【作者】 汤爱民；

【导师】 周志雄；

【作者基本信息】 湖南大学 ， 机械制造及其自动化， 2012， 博士

【摘要】 高速切削作为制造业中的一种重要共性基础技术，因其具有提高生产率和加工精度、降低切削力和能耗、简化工艺流程、缩短生产周期等优点，在航空航天、汽车、模具等行业中得到广泛的应用。然而，由于高速切削刀具技术性强，而国内高速切削刀具技术在刀具基体和涂层材料的研发、刀具制造工艺技术、刀具安全技术、刀具应用技术以及高速切削机理的基础共性研究等方面与国外存在较大差距，自主研发能力弱，导致我国高速切削刀具大部分依赖进口。本文以提高高速铣削稳定性为目标，通过理论研究、数值仿真以及试验研究等手段，对高速铣削过程中的动态切削力、切削颤振、铣削稳定性以及不等齿距动平衡进行深入研究，提出了新型不等齿距高速立铣刀结构设计的思路，所做的主要工作包括：（1）对高速铣削颤振机理与切削力进行了研究。研究高速铣削被加工表面颤振振纹，通过测量振纹间距以及分析切削力信号两种方法计算颤振频率，结果表明两者是一致的。根据该结论，基于加工表面轮廓为刀具切削刃运动形成的映射的原理，提出了一种用于研究高速铣削颤振的新方法，并设计了快速落刀实验装置。基于微刃瞬时刚性力模型，建立了高速铣削过程的静、动态切削力模型。（2）对等齿距与不等齿距立铣刀的切削稳定性进行了对比研究。根据切削力模型和动力学微分方程，求解出铣削稳定域的极限切深和极限转速，为绘制切削稳定性极限图提供理论支持。通过分析等齿距与不等齿距铣刀结构特点及铣削力频谱的差异，揭示不等齿距铣刀抑制颤振的本质原因是通过不等的齿间夹角，改变延时时间及颤振产生的条件，使振动频谱更加分散。通过仿真和试验手段，研究等齿距和不等齿距铣刀高速切削时的稳定性，以及齿距差角对不等齿距铣刀切削稳定性的影响规律，研究表明：增大齿距差角可以提高不等齿距铣刀的切削稳定域，有效抑制铣刀高频振动。（3）对不等齿距铣刀的动平衡进行了深入研究，揭示了刀具结构参数对其动不平衡的影响。基于动平衡的基本理论和铣刀容屑槽的几何特点，建立了不等齿距三刃高速立铣刀质量偏心和不平衡量的数学模型。在三维造型软件UG中建立铣刀对应的三维实体模型，计算出铣刀的质量偏心，并通过刀具动平衡测量仪测量铣刀的不平衡量。通过实验验证了质量偏心和不平衡量数学模型的可靠性。分析了新型高速立铣刀质量偏心和动不平衡的影响因素，研究发现：刀具刃长和螺旋角对质量偏心和动不平衡的影响最大，且其变化规律具有周期性。（4）从抗振性方面对等齿距与不等齿距铣刀切削性能进行了系统的对比试验研究。基于抗振和动平衡综合性能，提出了不等齿距高速立铣刀结构设计思路。针对铝合金高速铣削工况，以新型不等齿距高速立铣刀和普通高速立铣刀为对比刀具，开展切削力和切削振动对比试验研究。研究结果表明：当切削参数和不平衡量相同时，新型不等齿距高速立铣刀能够有效抑制切削振动，可提高刀具抗崩缺性能，特别是在小切深、大切宽高速铣削和薄壁件高速铣削两种工况下，其抗振性能更好。更多还原

【Abstract】 As an important common and basic technology of advanced manufacturing, highspeed cutting(HSC) is widely used in aerospace, automobile, and mould industries oweto its advantages, such as improving production efficiency and machining precision,reducing cutting force and power consuming, simplifying process flow, shorteningproduction cycle, and et al. However, HSC tool engineering is technical, and comparedto overseas technology, there is a big gap in tool substrate and coat material researchand development, tool manufacturing process and technology, tool safety technology,tool application technology and HSC mechanism research. Because the independentresearch and development capability is weaker, as a result, a majority of HSC tools areimported in our country. With the purpose of improving high speed milling(HSM)stability, dynamic cutting force, cutting chatter, and milling stability and dynamicbalance of end mill with unequal blade spaces are thoroughly researched by means oftheoretical research, simulation and experimental study, and a method to design a newtype of high speed end mill with variable pitch is put forward. The research workincludes four parts as follows:(1) Milling chatter and force in high speed milling processes are studied. Whenresearching milling chatter marks on the machined surface, it is discovered that thechatter frequency calculated from the distance between two vibration marks is nearlythe same with that calculated from the cutting force signal. According to theconclusion, based on the principle that machined surface contour reflects the movingtrack of cutting edge, a new method to study high speed milling chatter is proposed,and the fast tool-off experiment device is designed. At last, on the basis of theinstantaneous rigid force model for micro cutting edge, static and dynamic cuttingforce models for high speed milling processes are established.(2) The cutting stability of end mills with equal pitches and that of end mill withvariable pitches are researched and compared. Based on the force models and dynamicdifferential equation, the limited depth of cut and speed are solved, which lay thetheoretical basis for drawing the stability lobe diagram. By comparing the structureand cutting force spectrum of the two kinds of end mill, it is discovered that thesubstaintial cause for end mill suppressing chatter is that the unequal pitches dispersevibration spectrum by changing the delay time, and destroying chatter generatingconditions. By simulation and experiment, researches on HSM stability of end mill and the law for the difference of pitch to affect milling stability are carried out. The resultsindicate that increasing the difference of pitch can enlarge the stability domain andeffectively suppress the high frequency vibration.(3) In order to reveal the influence of structure parameters on dynamic balance,the dynamic balance for end mill with variable pitches is deeply investigated. Based onthe basic theories of dynamic balance and the geometry characteristics of helical flutes,a mathematical model of mass eccentricity and imbalance value of the high speed endmill with three unequal pitches is established. The3D solid model of the end mill isbuilt in the software UG, and its mass eccentricity value is calculated. Meanwhile, theimbalance value of the end mill is measured by a dynamic balance measuringinstrument, and the reliability of the mathematical model is verified by this dynamicbalance test experiment. According to the mathematical model of eccentricity andimbalance, influencing factors are thoroughly analyzed. It is found that the length ofcutting edge and helical angle have the most influence on mass eccentricity andimbalance value, and they change mass eccentricity and imbalance periodically.(4) The cutting performance of end mills with equal and variable pitches iscomprehensively researched from the aspect of anti-vibration. Considering the abilityin anti-vibration and dynamic balance, the structure optimal design method for the newtype of high speed end mill with variable pitched is proposed. Making high speedmilling aluminum alloy as the experimental condition, and end mill with equal andvariable pitches as the cutting tool, comparative tests of cutting force and vibration arecarried out. The results show that, when the cutting parameters and imbalance are thesame, the new end mill can effectively suppress chatter and enhance resistance tochipping, and especially under the condition of high speed milling thin-walled part ormilling in small cutting depth and big cutting width, the capability of the new end millto suppress vibration is better.更多还原