【作者】 王彪；

【导师】 陈根余； 朱更红；

【作者基本信息】 湖南大学 ， 机械工程（专业学位）， 2022， 硕士

【摘要】 碳纤维复合材料(CFRP)作为一种高性能复合材料,应用领域越来越广,对其进行连接的过程中需要进行大量孔加工,其加工方式目前以机械制孔为主,机械制孔存在分层等缺陷,且刀具磨损快导致使用成本高,故逐渐被新型加工方式所取代。CFRP激光制孔作为一种新的方法,因为没有力的作用克服了机械制孔的分层缺陷,但激光制孔时又存在热影响区和锥度等缺陷。本文针对厚板CFRP制备大孔提出激光与机械法复合的加工工艺路径,先激光环切预制底孔,然后机械扩孔去除变质层并减小锥度。设计并搭建激光环切制孔与机械扩孔试验平台,探究了激光环切制孔时工艺参数与加工质量的关系,计算了T800烧蚀阈值并分析了各类损伤的形成机理,在得到激光环切厚板CFRP材料预制孔后,对其机械制孔过程进行了动力学仿真,最后通过试验探究了扩孔参数的较优值。本文试验的主要研究内容如下:(1)列举了激光加工CFRP孔的优点,验证了其可行性。揭示了脉宽为10ps的脉冲激光呈现冷加工效果的机制,对厚板CFRP环切制孔过程中的锥度形成原因从遮蔽效应、光斑分散两方面建立数学模型对二维振镜加工的底部碗状截面形成原因进行了解释。(2)通过热传递计算模型计算了CFRP-T800材料中的碳纤维烧蚀阈值,证实了激光加工纤维增强材料的高效性。对环切CFRP的盲孔时切断的内径阈值进行拟合并预测,得到了不同板厚不同孔径的环切内径值,提供了最优的激光预制孔扫描路径,探究了功率对盲孔加工时底面与侧壁粗糙度的关系并从理论上进行了分析。(3)对盲孔加工时激光工艺参数与HAZ(热影响区)、锥度的关系进行了正交试验探究,得到了较优的功率以及重复频率,同时对扫描速度与截面不同位置锥度变化进行探究得到了最优扫描速度,采用最优扫描路径与加工参数进行了预制孔试验得到3组不同板厚及直径的预制孔,并对其锥度进行了对比。(4)采用较优激光预制孔参数进行激光预制孔后,进行了扩孔动力学仿真,分析了扩孔阶段轴向力变化原因,对比了不同刀具扩孔的出口损伤,确定了最优扩孔刀具,采用不同转速与进给速度对预制孔进行单因素扩孔试验,对比不同参数的孔口形貌得到了最优的机械扩孔工艺参数,对刀具的磨损与扩孔前后表面粗糙度进行了定性分析。更多还原

【Abstract】 Carbon fiber composite material(CFRP),as a high-performance composite material,has an increasingly wide range of applications.A large number of holes need to be processed during the connection process.At present,the processing method is mainly mechanical hole making,which has defects such as delamination,and the rapid tool wear leads to high cost of use,so it is gradually replaced by new processing methods.As a new method,CFRP laser drilling overcomes the delamination defects of mechanical drilling because there is no force,but there are defects such as heat-affected zone and taper when laser drilling.This paper proposes a combined processing path of laser and mechanical methods for the preparation of large holes in thick plate CFRP.First,the prefabricated bottom holes are cut by laser ring,and then the metamorphic layer is removed and the taper is reduced by mechanical hole expansion.Design and build a test platform for laser ring cutting hole making and mechanical hole reaming,explore the relationship between process parameters and processing quality during laser ring cutting hole making,calculate the T800 ablation threshold and analyze the formation mechanism of various damages.After the prefabricated holes of the thick plate CFRP material were prefabricated,the dynamic simulation of the mechanical holemaking process was carried out.The main research contents of this experiment are as follows:(1)The advantages of laser processing CFRP holes are listed and their feasibility is verified.The mechanism of the cold working effect of the pulsed laser with a pulse width of 10 ps was revealed.The reason for the formation of the taper in the process of cutting the thick plate CFRP ring was established from the shielding effect and the spot dispersion.The bottom bowl shape processed by the two-dimensional galvanometer The reason for the formation of the cross section is explained.(2)The carbon fiber ablation threshold in CFRP-T800 material was calculated by the heat transfer calculation model,which confirmed the high efficiency of laser processing fiber reinforced materials.By fitting and predicting the cut-off inner diameter threshold value of the blind hole of CFRP,the inner diameter value of the ring cut with different plate thicknesses and different apertures is obtained,and the optimal laser prefabricated hole scanning path is provided.The relationship between bottom surface and sidewall roughness is analyzed theoretically.(3)The relationship between laser process parameters and HAZ(heat affected zone)and taper during blind hole processing was investigated in orthogonal experiments,and better power and repetition frequency were obtained.The optimal scanning speed was obtained through exploration,and the prefabricated hole test was carried out using the optimal scanning path and processing parameters to obtain three groups of prefabricated holes with different plate thicknesses and diameters,and their tapers were compared.(4)After using the optimal laser prefabrication parameters for laser prefabrication,the dynamic simulation of hole reaming was carried out,the reasons for the change of axial force in the reaming stage were analyzed,the exit damage of reaming by different tools was compared,and the optimal expansion was determined.Hole cutters,single-factor hole reaming experiments were carried out on prefabricated holes with different rotational speeds and feed speeds,and the optimal mechanical hole reaming process parameters were obtained by comparing the orifice morphology of different parameters.A qualitative analysis was performed.更多还原