从理论上揭示了切屑形貌随刀具频率变化的原因;

3、采用双刀模型,研究了高速切削中首次切削造成的振纹和剪切带周期性失稳对刀具自激振动的影响。得到了自激振动切削过程中振纹频率、剪切带失稳频率以及刀具振动频率三者的关系,给出了描述刀具自激振动的控制方程;

4、应用ABAQUS材料本构子程序接口,编制了Vumat材料子程序。通过Vumat子程序可实现不同金属材料切削过程的模拟,从而研究应用不同材料本构对振动切削的影响。

基于本文的研究成果,可以对切削中振动问题的预测和对振动切削机理的理解提供一定的科学依据。

英文摘要

Metal machining, as a main forming processing of materials, has been widely applied in manufacturing industry. However, metal cutting processes is inevitably accompanied with the vibration phenomena of tool system, which not only decreasing the machining quality but also reducing the tool life . Therefore, it is necessary to deeply investigate the cutting mechanisms of metals involving vibration phenomenon of tool system.

Metal cutting process is usually involved in two types of mechanical vibration of tool system, called forced vibration (FV) and self-excited vibration (SEV). The tool FV is induced by exerted artificial conditions. It has been found that it usually produces bad effects on the cutting process, however, for the prescribed vibration frequency it can evidently improve the machining quality. The tool SEV attributes to internal harmonic excitations of tool-workpiece system and physical self-feedback. The rough machining surface, the instability of multiple shear bands and the friction at tool-chip interface may cause the SEV of tool system. The SEV always has a detrimental effect on the machining quality and the tool life.

In this master's thesis, the numerical simulations and theoretical analysis on the vibration cutting process of metals are performed successively. In numerical simulations, the one-tool and double-tool cutting models are established based on the coupling Eulerian-Lagrangian (CEL) finite element method, to simulate the FV and SEV cutting processes respectively. And in theoretical analysis, linear perturbation method is employed to analyze the chip formation mechanisms in the FV cutting process and the stability of the tool system vibration in the SEV cutting process. The main studies focus on the following aspects:

1. In the numerical simulation based on the CEL FE model, the effects of tool vibration frequency on chip form mechanisms was studied. Moreover, the cutting force and plastic instability behavior of chip material under different cutting conditions were also investigated.

2. Linear perturbation method was used to analyze the instability behavior of the adiabatic shear band of chip material in high-speed cutting process, and the influence of tool FV motion on the shear band instability was analyzed. The instability criterion is obtained for the evaluation of plastic flow stability of chip material in the FV cutting. The reasons of the shear banding formation and the transition from serrated chip to continuous chip are discussed.

3. The effects of the wave machining surface generated in cutting and the cyclic shear band instability on the tool SEV process were simulated by the double-tool FE model. Theoretically, the controlling equations describing the SEV process was obtained and the relationships among the wave surface frequency, the shear band instability frequency and the tool vibration frequency were established for studying the stability of the SEV process of tool system.

4. Vumat material subroutine was compiled through the ABAQUS material constitutive subroutine interface. The competed Vumat subroutine could simulate the cutting process of different metals and study the effects of different material constitution models on vibration cutting processes.

The studying results of this thesis are expected to be helpful for better understanding of the metal machining in engineering application.

语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/73143
专题流固耦合系统力学重点实验室
作者单位中国科学院力学研究所
推荐引用方式
GB/T 7714
孙宗涛. 金属振动切削过程的数值模拟及理论分析[D]. 北京. 中国科学院大学,2018.
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