双顶角钻尖几何参数对碳纤维复合材料钻削轴向力和制孔分层的影响

发布时间：2019-01-03 21:00

【摘要】：碳纤维复合材料(CFRP)零件的钻孔加工是实现此类零件装配连接必不可少的环节,然而由于CFRP材料是由软粘性的树脂基体和高强高硬的纤维增强相组成,具有独特的各向异性和层合特性,使得钻孔过程中极易产生分层、撕裂、毛刺等损伤。钻尖部分是钻头参与切削的主要区域,钻尖的几何特征直接决定钻头和工件的接触状态及切削过程,是影响制孔损伤的重要因素。本文以T800级CFRP层合板为研究对象,为探索适合于CFRP层合板钻削的钻尖几何,首先采用多种不同钻尖几何的钻头进行对比实验,确定了双顶角形状的钻尖较适合于钻削CFRP层合板；然后通过理论解析和实验研究相结合的方法,研究双顶角钻尖几何参数对钻削轴向力和出口分层的影响,为指导高质量制孔刀具的设计提供了依据。论文的主要研究内容和结论如下：(1)采用麻花钻、阶梯钻、双顶角钻和圆弧钻对CFRP层合板进行制孔试验,基于钻削过程中测量的切削力和切削温度,分析出口分层损伤产生的原因。研究可知双顶角钻头在钻出工件底部时分阶段钻出,钻削轴向力多阶段缓慢归零,且钻削温度相对较低,导致最终的出口分层小,制孔质量好。(2)基于双顶角形状的钻尖特征对其几何尺寸进行参数化,分别建立了基于Hertz接触理论的横刃轴向力模型和基于二维直角切削的主切削刃轴向力模型,采用13种不同几何参数的双顶角钻头对模型中的待定系数进行标定,并通过两种双顶角钻头的轴向力预测对模型进行了验证。横刃轴向力预测的平均误差约为11%,主切削刃轴向力的预测平均误差约为2%。最后通过分析双顶角钻削轴向力模型,获得钻削轴向力随钻头几何参数变化的规律。(3)按顶角分配类型将双顶角钻头分为凸双顶角和凹双顶角,通过分析轴向力的时变曲线得到了轴向力沿切削刃的分布情况,讨论了最后一层纤维所受的轴向力的变化及不同类型双顶角钻头的制孔出口分层的产生过程。结果表明,凸双顶角钻的刀具外围轴向力较小,可以缩短裂纹长度,产生较小的出口分层。钻头的总轴向力与出口分层因子并非正比关系,而轴向力沿切削刃的变化对于出口分层因子有着更直接的影响。刀具设计时应该首先考虑钻削轴向力随切削刃的变化规律,然后可以考虑如何整体降低轴向力。
[Abstract]:The drilling of (CFRP) parts of carbon fiber composites is an essential link to realize the assembly and connection of such parts. However, the CFRP material is composed of a soft viscous resin matrix and a high strength and high hardness fiber reinforced phase. Because of its unique anisotropy and lamination, it is easy to produce delamination, tear and burr. The drill tip part is the main area in which the bit takes part in cutting. The geometric characteristics of the drill tip directly determine the contact state and cutting process between the bit and the workpiece, which is an important factor affecting the hole making damage. In this paper, T800 CFRP laminated plate is taken as the research object. In order to explore the drill tip geometry suitable for CFRP laminate drilling, several kinds of drill bit with different drill tip geometry are used to carry on the contrast experiment at first, it is determined that the double top angle drill tip is more suitable for drilling the CFRP laminate. Then through the method of theoretical analysis and experimental study, the influence of the geometric parameters of double-top angle drilling tip on the axial force and exit delamination of drilling is studied, which provides the basis for guiding the design of high quality drilling tool. The main research contents and conclusions are as follows: (1) Hole making test of CFRP laminated plate is carried out by using twist drill, step drill, double top angle drill and circular arc drill, based on the cutting force and cutting temperature measured during drilling. The causes of exit delamination damage are analyzed. The research shows that the double vertex bit drilled out in the time division stage at the bottom of the workpiece, and the axial force of drilling is slowly returning to zero in many stages, and the drilling temperature is relatively low, which leads to the final exit delamination is small. The hole making quality is good. (2) the geometric dimension is parameterized based on the double vertex shape of drill tip. The axial force model of the horizontal edge based on Hertz contact theory and the axial force model of the main cutting edge based on two-dimensional right-angle cutting are established, respectively. The undetermined coefficients of the model are calibrated with 13 kinds of double-vertex bits with different geometric parameters, and the model is verified by predicting the axial force of two kinds of double-vertex bits. The average error of the axial force prediction of the cutting edge is about 11 and that of the main cutting edge is about 2. Finally, by analyzing the axial force model of double vertex drilling, the variation of drilling axial force with bit geometry parameters is obtained. (3) the double top angle bit is divided into convex double top angle and concave double top angle according to the type of vertical angle distribution. By analyzing the time-varying curve of axial force, the distribution of axial force along the cutting edge is obtained, and the variation of axial force on the last layer of fiber and the process of producing delamination at the outlet of different types of double-vertex bits are discussed. The results show that the external axial force of the tool is smaller, which can shorten the crack length and produce smaller exit delamination. The total axial force of the bit is not directly proportional to the exit stratification factor, but the variation of axial force along the cutting edge has a more direct effect on the exit stratification factor. In the design of the tool, the variation of the axial force with the cutting edge should be considered first, and then how to reduce the axial force as a whole can be considered.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG52

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