航空难加工材料螺旋铣制孔专用刀具设计及其质量研究

发布时间：2018-10-14 12:27

【摘要】：螺旋铣制孔技术与工业机器人相结合,可实现干切削工况下的高效制孔,并且在提高加工质量、降低生产成本方面较传统钻削体现出显著优势。但是,航空难加工材料物化属性特殊、切削性能差,使提高螺旋铣制孔质量、避免出口缺陷与抑制刀具磨损变得极具挑战性。为此,本文基于螺旋铣运动学特征,设计了一种专用刀具分屑结构,对其切削过程力学理论进行深入分析,并针对钛合金(TC4-DT)、碳纤维增强复合材料(CFRP)及CFRP/Ti叠层材料,开展系统性试验研究。首先,介绍螺旋铣技术及其刀具研究现状,以航空难加工材料为背景,分析钻削过程产生的质量问题,指出螺旋铣制孔工艺的优势。基于螺旋铣运动学分析,构建运动学方程,对关键运动学矢量进行数学描述;应用MATLAB实现运动轨迹仿真分析,明确切削范围特点及其与自转/公转转速比(R1)、孔径/刀具直径比(R2)之间的关系。提出了螺旋铣制孔专用刀具设计方案。介绍分段式端刃、螺旋状侧刃和齿背冷却孔结构特征,重点阐述分段式端刃分屑结构、四齿同结构和两两对称同结构的仿真设计方案;以不同方案获得的未变形切屑和加工表面形貌的仿真结果为依据,实现专用刀具的端刃结构优化与数学描述;根据优化后的刃型及其关键点的运动轨迹特征,综合R1、R2对轨迹形貌的影响,进一步研究各参数对未变形切屑仿真结果的作用规律;通过不同参数下产生的切屑几何形貌、切削力和制孔质量,验证专用刀具的分屑作用。针对螺旋铣制孔专用刀具,构建了一个非线性切削力模型。通过建立用于描述切削量的坐标系,重点对不同刀齿在稳定加工阶段半自转周期内产生的切屑厚度、切削宽度进行数学描述与数值计算;采用平均力模型的方法,设计实施切削力系数标定试验,对该系数进行线性拟合与计算;最后通过设计开展TC4-DT螺旋铣制孔试验,实现对该切削力模型的验证,并深入分析不同加工参数下的切削力变化规律。基于螺旋铣制孔专用刀具,针对航空难加工材料(TC4-DT、CFRP及CFRP/Ti叠层材料)进行了系统性试验研究。通过对不同参数下的切屑几何特征、切削力变化趋势和制孔质量变化规律进行深入分析,实现了单层TC4-DT、CFRP板螺旋铣制孔过程的参数优化,进而阐述了刀具磨损特征及其对切削力和制孔质量的影响;重点研究CFRP/Ti叠层材料螺旋铣制孔精度,阐述了 TC4-DT与CFRP平均孔径与圆度的变化规律,进一步验证了专用刀具的分屑优势。最后总结本文的主要研究内容、提炼创新点,并对未来的研究工作提出展望。
[Abstract]:The combination of spiral milling and industrial robot can realize efficient drilling under dry cutting condition, and it has obvious advantages over traditional drilling in improving machining quality and reducing production cost. However, because of the special physical and chemical properties and poor cutting performance, it is very challenging to improve the quality of helical milling holes, to avoid exit defects and to restrain tool wear. In this paper, based on the kinematic characteristics of spiral milling, a special cutting tool chip structure is designed, and the mechanical theory of cutting process is analyzed in depth. Aiming at titanium alloy (TC4-DT), carbon fiber reinforced composites (CFRP) and CFRP/Ti laminated materials, To carry out systematic experimental research. Firstly, this paper introduces the research status of helical milling technology and its cutting tools, analyzes the quality problems in drilling process, and points out the advantages of helical milling process. Based on the kinematics analysis of spiral milling, the kinematics equation is constructed, the key kinematics vector is described, and the motion trajectory is simulated and analyzed by MATLAB. The characteristics of cutting range and its relationship with rotation / rotation speed ratio (R1) and diameter ratio of aperture to tool diameter (R2) are determined. The design scheme of special tool for spiral milling hole is put forward. This paper introduces the structural characteristics of segmented end edge, spiral side edge and cooling hole on the back of teeth, with emphasis on the simulation design scheme of split end edge chip structure, four teeth same structure and two symmetrical same structure. Based on the simulation results of non-deformable chip and machined surface topography obtained from different schemes, the end edge structure optimization and mathematical description of special tool are realized, and the trajectory characteristics of the optimized edge and its key points are analyzed. By synthesizing the influence of R _ 1 / R _ 2 on the trajectory morphology, the effects of various parameters on the simulation results of undeformed chips are further studied, and the chip geometry, cutting force and hole quality produced by different parameters are used to verify the chip-splitting effect of special cutting tools. A nonlinear cutting force model is constructed for the special tool for screw milling hole making. By establishing a coordinate system to describe the cutting quantity, the cutting width and chip thickness produced by different cutter teeth during the semi-rotation period of stable machining are described and numerically calculated, and the average force model is used to calculate the thickness of chip and the cutting width. The calibration test of cutting force coefficient is carried out, and the coefficient is linear fitted and calculated. Finally, the TC4-DT spiral milling experiment is carried out to verify the cutting force model. The changing law of cutting force under different machining parameters is also analyzed in depth. Based on the special tool for helical milling hole making, the systematic experimental study was carried out on the aviation difficult materials (TC4-DT,CFRP and CFRP/Ti laminated materials). By analyzing the geometric characteristics of chip, the changing trend of cutting force and the changing rule of hole making quality under different parameters, the parameter optimization of single layer TC4-DT,CFRP plate helical milling process is realized. Furthermore, the characteristics of tool wear and its influence on cutting force and hole making quality are expounded, and the accuracy of helical milling of CFRP/Ti laminated material is studied, and the variation law of average aperture and roundness of TC4-DT and CFRP is expounded. Furthermore, the chip splitting advantage of special cutting tools is verified. Finally, this paper summarizes the main research content, refines the innovation, and puts forward the prospect to the future research work.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG54

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